Magnesium medium Rappaport-Vassiliadis, 500 g / pk, Cat. No 107700
- SalmonellaenrichmentbrothRAPPAPORT- Rappaport's magnesium medium, 500 g / pk, Cat.No 110236
- Tetrathionate enrichment broth Muller-Kauffman- Tetrationate broth, 500 g / pack, Cat. No 110863
- Muller- KauffmannTetrathionate- NovobiocinBroth (MKTTn) - Tetrationate broth with novobiocin, 500 g / pack, Cat. No 105878
- BismuthsulfiteagarWILSON- BLAIR- Bismuth sulfite agar, 500 g / pk, Cat.No 105418
- Hektoenentericagar- Hectoene agar, 500 g / pack, Cat. No 111681
- SS- agar- Salmonella-Shigella agar, 500 g / pack, Cat. No 107667
- BPLS (Brilliant- greenPhenol- redLactoseSucroseAgar) - Lactose-sucrose agar with brilliant green and phenol red, 500 g / pk, Cat. No 107232
- XLDagar- Xylose-lysine-deoxycholate agar for the isolation and differentiation of pathogenic enterobacteria, 500 g / pack, Cat. No 105287
- XLT4 agar- Xylose-lysine with tergitol 4 (completely inhibits the growth of Proteus), 500 g / pack, Cat. No 113919
- XLT4 Supplement- Selective supplement to XLT4 agar medium, 100 ml / pack, Cat. No 108981
- Rambach agar- Chromogenic Rambach agar for salmonella 250 determinations, 4 x 250 ml bottles, Cat. No 107500
- MSRV (Modified semi-solid Rappaport-Vassiliadis)- Semi-liquid medium for the accelerated isolation of Salmonella from products and raw materials, 500 g / pk, Cat. No 109878
- MSRV Selective Supplement- Selective additive (novobiocin, 10 mg) to MSRV medium, 10 vials / pack, Cat. No. 109874
- Salmosyst broth base- Non-selective beneficiation, 500 g / pack, Cat. No 110153
- Salmosyst selective tablets- Selective enrichment of Salmonella - tetrathionate medium in tablets, 250 tablets / pack, Cat.No 110141
- KLIGLER agar- Kligler Agar, 500 g / l, Cat. No 103913
- Triple sugar iron agar- Tri-Sugar Iron Agar, 500 g / pack, Cat. No 103915
- Lysine iron agar- Lysine agar with iron for the differentiation and identification of enterobacteria; determination of lysine decarboxylase and hydrogen sulfide, 500 g / pk, Cat. No 111640
- SIMMONS citrate agar- Simmons Citrate Agar for identification, 500 g / l, Cat. No 102501
- Singlepath Salmonella- Rapid test (20 min) for salmonella, 25 tests / pack, Cat. No 104140

Salmonella (Salmonellaspp.)
The genus Salmonella belongs to the Enterobacteriaceae family. The bacteria are rod-shaped, gram-negative, asporogenic, mostly mobile. Worldwide, Salmonella is one of the most common food poisoning agents that infect most types of raw foods (eg, meat, eggs, plant foods). The bacterial resistance to drying, combined with their high thermal stability, creates a pathogen protection challenge for most dry and semi-dry foods. According to nutritional legislation in most countries, salmonella content is not allowed in 25 g of food. To get a simple answer (yes / no) about the presence of Salmonella in food and feed using traditional microbiological methods, it is necessary to spend up to 5 days in total. For products that need quick implementation, this means a significant delay. To meet the demands of food manufacturers to sell finished products quickly and to reduce storage costs, innovative, fast-track Salmonella detection methods are needed. Thus, accelerated methods for the analysis of Salmonella are of increasing interest. Rapid tests offered for these purposes should be specific, sensitive, convenient and cost effective. Depending on the number of test samples and the requirements for the specificity of the method, the choice can be made either in favor of molecular analysis of bacterial DNA by PCR (as a rule, for a high-performance laboratory), or in favor of immunodiagnostic tests (when analyzing fewer samples).

Salmonellosis
Most people infected with Salmonella develop diarrhea, fever, and abdominal pain 12 to 72 hours after infection. The illness usually lasts 4-7 days, and most patients recover without treatment. However, in some cases, the disease can be so severe that hospitalization is required. In these patients, salmonella infection can spread from the intestines to the bloodstream and other parts of the body. If the patient does not undergo antibiotic treatment in a timely manner, then this can lead to death. The elderly, infants and those with impaired immune systems will be primarily affected by the most severe form of the disease.

Pathogenicity
Salmonella are among the most dangerous pathogens of intestinal infections in humans and farm animals. According to WHO, up to 1.3 billion cases of salmonellosis are registered in the world every year, while the dynamics of the disease in the population tends to grow. In the absence of effective treatment, deaths in humans range from 1-3 to 10-15%. Every year in the United States, the disease is recorded in 1.4 million residents, and the material costs associated with the consequences and prevention of the disease are estimated at $ 1-2.3 billion. In Russia, this disease ranks second in the structure of acute intestinal infections.

Taxonomy
Genus Salmonella, numbering over 2500 serovars (serotypes), is a member of the Enterobacteriaceae family (Enterobacteriaceae). According to the modern classification based on DNA analysis, the genus Salmonella includes S. enterica, pathogenic for humans and warm-blooded animals. This species is divided into 6 subspecies. Subspecies S. enterica subsp. Enteritidis is a causative agent of foodborne diseases. Subspecies S. enterica subsp. Typhi, S. enterica subsp. Paratyphi A, B - pathogens in humans of typhoid fever, paratyphoid fever A and B.

