Escherichia coli that produce Shiga Toxins: Prevalence and Possible Risk in Soft Cheese

Abstract

Though soft cheese is vital nutrition source for many people, yet if made from unpasteurized milk, it poses a concern to public health e.g Escherichia coli that can produce Shiga toxins (STEC). In this study totally, 150 soft cheese (50 Karish, 50 Tallaga, 40 processed and 10 feta cheeses) samples were collected indiscriminately from several areas in El-Gharbia Governorate and tested for STEC. By culturing on EMB, E.coli were detected in (18/50) 36%, (12/50) 24%, (1/40) 2.5% and none (0/10) of the examined samples, respectively. One hundred suspected isolates were examined biochemically; thirteen identified isolates were serotyped: of them 11 strains were confirmed as pathogenic STEC serotypes (O78:K80, O44:K74, O114:K90, O124:K63, O103:K- and O145:K-). Seven strains that obtained from Karish and Tallaga cheese were tested for virulence factors as Shiga toxins (stx1 and stx2) and intimin (eaeA) genes using polymerase chain reaction (PCR). Three out of the seven (42.9%) strains have stx1 and eaeA genes, 1/7 (14.3%) carry stx2 and eaeA genes, 1/7 (14.3%) carry stx1, stx2 and eaeA genes while 2/7 (28.6%) carry only eaeA gene. STEC strains that have shiga toxin with adherence genes are considered to pose high risk of illness that necessitates strict hygienic measures enforcement during soft cheese production.