Multiplex polymerase chain reaction for detection and characterization of shiga toxigenic Escherichia coli (STEC)

Abstract

Escherichia coli is ubiquitous in the cow's environment that is contaminated by feces, and it is also a frequent cause of bovine mastitis. Thus, the present study was targeted at the rapid detection and characterization of shiga toxigenic E. coli (STEC) in bovine fecal and milk samples. Twenty two strains of E. coli (39.29%) were isolated from 56 diarrheic calves, while only 5 strains (20.83%) were isolated from apparently normal contact calves. Moreover, 20 strains of E. coli (25%) were isolated from milk samples collected from 80 animals suffering from mastitis and subclinical mastitis. E. coli serovars yielded from bacteriological examination of milk samples were similar to that of fecal samples. Serogroup-specific multiplex polymerase chain reaction (PCR) assay could detect all the bacteriologically positive samples as well as 4 strains (7.98%), O157:H7 and 3 strains (5.36%), O111 from diarrheic calves and 2 strains (8.33%), O111 from normal calves. Such samples were proved to be negative by bacteriological examination. Multiplex PCR for detection of genes encoding accessory
STEC virulence factors, such as shiga toxin type-2 (stx2) and intimin gene (eaeA) revealed the specificity of such gene to O157:H7 serovars and small number of other sero-groups.