Morphology
Salmonella cells are motile (thanks to flagella), asporogenic gram-negative straight rods (0.5-1x1-3 microns) with rounded ends. There are also immobile individuals and strains. They do not form a capsule, facultative anaerobic chemoorganotrophs with oxidative and fermentative metabolism. Grow well on simple nutrient and bile media. On solid media, they can form colonies in R-form (rough) and S-form (smooth), on liquid they give diffuse turbidity. S-shaped colonies of medium size, glossy, translucent, with a bluish tinge. When sowing blood, the best liquid enrichment media is bile broth, when sowing biomaterials (feces, bile, urine) containing additional flora, selenite broth. On lactose-containing differential media, bacteria form colorless colonies, on bismuth-sulfite agar - black colonies.

Biochemical characterization
Salmonella have a pronounced biochemical activity characteristic of the genus. To identify them, it is important to take into account the following biochemical properties:
1) fermentation of glucose and other carbohydrates (mannitol, maltose) to acid and gas (subspecies S.typhi releases only acid),
2) lack of fermentation of lactose, sucrose, salicin and urea,
3) react with methylroth, produce hydrogen sulfide, (as a rule) do not form indole, - oxidase is negative, catalase is positive, the Voges-Proskauer reaction is negative,
4) the temperature optimum for growth is 35-37 o C, the growth completely stops at 5 o C; optimum pH = 7.2-7.4.

According to the serological classification, the vast majority of salmonella serovars (serotypes) pathogenic for humans belong to groups A, B, C, D and E. Salmonella are typed according to the Kauffman-White scheme in the agglutination reaction. For its setting, hyperimmune sera or monoclonal antibodies to salmonella are used. Diagnostics of salmonellosis and epidemiological analysis of pathogens are based on serotyping.

Sources and factors of transmission
Salmonellosis (typhoid fever, paratyphoid fever, gastroenteritis, septicemia, etc.) are widespread foodborne diseases in animals and humans with a fecal-oral transmission mechanism. In humans, foodborne infections are accompanied by damage to the gastrointestinal tract and dehydration. The infectious dose is from 1000 to 10 thousand cells. The permanent habitat is the intestines of humans and warm-blooded animals, which are a reservoir of infection. Contaminated food and raw materials, as well as water are the main sources and factors of transmission of the pathogen. The pathogen passes into food from contaminated raw materials. The soil is involved in the contact transmission of infection. The presence of Salmonella in soil or water always indicates contamination of these environments with the feces of infected people and / or animals - birds, cattle, pigs, cats, dogs, pigeons. Their salmonella infection ranges from 6-7 to 80%.

The main sources of infection
In the United States, salmonellosis accounts for about 9% of foodborne infections, and a significant part of the population of this country is its asymptomatic bacteria carriers. Contaminated poultry products, meat and meat products, milk, cheese, butter, vegetables and fruits, semi-finished products and seasonings (mayonnaise, egg powder, creams, etc.) are the main sources of salmonellosis. Foods are contaminated with bacteria also during cooking, contact with carriers, production equipment, animal carriers (flies, mouse rodents, pets). The duration of the viability of Salmonella depends on the type of product and environmental conditions. So, on the surface of vegetables and fruits, bacteria survive for 5-10 days, in milk - up to 20 days, in beer and kefir - up to 2 months, in sausages, meat (including salted), butter - from 2 to 6 months , in cheeses - up to 1 year, in frozen meat - up to 2-3 years.

Pathogenesis
The different nature of the disease is explained by the multiplicity of pathogenic factors (endo-, exotoxins, etc.), which have not yet been sufficiently studied. All virulent salmonella produce endotoxin, which induces the development of fever in infected people (with an increase in temperature to 39-40 o). After oral infection, once in the small intestine, salmonella invade the intestinal mucosa and, multiplying in macrophages, form the primary focus of infection. At the end of the incubation period (10-14 days after infection), once in the blood, salmonella cause bacteremia. The causative agents of typhoid and paratyphoid fever with blood flow are carried throughout the body, settling in the cells of the liver, spleen, lungs, bone marrow, and gallbladder. By the end of the 2nd week from the onset of the disease, the pathogen is excreted from the patient's body with urine, feces, breast milk, saliva. Disease immunity is not formed.

Detection methods
An important role is played by the specific prevention of salmonellosis, which consists in carrying out veterinary-sanitary, sanitary-hygienic and anti-epidemic measures. Prevention is accompanied by permanent control of the pathogen in food, forage, raw materials and water.

Classic method

Salmonella isolation media
- Buffered peptone water
- Wednesday Rappaport-Vassiliadis
- Selenite environment
- Tetrationate broth
- Xylose Lysine Deoxycholate Agar
- Diamond green agar
- Bismuth sulfite agar

The classical technique for the study of Salmonella using culture media. However, due to the duration of the analysis procedure, one classical method is not enough to determine the pathogen.

Immunochromatographic expresstests
To accelerate the detection of Salmonella, significantly reduce labor costs and save resources in recent decades, accelerated methods for identifying the pathogen have been developed, tested and widely used abroad. Accelerated methods can significantly (by 24-48 hours) reduce the duration of research. With their high sensitivity, they provide reliable detection of Salmonella in the analyzed material.

Normative documents
- МР 24 ФЦ 976 Methods for detecting pathogenic microorganisms using immunochromatographic express tests manufactured by Merck (Germany)
- GOST R 50455-92. Meat and meat products. Salmonella detection (arbitration method)
- GOST R 52814-2007 (ISO 6579: 2002). Food products. Method for detecting bacteria of the genus Salmonella.
- GOST R 53665-2009. Poultry meat, by-products and semi-finished products from poultry meat. Salmonella detection method;
- SP 3.1.7.2616-10. Sanitary and Epidemic Rules. Prevention of salmonellosis. M .: Rospotrebnadzor. 2010.18 p.

