Cholera Vibrio

According to WHO, cholera is an infectious disease, for which a severe severe dehydrating diarrhea with feces in the form of rice broth is a consequence of infection with Vibrio cholerae. Due to the fact that it has a pronounced capacity for widespread epidemic spread, severe course and high lethality, cholera is one of the most dangerous infections.

The historical homeland of cholera is India, more precisely, the delta of the Ganges and Brahmaputra (now East India and Bangladesh), where it has existed since time immemorial (epidemics of cholera in this region were observed even 500 years before BC). The long existence of an endemic foci of cholera is explained by many reasons. Cholera vibrio can not only persist for long in water, but also multiply in it under favorable conditions - temperature above 12 ° C, presence of organic substances. All these conditions are present in India: the tropical climate (average annual temperature is from 25 to 29 ° C), the abundance of precipitation and waterlogging, high population density, especially in the Ganges delta, the large amount of organic substances in the water, the continuous year-round pollution of water by sewage and feces , a low material standard of living and unique religious and religious rituals of the population.

In the history of cholera epidemics, four periods can be distinguished.

I period - until 1817, when cholera was concentrated only in East and South Asia, mainly in India, and did not go beyond it.

II period - from 1817 to 1926. With the establishment of broad economic and other ties of India with European and other countries, cholera went beyond India and, spreading along economic and religious links, caused 6 pandemics that claimed millions of human lives. Russia was the first of the European countries where cholera penetrated. During the period from 1823 to 1926, Russia experienced 57 cholera years. During this time more than 5.6 million people had cholera and 2.14 million people died ("40%").

III period - from 1926 to 1961. Cholera returned to its main endemic center, and a period of relative prosperity came. It seemed that with the development of modern systems for purifying drinking water, removing and disinfecting sewage and developing special anti-cholera measures, including the creation of a quarantine service, the countries of the world will be reliably protected from the next invasion of cholera.

IV period began in 1961 and continues to this day. The seventh pandemic began not in India, but in Indonesia, quickly swept the Philippines, China, the countries of Indochina, and then other countries of Asia, Africa and Europe. Features of this pandemic are included in the fact that, firstly, it is caused by a special variant of the cholera vibrio - V. Cholerae eltor, which until 1961 was not even officially recognized as a causative agent of cholera; second, in terms of duration, it surpassed all previous pandemics; thirdly, it proceeded in the form of two waves, the first of which lasted until 1990, and the second one began in 1991 and covered many countries in South and North America, including the USA, who did not know the cholera epidemics since 1866. Since 1961 By 1996, 3,943,239 people had been ill with cholera in 146 countries.

The causative agent of cholera Vibrio cholerae was discovered in 1883 during the fifth pandemic by R. Koch, however, for the first time the vibrio in feces of diarrhea patients was discovered as early as 1854 by F. Pacini.

V. Cholerae belongs to the family Vibrionaceae, which includes several genera (Vibrio, Aeromonas, Plesiomonas, Photobacterium). The genus Vibrio has more than 25 species since 1985, of which V. Cholerae, V. Parahaemolyticus, V. Alginolyticus, V. Vulnificus and V. Fluvialis are of greatest importance for humans.

[1], [2], [3], [4], [5], [6],

Key features of the genus Vibrio

Short, non-controversial and capsules, curved or straight gram-negative rods, 0.5 μm in diameter, 1.5-3.0 μm in length), mobile (V. Cholerae - monotrich, in some species two or more polar flagella) ; grow well and quickly on ordinary media, chemoorganotrophs, ferment carbohydrates to form acid without gas (glucose is fermented along the way of Embden-Meyerhof). Oxidase-positive, form indole, reduce nitrates to nitrites (V. Cholerae gives a positive nitrosoindol reaction), cleave gelatin, often give a positive reaction of Foges-Proskauer (ie form acetylmethyl carbinol), ureases do not form H2S, have lysine decarboxylases and Ornithine, but do not have arginine dihydrolase. A characteristic feature of the genus Vibrio is the sensitivity of most strains of bacteria to the preparation 0/129 (2,4-diamino-6,7-diazopropylpteridine), while representatives of the families Pseudomonadaceae and Enterobacteriaceae are resistant to this drug. Vibrios - aerobes and facultative anaerobes, temperature optimum for growth 18-37 C, pH 8.6-9.0 (grow in the pH range 6.0-9.6), some species (halophiles) do not grow in the absence of NaCl. The G + C content in DNA is 40-50 mole% (for V. Cholerae about 47 mole%). For differentiation within the Vibrionaceae family from the morphologically similar genera Aeromonas and Plesiomonas, as well as for differences from the Enterobacteriaceae family, biochemical tests are used.

