Analysis for typhoid fever in vitro. Blood test for typhoid with Vi antigen

Typhoid fever is a rare pathology that is accompanied by a harmful infection in the intestines. The treatment period is at least 1 month. To detect this disease, the doctor prescribes appropriate tests, which we will discuss in more detail in our material.

For the first time the name "typhus", which means clouding of consciousness, was introduced in 460 BC. Hippocrates. In 2017, typhoid fever (hereinafter referred to as BT) is an infectious disease associated with damage to the stomach and intestines due to the appearance in the body of a harmful bacterium called Salmonella typhi - a bacillus that exists in the outside world for up to 3 months, especially in the presence of a favorable environment for reproduction.

So, the signs of BT include: fatigue; heat; migraine; loss of appetite; sleep disturbance; pallor, dry skin; skin rash; dry cough.

Typhoid fever can only exist in the human body. So, every year about 20 million people become infected with this disease, of which 40% die. In the Russian Federation, the number of patients with a similar diagnosis does not exceed 1000 people per year.

There are 4 types of infection:

Food - when eating meat, milk.
Contact - touching contaminated household items, non-compliance with hygiene rules, as well as direct contact with a sick patient.
Water - consumption of water from reservoirs or industrial water from enterprises.
Insects - flies are carriers of harmful bacteria.

In addition, BT has several features:

What tests are required?

If BT is suspected, tests are performed before taking medications, since after 3 days the tests may show a negative result.

The initial study will be a complete blood count (hereinafter CBC), which does not guarantee a 100% result in the detection of BT. But the KLA establishes the presence of bacteria in the patient's body. So, when BT is confirmed, the ESR value increases, and the level of leukocytes decreases.

The downside is that KLA is taken if any type of infectious disease is suspected, so doctors prescribe additional studies, such as:

Blood sampling for medical records

Employees who are constantly in contact with other people are required to undergo a medical examination in order to obtain a sanitary or medical book. A similar document is received by employees of such areas as:

Medicine.
Food production.
Trade.
Educational institutions.

One of the laboratory tests is a test for typhoid fever, which is allowed to be taken in both private and public hospitals.

The frequency of tests for typhoid fever depends on the place of work. So, educators and catering workers are required to take a similar analysis at least once a year. In this case, a certificate of a study on BT is issued on the basis of any of the above types of analysis.

To obtain reliable information on the analyzes, the patient must prepare for the procedure. So, 2 days before blood sampling, it is forbidden to drink alcohol, fatty foods, and take medications.

How much is the price?

The cost of the analysis directly depends on a number of factors:

Testing for typhoid

The main source of the BT pathogen is a person with the presence of a harmful bacterium (hereinafter referred to as the carrier) or a sick person. According to statistics, the infection is transmitted in 95% of cases through the carrier, and in 5% through the sick patient.

In this case, bacteriocarrier can be chronic or acute. In the first variant, the release of harmful bacteria into the surrounding atmosphere lasts for 3–10 years or a lifetime, and in the second, up to 3 months.

In this case, the infection is transmitted in one of the following ways:

Water - consumption of dirty water, as well as seafood from a contaminated source.
Food - the infection enters the body of a healthy patient through the consumption of raw foods, milk, meat. In addition, the bacterium enters food through the carrier, which is engaged in the storage, preparation or sale of products.
Household items – such as using a toilet that is contaminated with bacteria. In this case, infection occurs when dirty hands touch the mouth. Also, the infection spreads when hygiene rules are not followed when changing bed linen, especially in medical institutions.
Personal contact - includes intimate relationships, including oral and anal sex.

Typhoid fever is common in countries with poor sanitation, such as Africa, South America or Asia. In Russia, this disease spreads after the patient travels to the above countries. But when an outbreak of infection is registered, BT can get sick up to 50% of the general population. At the same time, a lethal outcome is more often observed among people who have not left their country.

Important! Carriers are more often women than men over the age of 50 years - 88%.

Serological testing for typhoid fever

Serological blood sampling is an analysis of capillary blood, according to the results of which the doctor detects not only infectious diseases like BT, but also microbial, viral infections. In the presence of an infectious disease, the analysis is performed at the beginning of the development of the pathology when the patient enters the hospital and after 8-10 days.

In this case, there are several ways to detect specific bodies in the blood:

Immunoenzymatic (ELISA) - antibodies are fixed in a specially prepared tablet.
Agglutination reaction - provides information 14 days after the onset of the disease.
Indirect hemagglutination reaction - helps in the diagnosis of BT 7 days after the development of pathology.
The reaction of fluorescent antibodies - helps to determine any type of antibodies to the pathogen antigens.

For more information on typhoid fever, see the following video:

Thus, typhoid fever is a serious disease that requires timely treatment. The first stage is the delivery of all tests, which are discussed in more detail in our material.

It belongs to the group of typhoid and paratyphoid diseases, which have a high contagiousness, fecal-oral transmission of the pathogen and a similar clinical picture. This pathology is characterized by a severe course, the presence of fever, intoxication and damage to the lymphatic apparatus of the intestine.

Timely diagnosis and treatment of typhoid fever determines the prognosis for recovery, and also reduces the possibility of spreading the infection.

Establishing diagnosis

A preliminary diagnosis will be made on the basis of a characteristic clinical picture, anamnesis of life and illness.

From the point of view of the effectiveness of the therapy and anti-epidemic measures, the diagnosis of typhoid fever should be established within the first 5-10 days. After all, it is during this period that antibiotic therapy is most effective, and the patient is minimally contagious.

A doctor can suspect typhoid fever based on clinical and epidemiological data. A combination of the following symptoms should alert him:

increase in fever and intoxication without distinct organ lesions;
relative (discrepancy between the pulse rate and high body temperature);
pale skin;
roseolous rash;
characteristic changes in the tongue (its swelling, grayish-yellow plaque, teeth marks);
hepatolienal syndrome (and);
sleep disturbance;
adynamia.

From epidemiological data, of particular importance is:

having contact with a febrile patient;
stay in a territory unfavorable for typhoid fever;
drinking water from open reservoirs;
eating unwashed vegetables and fruits;
use for food purposes purchased from individuals.

All persons with a temperature of 5 days or more should be examined for typhoid infection.

