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Abstract
SUMMARY:Milk as well as milk products under the influence of their high nutritive value are considered excellent media for pathogenic as well as non pathogenic bacteria. This can lead to milk borne outbreaks caused by different types of bacteria such as Escherichia.
Two hundreds and fourty random samples were collected from different localities in Assiut City including to raw milk samples (90) and some dairy products as Damietta cheese, Kareish cheese, Yoghurt, Cooking butter and Ice cream (30 samples each).
Escherichia spp. could be detected in 6, 27, 17, 12, 28, 21, 17 and 26 in samples of raw milk collected from Dairy farms, Dairy shops, Street vendors, Damietta cheese, Kareish cheese, Yoghurt, Cooking butter and Ice cream with percentages of 20,90,56.67,40,93.33,70,56.7, and 86.67%, respectively, using H&L agar. With averages of 3X104, 7.5X106, 1.6X107, 1.5X106, 1.6X107, 12.5x106, 9x104 , and 11.5x106 cfu/ml-g, respectively.
Escherichia spp. could be isolated from 3, 25, 15, 9, 20, 21, 17 and 25 samples of raw milk samples collected from Dairy farms, Dairy shops, Street vendors, Damietta cheese, Kareish cheese, Yoghurt, Cooking butter and Ice cream with percentages of 10, 83.33, 30, 66.67, 70, 56.67 and 83.33 %,respectively, using E. M. B. agar. Their average values were 2.5X102, 3.5X106, 1X106, 3.5X104, 1.1X107, 9x106,-- and 1x107cfu /ml-g, respectively.
Comparison between H&L agar and E.M.B. agar for isolation of Escherichia spp. revealed the superiority of the first medium in cultivating the bacteria.
Biochemical tests used for differentiation between different Escherichia spp. revealed that the incidence of E. coli on the top with a percentage of 45.83% on H&L agar and 40.42% on E.M.B. agar, E. vulneris percentage was 9.58% on H&L agar and 7.92% on E.M.B. agar, E. hermannii had incidence of 5% on H&L agar and 4.17% on E.M.B. agar, E. fergusonii percentage was 1.76% on H&L agar and 1.25% on E.M.B. agar, E. blattae and E. albertii with a percentage of 1.25% for both media used.
Latex agglutination test was done on 4 samples of E. coli isolated on Sorbitol MacConkey agar showed colorless colonies (non sorbitol fermenter). 3 positive samples for E. coli O157:H7 in an incidence of 75%
6 samples of E. albertii previously identified by biochemical tests were estimated by Polymerase Chain Reaction (PCR), where the result were negative for 5 samples. However, one sample was positive. So, genetic sequencing showed be carried out for the isolated E. albertii samples and creating specific primers for locally isolated strains.
The public health significance of the organisms and the precautions, which should be taken to control these organisms in dairy industry, as well as, the suggested sanitary measures, were also discussed