Molecular characterization of enterohemorrhagic E. coli O157 isolated from animal fecal and food samples in Eastern China.

Shaohui Wang,Pingping Liu,Donghua Shao,Beibei Li,Shuxiao Zhang,Jianchao Wei,Zhe Liu,Zhiyong Ma,Zixue Shi

doi:10.1155/2014/946394

Abstract

Objective. To elucidate the extent of food contamination by enterohemorrhagic Escherichia coli (EHEC) O157 in Eastern China. Methods. A total of 1100 food and animal fecal samples were screened for EHEC O157. Then, molecular characterization of each isolate was determined. Results. EHEC O157 was isolated as follows: pig feces, 4% (20/500); cattle feces, 3.3% (2/60); chicken feces, 1.43% (2/140); pork, 2.14% (3/140), milk, 1.67% (1/60); and chicken meat, 1.67% (1/60). The stx1, stx2, eae, and hlyA genes were present in 26.7% (8/30), 40% (12/30), 63.3% (19/30), and 50% (15/30) of the O157 isolates, respectively. Molecular typing showed that strains from fecal and food samples were clustered into the same molecular typing group. Furthermore, the isolates from pork and pig feces possessed the same characterization as the clinical strains ATCC35150 and ATCC43889. Biofilm formation assays showed that 53.3% of the EHEC O157 isolates could produce biofilm. However, composite analyses showed that biofilm formation of EHEC O157 was independent of genetic background. Conclusions. Animal feces, especially from pigs, serve as reservoirs for food contamination by EHEC O157. Thus, it is important to control contamination by EHEC O157 on farms and in abattoirs to reduce the incidence of foodborne infections in humans.

Highlights

Enterohemorrhagic Escherichia coli (EHEC) is an important emerging zoonotic foodborne pathogen that can cause watery and/or bloody diarrhea, hemorrhagic colitis (HC), hemolytic-uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP)
EHEC O157 was detected in 4% (20/500) of the pig samples, 3.3% (2/60) of the cattle samples, 1.43% (2/140) of the chicken samples, and 1% (1/100) of the duck samples
The results indicated that biofilm formation occurred in 16 (53.3%) of the EHEC O157 strains after a 24 h incubation at 37∘C (Figure 1, Table 3)

Summary

Introduction

Enterohemorrhagic Escherichia coli (EHEC) is an important emerging zoonotic foodborne pathogen that can cause watery and/or bloody diarrhea, hemorrhagic colitis (HC), hemolytic-uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP). EHEC O157 is recognized as a major etiological agent of these diseases [1,2,3]. Biofilm is composed of surface-bound microbes enclosed in an amorphous extracellular matrix [6], which is often an assembly of exopolysaccharides, proteins, and nucleic acids [7]. Residence in a biofilm community offers certain advantages to bacteria, such as enhanced resistance to the environmental stresses. Food contamination has been identified as a potential source of pathogenic EHEC O157 transmission in humans [8, 9].

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Results

Conclusion