Testing for typhoid fever

The diagnosis of typhoid fever must have laboratory confirmation. For this purpose, the following research methods are used:

Isolation of the pathogen's blood culture (blood sampling is carried out at the height of fever for 2-3 days daily; inoculation is performed on nutrient media containing bile).
Immunofluorescence method (allows you to get a preliminary result 10-12 hours after sowing).
Bacteriological examination of feces, urine and duodenal contents (may be reliable from the 2nd week of illness; the results are evaluated after 4-5 days).
Determination of antibody titer and its increase by studying paired blood sera in the reaction of indirect agglutination and complement fixation (a titer of 1:200 is considered diagnostic; it becomes positive from the 5-7th day of the disease).
ELISA (highly sensitive method based on the detection of complexes of microbial antigen and protective antibodies in the test material).

It should be noted that in addition to specific diagnostic methods, changes are informative:

a decrease in the total number of leukocytes and neutrophils with a shift in the white blood formula to the left;
relative lymphocytosis;
increase in ESR;
decrease in hemoglobin and platelet levels;
absence of eosinophils.

Differential Diagnosis

Considering that at the beginning of the disease, the diagnosis of typhoid fever is difficult due to the scarcity of clinical manifestations, it must be distinguished from many pathological conditions that occur with fever and intoxication:

and other SARS;
sepsis, etc.

Principles of treatment

All patients diagnosed with or suspected of typhoid fever are subject to mandatory hospitalization with isolation and anti-epidemic measures in the focus of infection. Contact persons are monitored for a possible incubation period (21 days).

Treatment is carried out taking into account:

the severity of the disease;
phases of the pathological process;
the presence of complications and comorbidities.

Such patients are provided with:

peace;
bed rest in the acute period;
sparing diet.

Food should not burden the digestive system and at the same time should be high in calories. Pureed dishes and plentiful drinking (water, tea, fruit drinks) are recommended.

The basis of treatment is antibacterial drugs, taking into account the sensitivity of the pathogen. For this, medicines from the group can be used:

chloramphenicols;
cephalosporins;
fluoroquinolones;
macrolides.

The course of treatment continues until the 10th day of normal temperature.

To restore impaired body functions and alleviate the patient's condition, therapeutic measures include:

detoxification and correction of water and electrolyte balance (infusion of glucose-salt and colloidal solutions);
fight against hypoxia (oxygen therapy);
appointment of immunomodulators;
the use of cardiotropic, hypnotic drugs according to indications;
vitamin therapy.

The tactics of managing patients with the development of complications has certain features.

With intestinal bleeding, conservative therapy is performed with the appointment of cold on the stomach, hunger for 10-12 hours and hemostatic drugs. If the patient has significant blood loss, then he is shown the introduction of plasma-substituting solutions or erythrocyte mass.
With the development of intestinal perforation, an urgent surgical intervention is performed.

After clinical recovery and normalization of laboratory parameters, but not earlier than 21 days after normalization of body temperature, such persons can be discharged home. They are subject to dispensary observation during the year with periodic laboratory examination. Relapses are treated according to the same principles as the primary disease.

Chronic carriers also need treatment. It includes long-term use of antibiotics and vaccine therapy. After the cessation of bacterial excretion, such persons remain registered, since after a while it can be resumed.

Prevention

In order to prevent the disease, people at risk are vaccinated.

To prevent the spread of infection and infection of healthy individuals, the following measures are taken:

control over the operation of the water supply system and disinfection of drinking water;
Cleaning of drains;
compliance with the rules of preparation, storage and sale of food products;
periodic examination of workers in the food industry and children's institutions;
timely detection and isolation of patients with typhoid fever, as well as bacteria carriers;
anti-epidemic measures in the focus of infection;
dispensary observation of recovered and treated carriers of the infection;
preventive vaccination in risk groups for the development of the disease (living in an area with a high incidence rate, having constant contact with patients or working in a laboratory with infected material).

At present, thanks to modern methods of diagnosis and treatment, the prognosis for typhoid fever has improved. If earlier mortality reached 20%, then against the background of the use of antibiotics, it decreased to 0.1-0.3%. However, this does not exclude severe cases of the disease with the development of complications, which are much less common, but still possible.

Thank you

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What is typhoid fever?

Typhoid fever is an acute infectious disease with a primary lesion of the gastrointestinal tract, which is caused by bacteria of the genus Salmonella. Typhoid fever belongs to the category of anthroponotic diseases, which means that the causative agent of this pathology can only exist in the human body.

Typhoid fever refers to diseases, the prevalence of which largely depends on socio-economic conditions. Thus, in the past, outbreaks of this disease occurred during periods of war, economic crisis and other social disasters.

Taking into account the statistics of the World Health Organization, all countries of the world, depending on the prevalence of typhoid fever, are conditionally divided into several groups. The first group includes Canada, Belgium, Sweden and other countries with a high level of economic development. In these regions, there is no more than 1 annual case of this infection per 100,000 people. The last group includes such countries as Chile, Colombia, Peru. More than 30 cases per 100,000 people are registered annually in these countries.

On the territory of the Russian Federation since 2007, the number of cases of typhoid fever has decreased significantly. If from 2003 to 2006 the annual number of patients varied from 150 to 180, then from 2007 to 2013 this figure did not exceed 80 people. In 2014, 14 patients (13 adults and 1 child) were registered.

Causes of typhoid fever

Typhoid fever develops due to the penetration of pathogenic bacteria called salmonella into the body. There are two types of Salmonella, including Salmonella enterica and Salmonella bongori. Each of the species is represented by various subspecies. Typhoid fever is caused by the bacterium Salmonella typhi, which belongs to the subspecies Salmonella enterica. This species also includes such serovars (subspecies) as Salmonella typhimurium, derby, paratyphi A and B.

The causative agent of typhoid fever

The causative agent of typhoid fever is Salmonella typhi, a mobile bacillus with a complex antigenic structure. This is a fairly stable bacterium in the external environment, which persists for many months in water bodies, soil, vegetables and fruits, as well as in dairy products (Salmonella can multiply in them for a long time). Bacteria can be killed with 96% ethanol or 3% chloramine. The main characteristic of Salmonella is its complex antigenic structure. It is represented by somatic and flagellar antigen.

Salmonella produce and secrete a strong endotoxin, which determines the clinical picture of the disease.

The antigenic structure of Salmonella includes:

O-somatic antigen, represented by a liposaccharide complex resistant to high temperatures;
H-flagella antigen, rapidly decomposing at high temperatures.

Typhoid fever bacteria are capable of L-transformation, that is, they can become chronic. In this process, the bacteria seem to fall asleep, but retain their pathogenic properties. After a while, when a person's immune forces decrease, they are activated again. This explains the possibility of long-term persistence (presence) of bacteria in the body.