From the family Pseudomonadaceae the cholera vibrio differs in that it ferments glucose only along the path of Embden-Meyerhof (without the participation of O2), while the former consume glucose only in the presence of O2. This difference between them is easily revealed on Hugh-Leifson medium. The medium contains nutrient agar, glucose and indicator. Sowing is done in two columns with Hugh-Leifson medium, one of them is filled with petroleum jelly (to create anaerobic conditions). In the case of growth of the cholera vibrio, the color of the medium changes in both test tubes, in the case of pseudomonad growth, only in a test tube without petrolatum (aerobic growth conditions).

Cholera vibrio is very unpretentious to nutrient media. It reproduces well and quickly at a 1% alkaline (pH 8.6-9.0) peptone water (PV) containing 0.5-1.0% NaCl, overtaking the growth of other bacteria. To suppress the growth of the protein to 1% PV it is recommended to add potassium tellurite (in the final dilution 1: 100,000). 1% PV is the best enrichment medium for cholera vibrio. With growth, it forms after 6-8 hours on the surface of the PV a soft, friable, grayish color film, which, when shaken, easily breaks down and falls to the bottom in the form of flakes, the PV moderately grows turbid. Various selection media have been proposed for isolation of the cholera vibrio: alkaline agar, bile salt agar, alkaline albumin, alkaline agar with blood, lactose-sucrose and other media. The best medium is TCBS (thiosulfate citrate-bromothymol sucrose agar) and its modifications. However, most often used alkaline MPA, on which the cholera vibrio forms smooth glassy-transparent with a bluish tinge discoid colonies of viscous consistency.

When planting with a stab in the gelatin column, the vibrio occurs after 2 days. At a temperature of 22 - 23 C causes liquefaction from the surface in the form of a bubble, then funnel-shaped and, finally, layered.

In milk, the vibrio multiplies rapidly, causing clotting after 24-48 h, and then peptonization of milk occurs, and after 3-4 days the vibrio dies due to a shift in the pH of the milk to the acidic side.

B. Heiberg on the ability to ferment mannose, sucrose and arabinose distributed all the vibrios (cholera and cholera-like) to a number of groups, the number of which is now 8.

Cholera vibrio belongs to the first group of Heyberg.

Vibrios, similar in morphological, cultural and biochemical characteristics to cholera, were named and named in different ways: paracholera, cholera-like, NAG-vibrios (non-agglutinated vibrios); vibrios not belonging to the O1 group. The latter name most accurately emphasizes their relation to the cholera vibrio. As established by A. Gardner and K. Venkat-Raman, cholera and cholera-like vibrios have a common H-antigen, but differ in O-antigens. According to the O-antigen, cholerae and cholera-like vibrios are currently distributed to 139 O-serogroups, but their number is constantly being replenished. Cholera Vibrio belongs to the O1 group. It has a common A antigen and two type-specific antigens - B and C, for which three serotypes of V. Cholerae are identified - the serotype Ogawa (AB), the serotype Inaba (AC) and the serotype of Gikoshima (ABC). The cholera vibrio in the dissociation stage has an OR antigen. In this connection, O-serum, OR-serum and type-specific sera of Inaba and Ogawa are used to identify V. Cholerae.