13.1.3 Salmonella

In 1880 the German researcher K. Ebert first described the bacterium - the causative agent of typhoid fever. In 1884 this microorganism was isolated and thoroughly studied by G. Gaffki.

A similar pathogen that causes disease in pigs was discovered in 1885 by D. Salmon. Subsequently, the entire genus to which these bacteria belong was named Salmonella, and the causative agent was named S. choleraesuis .

Further, Salmonella was identified - the causative agents of animal diseases and food toxicoinfections in humans - S.enteritidis(A. Gartner, 1888) and S.typhimurium(K. Kensh and E. Nobel, 1898).

Later, in 1900, G. Schottmüller studied in detail Salmonella - the causative agents of paratyphoid infections in humans - S. paratyphi B or S . schottmuelleri... In turn, the causative agent of paratyphoid A was isolated and studied by A. Brion and G. Kaiser.

Classification

According to modern taxonomy, the genus Salmonella includes only 2 types - S. enterica and S. bongori... Pathogenic representatives refer only to the species S. enterica.

View S. enterica includes subspecies enterica, salamae, arizonae, diarizonae, houtenae and indica... More than 99% of human diseases are caused by salmonella subspecies enterica.

Salmonella is extremely variable antigenically. More than 2500 serovars are known. For a long time, serovars of bacteria were considered different kinds, which were designated separately.

Only serovars of the subspecies have their own names. enterica... Moreover, the names of most of their variants have become common in medical practice.

Serovars of other subspecies are designated by numbers.

In humans, salmonella is caused by anthroponous ( typhoid fever, paratyphoid fever) and zooanthroponous infections ( salmonellosis).

The causative agent of typhoid fever is S. enterica serovar Typhi. His short name taking into account the name of the serovar - S. Typhi (denoted by a font without italics with a capital letter).

The causative agents of paratyphoid diseases are S. Paratyphi A, S. Paratyphi B, S. Paratyphi C.

The main serovars causing salmonellosis are S. Enteritidis and S. Typhimurium. Many other variants can also cause these diseases (S. Choleraesuis, S. Heidelberg, S. Derby, etc.)

Morphology

All Salmonella - gram-negative movable rods have multiple pili and flagella (peritrichous), do not form spores, and may have a polysaccharide capsule.

Cultural properties

Facultative anaerobes, chemoorganotrophs.

They are able to grow at temperatures from 8 to 45 0 C.

They multiply well on simple nutrient media. On MPA, translucent, colorless colonies are formed.

Bile media are selective (bile broth, Rapoport liquid medium with glucose, bile salts and Andrade's indicator). Able to grow in selenite broth.

In a liquid medium, the S-forms cause uniform turbidity.

On differential diagnostic media Endo, Levin, McConkey form colorless colonies, tk. Salmonella does not break down lactose.

The selective medium for Salmonella is bismuth sulfite agar, where they grow in the form of black shiny colonies.

Biochemical properties

Salmonella ferments carbohydrates (glucose, maltose, mannitol, arabinose, mannose) to form acid and gas. Does not ferment lactose, sucrose.

Unlike other serovars, S. Typhi does not emit gas during carbohydrate fermentation.

When proteins are broken down, they form hydrogen sulfide, with the exception of S. Paratyphi A. They do not form indole.

Oxidase negative, catalase positive

Antigenic structure and Kaufman-White classification

Salmonella has 3 main antigens: O-AG, H-AG, some - capsular Vi-AG.

O-antigen thermostable, can withstand boiling for 2.5 hours. It is a cell wall LPS with endotoxin properties.

H antigen- flagellate, heat-labile, degrades at a temperature of 75-100 o C. It is a flagellin protein.

Unlike other enterobacteria, it has 2 phases: first - specific and the second one is non-specific... Phases are individual antigens that are determined by different genes. Most Salmonella are biphasic. There are monophasic salmonella expressing only one variant of H-AG.

F. Kaufman and P. White classified salmonella by antigenic structure.

According to O-AG, all salmonella are divided into 67 groups (A, B, C, D, E, etc.) One group includes salmonella, which have a common determinant of the O-antigen, indicated by a number.

According to N-AG, within the groups, salmonella are divided into serovars. Specific 1 phase of the H-antigen is indicated by Latin lowercase letters, 2 phase - by Arabic numerals (or together with Latin letters). According to the 1st phase of the H-antigen, the serovar is directly determined.

Vi-AG belongs to the group of superficial or capsular AGs. In most cases, it is found only in S. Typhi, rarely in S. Paratyphi C and S. Dublin.

It is thermolabile, completely destroyed by boiling for 10 minutes, partially inactivated at a temperature of 60 ° C for 1 hour.

Salmonella with Vi-antigen are lysed by typhoid Vi-bacteriophages. Phage typing is carried out in order to establish the source of infection, which is of epidemiological significance. About 100 phage types are known. Polysaccharide Vi-AG provides specific interaction with Vi-phages.

Pathogenic factors

Salmonella has at least 10 genetic pathogenic islands that can be found in many pathogens. In addition, S. typhi possesses the main island of pathogenicity distinguishing it from the rest of the representatives.

Two main islands of pathogenicity play a leading role in the pathogenesis of infections. SPI-1 and SPI-2 localized in the nucleoid. Some of the genes of these islands were obtained as a result of transduction of temperate bacteriophages.

Both islands are responsible for the formation of structures IIItype of secretion(injektis and effector proteins invasion), but these structures are different .

Island effector moleculesSPI-1 are responsible for the penetration of the pathogen into the epithelial cells and the development of enterocolitis.

Some of them form injectisoma(or iglocomplex). The rest, after contact of bacteria with the epithelium, with the help of injectisome, enter the cells.