Transmission of typhoid fever

Typhoid fever refers to infections with a fecal-oral transmission mechanism, which means that the penetration of pathogenic bacteria into the body occurs mainly through the mouth. Infection can be carried out by food or water. Salmonella persist in soil or water for a long time, which makes this route of infection the most frequent. The contact or household route of infection is extremely rare, mainly in children. This can happen through direct contact with a source of infection (for example, a child may put a toy that has been contaminated with salmonella in their mouth).

Once in the blood, salmonella leads to the development of bacteremia. Bacteremia is the circulation of bacteria in the blood (which is normally sterile). This process coincides with the appearance of the first symptoms of typhoid fever and the end of the incubation period. The more massive the bacteremia, the stronger and more pronounced the symptoms of the disease.

The pathogenesis of typhoid fever

Pathogenesis is the whole complex of mechanisms necessary for the development of the disease. In typhoid fever, pathogenesis is realized at several stages.

The stages of the pathogenesis of typhoid fever are:

penetration of salmonella into the gastrointestinal tract along with the source of infection (food, water);
the introduction of bacteria into the ileal mucosa;
reproduction of Salmonella in solitary follicles and Peyer's patches, from where they migrate to the mesenteric lymph nodes;
the development of inflammation in the mesenteric lymph nodes and an increase in the concentration of salmonella in them;
the release of bacteria into the blood and the development of bacteremia;
distribution with the bloodstream of bacteria to all organs and tissues;
the formation of foci of infection in the spleen, liver and other organs.

An important point in the pathogenesis of typhoid fever is bacteremia. It is primary and secondary. Primary bacteremia is when salmonella first enters the blood from the lymph nodes. However, when bacteria enter the bloodstream, they die due to its bactericidal action. Dying, they release endotoxin, which has a neurotropic effect. Thus, part of the bacteria in the bloodstream constantly dies and releases endotoxin. To prolong the circulation of salmonella, bacteria again begin to migrate from the internal organs into the blood. The process of salmonella release into the blood from the internal organs is called secondary bacteremia.

Thus, a vicious circle develops - bacteria enter the bloodstream, where they die and secrete endotoxin, and they are replaced by new salmonella from the internal organs and lymph nodes. At the same time, endotoxin, having a strong neurotropic effect, determines the clinical picture of typhoid fever.

The effects of Salmonella endotoxin are:

neurotoxic effect with damage to the central nervous system and the development of toxic encephalopathy;
damage to nerve endings and autonomic ganglia, which leads to the development of ulcers on the intestinal mucosa;
cardiotoxic effect, which manifests itself in dystrophic changes in the heart, which ultimately leads to the development of toxic myocarditis;
violation of the tone of peripheral vessels, leading to a drop in blood pressure and the development of collapse;
the development of infectious-toxic shock, which is accompanied by a violation of the water and electrolyte balance;
kidney damage and the development of the "shock kidney" syndrome.

All these effects lead to the development of numerous symptoms and cause a varied clinical picture.

Carrier for typhoid fever

The source of Salmonella typhoid for a healthy person in most cases is a bacteriocarrier. A carrier is a person who, practically remaining healthy, without showing any signs of illness, releases pathogenic bacteria into the environment. Isolation can last from several weeks to several decades. This phenomenon can be explained by several reasons. First of all, it can be a convalescent bacteriocarrier, that is, a person recovering from a disease. During the recovery period, bacteriocarrier can be both short-term and long-term. Short-term carriage is observed with dysentery or diphtheria (from 3 to 4 months). As for typhoid fever, in this case, the carriage is delayed up to 10 years.

The source of infection can also be patients with atypical forms of typhoid fever. In this case, the disease proceeds without classical symptoms and therefore is not diagnosed in time. People with such forms of typhoid fever are treated on an outpatient basis (that is, at home) for a long time and remain not isolated from family members. In this case, infection can occur through the use of contaminated food, water. Dairy products pose a great danger, since in them bacteria can not only persist for a long time, but also multiply.

The susceptibility of the population to typhoid fever is very high. In foci where an outbreak of typhoid fever is recorded, up to 50-60 percent of the general population can become ill.

Clinical picture of typhoid fever

There are several stages in the clinical picture of typhoid fever. Each of these stages (or periods) characterizes a certain mechanism of pathogenesis. For example, the incubation period corresponds to the period of dissemination of typhoid bacteria in the lymph nodes. The moment of release of bacteria into the blood is accompanied by the appearance of the first symptoms and corresponds to the initial period of the disease.

The periods (stages) of typhoid fever include:

incubation period;
initial period;
the period of the peak of the disease;
the period of extinction of the main symptoms;
recovery period.

Incubation period for typhoid fever

The incubation period is the period from the moment Salmonella enters the human body until the first symptoms appear. In typhoid fever, the incubation period is usually 9 to 14 days. It can take up to 25 days maximum. During this time, Salmonella that have entered the body actively multiply in the mucosa of the ileum and lymph nodes. At the moment when the bacteria enter the bloodstream, the incubation period ends, and the first signs of the disease appear.

The duration of this period depends on the concentration of microbes that initially entered the body and on the route of infection. With food contamination, the incubation period is short - from 7 to 9 days, and the disease is highly severe. The water route of infection is characterized by a longer incubation period.

The period of onset of the disease

As a rule, the disease begins gradually. Even for severe forms of typhoid fever, a gradual development of the clinic is characteristic. Typhoid fever begins with the appearance of weakness, malaise, a feeling of weakness. The temperature also rises, moderate headache and chills appear. It seems that the person is catching a common cold. This state continues for a week. During this week, the headache intensifies, weakness and adynamia increase, appetite disappears, stool retention is noted. By the end of 7-8 days, the temperature reaches its maximum of 40 degrees, which means the height of the disease. Extremely rarely, with an acute onset of the disease, all these symptoms develop within one to two days.

The peak period in typhoid fever

It starts from 7-8 days from the onset of the first symptoms. During this period, the general symptoms of intoxication are most pronounced. Due to the neurotropic action of endotoxin, encephalopathy develops, which is manifested by lethargy of patients. The patient's mind is clouded and confused (typhos means fog, hence the name of the disease), most often he lies in bed with his eyes closed. Answers questions with difficulty, in monosyllables. The patient's skin is sharply pale, hot and dry. On examination, the lymph nodes are enlarged, the heart rate is low (bradycardia), and blood pressure is also reduced. The tongue is dry, covered with a brown coating (coated tongue), thickened, and teeth marks are visible along its edges. On the 8th - 9th day, specific symptoms of typhoid fever appear - roseolous rash, enteritis, toxic myocarditis.