In 1992-1993 years. In Bangladesh, India, China, Malaysia and other countries, a major cholera epidemic began, the causative agent of which was a new, previously unknown serovar of the species Vibrio cholerae. It differs from V. Cholerae O1 on antigenic signs: it has antigen 0139 and a polysaccharide capsule and is not agglutinated by any other O-sera. All its other morphological and biological properties, including the ability to induce cholera, ie, synthesize exotoxin-cholerogen, were similar to those of V. Cholerae O1. Consequently, a new cholera causative agent, V. Cholerae 0139, appeared, apparently due to a mutation that changed the O-antigen, and was called V. Cholerae 0139 bengal.

The question of the relation of so-called cholera-like vibrios to V. Cholerae was not clear for a long time. However, comparison of V. Cholerae and cholera-like (NAG-vibrios) by more than 70 signs revealed their similarity by 90%, and the degree of homology of V. Cholerae DNA and the studied NAG-vibrios is 70-100%. Therefore, cholera-like vibrios are combined into one species with cholera vibrio, from which they differ mainly in their O-antigens, and therefore they are called vibrios of the non-01 group-V. Cholerae pop 01.

The species V. Cholerae is subdivided into 4 biotypes: V. Cholerae, V. Eltor, V. Proteus and V. Albensis. For many years, the question of the nature of the vibrio El Tor has been discussed. This vibrio was isolated in 1906 by F. Gotschlich at the quarantine station El Tor from the corpse of a pilgrim who died from dysentery. F. Gottshlich identified several of these strains. By all properties, they did not differ from the cholera vibrio and were agglutinated with cholera O-serum. But since there was no cholera among the pilgrims at this time, and the prolonged carriage of the cholera vibrio was considered to be unlikely, the question of the possible etiological role of V. Eltor in cholera for a long time remained controversial. In addition, the vibrio El Tor, unlike V. Cholerae, had a hemolytic effect. However, in 1937 this vibrio caused a major and severe epidemic of cholera on the island of Sulawesi (Indonesia) with a mortality rate of over 60%. Finally, in 1961 he became the culprit of the 7th pandemic, and in 1962 the issue of his cholera nature was finally decided. The differences between V. Cholerae and V. Eltor concern only certain features. For all other properties, V. Eltor does not fundamentally differ from V. Cholerae. In addition, it has now been established that the V. Proteus (V. Finklerpriori) biotype includes the entire group of vibrios, except for the 01-group (and now 0139), previously called NAG-vibrios. The V. Albensis biotype was isolated from the Elbe River and has the ability to phosphoresce, but losing it, it does not differ from V. Proteus. In connection with these data, the species Vibrio cholerae is now subdivided into 4 biotypes: V. Cholerae 01 cholerae, V. Cholerae eltor, V. Cholerae 0139 bengal and V. Cholerae non 01. The first three belong to two serovars 01 and 0139. The last biovar includes the former biotypes of V. Proteus and V. Albensis and is represented by many other serovars of vibrios that are not agglutinated by 01- and 0139-sera, ie, HAg-vibrios.

Factors of pathogenicity of the cholera vibrio

[7], [8], [9], [10], [11], [12],

Chemotaxis of cholera vibrio

With the help of these properties, the vibrio interacts with epitheliocytes. In mutants of the cholera vibrio (which have lost the ability to chemotaxis), virulence decreases significantly, in Mob mutants (which have lost their mobility) either completely disappears or sharply decreases.

The factors of adhesion and colonization, through which the vibrio adheres to the microvilli and colonizes the mucosa of the small intestine. Adhesion factors include mucinase, soluble haemagglutinin / protease, neuraminidase, etc. They promote adhesion and colonization, as they destroy substances that make up mucus. Soluble hemagglutinin / protease promotes the separation of vibrios from the receptors of epithelial cells and their escape from the intestine into the external environment, providing them with epidemic spread. Neuraminidase strengthens the bond of cholerogen to epithelial cells and facilitates the penetration of toxins into cells, which increases the severity of diarrhea.

Cholera toxin is a cholerogen.

The so-called new toxins that can cause diarrhea, but do not have a genetic and immunological relationship to the cholerogen.

Dermoneyrotic and hemorrhagic factors. The nature of these toxic factors and their role in the pathogenesis of cholera are not well understood.

