MOLECULAR CHARACTERIZATION OF ANTIBIOTIC RESISTANT SHIGA TOXIN-PRODUCING ESCHERICHIA COLI FROM CLINICAL AND FOOD SAMPLES

Abstract

ABSTRACT Antimicrobial resistance (AMR) in foodborne pathogens can be a consequence of using antimicrobial drugs in food-producing animals. The emergence of antimicrobial resistance in foodborne pathogens is of great concern due to adverse patient health outcomes and the possibility of transferring genes encoding AMR to other clinically relevant pathogens. One of these bacteria is Shiga toxin-producing Escherichia coli (STEC), which can cause serious illness in humans for a haemolytic uremic syndrome (HUS). This study characterized and determined the mechanism of antibiotic resistance in 46 Shiga toxin-producing Escherichia coli strains collected by the U.S. Food and Drug Administration from food and clinical samples. All isolates were resistant to novobiocin. Forty-two isolates were resistant to tetracycline, and ten isolated were resistant to ampicillin. Seven isolates were resistant to trimethoprim-sulfamethoxazole and kanamycin. PFGE typing of forty-six isolates by XbaI grouped into more than ten clusters, with similarities ranging from 30 to 70%. Most isolates were positive for one or more of the fifteen virulence genes, primarily found in STEC. All isolates typically carried more than 20 kb plasmids, and most of the isolates had large and small plasmids. Twenty-nine isolates were positive by PCR for X plasmid replicon type, twenty isolates for FIB plasmid and seven isolates were positive for Y plasmid replicon type. Three isolates were positive for I1 and HI1 genes. Only two isolates were positive for B/O and W plasmid replicon type. Invasion and persistence in the HRT-18 cell line by multidrug-resistant STEC showed higher persistence and invasion. Whole-genome sequencing was used as a clinical diagnostic tool to detect antibiotic resistance genes in the STEC and virulence genes. The further role of efflux pumps that plays an important role in antibiotic resistance was analysed based on genome sequences data. These STEC isolates have several virulent and antibiotic-resistant genes, which can be added to mobile genetic elements to understand their contribution to the potential transmission to other microorganisms. Surveillance and characterization of STEC can provide helpful information about the trend of STEC infection and identify STEC serotypes that are highly pathogenic to humans.