The period of extinction of the main symptoms

The period of extinction of the main symptoms begins from the moment the temperature drops, the tongue is cleansed, and the stool normalizes. All manifestations of general intoxication - headache, weakness, weakness - go away. Body temperature begins to drop, but still does not reach normal.

Despite the reduction of symptoms, this period of the disease is very dangerous. It is at this moment that the disease can manifest itself again, that is, a relapse of typhoid fever is possible. Therefore, during the period of extinction of the main clinical symptoms, the patient continues to remain in the hospital under constant supervision.

convalescence period

The recovery period for typhoid fever begins with the normalization of body temperature. It lasts 2 weeks.

Symptoms of typhoid fever

Typhoid fever is characterized by numerous clinical symptoms. The presence of certain signs of the disease depends on the shape and severity of the abdominal type. All symptoms may be mild, moderate or extremely severe. Also, the symptoms may vary depending on the nature of the course of the disease. Typhoid fever can occur cyclically and with periods of exacerbations (recurrent nature of the course).

The symptoms of typhoid fever are:

fever;
rash;
intestinal bleeding;
damage to internal organs.

Fever in typhoid fever

Fever in typhoid fever is a manifestation of a general intoxication syndrome. Fever develops in response to bacteremia. Having reached the mark of 39 - 40 degrees by the end of the week, the temperature continues to remain at this level for 2 - 3 weeks. Sometimes it can acquire a Botkin character, in which case the temperature proceeds in waves. The decrease in fever occurs slowly and in stages, also with fluctuations between morning and evening temperatures.

Rash in typhoid fever

A specific manifestation of typhoid fever is a rash. It is caused by a violation of the permeability of blood vessels and impregnation of the epidermis with blood elements. In typhoid fever, the rash is usually roseolous, and the element of such a rash is roseola. Roseola is a rounded red spot, ranging in size from 1 to 5 millimeters. It does not flake off and does not create itching, and therefore does not cause concern to the patient. However, despite this, the period of the rash itself is accompanied by a sharp rise in body temperature and a deterioration in the patient's condition. The patient's consciousness becomes even more clouded, and he becomes sleepy, lethargic, apathetic.

With typhoid fever, a rash appears on the 8th - 9th day from the onset of the disease. It is localized in the upper abdomen and chest. Sometimes the elements of the rash can protrude above the level of the skin and acquire clear boundaries. Most often, the rash is mild and lasts from 3 to 5 days. It may disappear after one or two days, but then it will reappear. In severe cases, the rash acquires a petechial-hemorrhagic character. The elements of the rash in this case are saturated with blood, which indicates an unfavorable prognosis.

In rare cases, the rash characteristic of typhoid fever may be absent. The absence of a rash on the patient's body should not exclude the diagnosis of typhoid fever.

Intestinal bleeding in typhoid fever

In typhoid fever, due to the specific lesion of the gastrointestinal tract by Salmonella, signs of enteritis are revealed. In the initial stages, stool retention is noted, but already during the stage of advanced clinical manifestations, enteric stools (that is, diarrhea) are present. Some patients have constipation.

The abdomen of a patient with typhoid fever is swollen, painful on palpation. In moderate and severe cases, intestinal paresis develops, which is characterized by a complete absence of peristalsis. In this case, gases and intestinal contents accumulate in the intestinal lumen, making the stomach tense and painful.

As a result of the specific effect of Salmonella endotoxin on nerve endings, trophic and vascular changes develop in the intestinal mucosa. They, in turn, lead to malnutrition of the intestinal mucosa and the development of trophic ulcers. Trophic ulcers are those that develop as a result of malnutrition (trophism) of the mucous membrane. Ulcers go through several stages in their development.

The stages of development of ulcers are:

first week- an increase in the lymphatic follicles of the intestinal mucosa;
second week- necrosis (necrosis) of enlarged formations;
third week- rejection of necrotic (dead) masses and the formation of small depressions in their place, that is, ulcers;
fourth week- stage of pure ulcers;
fifth week- the stage of ulcer healing.

All these stages can follow one after another without the development of consequences for the intestinal mucosa. However, with the formation of extensive and deep ulcers, the course of typhoid fever is complicated by intestinal bleeding. This happens due to perforation (perforation) of the mucosal ulcer. In this case, the integrity of the intestinal membranes is violated, and with them the blood vessels that are embedded in them. Violation of the integrity of blood vessels leads to the outflow of blood into the intestinal lumen, which is the cause of intestinal bleeding.

Intestinal bleeding in typhoid fever, as a rule, occurs 3 to 4 weeks from the onset of the disease. An integral symptom of perforation of the intestinal ulcer is pain. The patient complains of sudden onset of acute pain.

Often the pain is localized in the lower abdomen on the right, but it can also be diffuse. The pain syndrome is accompanied by a pronounced tension of the abdominal muscles, rapid breathing and a drop in blood pressure. Symptoms of ulcer perforation are pronounced in moderate forms of typhoid fever. This is explained by the fact that the patient's consciousness in this case is not very clouded, and pain sensitivity is preserved. If intestinal bleeding begins against the background of high temperature and the patient's blurred consciousness, then his clinic is very erased.

On examination, a pronounced protective tension of the abdominal muscles is revealed. The abdomen is dense, painful, movements of the abdominal wall during the act of breathing are barely noticeable or completely absent. There are signs of peritoneal irritation, such as Shchetkin-Blumberg symptom.

Damage to the internal organs in typhoid fever

After the typhoid bacteria enter the bloodstream, they are carried with the bloodstream throughout the body to various organs and systems. So, together with the blood flow, they enter the liver, spleen, kidneys, heart.

Heart failure
Salmonella endotoxin leads to dystrophic changes in the heart with the development of toxic myocarditis. The term "myocarditis" means that the muscle layer of the heart is covered by the inflammatory process. This leads to the fact that the heart ceases to perform its basic functions. Normally, the main function of the heart is the “pump function”, which provides blood supply throughout the body. Due to damage to the muscle layer, the heart stops contracting effectively and pumping blood. Contractions become weak, deaf, which explains bradycardia (rare heart contractions), arterial hypotension (lowering blood pressure). When examining a patient, heart sounds are muffled, weak, blood pressure is low, pulse is within 50 beats per minute.

