Feces of Finisher Pigs Have a Low Prevalence of Shiga Toxin-Producing Escherichia coli that are of Public Health Importance

R G Amachawadi,J Bai,R D Goodband,S S Dritz,X Shi,M D Tokach,J M Derouchey,T G Nagaraja,J C Woodworth

doi:10.4148/2378-5977.8014

Abstract

Shiga toxin-producing Escherichia coli (STEC) are major food pathogens that cause mild to bloody diarrhea, including complications of kidney damage and even death, particularly in children and elderly. Seven serogroups of STEC, O26, O45, O103, O111, O121, O145, and O157, called top-7 STEC, are responsible for the majority of STEC infections in the US. Shiga toxins, which are proteins secreted by the bacteria, are major virulence factors contributing to the disease. There are two Shiga toxin types, 1 and 2, encoded stx1 and stx2 gene, respectively and each type has several subtypes. Another major virulence factor, intimin, a protein on the bacterial cell surface encoded by the eae gene, mediates attachment of the bacterial cell to the intestinal epithelial cells. The severity of STEC infections in humans is dependent on the Shiga toxin type and subtype. Cattle are a major reservoir of STEC and carry the bacteria in the hindgut and shed them in the feces, which is a source of contamination of food and water. Swine have also been shown to harbor STEC in the gut and shed in the feces, and a few outbreaks of STEC infections in humans have been linked to pork and pork products. The STEC does not cause infections in cattle, but in swine, particularly in weaned piglets, it causes edema disease. We conducted a study that utilized molecular (polymerase chain reaction [PCR]) and culture methods to determine prevalence and characteristics of top-7 STEC in the feces of finisher pigs collected from ten pig flows in eight states. A total of 598 fecal samples were collected and analyzed. The overall prevalence of Shiga toxin genes, stx1 or stx2, was 70.1%, and eae was detected in 66.7% of the samples. Based on the PCR method, among the top-7 STEC, O26 (14.4%), O121 (22.9%) and O157 (18.5%) were the predominant serogroups detected. None of the E. coli O157 isolated, a serogroup implicated in pork-linked outbreaks, contained Shiga toxin genes. Although a number of fecal samples were positive for the top-7 STEC serogroups, culture method identified one strain each of stx1-positive O26 (0.2%) and O103 (0.2%), and 23 strains of stx2-positive O121 (3.9%). Serogroups O26 and O103 possessed stx1a subtype and eae, which have the potential to cause serious infections in humans. Serogroup O121 carried the stx2e subtype, which is involved in causing edema disease in swine and rarely implicated in human infections. Our results indicated that

Highlights

Shiga toxin-producing Escherichia coli (STEC) are major foodborne pathogens and seven serogroups, O26, O45, O103, O111, O121, O145, and O157 account for the majority of the STEC-associated illnesses in humans.[4]
Shiga toxin-producing Escherichia coli (STEC) are major food pathogens that cause mild to bloody diarrhea, including complications of kidney damage and even death, in children and elderly
Shiga toxins, which are proteins secreted by the bacteria, are major virulence factors contributing to the disease

Summary

Introduction

Shiga toxin-producing Escherichia coli (STEC) are major foodborne pathogens and seven serogroups, O26, O45, O103, O111, O121, O145, and O157 account for the majority of the STEC-associated illnesses in humans.[4]. Shiga toxins, which are proteins secreted by the bacteria, are major factors responsible for the disease. There are two types of Shiga toxins, 1 and 2, and within each type there are several subtypes Another protein, intimin, encoded by the eae gene, which mediates attachment of E. coli to intestinal cells, is an important factor for infection. Serotype E. coli O157:H7 is the frequent cause of several major outbreaks, which are estimated to cause approximately $405 million in losses every year.[5] Similar to cattle, swine harbor STEC in the gut and shed them in the feces, which can be a source of food contaminations. The disease in pigs is caused by STEC that produce a subtype of Shiga toxin, called 2e. Our objective was to utilize PCR and culture methods to determine prevalence, isolate STEC strains of top-7 serogroups, and subtype Shiga toxin genes to assess public health importance

Objectives

Results

Conclusion