[13], [14], [15], [16], [17], [18]

Cholera Vibrio Endotoxins

Lipopolysaccharides V. Cholerae have a strong endotoxic property and cause a general intoxication of the body.

The main of the listed pathogenicity factors of the cholera vibrio is exotoxin cholerogen (CTX AB), which determines the pathogenesis of this disease. The molecule of cholerogen consists of two fragments - A and B. Fragment A consists of two peptides - A1 and A2, it has a specific property of cholera toxin and gives it the qualities of a superantigen. Fragment B consists of 5 identical subunits. It performs two functions: 1) recognizes the receptor (monosialoganglionide) of the enterocyte and binds to it; 2) forms an intramembrane hydrophobic channel for the passage of subunit A. Peptide A2 serves to bind fragments A and B. Actually, the toxic function is performed by peptide Aj (ADP-ribosyltransferase). It interacts with NAD, causes its hydrolysis; the resulting ADP-ribose binds to the regulatory subunit of adenylate cyclase. This leads to inhibition of hydrolysis of GTP. The resulting complex of GTP + adenylate cyclase causes hydrolysis of ATP with the formation of cAMP. (Another way to accumulate cAMP is cholerogen suppression of an enzyme that hydrolyses cAMP to 5-AMP). The manifestation of the function of the ctxAB gene coding for exotoxin synthesis depends on the function of a number of other pathogenesis genes, in particular tcp genes, toxR, toxS and toxT regulatory genes, hap (soluble haemagglutenin / protease) genes and pei (neuraminidase). Therefore, genetic control of the pathogenicity of V. Cholerae is complex.

As it turned out, there are two islands of pathogenicity in the chromosome of V. Cholerae. One of them is the genome of the filamentary, moderate converting phage STXf, and the other is the genome of the filiform, moderate converting phage VPIcp. Each of these pathogenetic islands contains cassettes of genes of said prophase, which determine the pathogenicity of the causative agent of cholera. The prophage CTXf carries the CTX genes, the genes of new toxins zot and ace, the ser gene (the synthesis of the adhesin), the ortU gene (synthesis of a product with an unknown function). The same gene cassette includes the pei gene and the phage region of RS2, which codes for replication, as well as integration of the prophage into chromosomes. The genes zot, ace and ortU are necessary for the formation of phage virions with the exception of the prophage from the causative agent chromosome.

The VPIcp prophylaxis carries the tcp genes (encode the production of pili (TKPA protein)), the toxT genes, toxR, act (an additional colonization factor, mobility genes (integrase and transposase)). The transcription of the virulence genes is regulated by three regulator genes: toxR, toxS, and toxT. These genes coordinate, at the level of transcription, change the activity of more than 20 genes of virulence, including genes ctxAB, tcp, etc. The main gene-regulator is the toxR gene. Its damage or absence leads to avirulence or to a decrease in the production of CTX and TCHA cholera toxin by more than 100 times. Perhaps, in this way, the coordinated expression of virulence genes in the islands of pathogenicity formed by moderate converting phages and in other species of bacteria is regulated. It is established that in V. Cholerae eltor chromosome there is one more prophage K139, but its genome is not well studied.

The hap gene is localized on the chromosome. Thus, virulence (pathogenicity) and epidemic ability of V. Cholerae are determined by 4 genes: ctxAB, tcp, toxR and hap.

To detect the ability of V. Cholerae to produce a cholerogen, various methods can be used.

Biological test on rabbits. When intramuscular introduction of cholera vibrios to rabbit-suckers (age not more than 2 weeks) they develop a typical cholera syndrome: diarrhea, dehydration and death of a rabbit.

Direct detection of the cholerogen by PCR, IFM or passive immune hemolysis reaction (the cholerogen binds to Gmj of erythrocytes, and when they add antitoxic antibodies and complement they are lysed). However, detecting only the ability to produce toxin is not enough to determine the epidemic danger of such strains. To do this, it is necessary to identify the presence of the hap gene, so it is better and more reliable to differentiate the toxigenic and epidemic strains of serogroup 01 and 0139 cholera vibrios by PCR using specific primers to detect all 4 genes of pathogenicity: ctxAB, tcp, toxR, and hap.