The consequence of heart damage is hypoxia or oxygen starvation, a violation of the water and electrolyte balance, hypovolemia (a decrease in the volume of circulating blood).

Damage to the kidneys and lungs
Against the background of hypovolemia, the syndrome of "shock kidney" and "shock lung" develops. Shock kidney is a condition in which all the functions of the kidney - filtration, secretion and excretion - are impaired. Diuresis (daily volume of urine) with this complication is sharply reduced, up to anuria. Due to impaired excretory function, metabolic products begin to accumulate in the body - creatinine, urea. This further aggravates the course of the disease and causes the development of infectious-toxic shock. Treatment of a shock kidney should be urgent and include measures to restore diuresis, remove toxic metabolic products.

Another consequence of hypovolemia is a shock lung. In this syndrome, a large amount of fluid accumulates in the alveoli of the lungs. Thus, the lungs are not filled with air, but with water, which underlies pulmonary edema. It becomes difficult for the patient to breathe, shortness of breath increases.

Typhoid and typhoid fever

Typhoid fever is often confused with typhus, which is incorrect. Typhus is an acute infectious disease caused by bacteria of the genus Rickettsia. Unlike typhoid fever, this disease does not apply to intestinal infections. Typhoid fever is characterized by a predominant lesion of the nervous and cardiovascular systems. This infection is transmitted, mainly through lice, most often body lice and less often head lice. Infection occurs through the bites of these insects. Lice themselves become infected from sick people. Thus, body lice are carriers of infection.

After a louse has bitten a sick person, it can live from 30 to 45 days. The bite of a louse is very painful, because of which the person begins to painfully comb the bite site. Combing the bite, he rubs the feces of the louse into the skin, through which the infection occurs. Rickettsia then enter the bloodstream and are carried by the blood throughout the body. The target for rickettsiae are endothelial cells, that is, the structural elements of the vascular wall. Developing inside the vascular wall, rickettsia destroy it, which leads to the destruction of blood vessels. For typhus, the phenomenon of vasculitis is characteristic, that is, damage to the endothelial wall of blood vessels. This causes the development in the clinical picture of the disease of such symptoms as hemorrhages in the skin and mucous membranes, an enlarged spleen, and a decrease in blood pressure.

Another distinctive feature of typhus is the defeat of the nervous system. The patient's consciousness is confused, sometimes signs of meningism may develop. An extremely severe manifestation of typhus is typhoid status. During it, the patient has psychomotor agitation, memory disorders, and insomnia progresses. If the patient falls asleep, then he will have nightmares. Sometimes delusions, hallucinations, and other psychotic symptoms may develop.

Types of typhoid fever

Sometimes typhoid fever can be atypical, that is, not include specific symptoms. There are abortive and obliterated subclinical forms. The abortive form is characterized by the classic onset of the disease with a sharp and sudden disappearance of all symptoms. Initially, the disease develops as usual - the temperature rises, weakness, apathy develops. For 2-3 days, gastrointestinal symptoms increase. However, on the 5th - 6th day from the onset of the disease, all symptoms suddenly disappear - the temperature drops sharply, the pain disappears, and recovery occurs. With erased and atypical forms of typhoid fever, many characteristic symptoms are not expressed or are completely absent. So, the temperature may not exceed 38 degrees, the pain in the abdomen is of a weak nature, and the rash is completely absent.

Consequences of typhoid fever

Typhoid fever is a serious disease and often leads to various negative consequences for the patient's health. The cause of complications is the active activity of bacteria in the human body. An important factor is the age of the patient, since most often the consequences are diagnosed in the elderly. The consequences of typhoid fever are divided into specific and non-specific.

Specific complications of typhoid fever

This category includes those consequences that are characteristic only of typhoid fever. The most important among the specific consequences of this disease is toxic shock. This condition develops at the height of the disease due to the massive intake of toxins into the blood, which are secreted by typhoid bacteria. These toxins provoke vasospasm, as a result of which blood circulation is disturbed.

Also, toxins contribute to increased release of adrenaline and other hormones into the blood, which increase vascular spasm. Blood ceases to fulfill its transport function, which leads to tissue ischemia (insufficient blood supply to tissues) and metabolic acidosis (increased levels of acidic products in the blood). All this causes degenerative (destructive) changes in organs and tissues, edema and other pathological conditions that can lead to death. Infectious-toxic shock begins with an increase in body temperature and develops in several stages.

The stages of infectious-toxic shock are:

Early. The patient's consciousness remains clear, there may be anxiety, restlessness, swelling of the face and upper half of the body. At the same time, breathing is quickened, blood pressure rises and falls in waves. In children, the early stage is usually accompanied by vomiting, diarrhea, abdominal pain (in the upper part).
Expressed. Anxiety and general excitement of the first stage is replaced by an apathetic state, motor inhibition. The patient's skin becomes pale, cold and moist. Over time, hemorrhages may appear on the skin. The limbs acquire a bluish tint. Temperature and blood pressure decrease, breathing and pulse become weak. The volume of urine decreases sharply. During this period, various pathologies from the side of the kidneys and the respiratory system develop.
Decompensated. Blood pressure and body temperature continue to fall. The patient suffers from convulsions, loss of consciousness or coma is possible. The skin takes on a pronounced blue tint. There is no urination. Symptoms of dysfunction from all organs begin to appear.

Nonspecific complications of typhoid fever

This group includes diseases that can act as consequences of not only typhoid fever, but also other diseases. Typhoid bacteria, in addition to the intestines, can also affect other organs, provoking inflammatory processes. The situation becomes more complicated when a secondary bacterial infection joins the primary inflammation.

The non-specific consequences of typhoid fever include:

from the respiratory system- pneumonia (inflammation of the lung tissue);
from the vessels- thrombophlebitis (inflammation of the veins);
from the side of the heart- myocarditis (inflammation of the heart muscle);
from the side of the kidneys- pyelitis (inflammation in the renal pelvis), pyelonephritis (inflammation of the renal tissue);
from the nervous system- peripheral neuritis (inflammation of the nerves), meningoencephalitis (inflammation of the brain and, in some cases, the spinal cord, followed by paralysis);
from the musculoskeletal system- arthritis (inflammation of the joints), chondritis (inflammation of the cartilaginous tissue), periostitis (inflammation of the periosteum);
from the urinary tract- cystitis (inflammation of the bladder), prostatitis (inflammation of the prostate).

