AmpC- and Extended-spectrum β-lactamase-producing Enterobacteriaceae detected in fresh produce in central Ohio

Salad vegetables purchased from farmers’ markets and grocery stores in central Ohio during the summers of 2015 and 2016 were tested for the presence of Enterobacteriaceae resistant to extended spectrum cephalosporins and carbapenems, Salmonella contamination, and coliform bacteria count. A total of 364 samples were collected from 36 farmers’ markets and 33 grocery stores. Using selective media we found 23 (6.3%) samples which produced Enterobacteriaceae expressing an AmpC β-lactamase phenotype, with 11 (3.0%) confirmed to contain bla CMY , and six (1.6%) samples which produced Enterobacteriaceae  with an ESBL β-lactamase phenotype, with one (0.3%) confirmed to contain bla CTX-M . All bla CMY and bla CTX-M were isolated from leafy greens. No Salmonella spp. or carbapenem-resistant Enterobacteriaceae were recovered from fresh produce samples. Adjusting for year, the geometric mean coliform count differed (P < 0.05) between produce types, tomatoes (15 CFU/mL) lower than cucumbers (77.4 CFU/mL) and leafy greens (75.0 CFU/mL). Coliform count also differed (P < 0.05) between years with 19.6 CFU/mL in 2015 and 96.0 CFU/mL in 2016. There was no difference in coliform count or the prevalence of Enterobacteriaceae expressing AmpC or ESβL phenotypes in produce purchased from farmers’ markets or grocery stores.