The ability of V. Cholerae not belonging to serogroups 01 or 0139 to cause sporadic or group diarrheal diseases in humans can be related either to the presence of LT or ST enterotoxins stimulating adenylate or guanylate cyclase systems, respectively, or to the presence of only ctxAB genes, but lack of hap gene.

During the seventh pandemic strains of V. Cholerae with different degree of virulence were isolated: cholerogenic (virulent), slightly cholerogenic (malovirulent) and noncholerogenic (neurulent). Noncholerogenic V. Cholerae, as a rule, show hemolytic activity, are not lysed by the cholera diagnostic phage of HDF (5) and do not cause human disease.

For the phage typing of V. Cholerae 01 (including the eltor) S. Mukherjee, sets of phages were proposed, which were then supplemented in Russia with other phages. A set of such phages (1-7) allows us to distinguish among the V. Cholerae 0116 phagotypes. To identify toxic and nontoxigenic V. Cholerae eltor in place of HDF-3, HDF-4 and HDF-5, phages of CTX * (lysing the toxigenic vibrio elter) and CTX (now non-toxicogenic eltor vibrios) are now proposed in Russia.

[19], [20], [21],

Resistance of cholera pathogens

Cholera vibrios survive well at low temperature; in the ice retain viability up to 1 month; in sea water - up to 47 days, in the river - from 3-5 days to several weeks, boiled mineral water persists for more than 1 year, in the soil - from 8 days to 3 months, in fresh stools - up to 3 days, on boiled products (rice, noodles, meat, cereals, etc.) survive 2-5 days, on raw vegetables - 2-4 days, on fruits - 1-2 days, in milk and dairy products - 5 days; when stored in the cold, the survival period is increased by 1-3 days; on linen laundry contaminated with excrements, stored up to 2 days, and on wet material - a week. Cholera vibrios at 80 ° C die after 5 minutes, at 100 ° C - instantly; highly sensitive to acids; under the influence of chloramine and other disinfectants die after 5-15 minutes. They are sensitive to drying and the action of direct sunlight, but they persist for a long time and even multiply in open reservoirs and wastewater rich in organic substances, having an alkaline pH and a temperature above 10-12 ° C. Highly sensitive to chlorine: a dose of active chlorine 0.3-0.4 mg / l of water for 30 minutes causes reliable disinfection from the cholera vibrio.

Pathogenic for human vibrios, not related to the species Vibrio Cholerae

More than 25 species belong to the genus Vibrio, of which, in addition to V. Cholerae, at least the following eight are capable of causing disease in humans: V. Rahaemolyticus, V. Alginolyticus, V. Vulnificus, V. Fluvialis, V. Fumissii, V. Mimicus, V damsela and V. Hollisae. All these vibrios are inhabitants of the seas and bays. Infection occurs by either bathing or eating food of marine origin. As it turned out, cholera and non-cholera vibrios can cause not only gastroenteritis, but also wound infections. This ability was found in V. Cholerae 01- and not 01-groups, in V. Parahaemolyticus, V. Alginolyticus, V. Mimicus, V. Damsela and V. Vulnificus. They cause inflammatory processes in soft tissues when they are damaged by the shell of marine animals or in direct contact with infected sea water.

Of the listed pathogenic non-cholerae vibrios, V. Parahaemolyticus, V. Alginolyticus, V. Vulnificus and V. Fluvialis are of greatest practical interest.

V. Parahaemolyticus - paragemolytic vibrio - was first isolated in Japan in 1950 during a large outbreak of foodborne infection caused by the use of semi-dried sardines (mortality was 7.5%). The causative agent for the genus Vibrio was established by R. Sakazaki in 1963. He divided the strains studied into 2 species: V. Parahaemolyticus and V. Alginolyticus. Both species are found in coastal sea water and its inhabitants, they are halophiles (Greek hals - salt); unlike conventional vibrios, halophilic ones do not grow on media without NaCl and reproduce well at high concentrations of it. The species belonging to halophilic vibrios is determined by their ability to ferment sucrose, form acetylmethyl carbinol, multiply in 10% NaCl with PV. All these signs are inherent in the species V. Alginolyticus, but absent in V. Parahaemolyticus.