They rearrange the actin of the cellular cytoskeleton, which leads to the formation of folds on the surface of M-cells of Peyer's patches and intestinal epithelium. Thus, epithelial cells acquire the ability to capture bacteria, which penetrate inside by macropinocytosis.

In addition, the SPI-1 island virulence proteins activate membrane channels in the epithelium, which increases chloride secretion and leads to diarrhea.

When introduced into macrophages, these molecules activate caspase-1. On the one hand, this stimulates the production of proinflammatory cytokines (IL 1, neutrophil chemokine IL 8, etc.). On the other hand, it activates the death of macrophages through apoptosis. Thus, these proteins cause an immune-inflammatory process in the intestinal wall with the penetration of neutrophils there.

Effector molecules another island of pathogenicity SPI-2 are responsible for the survival of bacteria inside phagocytes and cells of affected organs. Thus, they determine the development of not local, but systemic infections with salmonellosis.

The proteins of the SPI-2 island also form injectisoma... After the pathogen enters the phagocyte, it is located inside the vacuole, where it is capable of multiplying. Effector molecules inhibit respiratory burst enzymes, which ensures long-term survival of bacteria. In addition, these proteins support the wall structure of salmonella-containing vacuoles.

Another island of pathogenicity SPI-3 encodes enzymes that provide salmonella with magnesium cations. It is also necessary for the survival of bacteria inside phagocytes.

Salmonella, when destroyed, secrete endotoxin, which, through TLR-4 receptors on cells, stimulates the release of pro-inflammatory cytokines. Has a pyrogenic effect, damages the vascular endothelium.

Some pathogens are capable of producing enterotoxins that cause secretory diarrhea.

The main island of pathogenicity S. Typhi determines the invasiveness of the pathogen, as well as the ability to produce capsular Vi-AG.

Two plasmids of S. typhi contain genes for antibiotic resistance. In addition, part of Salmonella has a set of genes for multiple antibiotic resistance, which are located in the nucleoid.

Resistance

In the external environment, salmonella retain their viability for a long time: in open water they live up to 120 days, in sea water - up to a month, in soil up to 9 months, in room dust up to 1.5 years, in sausages 2-4 months, in frozen meat and eggs up to 1 year. Salmonella is not only preserved in products, but also multiplied (milk, sour cream, cottage cheese, minced meat). Flies can play a role in food contamination.

Bacteria tolerate low temperatures well, but they are sensitive to high temperatures - when heated to 60 0 С they die in 30 minutes, at 100 0 С - almost instantly. Disinfectants (chloramine, hypochlorite, lysol) in normal concentrations kill pathogens after a few minutes.

Characteristics of diseases

Salmonella causes 3 groups of lesions: typhoid and paratyphoid fever, salmonella gastroenteritis and septicemia... Their development depends on the virulence of the pathogen, its infectious dose and the state of immunity of the macroorganism. For the occurrence of typhoid fever, 10 3 -10 5 microbial cells are required. For the development of salmonellosis, the infectious dose is significantly higher - 10 6 -10 9 bacteria, but with a high virulence of the pathogen or with an immunodeficient state of a person, the number of bacteria can be many times less.

Typhoid fever and paratyphoid diseases

Typhoid fever and paratyphoid- these are acute infectious diseases, which are characterized by inflammatory damage to the small intestine with destruction of lymphoid tissue and ulceration, bacteremia, fever, general intoxication, enlargement of the spleen and liver.

Typhoid fever is the most severe.

This disease is a serious public health problem, especially in developing countries. Every year in the world there are 15 to 30 million cases of typhoid fever, while 250 to 500 thousand deaths are recorded. In developing countries, children and young people are mainly affected. In developed countries, the disease occurs in sporadic cases.

Typhoid fever and paratyphoid A - anthroponous infections, the reservoir of which is a person. The causative agents of paratyphoid B and C have also been isolated from some animals and birds.

Sources of infection there are patients or bacteria carriers that excrete the pathogen with feces, urine, saliva. The main mechanism of infection- fecal-oral (water, food and contact-household).

Incubation period can last up to 2-3 weeks.

When ingested through the mouth, breaking the protective barriers of the stomach, bacteria penetrate into the small intestine ( phase of infection). In pathogenesis, the most important role is played by invasive system proteinsIIItype of secretion(see above). Some of the proteins of the invasion show translocation activity - form injectisoma and ensure the penetration of Salmonella into epithelial M-cells and enterocytes. The rest block the metabolism of infected cells, leading to disruption of their function. There is an increase in the production of chemokines (for example, IL-8), other pro-inflammatory cytokines by enterocytes and intestinal macrophages.

Salmonella remain viable in vacuoles of affected cells and induce apoptosis of macrophages by activating caspase-1.

As a result of a violation of the hemolymphatic barrier, Salmonella enter the blood ( phase of bacteremia). The causative agents of typhoid fever survive and multiply in phagocytes, and after the death of the latter in large quantities get into the blood. Wherein Vi-AG inhibits the action of serum and phagocytic bactericidal factors.

At this time, clinical symptoms of the disease appear ( first week of illness). The temperature rises to 39-40 o. Under the influence of the bactericidal properties of blood and due to phagocytosis, Salmonella is destroyed, released endotoxin, which affects the vessels of the microcirculation and has a pronounced neurotropic effect. In severe cases, as a result of damage to the central nervous system, status typhosus(severe headache, insomnia, severe weakness, apathy, impaired consciousness, up to coma). The defeat of the intestine is accompanied by edema, desquamation of the epithelium. Disorder of the autonomic nervous system is accompanied by flatulence, abdominal pain. Diarrhea develops.

At 2 weeks of illness (the height of the disease) salmonella with blood spread to the internal organs, affect the liver, gallbladder, spleen, kidneys, a rash appears on the skin. From the 2nd week, Salmonella with bile again enter the small intestine, the lymphoid formations of which are already sensitized by Salmonella antigens. The result is autoimmune inflammatory response, sometimes necrosis is formed in places of accumulation of lymphoid cells. The consequence of mucosal necrosis can be bleeding, intestinal perforation.

