Isolation of shiga toxin-producing Escherichia coli O157:H7/NM from hamburger and chicken nugget

Abstract

Aims: This study was conducted to determine the prevalence rate, virulence genes and antimicrobial resistance of Escherichia coli O157:H7/NM isolated from hamburger and chicken nugget in Isfahan, Iran. Material and Methods: From June 2013 to July 2013, a total of 190 hamburger (120) and chicken nugget (70), were collected from four randomly selected factories in Isfahan, Iran. They were evaluated for the presence of E. coli O157:H7/NM using microbiological culture and polymerase chain reaction. Statistical analysis was performed using SPSS software version 16.0 (SPSS Inc., Chicago o, IL, USA). Results: From a total of 190 samples analyzed four samples (2.1%) were contaminated with E. coli O157. All of the E. coli O157 were isolated from hamburger samples (3.3%) and chicken nugget samples were negative. Of four E. coli O157 isolated, only one sample was serotype E. coli O157:H7 and others were serotype E. coli O157:NM. Among four E. coli O157:H7/NM isolates, one strain was positive for all stx1, stx2, eaeA and ehxA genes. One strain was positive for stx2 gene. The other two were negative for these genes. All isolates (100%) were resistant to one or more antimicrobial agents. Conclusions: The results of this study showed that hamburger could be a significant source of E. coli O157:H7 and E. coli O157:NM serotypes in Iran and multi-resistance was found in 27% of E. coli O157 strains and this is a major public health concern.