The paragemolytic vibrio has three types of antigens: thermolabile flagellate H-antigens, heat-stable, not destroyed by heating to 120 ° C for 2 hours, O-antigens and surface K-antigens that decompose on heating. Freshly isolated V. Parahaemolyticus cultures have well-pronounced K-antigens, which protect living vibrios from agglutination by homologous O-sera. H-antigens in all strains are the same, but the monotrich's H antigens differ from the peritrichs H antigens. On the O-antigen of V. Parahaemolyticus are divided into 14 serogroups. Inside serogroups, vibrios are classified into serotypes of K antigens, the total number of which is 61. The antigenic scheme of V. Parahaemolyticus has been developed only for its strains isolated from humans.

The pathogenicity of V. Parahaemolyticus is related to its ability to synthesize hemolysin, which has an enterotoxic property. The latter is revealed using the Kanagawa method. Its essence lies in the fact that pathogenic for human V. Parahaemolyticus cause a clear hemolysis on blood agar containing 7% NaCl. On blood agar containing less than 5% NaCl, hemolysis causes many strains of V. Parahaemolyticus, and on blood agar with 7% NaCl only strains with enteropathogenic properties. Paragemolytic vibrio is found on the coasts of the Japanese, Caspian, Black and other seas. It causes food-borne diseases and dysentery-like diseases. Infection occurs when eating raw or semi-raw marine products infected with V-parahaemolyticus (sea fish, oysters, crustaceans, etc.).

Among the above eight species of non-cholerae vibrios, V. Vulnificus is the most pathogenic for humans, which was first described in 1976 as Beneckea vulnificus, and then in 1980 it was reclassified to Vibrio vulnificus. It is often found in sea water and its inhabitants and is the cause of various human diseases. Strains of V. Vulnificus of marine and clinical origin do not differ from each other either phenotypically or genetically.

Wound infections caused by V. Vulnificus rapidly progress and lead to the formation of tumors followed by necrosis of the tissue, accompanied by fever, chills, sometimes severe pain, in some cases require amputation.

V. Vulnificus has the ability to produce exotoxin. In animal experiments, it was found that the causative agent causes severe local damage with the development of edema and tissue necrosis followed by a fatal outcome. The role of exotoxin in the pathogenesis of the disease is being studied.

In addition to wound infections, V. Vulnificus can cause pneumonia in drowned people and endometritis in women after being in seawater. The most severe form of infection caused by V. Vulnificus is the primary septicemia associated with the consumption of raw oysters (possibly other marine animals). This disease develops very quickly: the patient has malaise, fever, chills and prostration, then severe hypotension, which is the main cause of death (lethality about 50%).

V. Fluvialis for the first time as a causative agent of gastroenteritis was described in 1981. It refers to a subset of noncholerogenic pathogenic vibrios that have arginine hydrolase but nontornithine and lysine decarboxylase (V. Fluvialis, V. Furnissii, V. Damsela, i.e., phenotypically similar to Aeromonas). V. Fluvialis is a frequent causative agent of gastroenteritis accompanied by severe vomiting, diarrhea, abdominal pain, fever and severe or moderate severity of dehydration. The main factor of pathogenicity is enterotoxin.

Epidemiology of cholera

The main source of infection is only a person - a patient with cholera or a vibrio carrier, as well as contaminated water. No animals in nature have cholera. The method of infection is fecal-oral. Ways of infection: a) main - through the water used for drinking, bathing and household needs; b) contact-household and c) through food. All major epidemics and cholera pandemics were associated with water. Cholera vibrios possess such adaptive mechanisms that ensure the existence of their populations both in the human body and in certain ecosystems of open water bodies. Abundant diarrhea, which causes cholera vibrio, leads to the cleansing of the intestines from competing bacteria and promotes a wide spread of the pathogen in the environment, primarily in sewage and in open reservoirs, where they are dumped. A person with cholera, isolates the pathogen in a huge amount - from 100 million to 1 billion per 1 ml of stool, the vibrio carrier releases 100-100,000 vibrios in 1 ml, the infecting dose is about 1 million vibrios. Duration of allocation of cholera vibrio in healthy carriers is from 7 to 42 days and 7-10 days in patients who have recovered. Longer release is very rare.