After the height of the disease, there is a gradual extinction of clinical manifestations diseases. Excretion of pathogens from the body occurs with feces, urine, sweat, saliva, breast milk (in lactating women). The immune response ensures the gradual elimination of Salmonella.

Patients who received antibiotics are discharged from the hospital no earlier than 21 days of normal temperature. Before discharge, a three-time bacteriological study of feces and urine and a single study of bile are performed.

Usually the disease ends recovery... Mortality does not exceed 0.5-1%. However, in the absence of adequate medical care, in some outbreaks of typhoid fever in tropical countries, the mortality rate exceeded 30%.

Paratyphoid A and B are more favorable. Their clinical symptoms are similar. In general, these diseases are characterized by a milder course in comparison with typhoid fever.

Immunity

After an infection, immunity is generally stable, but there may be relapses and repeated diseases.

Recovery does not always end with complete release from the pathogen. More than 2% of patients are carriers of bacteria. Since bacteria are resistant to bile, they are concentrated in the gallbladder, in isolation from the action of immunity factors. Such pathogens produce an increased amount of Vi-AG. Capable of persisting inside macrophages.

Bacteria carriers are dangerous as sources of infection. They can retain pathogens for many months. Chronic carriers were found to have a deficiency of IgM antibodies against O-AG.

Carriage of paratyphoid pathogens is formed more often than with typhoid fever, but it is shorter - within a few weeks.

Laboratory diagnostics of typhoid fever

Use bacteriological and serological methods, which are carried out taking into account the period of the infectious process.

Selection material are blood ( blood culture), excreta ( copculture), urine ( urinoculture), duodenal contents, bile ( biliculture), scraping roseol, bone marrow.

V bacteriological research early method is the isolation of the pathogen from the blood (blood culture) during the period of bacteremia (the first week of the disease).

Blood is inoculated into bile broth or Rapoport medium in a ratio of 1:10 (to reduce the bactericidal properties of blood proteins). On the 2nd day, subculture is carried out on Endo or Levin's medium, or bismuth-sulfite agar. Suspicious (transparent or black, depending on the media) colonies are subcultured on slant agar or one of the combined media (Olkenitsky, Ressel, Kligler). On these media, for primary identification, the fermentation of glucose, the ability to generate gas, the release of hydrogen sulfide, and the absence of urease are determined.

Morphology and tinctorial properties are studied at the same time.

Determine biochemical properties. Bacteria of the typhoid-paratyphoid group do not decompose sucrose, lactose, and do not form indole.

When isolating cultures with enzymatic properties characteristic of Salmonella, their antigenic structure is studied in the agglutination reaction on glass with O- and H-diagnostic antisera, sensitivity to antibiotics is determined, and phage typing is performed.

For serological diagnostics of typhoid and paratyphoid fever from 5-7 days of the disease is mainly used by RPHA with O- and H-erythrocyte diagnostics. A reaction in a titer of 1: 160 and higher is considered positive. When examined in RPHA, the antibody titer increases in the dynamics of the disease.

It is possible to use the Vidal agglutination reaction with O- and H-monodiagnostics to specific pathogens (positive reaction titer - 1: 200 and higher). Serological diagnosis is retrospective.

To identify bacteria carriers use RPHA with erythrocyte Vi-diagnosticum (reaction titer - 1:40). Explore bili- and coproculture. Phage typing with Vi-1 antigen is carried out.

In case of epidemic outbreaks of typhoid fever, RIF and ELISA are used for express diagnostics in order to detect hypertension in blood, bone marrow and other material.

Typhoid fever treatment

Etiotropic therapy is carried out immediately after the establishment of the clinical diagnosis. For treatment, fluoroquinolones are used. With resistance to them, cephalosporins of the third generation, azithromycin are used.

Levomycetin and co-trimoxazole are currently used less frequently due to the spread of multi-resistant strains. Pathogenetic treatment includes infusion-detoxification therapy.

Prophylaxis

Sanitary and hygienic and anti-epidemic measures are being taken to neutralize sources of infection, suppress transmission routes, and increase the body's immunity.

For specific immunoprophylaxis of typhoid fever, 3 types of vaccines have been developed. Inactivated vaccines are used (efficiency 50-70%), a live attenuated vaccine from the Tu21a strain has been developed (it has a greater protective effect, is at the stage of clinical trials). The polysaccharide vaccine from the S. typhi Vi antigen is effective. (for example, Vianvac pr-va Russian Federation), is used for epidemiological indications, the protective effect lasts up to 2 years.

Salmonellosis

Salmonellosis- a group of polyetiologic acute infectious diseases of humans, animals and birds, characterized by a predominant lesion of the gastrointestinal tract, diarrhea and bacteremia.

The most common clinical form of salmonella infection is salmonella gastroenteritis... The main causative agents of gastroenteritis: S. Enteritidis, S. Choleraesuis, S. Anatum, S. Derby, although diseases can be caused by many other variants of bacteria.

A much more severe form is generalized salmonella infection - septicemia... Its leading pathogen is S. Typhimurium.

Most pathogens are isolated from various animals (main reservoir) and humans.

The source of infection Most often, humans are poultry (50%), especially chickens and ducks, as well as their eggs (Salmonella can penetrate through the shell inside). Carriage of Salmonella has been identified in livestock, dogs, cats, rodents, and many wild animals and birds. Infected animals excrete bacteria with urine and feces, milk, saliva, polluting the environment.