Diagnosis of typhoid fever

Due to the pronounced clinical signs of the disease, doctors establish a preliminary diagnosis of typhoid fever even before the results of laboratory tests. Information about the epidemiological situation also contributes to the establishment of a preliminary diagnosis.

The main symptoms, the presence of which raises the suspicion of typhoid fever, are:

dryness and pallor of the skin;

elevated temperature;
changes in the tongue - its increase, dryness and coating in the center with plaque;
the appearance of a reddish rash on the body;
dyspeptic disorders;
manifestations of the intoxication syndrome.

When a patient has similar symptoms for 5 to 6 days, it is necessary to take laboratory tests for typhoid fever and undergo a series of diagnostic tests, through which the causative agent of the disease is detected.

Testing for typhoid fever

Tests for typhoid fever are prescribed both to identify the causative agent of the disease, and to determine the severity of the disease and monitor the effectiveness of treatment.

The tests that are prescribed in the diagnosis of typhoid fever include:

general clinical tests;
bacteriological analyzes (crops);
serological tests.

The results of general clinical tests indicate the presence of an inflammatory process in the body, the degree of dehydration and the state of the patient's body as a whole.
Bacteriological studies help to detect the causative agent of typhoid fever in biological fluids of the body. Serological studies are used to determine the antigens of the causative agent of typhoid fever in the human body. Serological tests are especially important in the diagnosis of bacteriocarrier.

Testing for typhoid fever

General clinical tests for typhoid fever
General clinical tests for typhoid fever are prescribed from the moment the patient contacts the doctor. Changes in the analyzes are not specific for this disease, but they help to determine the state of the patient's body as a whole. The main analyzes are a hemogram and a general urine test.

Possible changes in the clinical blood test for typhoid fever are:

moderate increase in leukocytes (white blood cells);
leukopenia (decrease in the number of leukocytes);
absence of eosinophils (a subspecies of leukocytes);
a moderate increase in the number of lymphocytes (a subspecies of non-nuclear leukocytes);
moderate acceleration of erythrocyte sedimentation.

The number of leukocytes can be increased only in the first days of the disease. Over the next week of illness, their level drops sharply. Leukopenia persists for the entire period of the pronounced clinical picture of typhoid fever.

Possible changes in the general analysis of urine for typhoid fever are:

the presence of protein;
high levels of erythrocytes (red blood cells);
high level of cylinders.

Cultures for typhoid fever

Early specific diagnosis of typhoid fever begins with culture-based bacteriological studies. Various biological fluids of the body act as a material for sowing.

Body fluids used for culture in typhoid fever include:

blood;
urine;
fecal masses;
the contents of the duodenum (bile);

The causative agent of typhoid fever can also be detected by bacteriological examination of roseola and bone marrow.
To make a diagnosis, the sampling of biological fluids should be carried out before the start of etiotropic therapy.

Blood culture
With the early diagnosis of typhoid fever, blood cultures are most often used, in which the pathogen is easily detected even during the incubation period. It is best to take blood during a period of fever. In the case of starting antibiotic therapy, blood is taken immediately before the next dose of the drug is administered. Up to 20 milliliters of blood are sown on special liquid nutrient media. The most commonly used blood culture medium for typhoid fever is Rappoport's medium, which consists of a bile broth with the addition of glucose and a special dye. The nutrient medium with blood is placed for 10 days in an incubator with a temperature of 37 degrees Celsius. Laboratory assistants check crops every day for signs of growth of bacterial colonies - turbidity of the liquid, a change in its color. If at the end of ten days there is no growth, the result of the analysis is negative. If signs of colony growth are found, inoculations are made on dense media in Petri dishes. New crops are again incubated at 37 degrees Celsius for a day. As a result, bacterial colonies grow on the surface of the dense medium, which are subject to identification using a series of biochemical tests. In parallel with this, the sensitivity of bacteria to various antibacterial drugs is also determined. The final blood culture results are obtained after four days.

Urine culture
A urine test to identify the causative agent of typhoid fever can be carried out throughout the entire period of the disease. Given the fact that the pathogen is excreted in the urine intermittently and for a short time, urine cultures should be repeated every 5 to 7 days. The collected urine should be delivered to the laboratory for inoculation no later than two hours after collection. The longer the material is stored, the greater the chance of the pathogen dying off or the growth of other bacteria. Uroculture is obtained by the same inoculation and incubation process as blood culture.

Sowing of feces
Fecal cultures for the diagnosis of typhoid fever are performed starting from the second week of illness. Feces are taken with a sterile spatula, wire loop or spoon. A sterile container is used to transport the material. In the laboratory, coproculture is prepared by sowing feces on solid nutrient media and incubating at 37 degrees Celsius for 18 to 24 hours.

Serological testing for typhoid fever

Serological tests in the diagnosis of typhoid fever reveal specific antigens and antibodies in the patient's blood. There are several main antigens that are found when examining a patient's blood.

The main antigens that are found in the blood of a patient with typhoid fever are:

O antigen;
H-antigen;
Vi antigen.

O-antigens and Vi-antigens are represented by particles of pathogen membranes, and H-antigens are structural elements of flagella.
Antibodies are special proteins that are produced by the human immune system to neutralize the antigens of the pathogen. High levels of antibodies indicate the formation of persistent immunity to the pathogen, which is observed during the recovery period or during bacteriocarrier. Antigens and antibodies are determined in the patient's blood using special serological reactions.

Serological tests for typhoid fever include:

Vidal reaction;
indirect hemagglutination reaction;
fluorescent antibody reactions.

Serological diagnosis of typhoid fever is carried out not earlier than the second week of the disease.

Vidal reaction in typhoid fever

The Vidal reaction is a direct agglutination (gluing) reaction, which allows you to determine the presence of O-antigen in the patient's serum. This reaction is widely used in the diagnosis of typhoid fever, but it is not specific, giving false positive results due to the recognition of other types of Salmonella. For the Vidal reaction, 2 to 3 milliliters of venous blood is needed - usually from the cubital vein. The blood is left for some time in a test tube until it is completely coagulated. The serum formed on the surface is sucked off with a sterile syringe and placed in another test tube. The agglutination reaction consists in a gradual dilution of the patient's serum to a ratio of 1 to 800 and the addition of a special diagnosticum (antibodies to the desired antigens).

