P2-118 The Prevalence of Antibiotic-resistant Bacteria in Fresh Produce Purchased from Farmers Markets and Grocery Outlets

Tuesday, August 2, 2016
America's Center - St. Louis
Michelle Stark, Virginia Tech, Blacksburg, VA
Stephanie Pollard, Virginia Tech, Blacksburg, VA
Renee Boyer, Virginia Tech, Blacksburg, VA
Josh Boron, Virginia Tech, Blacksburg, VA
John di Stefano, Virginia Tech, Blacksburg, VA
Monica Ponder, Virginia Tech, Blacksburg, VA
Robert C. Williams, Virginia Tech, Blacksburg, VA
Introduction: Antibiotic-resistant bacteria present a growing public health challenge. Although a number of sources of antibiotic-resistant bacteria have been identified, very little is known about the presence of antibiotic-resistant bacteria on fresh fruits and vegetables.

Purpose: The purpose of this study was to assess the presence of antibiotic-resistant bacteria on fresh produce acquired at farmers markets and a grocery store in Virginia.

Methods: Nine different produce commodities (180 total samples) from five different farmers’ markets and a retail store were separately homogenized and enriched in tryptic soy broth. Homogenates were spread plated on selective media for Enterococci and enteric bacteria. Typical colonies were tested for susceptibility to tetracycline, sulfamethoxazole, ceftazidime, trimethoprim, ampicillin, vancomycin, and gentamicin using the Kirby Bauer disk diffusion assay. The zone of inhibition around each antibiotic was measured. Susceptibility limits were determined using CLSI Document M100-S21 (M2).

Results: Produce isolated enteric bacteria were resistant to tetracycline (68%), sulfamethoxazole (71%), ceftazidime (69%), and trimethoprim (94%). The Enterococci isolated were resistant to vancomycin (49%), ampicillin (32%), and gentamicin (27%). Produce samples traditionally grown touching soil (e.g., green onion) had a significantly greater number of enteric bacteria resistant to ceftazidime (P = 0.009) and trimethoprim (P = 0.03) when compared to produce that does not touch the soil (e.g., tomato). Proximity to soil did not influence enterococci resistance. Generally there were no differences in bacterial resistance profiles between products purchased from farmers’ markets versus the grocery; however, more isolates recovered from samples purchased at farmers’ markets were susceptible to ampicillin when compared to retail samples (P < 0.05).

Significance: Antibiotic resistant profiles from bacteria recovered from fresh produce may provide important information. Identifying the prevalence of antibiotic resistant bacteria in fresh produce may raise awareness of potential environmental contamination routes.