Basic transmission path Salmonella is food grade. Diseases occur in humans due to the consumption of meat products (beef, pork - up to 20% of cases, poultry meat), eggs, less often fish, vegetables, fruits, shellfish, crayfish, and crabs.

Meat can become infected endogenously during the life of an animal during its illness, as well as exogenously during transportation, processing, storage. Sometimes food products become infected if they are improperly cooked and cooked.

If sanitary and hygienic standards are not observed, contact-household way transmission, which is characteristic of nosocomial outbreaks salmonellosis. Such outbreaks were noted in obstetric institutions, surgical, children's and other hospitals. In hospital salmonellosis, S. typhimurium is more often excreted and S. Haifa. In the Republic of Belarus, salmonella infections account for more than 50% of all cases of hospital infections

The causative agents of hospital salmonellosis are distinguished by high multiresistance to chemotherapeutic drugs and antibiotics.

Children under the age of 1 year and persons with various immunodeficiencies are most susceptible to salmonellosis.

The incubation period of the disease is from 2-6 hours to 2-3 days (the average is 7-24 hours).

The pathogenesis of salmonellosis is determined by the virulence factors of the pathogens. Among them, the most important role is played by invasive secretion type III proteins.

Some of the proteins of invasion ensure the penetration of Salmonella into the intestinal epithelial cells, their survival inside the vacuoles. In addition, they stimulate the release of proinflammatory cytokines and chemokines from diseased cells, apoptosis of macrophages.

Inside macrophages, bacteria not only multiply, but also partially die with the release of endotoxin, which affects the intestinal neurovascular apparatus and increases the permeability of cell membranes.

Within 1 hour from the penetration of Salmonella into the cells, pronounced neutrophilic infiltration of the intestinal wall develops. Intestinal inflammation is accompanied by the release of protein from the affected enterocytes, increased secretion of chlorides with the development of profuse diarrhea.

Part of Salmonella can produce enterotoxin, which, by increasing the cAMP content in enterocytes, stimulates the excretion of chlorides, which aggravates diarrhea.

In most cases, at this stage, the infectious process can end ( gastrointestinal form).

In severe cases, bacteremia and generalization of the infection occurs, which leads to septicemia.

This form of salmonellosis is most typical for S. Typhimurium and S. Enteritidis. Its development is due to virulence proteins, which are encoded by the island of pathogenicity. SPI-2 ... These proteins suppress phagocytosis, which ensures the survival and reproduction of bacteria inside phagocytes, their penetration into the blood and parenchymal organs.

As a result, salmonella can cause degenerative changes in the affected organs (spleen, liver) with the formation of secondary purulent foci.

Usually the disease ends with recovery, but septic infections can be fatal.

Immunity

Post-infectious immunity is short-lived, unstable, type-specific. In the serum of patients and convalescents, agglutinins, precipitins, bacteriolysins and other antibodies are found. The disease caused by one serovar does not create immunity to others, and the transferred infection does not exclude reinfection.

Laboratory diagnostics of salmonellosis

Diagnostics is based on bacteriological method... For research, take various materials: feces, vomit, gastric lavage, urine, food debris, as well as the original products used for its preparation; flushes from various equipment and objects.

To diagnose septicemia, blood is examined.

Selenite broth, selenite agar, 20% bile broth are used as enrichment media. Among the differential diagnostic media for primary crops and inoculations from the enrichment media, selective media (bismuth-sulfite agar or agar with brilliant green) and differential diagnostic media (Endo and Levin) are distinguished. Suspicious colonies are subcultured into tubes with one of the combined media (Olkenitsky, Kligler, Ressel) and on a slanted MPA.

The morphological, tinctorial, biochemical properties of pathogens are studied.

With crops grown on the MPA, they carry out serological typing according to the Kaufman-White scheme. Agglutination reaction is performed on glass with O- and H-agglutinating antisera. According to the results of the reaction, the final bacteriological diagnosis is established.

Serological diagnostics are rarely used (RA, RPHA).

ELISA methods have been developed for detection of salmonella antigens in the blood and urine.

Treatment

Pathogenetic therapy of salmonellosis is aimed at detoxification, restoration of water-electrolyte balance and hemodynamics. Antibiotic therapy for mild forms of gastroenteritis is not indicated. In case of generalized infection, fluoroquinolones are prescribed, with resistance to them - cephalosporins of the third generation (ceftriaxone).

In the complex treatment of salmonellosis, it is possible to use a polyvalent salmonella bacteriophage.

Prophylaxis

Includes veterinary and sanitary, sanitary and hygienic and anti-epidemic measures. In the event of a nosocomial outbreak of salmonellosis, a special operating mode of the medical institution is established.

Vaccine prophylaxis has not been developed.

Salmonella identification

After 18-20 hours of incubation of plates with differential diagnostic media (bismuth-sulfite agar 48 hours), the growth pattern is taken into account with the selection of 3-5 suspicious colonies on one of the media for primary identification (Kligler, Ressel, Olkenitsky) and on the slant nutrient agar. In the event of an epidemic emergency, the culture grown on these media is used for the subsequent staging of the agglutination reaction. The results of this reaction are indicative and require confirmation at the stage of completion of biochemical identification.

Cultural properties

The commonality of the morphology and a number of cultural properties of bacteria of the genus Salmonella does not allow them to be typed according to the indicated characters. For this, in addition to morphology and cultural properties, enzymatic properties and antigenic structure are studied, in some cases, a biological test is performed on laboratory animals.

The enzymatic properties of bacteria are due to a set of enzymes, reflect certain conditions of nutrition and metabolism inherent in this type of microorganism in certain environmental conditions. Bacteria of the genus Salmonella are characterized by the following enzymatic properties: they do not liquefy gelatin, do not decompose adonite and do not ferment sucrose; the overwhelming majority does not break down salicin and does not break down lactose, does not form indole, does not break down urea, does not give the Voges-Proskauer reaction (reaction to acetylmethylcarbinol); ferments (with a few exceptions maltose, mannitol, sorbitol, breaks down glucose to form gas (S. typhi, S. pullorum usually do not form gas); gives a positive reaction with methyl red, utilizes ammonium and reduces nitrates; most of them produce hydrogen sulfide.