The steps of the Vidal reaction are:

filling a number of test tubes with 1 milliliter of physiological solution;
adding 1 milliliter of serum to the first tube and obtaining a dilution of 1 to 50;
suction with a pipette from the first test tube 1 milliliter and adding it to the second test tube - a dilution of 1 to 100 is obtained;
repetition of manipulations until solutions are obtained in a ratio of 1 to 800;
adding a special diagnosticum to each test tube;
two-hour incubation at 37 degrees Celsius;
the subsequent maintenance of test tubes at room temperature during the day.

The agglutination reaction is manifested as the formation of a small precipitate at the bottom of the tube. The Vidal reaction is positive if agglutination is present in a test tube with a dilution of 1 to 200 or more. A positive result may indicate not only the presence of the disease, but also a possible carriage. To differentiate these conditions, the reaction is repeated after 5-6 days. If agglutination appears in test tubes with high antibody titers, this indicates the presence of a disease. In bacteriocarriers, antibody titers do not change during repeated studies.

Indirect hemagglutination reaction
The reaction of indirect hemagglutination is more specific and sensitive for the diagnosis of typhoid fever. With its help, all three main antigens of the pathogen are determined. As a diagnosticum, erythrocytes sensitized to salmonella antigens act. The reaction procedure is similar to the Vidal reaction technique, however, dilutions start from 1 to 10. Hemagglutination appears as a red precipitate at the bottom of the tube, similar to an inverted umbrella. A reaction is considered positive if a precipitate is formed in a test tube with a dilution of 1 to 40 or more. In subsequent analyzes after 5 and 10 days, antibody titers increase by 2-3 times, especially O-antibodies. An increase in the titer of Vi- and H-antibodies is observed in patients during the recovery period. Their levels can also be high in carriers.

Fluorescent antibody reactions
From the first days of the disease, the pathogen can be identified using the reactions of fluorescent antibodies. These reactions consist in the detection of pathogen antigens using antibodies marked with fluorescent substances. “Marked” antibodies are added to the biological diagnostic material (blood, feces, urine) and studied using special microscopes. When the antibody binds to the antigen of the pathogen, a glow is visible in the microscope. Preliminary results of reactions are ready within one hour, and final results in 10-20 hours. The reactions of fluorescent antibodies are quite specific and highly sensitive, but are rarely used in the diagnosis of typhoid fever.

Before use, you should consult with a specialist.

It is necessary to accurately identify the pathogen, it is desirable to undergo diagnostics before starting antibiotic therapy. The disease is dangerous and the carrier of the pathogen not only endangers its own health, but also becomes a source of infection for others. Therefore, at the first suspicion of a pathology, an urgent appeal to the clinic is necessary.

When are tests for typhoid fever ordered?

The infection develops as a result of the active activity of salmonella. However, the signs are not specific, often observed in other diseases of the gastrointestinal tract:

Emptying disorder. Both constipation and severe diarrhea are possible.
Bleeding of the gastrointestinal tract. There is blood in the stool.
Nausea and vomiting.
Insomnia, apathy, weakness, loss of appetite.
Strong thirst.
Skin rash.
The temperature rises up to 40 degrees.
Soreness in the abdomen and right hypochondrium.
The tongue is coated with a gray tint, but the tip is still red.

In severe condition, the clinical picture includes delirium and disorientation in space.

The Russian Federation provides for mandatory annual screening for typhoid fever for workers in the food industry, hospitals, and children's institutions. It is advisable to undergo diagnostics for tourists who have returned from exotic countries where pathology is common.

It is easy to isolate the pathogen in the first 2 days. Therefore, you need to go to the hospital at the initial signs.

Where can I take biomaterial for analysis?

Today, research is carried out in municipal and private laboratories, as it is necessary for issuing a sanitary book. Naturally, in a paid clinic, you will have to pay a small amount for a certificate. But you can get results much faster.

The cost of a blood test for typhoid fever

According to statistics:

Serological diagnosis will require 600-800 rubles.
A general blood test will cost 300-400 rubles.
Bacteriological culture in 700–900 r.
Biochemistry at 300–400.
ELISA and RIF on average 500–800 r.

Of course, a decent amount is obtained, but for an accurate diagnosis, a comparison of several types of studies is necessary. Deciphering the results helps not only to identify the pathogen, but also to determine the therapy program.

In the municipal clinic, most of the work on the study of blood, urine or feces samples is performed free of charge.

Types of analyzes

Basically, they prefer to take biological materials for study. If typhoid fever is suspected, various laboratory diagnostic methods are used.

General blood analysis

The method is applied in the first place, but does not give a full guarantee. Indirect indicators are taken into account - an overestimated ESR, a decrease in the concentration of leukocytes, an increase in the level of lymphocytes, and the absence of eosinophils. The results help to establish the presence of an infection, an inflammatory process.

To examine a patient in vitro, in laboratory conditions, it is enough to take a sample from a finger or a venous vessel.

Should be done before antibiotic therapy. It takes 5-10 ml to detect proteins in the acute phase, which are produced by the body in typhoid fever.

Serological blood test

You need to take a sample from the capillary. The period is 4–5 days from the moment of infection, when antigens of the type O, Vi and H, characteristic of salmonella, are present in the plasma. The study is repeated on the 8–10th day of the patient's stay in the inpatient department.

RIHA (reaction of indirect hemagglutination)

The RPG method for typhoid fever helps to detect antibodies and antigens based on the rate of erythrocyte precipitation. The sampling is done on an empty stomach, as with other methods of examination. It is necessary to refrain from food for 8 hours. The material is taken from the cubital vein.

A positive result is diagnosed with minimal indicators - for O titer 1:200, for Vi 1:80.

RPHA (passive hemagglutination reaction)

The main direction is the search for antibodies present in the serum. This blood test for typhoid fever is carried out by the end of 2 weeks of illness and is repeated after 5 days. In the acute form of the pathology, an increase in titers is noted.

The sample is taken from the cubital vessel, on an empty stomach. A positive result corresponds to a reading of 1:40 for Vi antibodies and 1:200 for O.

Bacterial culture

There is not enough Salmonella in the blood, so the tissue taken for analysis is placed in a nutrient broth and cleaned in a thermostat. Reproducing, the microorganism forms colonies. Laboratory research allows you to determine the type of bacteria.

The result is ready for 4-5 days. Of all the methods, bacterial culture is the most accurate. Helps identify antibiotics that are effective for typhoid fever. Blood, urine are suitable for work, if about a week has passed since the infection, feces can be used.

