Bacteria of the Escherichia coli group (ECG) and Salmonella: characteristics, sanitary and indicative value, methods of determination, regulation in food products.

BGKP. The bacteria of the Escherichia coli (coliform) group include the genera Escherichia (typical representative of E. coli ), Citrobacter (typical representative of C. colicitrovorum ), Enterobacter (typical representative of E. aerogenes), which are combined into one family Enterobacteriaceae due to their common properties.

General characteristics of BGKP : – rods are gram-negative, short; – not spore-forming; – on End’s medium they give red colonies with a metallic sheen – E. coli , red – enterobacteria, pink – citrobacteria, b / color – lactose – negative. biochemical properties. Most bacteria of the Escherichia coli group (ECG) do not liquefy gelatin, coagulate milk, break down peptones with the formation of amines, ammonia, hydrogen sulfide, and have high enzymatic activity against lactose, glucose and other sugars, as well as alcohols. They do not have oxidase activity. Sustainability. Bacteria of the Escherichia coli group are neutralized by conventional pasteurization methods (65-75°C). At 60°C, Escherichia coli dies within 15 minutes. A 1% solution of phenol causes the death of the microbe in 5-15 minutes. Sanitary and indicative value. Bacteria of the genus Escherichia intestinal inhabitants of humans and animals, and their detection in water and PP is evidence of fresh faecal contamination. Bacteria of the genera Citrobacter and Enterobacter can be found everywhere: in the soil, on plants, less often in the intestines. It is believed that they are the result of changes in ischerichia after their exposure to the external environment and therefore are indicators of older faecal contamination. BGKP value:

– in raw milk indicates – an epidemiological danger

– after a few hours at 8-10 ° C – about the violation of the conditions of storage and sale, protractors.

– appeared. BGKP after pasteurization is regarded as the 2nd contamination

– the presence of BGKP in the finished product indicates – poor washing and disinfection of equipment.

Genus Salmonella . Salmonellosis are among the most common toxicoinfections. Finding Salmonella is always indicative of faecal contamination. Salmonella are resistant to high concentrations of sodium chloride (especially in media containing protein) and desiccation. Retain their viability in room dust, in various soils (97 months), in the water of open reservoirs (up to 45 days). Being in PP, especially in meat, Salmonella is very resistant to heat treatment. Salting and smoking meat have little effect on Salmonella. During the reproduction of Salmonella in milk, its appearance and taste do not change; pasteurization of milk for 30 minutes at 85ºС under production conditions contributes to the complete destruction of these bacteria. A person becomes infected with salmonella as a result of the consumption of meat and meat products. Milk and dairy products are much less likely to cause food poisoning. Infection of milk mainly occurs through contaminated dishes, milking machines, hands of milkers, etc. Salmonellosis pathogens can get into food products made from vegetable raw materials (salads and table sauces) not only during the production process, but also with food ingredients, in particular with dry vegetable seasonings and spices.

Microbiol Sanitary and hygienic value Quantity criterion, Characteristic
BGKP For Har-ki sanitary-epidemic. the state of food products and the conditions for their manufacture More than 10 3 CFU / g (cm 3 ) Presence of E. coli Low sanitary. the state of the food product and its conditional manufacturer. Fresh fecal contamination
Salmonella -//-and for safety data for the consumer detection in 25g of product Low sanitary. the state of the food product and the condition of its manufacture, the danger of the product for people

BGKP identification:

● Seeding on the enrichment medium – Kessler, simultaneous identification by gaseous formations: there is gas formation – BKGP is possible;

● Identification of CGB on Endo medium: Take 1 ml from gas (+) tubes and inoculate on Endo solid medium, identify CGB colonies by color, differentiate by genera depending on the color of the colonies: If there are red, pink and pale pink cultures – it means there are BGKP, if there are no colonies – there is no BGKP. If there are colonies, but colorless – suspicion of pathogens. Further, the genera of BGKP are identified by color: 1) red – with metallic. shade. – Escherichia 2) pink – Enterobacter 3) pale pink – with mucus – Klebsiela 4) pale pink – citrobacter, cerrations 5) colorless (lactose (-)) – Proteus 6) transparent small – pathogenic

● Identification on the Coser medium: cultivation on the medium with glucose/citric acid, T=43°C, 24h. M / o citrate (+) change the color of the dye from green to cornflower blue. M / o citrate (-) do not change color.

Determined by the number of positive samples in 3 test tubes.

Salmonella are pathogenic, they are analyzed in 25 g of the product, they should not be there. Serves as an indicator of pathogens.

Salmonella detection is carried out in 4 stages

1) primary (direct) sowing – Sowing on the environment of End and Ploskirav for a day and T = 37 0 C. On cf. Enda – transparent colonies,

2) enrichment (inoculation on liquid selective media, temperature control)

3) sowing from the enrichment medium after enrichment on dense diagnostic media, temperature control – on cf. Ploskirava – transparent, but smaller than on Endo medium

4) confirmation by establishing the enzymatic and serological properties of Salmonella

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