Abstract
Isolates of Enterohaemorrhagic E.coli O157:H7 were isolated from 51 and 41 of locally produced bovine and ovine soft cheese samples. Their identification were confirmed based on the biochemical reactions and both the morphological cultural and serological properties. Presumptive E.coli O157:H7 isolates obtained by using the conventional selective plating on the chromogenic agar were tested further for the presence of both O157 and H7 antigenes using the latex agglutination test antisera. The current microbiological studies revealed that 31 (33.70 %) out of 92 bovine and ovine soft cheese samples were positive for E.coli O157:H7. The highest non significant (P>0.05) prevalence level of E.coli O157:H7 was found in the ewe᾿s soft cheese samples (36.59 %) followed by cow᾿s soft cheese samples (31.37 %). Agar well diffusion bioassay method was used for measuring the antibacterial activity of the crude bacteriocin that was produced by Lactobacillus rhamnosus GG-ATCC against Escherichia coli and the closely related sensitive strains such as L.acidophilus LA-K and L.acidophilus ROO52. The crude bacteriocin that was produced by the L.rhamnosus GG-TACC exhibited significantly (P<0.05) the highest antibacterial potency (100 %) against both the closely related strains of lactobacilli and the stressed E.coli O157:H7 by the activation of the LPS. The activation of the natural LPS of inoculated pasteurized milk had significantly (P<0.05) influenced the inactivation degree of the crude bacteriocin against E.coli O157:H7. There was a significant (P<0.05) reduction in the viable counts of stressed E.coli O157:H7 after each exposure time period (6, 24 and 48 hrs.) to the crude bacteriocin at room storage temperature. An overall conclusion on the basis of the current results pointed out that complete elimination of viable bacterial cells was not achieved neither in the stabilized milk (Activation of LPS) nor after subjecting the stabilized milk to the action of the crude bacteriocin produced by L.rhamnosus GG-ATCC at room storage temperature.
Highlights
E.coli (STEC) espicially the serotype O157Milk is a perishable food which is highly that could be found in their feces and susceptible to bacterial spoilage since it can be approximately 75% of the haemorrhagic colitis regarded as a good medium for the growth and outbreaks were linked to the consumption of multiplication of different kinds of spoilage bovine derived products such as raw milk that and pathogenic bacteria (1 and 2)
Agar well diffusion bioassay method was used for measuring the antibacterial activity of the crude bacteriocin that was produced by Lactobacillus rhamnosus GG-ATCC against Escherichia coli and the closely related sensitive L.acidophilus LA-K and L.acidophilus ROO52
The current microbiological studies revealed that 31(33.70 %) out of 92 bovine and ovine soft cheese samples were positive for E.coli O157:H7
Summary
E.coli (STEC) espicially the serotype O157Milk is a perishable food which is highly that could be found in their feces and susceptible to bacterial spoilage since it can be approximately 75% of the haemorrhagic colitis regarded as a good medium for the growth and outbreaks were linked to the consumption of multiplication of different kinds of spoilage bovine derived products such as raw milk that and pathogenic bacteria (1 and 2). In Iraq milk is produced by a large of small infection which harbored the E.coli O157:H7 holders with small quantities of milk leading in their intestinal tracts without showing any to both the milk collection and delivery to the clinical symptoms (5 and 6). This condition dairy processing plant time consuming. Tokar Crude bacteriocin that extracted from and Teger (4) mentioned that the cattle were a Lactobacillus rhamnosus GG-ATCC in natural reservoir for the shiga toxin producing combination with activation of the naturally lactoperoxidase system provide new opportunities for controlling the pathogenic E.coli O157:H7 and extending milk shelf life (8). This study aimed to inactivate the vital metabolic bacterial enzymes with blocking their metabolism and ability to multiply by the synergistic antibacterial effect of the crude bacteriocin that extracted from L.rhamnosus GGATCC in combination with the activated LPS against E.coli O157:H7 in raw milk that stored at room temperature (30OC)
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