To study the enzymatic properties of bacteria of the genus Salmonella, a short colored (variegated) row is usually used, consisting of media with glucose, mannitol, arabinose, dulcite, rhamnose (Bitter's medium); glycerin fuchsin broth (Stern broth). In addition to these media for the differentiation of serological types of Salmonella, media with maltose, inositol, trehalose, xylose are also used; litmus milk (the change in litmus milk with the growth of Salmonella allows them to be differentiated by their ability to form acid or alkali). Instead of litmus, you can use skim milk with an indicator bromothymol blue (1 ml of a 0.4% solution in 100 ml of milk). The formation of hydrogen sulfide by culture is of known importance for the differentiation of Salmonella. Proteolytic properties are investigated by sowing the studied Salmonella culture on NRM and milk.

Due to the similarity of bacteria of the genus Salmonella with other microorganisms of the family Enterobacteriaceae, it becomes necessary to differentiate them. At present, dense differential diagnostic nutrient media with lactose (Ploskirev, Endo, Levin media) are widely used in bacteriological practice. By the ability of bacteria to ferment lactose, Salmonella is distinguished from the often accompanying E. coli, therefore, when examining the material for Salmonella, first sowing is performed on one of the differential diagnostic media. On these media, E. coli, fermenting lactose with the formation of acid and a change in the color of the indicator, forms colonies that differ in color from the colonies of Salmonella, which do not ferment lactose. On Endo medium, E. coli bacteria give colonies of red color, often with a metallic sheen, Salmonella - colorless or pale pink (colored in the color of the medium); on Ploskirev's medium E. coli - orange-red colonies, salmonella - transparent or pale pink; on Levin's medium E. - coli form black colonies surrounded by a rim, salmonella - transparent, pale pink or pinkish-purple. To differentiate Salmonella and cultured similar strains, as well as bacteria of the Proteus genus and bacteria of the E. coli group, media with urea (Preuss, Ressel, Olkenitsky media), SS-agar (Salmonella - Shigella - agar), etc. are used. The color of these media is due to the unequal intensity of the breakdown of nitrogenous substances by microorganisms with the formation of alkaline products. Coli and Proteus bacteria (with the exception of the 0-form), as a rule, do not grow on SS-agape, and Salmonella grow in the form of delicate, colorless colonies.

Dense differential diagnostic media serve only to determine whether bacteria belong to the genus Salmonella and to separate them from the accompanying microflora.

The enzymatic properties of Salmonella are not always stable and can change depending on environmental conditions, therefore, the correct typing of Salmonella is possible only as a result of studying a complex of morphological, cultural, enzymatic properties and antigenic structure

Small gram-negative sticks with rounded ends. Dimensions: 0.7 -1.5 microns. in diameter, 2-5 microns in length. Mobile microorganisms (peritrichous), but there are stationary variants. Some have a microcapsule.

Cultural properties

Facultative anaerobes, chemoorganoheterotrophs, optimum growth temperature 37 ° C, pH 6.8-7.2. Grow well on simple nutrient media. Diffuse turbidity (S - shape) or sediment (R - shape) are formed in BCH. On MPA, colonies are smaller than E. coli, translucent, tender. They can grow as R-, S-, Q- colonies. Selenite broth is used as a storage medium. On differential diagnostic media, endo Levin and Ploskirev grow in the form of transparent or whitish colonies, which distinguishes them from the indicator-colored E. coli colonies. On bismuth-sulfite agar (Wilson-Blair medium), colonies of black color with a metallic luster are formed, surrounded by a black rim of the stained medium. After removal of the colony, a dark spot remains on the agar.

Unlike S. paratyphi - A, most strains of S. paratyphi - B, when growing on agar, are capable of forming a mucous cushion along the edge of the colonies.

Biochemical properties:

The biochemical and antigenic properties of Salmonella are essential for their species differentiation. The paratyphoid pathogens are more biochemically active than the typhoid bacillus. Salmonella does not ferment lactose and sucrose. Glucose, beckons, maltose are broken down to acid (typhoid) or to acid and gas (paratyphoid). According to the ability to decompose xylose and arabinose, 4 types are distinguished: K + A +; K-A-; K + A-; K-A +. They do not form indole, do not liquefy gelatin, form H 2 S (unlike shigella) convert nitrates into nitrites. Salmonella - oxidase-negative, catalase-positive, Voges-Proskauer reaction - negative

Antigenic structure

The antigenic structure of Salmonella is rather complex, there are O-, H-, Vi-, M- antigens.

O-antigen - lipolysaccharide-protein complex, thermostable (withstand boiling for 2.5 hours, autoclaving at 120 0 C - 30 minutes), sensitive to formaldehyde, but resistant to alcohol. This is a group antigen - according to it, according to the classification of Kaufman and White, the family is divided into 67 serogroups. They are designated in capital letters Latin alphabet (A, B, C, D, etc.). Some groups share O antigens in common, but each group contains one major antigen. (For example, in group A - this is 2, in group B - 4, in group C - 6, D - 9, etc.)

H-antigen - protein, type-specific (divides salmonella into serovars), thermolabile, destroyed when heated to 75 0 -100 0 C, as well as under the action of hydrochloric acid, alcohol, proteolytic enzymes. This is the basis for obtaining H-diagnostics. Salmonella H antigens have 2 phases. The first of them (specific) is different for serotypes belonging to the same group. Salmonella of this phase are designated by lowercase Latin letters from a to z. Salmonella with H-antigens of phase II (nonspecific) contain components common to the entire group; this phase is indicated by Arabic numerals.

