title: Molecular analysis of multidrug resistance in Shiga toxin-producing Escherichia coli O157:H7 isolated from meat and dairy products.
abstract: Shiga toxin-producing Escherichia coli (STEC) O157:H7 is an important food-borne pathogen that has been implicated in numerous disease outbreaks worldwide. Little is known about the extent and molecular basis of antimicrobial resistance in STEC O157:H7 of food origin. Therefore, the current study aimed to characterize the genetic basis of multidrug resistance in 54 STEC O157:H7 strains isolated from 1600 food samples (800 meat products and 800 dairy products) collected from different street venders, butchers, retail markets, and slaughterhouses in Egypt. Thirty-one of 54 (57.4%) isolates showed multidrug resistance phenotypes to at least three classes of antimicrobials. The highest incidence of antimicrobial resistance was to kanamycin (96.8%), followed by spectinomycin (93.6%), ampicillin (90.3%), streptomycin (87.1%), and tetracycline (80.6%). PCR and DNA sequencing were used to screen and characterize integrons and antibiotic resistance genes, and 29.6% and 5.6% of isolates were positive for class 1 and class 2 integrons, respectively. β-Lactamase-encoding genes were identified in 63.0% of isolates as follows: blaTEM₋₁ and blaTEM₋₅₂ in 35.2% and 1.9% isolates respectively; blaCMY₋₂ in 13.0% isolates; blaCTX-M in 5.6% isolates; blaSHV₋₁₂ in 5.6% isolates; and blaOXA₋₁ in 1.9% isolate. The plasmid-mediated quinolone resistance genes were identified in 13.0% of isolates as follows: qnrB, qnrS, and aac(6')-Ib-cr in 5.6%, 3.7%, and 3.7% isolates, respectively. Finally, the florfenicol resistance gene floR was identified in 7.4% of isolates. This study demonstrated that meat and dairy products are potential sources of multidrug resistant STEC O157:H7. To our knowledge, this is the first report of the occurrence of class 2 integrons, qnrB, qnrS, and aac(6')-Ib-cr in STEC O157:H7.
authors.affiliation: Department of Bacteriology, Mycology and Immunology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
authors.forename: Ashraf M
authors.initials: AM
authors.lastname: Ahmed
authors.affiliation: Laboratory of Food Microbiology and Hygiene, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japan. Electronic address: tadashis@hiroshima-u.ac.jp.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shimamoto
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003611:Dairy Products / Q000382:microbiology*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D018432:Drug Resistance, Multiple / Q000235:genetics; D004534:Egypt; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000235:genetics; D032023:Integrons / Q000235:genetics; D008460:Meat / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D001618:beta-Lactamases
keywords: Antimicrobial resistance; Beef; Dairy; Integron; O157:H7