Date

2014

Author

Kyere, Emmanuel Owusu

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Even though Escherichia coli (E. coli) is part of the intestinal microflora of healthy human beings and warm blooded animals, some strains of E. coli can be important food borne pathogens that can cause a wide spectrum of diseases, ranging from self-limiting to life threatening intestinal and extra-intestinal illnesses. Pathogenic E. coli that affect the intestines of humans have been grouped into six main pathotypes: Shiga-toxin-producing E. coli (STEC); of which enterohaemorrhagic E. coli (EHEC) is a pathogenic sub-group; enteropathogenic E. coli (EPEC); enterotoxigenic E. coli (ETEC); enteroaggregative E. coli (EAEC); enteroinvasive E. coli (EIEC); and diffusely adherent E. coli (DAEC). In this study, random assessment of the most common subtypes of E. coli that were collected from street foods in Van, Turkey was done. Out of 37 food samples, 28 E. coli isolates (i.e., 76% of food samples) were isolated. 28 E. coli isolates were screened for indicator genes for pathogenic subgroups using Polymerase Chain Reaction (PCR). For STEC screening, we used 6 genes (i.e., stx1, stx2, eae, fliC, hlyA and rfbE), while we used one gene for each pathogenic subgroup; lt/st genes for ETEC bfpA gene for EPEC, aggR gene for EAEC, ipaH gene for EIEC and daaD gene for DAEC. Further genomic characterization of E. coli isolates was done by pulsed field gel electrophoresis (PFGE) with restriction enzyme XbaI. In addition, phenotypic characterization of E. coli isolates was performed by disk diffusion method for determining their antimicrobial resistance profiles. PCR screening of indicator genes for pathogenic E. coli subgroups revealed that E. coli isolates, used in this study, did not belong to any pathogenic subgroups. Molecular characterization of 28 E. coli isolates by PFGE detected 25 distinguishable PFGE patterns. Only 2 PFGE patterns (i.e., pattern 2 and pattern 3) were shared by more than one isolate; three isolates from raw milk and two isolates from herby cheese had the same pattern. Apart from them, each isolate had a unique band pattern. Antimicrobial susceptibility testing by disc diffusion method revealed that, 53.5% of the E. coli isolates showed resistance to ampicillin, 46.4 % of the E. coli isolates showed resistance both sulphafurazole and tetracycline. 15 isolates were multidrug resistant (i.e., resistant to more than 2 antimicrobials) which represent about 53.5% of the total isolates used. This study provides baseline information on antimicrobial susceptibility of E. coli isolates from various foods in Turkey that can serve as a benchmark for future research. Moreover, the prevalence of E. coli in Turkish foods should be monitored periodically because of its large diversity. E. coli’s large diversity and multiple resistance to a wide range of antibiotics might affect public health regarding to emerging pathogenic E. coli isolates with antimicrobial resistance. Stakeholders must be informed and public health education about personal hygiene should be intensified to avoid future outbreaks.

Subject Keywords

Escherichia coli., Pathogenic microorganisms., Microbial sensitivity tests., Foodborne diseases., Food

URI

http://etd.lib.metu.edu.tr/upload/12617606/index.pdf
https://hdl.handle.net/11511/23776

Collections

Graduate School of Natural and Applied Sciences, Thesis