Vi- antigen - surface (capsule), heat-labile, sensitive to hydrochloric acid and alcohol, destroyed by boiling for 10 minutes. It prevents the agglutination of Salmonella O-antisera. Vi- antigen is found only in virulent Salmonella. It is not a direct carrier of virulence, however, a parallelism has been established between its presence and the effect of bacteria on a macroorganism.

M - antigen - slimy, water-insoluble, destroyed by acids and alcohols.

Despite the multiplicity of antigens, serological identification takes into account 3 of them: O-, H-, Vi.

Pathogenicity factors:

a) toxins: endotoxin (lipopolysaccharidoprotein complex), form microorganisms in the S-form, is released during mass death of pathogens; plays a major role in the pathogenesis of typhoid fever;

b) enzymes of pathogenicity: hyaluronidase, fibrinolysin, lecithinase;

v) structural elements of cells: fimbria, microcapsule (in some strains), due to its pathogens attach to the epithelial cells of the small intestine;

G) an important biological feature of Salmonella-the ability to penetrate macrophages and resist phagocytosis, and after their death enter the bloodstream, causing the generalization of the infectious process;

e) drank I order perform an adhesive function.

Resistance.

Salmonella is relatively stable in the external environment. They remain in ice for more than 60 days, in open water - 120 days, in frozen meat - 6-13 months, in bread - up to 3 months, in eggs - up to 13 months, in soil - up to 3 months. When heated, pathogens quickly die. Sensitive to disinfectants in working concentration (0.3% chloramine solution kills Salmonella in 1 hour).

Epidemiology.

Reservoir and source of causative agents of typhoid fever and paratyphoid A - a person (sick or carrier of bacteria); the reservoir of paratyphoid B can be not only people, but also animals (cattle, pigs, poultry).

The mechanism of infection is fecal-oral; ways of transmission: food, water, contact and household. Typhoid fever and paratyphoid A spread more often by water (drinking water from shallow polluted reservoirs, technical water pipelines, in cases of sewage breakthrough). With paratyphoid B, the food route predominates (infection often occurs through milk, dairy products, creams, vegetable salads). The household route is realized, as a rule, through bacteria carriers; wherein great importance has a low sanitary culture.

Typhoid fever is recorded everywhere in all climatic zones. Paratyphoid A occurs most often in Southeast Asia, Africa in the form of sporadic cases or in the form of limited outbreaks

Most high level morbidity is reported in developing countries. In the Russian Federation, with a low average incidence of this pathology, there are regions with high incidence rates. So, in last years they are quite often registered in Dagestan, Karachay-Cherkessia, Kaliningrad Region, Primorsky Territory. This is due to population migration, the expansion of street food trade and the ensuing consequences.

№ 2 Causative agents of salmonellosis. Taxonomy. Feature. Microbiological diagnosis of salmonellosis. Treatment.
Acute intestinal zoonotic infection caused by salmonella serovars, characterized by gastrointestinal lesions.
Morphological properties: mobile, gram "-" sticks, no capsule. Grow well on simple nutrient and bile media. On dense - form colonies in R- and S-shapes, on liquid - turbidity. Colorless colonies are formed on lactose-containing media.
Biochemical activity: fermentation glitch. to acid and gas, no lactose fermentation, hydrogen sulfide production, no indole formation.
Antigenic structure: somatic O-antigen, flagellar H-antigen, Some - K-antigen. Genus Salmonella consists of two types - type S.enterica, which includes all salmonella, which are pathogens of humans and warm-blooded animals, and the species S.bongori, which is subdivided into 10 serovars.
View S.enterica divided into 6 subspecies, which are subdivided into serovars. Some Salmonella serovars, in particular S. typhi, have the polysaccharide Vi antigen, which is a type of K antigen.
Epidemiology. The causative agents of salmonellosis are a large group of salmonella, which belongs to the subspecies enterica... The most common causative agents of salmonellosis in humans are serovars S. Typhimurium, S. Dublin, S. Choleraesuis. The main transmission factors are meat, milk, eggs, water.
Pathogenesis and clinic. The disease proceeds in a local form of gastroenteritis, the leading syndrome is diarrheal. Having invaded the mucous membrane of the small intestine through M-cells and penetrating into the submucosa, salmonella are captured by macrophages, transferring them to Peyer's patches, where they form the primary focus of infection. In this case, endotoxin and protein enterotoxin are released. Enterotoxin activates the flow into the intestinal lumen of a large amount of liquid, K, Na. Diarrhea, vomiting.
Immunity: Relaxed, serovar-specific, mediated by secretory IgA, which prevents the process of penetration of salmonella into the mucous membrane of the small intestine. Antibodies can be detected in the blood.
Microbiological diagnostics. Vomit, gastric lavage, feces, bile, urine, blood are subjected to bacteriological research. When identifying isolated cultures, a wide range of diagnostic O- and H-sera is required.
For serological research, RNGA, ELISA are used. An increase in the titer of antibodies in the dynamics of the disease is of great diagnostic value.
Treatment. Pathogenetic therapy is used to normalize water-salt metabolism. In generalized forms - etiotropic antibiotic therapy.
Salmonella group, adsorbed O- and H-agglutinating sera. They are used to establish serogroups and serovars of Salmonella in the agglutination reaction.
Salmonella O- and H-monodiagnosticums are suspensions of Salmonella killed by heating (O-diagnostics) or formalin treatment (H-diagnostics). They are used for serodiagnosis of typhoid fever.
Prophylaxis . Specific prophylaxis of salmonellosis in agricultural animals and birds. Non-specific prophylaxis - carrying out veterinary and sanitary measures.