Immune fluorescence reaction (RIF)

A quick way to identify pathology in the initial development. Antibodies pre-labeled with specific substances are introduced into the biomaterial. In the presence of antigens, microscopic examination of the sample reveals a characteristic glow.

Enzyme immunoassay (ELISA)

A highly sensitive method that detects the presence of antibodies and antigens, helping to clarify their concentration. It is important both for diagnosis and for monitoring the dynamics in the patient's condition.

Bacteriological examination of feces (coproculture)

Most often, a patient takes blood for typhoid fever. But after 1–1.5 weeks, the pathogen is present in the feces. It is used to identify infected, but not sick.

Bacteriological examination of urine (urine culture)

8–10 days after infection, the pathogen can be detected in urine. At the same time, leukocytosis is noted - an increase in the concentration of white cells in the initial stage of the disease and a sharp drop in the rate after a week.

For the reliability of the analysis, careful preparation is needed: it is necessary to stock up on a sterile container and rinse the external genitalia. It is enough to collect only 40-50 ml of liquid.

Bacteriological study of bile (biliculture)

The analysis is used if about 2 weeks have passed since the onset of infection. By this time, salmonella has disappeared from the blood serum, but spreads to other fluids.

Sometimes a bone marrow puncture is taken for research. The technique is complex, but reliable, since the presence of pathogens of other pathologies is excluded.

How are tests done?

In order for the diagnosis to be as accurate as possible, it is necessary to prepare in advance for the collection of tissue samples:

For 72 hours, it is advisable not to take any pharmacological agents, especially antibiotics. Otherwise, it is necessary to inform the doctor about the type of drug, time of administration, dosage.
It is optimal to donate blood in the morning from 8 to 11.
In the evening they refuse dinner. The day before the analysis, stop drinking alcohol, fried, fatty, hot spices, dairy products and eggs.
Do not smoke for several hours before sampling.

It is better to refrain from physical exertion, to be less nervous, since even these factors can affect the biochemical composition of the material.

How to read test results?

With typhoid fever, there is an overestimated content of leukocytes in the first 2 days and a decrease in the level in the future. At the same time observed:

An increase in the concentration of lymphocytes.
Increase in platelets.
High ESR.

After a serological analysis, a certificate is issued in which the verdict is affixed. When "positive" is the number of antibodies.

Does a “negative” result on a form always indicate the absence of the disease?

Optional means that the person does not have the pathogen. Characteristic protein compounds sometimes appear in the blood later, therefore, when the patient enters the hospital, they are not detected at first. Then conduct an additional examination after a few days.

The absence of antibodies often indicates that the patient was sick, but managed to recover.

What does the result of the analysis say "positive"?

This verdict means 2 options:

The disease is in the acute phase.
Presence of inactive salmonella.

Carriers of the pathogen are 3-4% of people who have had typhoid fever. There are risks of infecting others.

Which doctor should I contact?

With severe symptoms, it is necessary to ensure the rapid admission of the patient to the hospital. But sometimes a person visits a medical facility on his own, complaining of signs of poisoning. In this case, it is better to go to an appointment with an infectious disease specialist, but even an experienced therapist will suspect the clinical picture of typhoid fever.

Conclusion

The disease is easily transmitted through personal contact, with food and household items. To protect yourself and loved ones, it is advisable to perform all recommended tests at the first symptoms.

Diagnostic serological analysis to detect antibodies to Vi-antigens of the causative agent of typhoid fever in the blood serum is intended to confirm or deny the fact of carriage.

Deadlines	7-8 days

Synonyms (rus)	Serological analysis for Vi-antibodies of the causative agent of typhoid fever in blood serum

Synonyms (eng)	Indirect hemagglutination assay for Salmonella typhi Vi antibodies

Analysis method	The reaction of indirect hemagglutination (RIHA)

Study preparation	The analysis is carried out in the morning, on an empty stomach. At least 8 hours must have elapsed since the last meal.
	Exclude alcohol intake at least 24 hours before taking the biomaterial.
	It is not recommended to donate blood for serology after fluorography, x-rays, physiotherapy procedures.

Biomaterial and methods of taking it	Deoxygenated blood

General information about typhoid fever and its detection

Typhoid fever refers to acute infectious intestinal diseases. It is characterized by a cyclic course with systemic damage to the intestinal organs, central nervous system, liver, lymphatic system; general intoxication of the body, stable bacteremia, in which the presence of bacteria is detected in the blood. The source of infection are sick, ill carriers.

The causative agent of typhoid fever - Salmonella typhi, refers to intestinal bacteria.

The antigenic system of the pathogen is represented by antigens O, H, Vi.

The Vi antigen is the virulence antigen, forming the resistance of the causative agent of typhoid salmonella to the protective reactions of the body. The presence of antibodies to Vi-antigens of Salmonella typhi during a serological study of blood samples serves as a marker of bacteriocarrier.

Vi-antigen blood test method

Detection of antibodies to erythrocyte Vi antigens is carried out using serological reaction of indirect hemagglutination, RNGA using special diagnostics.

RNGA method:

based on the ability of the interaction of blood serum antibodies and antigens that are fixed on erythrocytes (erythrocyte diagnosticum); the result of the reaction is the aggregation of red blood cells, followed by sedimentation, agglutination;
by the nature of the erythrocyte sediment, the presence of antibodies is judged (a characteristic "umbrella"), or their absence (a precipitate in the form of a "dot");
is semiquantitative; to carry out the reaction, dilutions of blood serum are used to detect a diagnostic titer;
the minimum diagnostic titer during the reaction is 1:40;
an increase in the diagnostic value of the reaction is observed when using repeated analysis (paired sera method);
the reaction is highly sensitive and specific, can be used on the fifth to seventh days of the disease.

The main purpose of the study is to identify the bacteriocarrier of typhoid salmonella.

Analysis results and their interpretation

The test results may be positive or negative.

A positive response:

detection of antibodies to Vi-antigens of the typhoid pathogen in the blood (the minimum value of the diagnostic titer is 1:40) is considered as an indication of the fact of a bacteriocarrier and the need for re-testing;
the value of the titer is fixed in the answer;
may indicate the course of an acute infection, a past illness, a vaccination;
in rare cases, it can be false positive due to cross-reactivity.

Negative answer issued if no antibodies are detected. A similar situation is possible both in the absence of infection with a typhoid pathogen, and in the early stages of the disease.

Conducting this study is of particular importance to prevent cases of the spread of typhoid fever by bacteria carriers.