Survival Enterohaemorrhagic E.coli O157in locally produce soft cheese in Baghdad city and studying the effect of some physical factors on its viability

Abstract

A total of 24 samples of three different kinds of locally produced soft cheese manufactured from raw milk of Cows , Buffaloes and Ewes ( 8 samples of each) were collected at weekly intervals from different areas of Baghdad city in the period from the beginning of December 2007 till the end of January 2008. The main objective of this study was to isolats , identify and enumerate Enterohaemorrhagic E.coli O157from locally produced soft cheese , besides that , to study the effect of cheese storage temperature (4 C) and different salt concentration solutions on the viability and survival of E.coli O157 in stored cheese . Data demonstrate that 11 out 24 of samples 45.84% were found to have Enterohaemorrhagic E.coli O157 and their average counts were 1.6× 104 CFU/gm. The result of statistical analysis demonstrate that cheese samples manufactured from cows raw milk had significantly ( P> 0.05) higher E.coli O157 counts and isolation rates over both cheese samples that were manufactured from Ewes and buffaloes raw milk . the average count of Enterohaemorrhagic E.coli O157 in cheese manufactured from cows milk were 3.8× 104 CFU/gm and the isolation percentage was 75% while their average counts in cheese manufactured from Ewes and buffaloes milk were 7.3 ×103 & 2.4 ×103 CFU/gm respectively and the isolation percentages were 37.5 % & 12.5% respectively. Data revealed that all soft cheese samples that were found to have Enterohaemorrhagic E.coli O157 and stored at refrigeration temperature (4 C) had non significant ( P<0.05) reduction in the average counts of E.coli O157after 3 weeks of storage and this indicate that the refrigeration storage temperature (4 C) had no significant effect on the viability and survival of E.col O157 .All soft cheese samples that were found to have Enterohaemorrhagic E.coli O157 were stored in brine solutions at different salt concentrations such as 2.5%, 5%,7% and 10% for 24 hr,1 week, 2weeks & 3weeks . Data revealed that brine solution at high concentration of salt such as 10% had non significant effect on the viability and survival of E.coli O157after 3 weeks of storage.