1. General description of the Enterobacteriaceae family bacteria.
2. Biological properties of E. coli, antigen structure and classification of pathogenic intestinal rods.
3. Microbiological diagnostics of Escherichiosis: diarrhoeal Escherichiosis and coli-bacteriosis.
4. Epidemiology and pathogenesis of diarrhoeal Escherichiosis. Specific features of immunity in such cases of Escherichiosis.
5. Principles of prophylaxis and medical treatment of such type of diarrhea.
PROCEDURE OF PRACTICAL SESSION
Task 1. Study the preparation from the pure cultures of E. coli O1: K1”and ”E. coli O55: K59:H1”, microscopically; draw them in the protocol.
Task 2. Study cultural properties of causative agents on Endo and EMB agar: to sketch colonies, to
make conclusions and to mark the plan of the further researches.
Task 3. Study the antigenic structure of Escherichia and estimate the reaction of agglutination on glass
with Escherichiosis polyvalent agglutination OK- and monovalent group sera.
Task 4. Study the growth of E. coli on the Triple sugar iron (TSI) agar.
Task 5. Study the biochemical properties of E. coli on the Hiss mideum.
Task 6. Study the sensitivity of E. coli to antibacterial preparations.
Task 7. Study the main antimicrobial drugs used for treatment, prevention and diagnostics of suppurative diseases. Write them in your copybook.
RECOMMENDATIONS FOR PRACTICAL WORK
All types of E. coli. have identical staining and morphological properties. Therefore, stained by Gram method of pure culture of E. coli in preparation it is possible to see gram- negative monobacteria of middle sizes. Morphological and tinctorial properties of cultures of pathogenic (E. coli O55:Ê59:Í1) and conditional-pathogenic (E. coli O1:Ê1) E. coli do not differ.
Endo and EMB agar are special media capable to expose the ability of bacteria to form a pigment. All colonies of E.coli on the Endo agar are convex, rounded with the even edges, with middle sizes and crimson with the metallic sheen. On the EMB agar the E. coli formed dark blue-violet colonies with the green sheen.
The antigen structure of E. coli the relation of microorganism to the pathogenic serogroup is set, because colonies of pathogenic and conditional-pathogenic intestinal rods on the Endo and EMB agars do not differ from each other. For this purpose put the reaction of agglutination on glass with the esherichiosis polivalent agglutinating OKA-serum (contains agglutinins for 22 O- and K-antigen of E. coli), and further – with OKB-, OKC-, OKD- or OKE-sera (the reaction of agglutination on glass is performed according to the general method).
Agglutinable E. coli ferments the glucose, lactose which enters to the component of the medium to acid and gas. Discoloration of all volume of medium occurs in comparison with initial (a rose color of medium changed on yellow).
Agglutinable E. coli ferments the Hiss media with glucose, lactose, mannitol, maltose with formation of acid and gas. The proof of the fermentation of sugars is the discoloration of the media, and of gasification - formation of bubbles of gas. E. coli does not ferment sucrose, gave the negative reaction on the sulphuretted hydrogen at the cultivation of it on the peptone water, but the reaction on the indol is positive.
The size of the zones of growth retardation of microorganisms around the disks depends on die degree of sensitivity of the causative agent to a given antibiotic. The strain is considered stable if the diameter of the zone is less than 10 mm, weakly sensitive if it averages 11-15 mm, and sensitive if it reaches 15-25 mm. Zones exceeding 25 mm in diameter indicate high sensitivity of the microorganism to the given antibiotic.
Agglutinating escherichiosis polivalent OKA-serumisdiagnosticpreparation, which contains specific antibody to the superficial (Ê-) and somatic (Î-) antigens of E. coli, which together with the proper antigens of E. coli cause their agglutination. Preparation is obtained from the serum of the rabbit, hyperimmunized by the mixture of corpuscular antigens of E. coli (O18ac:K84, O23: K11, O75:Ê_ and other). Preparation is used for the raising of reaction of agglutination on glass with the target of reference determination of the serogroup of pathogenic E. coli. Preparation is canned by chloroform, packed up and lyophilized. At the reaction of agglutination it is necessary to make the working solution of the serum 1:10.
Agglutinating adsorbed esherichiosis monovalency serum O55. isdiagnosticpreparation, which contains specific antibody to the somatic (O55) antigen of E. coli, which together with antigen O55 of E. coli causes their agglutination. Preparation is obtained from the serum of the rabbit, hyperimmunized by a corpuscular O55 antigen of E. coli with the subsequent adsorption of unspecific antibodies. Preparation is used for the raising of reaction of agglutination (with the warmed culture) to determine O55 antigen of E. coli, the serogroup of E. coli.
Coli-bacterinis treatment and prophylactic preparation,which contains lyophilical cells of the E. coli culture of M17, which express antagonistic characteristics in relation to the definite pathogenic intestinal bacteria. Preparation is used for prevention and treatment of the dysbacteriosis at children. Coli-bacterin is administered to children from 6-month age. While using this remedy the simultaneous application of vitamins is necessary.
Bifidumbacterinis treatment and prophylactic preparationwhich contains the lyophilical cells Bifidobacterium bifidum is used for prevention and treatment of the dysbacteriosis in children.
Bificolis therapeutic and prophylactic preparation which contains lyophilical cells of the E. coli culture M17 and B. bifidum is used for normalization of the intestinal microflora at dysbacteriosis.
Lactobacterinis therapeutic preparation,contains obligate for the man milky-sour bacteria and products of their vital activity, which show antagonistic activity in relation to the pathogenic and to the conditional-pathogenic enterobacteria. It is produced in the form of tablets used for the medical treatment of dysbacteriosis at children.