Bacteriological flora of meat and meat products.

The bacterial flora of meat and meat products consumed by Egyptian people was estimated. The highest counts, either for total viable bacteria and coliforms were found in sausage and in raw kofta and kabab, but they markedly decreased after grilling. Heavy loads of bacteria were also observed in the fresh beef samples, frozen imported beef, minced meat, and liver. The luncheon meat samples gave the lowest total bacterial counts and seemed to be free of coliforms. Gram-negative rods constituted most of the total isolates of the different types of meat. In the heat-treated meat products, the most predominant bacteria were Gram-positive cocci. The predominating organisms in fresh beef were Pseudomonas, Bacillus and Micrococcus spp. as well as E. coli and Lactobacillus plantarum. On adopting the total viable and coliform standard counts suggested in the U.S.A., it was found that some of the meat products (sausage, raw kabab and kofta) contained higher total and coliform counts than that of the standard, whereas the total counts of the other meat products were lower.

Occurrence of Bacillus cereus in milk and milk products in Egypt.

The presence of B. cereus spores in raw, pasteurized, and dry milk as well as in Damietta and processed cheese and in a baby food product was investigated, using three selective agar media for enumeration. The organism was detected in 70, 90, and 50% of milk, in processed and Damietta cheese samples, respectively. Spore counts varied from 10(2) to 10(6) and from 10 to 10(2)/ml of raw and pasteurized milk, respectively. In the two types of cheese and dried milk spore densities reached 10 to 10(3)/g. Egg yolk agar (E) gave better recovery rate of B. cereus when compared to the other two media, containing lithium chloride plus polymyxine B- sulphat (I) or polymyxin B-sulphate alone (KG). The latter agar medium favoured the development of larger colonies, surrounded by a more distinctive zone of precipitation.

Factors affecting germination and growth of Bacillus cereus spores in milk.

The effect of salt concentration, acidity, and storage temperature on the spore germination of Bacillus cereus and the growth rate of the organism was investigated. Increasing the amount of salt to more than 5% or acidifying the milk to pH 5.0 or 4.5 greatly affected the germination and growth of B. cereus spores. When a culture of Streptococcus lactis was used as an acidifying agent, B. cereus showed a normal growth rate during the first 12 h, followed by a sharpe reduction in numbers. When B. cereus spores were inoculated in reconstituted dry milk or baby food, a higher multiplication rate was obtained at 30 degrees C than at 8 degrees C.

On the transformation of coliform types, proper and irregular forms.

Physiological changes have been induced in strains of E. coli I and its irregular forms, using a basal synthetic medium and addition of sodium pyruvate, or glucose, or yeast extract, or peptone. Changes in biochemical patterns, using the IMViC reactions plus growth at 44.5 degrees C, were induced, thus brining transformations between the regular types and irregular forms. Ultra-violet irradiation of E. coli I for 90 seconds may turn it into a methyl-red negative strain, while education of E. coli III for producing acid and gas at 44.5 degrees C was possible. Thus, E. coli I could be transformed to give the same reactions as the untyped form 1 of Geldreich (1966) through U.V. irradiation, while E. coli III may give the biochemical reactions of E. coli I via heat-resistance and training in MacConkey broth. The relationship between regular and irregular coliforms was also verified by phage typing. The results obtained were discussed both qualitatively, using "lytic activity", and quantitatively in terms of "efficiency of plating", especially with sewage-derived phages and irregular coliforms.