The peculiarity of cholera is that after it, as a rule, there is no long-term carrier and no stable endemic foci are formed. However, as already mentioned above, in connection with the contamination of open reservoirs with sewage containing large amounts of organic substances, detergents and table salt, in the summer, the cholera vibrio in them not only survives long, but even reproduces.

An important epidemiological significance is the fact that the 01-group cholera vibrios, both nontoxigenic and toxigenic, can persist for a long time in various aquatic ecosystems in the form of noncultivated forms. With the help of a chain polymerase reaction with negative bacteriological studies in a number of endemic CIS territories, vct-genes of the nonculturable forms of V. Chokrae were found in various reservoirs.

The endemic focal point of the cholera vibrio El Tor is Indonesia, the exit from it of this culprit of the seventh pandemic is believed to be due to the expansion of economic ties between Indonesia and the outside world after independence, and the duration and lightning development of the pandemic, especially its second wave, had lack of immunity to cholera and various social upheavals in the countries of Asia, Africa and America.

When a disease of cholera occurs, a complex of anti-epidemic measures is implemented, among which the leading and decisive is the active timely detection and isolation (hospitalization, treatment) of patients in acute and atypical form and healthy vibrio carriers; measures are being taken to curb possible ways of spreading the infection; special attention is paid to water supply (chlorination of drinking water), adherence to the sanitary and hygienic regime at food enterprises, children's institutions, public places; strict control is carried out, including bacteriological, for open reservoirs, immunization of the population is carried out, etc.

[22], [23], [24], [25], [26],

Symptoms of cholera

The incubation period with cholera varies from a few hours to 6 days, most often 2-3 days. Once in the lumen of the small intestine, cholera vibrios due to mobility and chemotaxis to the mucous membrane are sent to the mucus. To penetrate it, vibrios produce a number of enzymes: neuraminidase, mucinase, proteases, lecithinase, which destroy substances contained in mucus, and facilitate the progress of vibrios to epithelial cells. By adhesion, the vibrios attach to the glycocalyx of the epithelium and, losing their mobility, begin to multiply intensively, colonizing the microvilli of the small intestine (see color, incl., Figure 101.2), and simultaneously produce a large amount of exotoxin-cholerogen. Cholecar molecules bind to monosialoganglioside Gni! And penetrate the cell membrane, where the adenylate cyclase system is activated, and accumulating cAMP causes hypersecretion of liquid, cations and anions of Na, HCO, Cl, Cl from enterocytes, which leads to cholera diarrhea, dehydration and desalination. There are three types of disease:

• a violent, severe dehydrating diarrheal disease leading to the patient's death in a few hours;
• less severe course, or diarrhea without dehydration;
• asymptomatic course of the disease (vibrio-carrying).

With severe form of cholera, diarrhea appears in the patients, the stool becomes more frequent, the bowel movements become more abundant, take a watery character, lose the fecal odor and look like a rice broth (turbid liquid with floating mucus residues and epithelial cells). Then, debilitating vomiting is attached, first to the contents of the intestine, and then the vomit becomes a rice decoction. The temperature of the patient falls below the norm, the skin becomes cyanotic, wrinkled and cold - the cholera algid. As a result of dehydration, the blood thickens, cyanosis develops, oxygen starvation, kidney function sharply suffers, convulsions appear, the patient loses consciousness and death occurs. Mortality from cholera during the seventh pandemic varied from 1.5% in developed countries to 50% in developing countries.

Post-infectious immunity is strong, prolonged, repeated diseases are rare. Immunity is antitoxic and antimicrobial, due to antibodies (antitoxins persist longer than antimicrobial antibodies), immune memory cells and phagocytes.

Laboratory diagnostics of cholera

The main and decisive method for diagnosing cholera is bacteriological. Materials for research from the patient include bowel movements and vomit; on vibrio-carrying, investigate excrement; in persons who died from cholera, a ligated segment of the small intestine and the gallbladder are taken for examination; From the objects of the environment, water from open reservoirs and sewage are most often investigated.

When conducting a bacteriological study, the following three conditions must be observed:

• as soon as possible to sow the material from the patient (the cholera vibrio persists in the excrement for a short time);
• The dishes in which the material is taken should not be disinfected with chemicals and should not contain traces of it, since the cholera vibrio is very sensitive to them;
• Exclude the possibility of contamination and contamination of others.

Isolation of the culture is carried out according to the scheme: sowing on PV, simultaneously on alkaline MPA or any selective medium (TCBS is best). After 6 hours, examine the film formed on the PV, and, if necessary, do the reseeding on the second PV (the seeding of the cholera vibrio in this case is increased by 10%). With PV, they are done by reseeding on an alkaline MPA. Suspicious colonies (vitreous-transparent) are crossed to obtain a pure culture, which is identified by morphological, cultural, biochemical properties, mobility and finally typed using diagnostic agglutinating sera O-, OR-, Inaba and Ogawa and phage (HDF). Various variants of accelerated diagnostics are offered, the best of them is the luminescent-serological method. It allows to detect cholera vibrio directly in the test material (or after preliminary growth in two test tubes with 1% PV, in one of which a cholera phage is added) for 1.5-2 hours. For the accelerated detection of cholera vibrio, paper indicator discs consisting of 13 biochemical tests (oxidase, indole, urease, lactose, glucose, sucrose, mannose, arabinose, mannitol, inositol, arginine, ornithine, lysine), which allow to differentiate representatives of the genus Vibrio from the genera Aeromon as, Plesiomonas, Pseudomonas, Comamonas and from the family Enterobacteriaceae. For rapid detection of cholera vibrio in feces and in objects of the external environment, RPGA with an anti-inflammatory diagnosticum can be used. In order to identify noncultivated forms of cholera vibrio in the objects of the external environment, only the chain polymerase reaction method is used.

In cases where V. Cholerae is not Ol-group, they should be typed with the appropriate agglutinating sera of other serogroups. Isolation from a patient with diarrhea (including cholera-like) V. Cholerae not of the Ol-group requires the same anti-epidemic measures as in the case of the V. Cholerae Ol group. If necessary, these genes with the help of PCR determine the presence of pathogenicity genes ctxAB, tcp, toxR and hap.

Serological diagnosis of cholera has an auxiliary character. For this purpose, the agglutination test can be used, but it is better to determine the titer of vibriocidal antibodies or antitoxins (antibodies to the cholerogen are determined by immunoenzyme or immunofluorescence methods).

Laboratory diagnostics of non-cholera pathogenic vibrios

The main method for diagnosing diseases caused by noncholerous pathogenic vibrios is bacteriological using selective media such as TCBS, McConkey, etc. The attribution of the isolated culture to the genus Vibrio is determined based on the key features of the bacteria of this genus.

Treatment of cholera

Treatment of patients with cholera should consist primarily in rehydration and restoration of normal water-salt metabolism. To this end, it is recommended to use saline solutions, for example of the following composition: NaCl - 3.5; NaHC03 - 2.5; KC1 - 1.5 and glucose - 20.0 g per 1 liter of water. Such pathogenetically grounded treatment in combination with rational antibiotic therapy allows to reduce mortality in case of cholera up to 1% or less.

Specific prevention of cholera

To create artificial immunity, a vaccination against cholera was suggested , including the killed strains of Inaba and Ogawa; cholerogen-anatoxin for subcutaneous administration and an enteric chemical bivalent vaccine consisting of an anatoxin and somatic antigens of Inaba and Ogawa serotypes, since no cross immunity is formed. However, the duration of postvaccinal immunity is no more than 6-8 months, so vaccinations are carried out only on epidemic indications. In the foci of cholera, antibiotic prophylaxis, in particular tetracycline, to which the cholera vibrio shows high sensitivity has proved to be quite good. For the same purpose, other antibiotics effective against V. Cholerae can be used.