Abstract #415

Section: Food Safety
Session: Food Safety
Format: Oral
Day/Time: Tuesday 10:15 AM–10:30 AM
Location: Wekiwa 5
# 415
Antibiotic resistance of bacteria from commercial silages in Israel.
Zwi Weinberg*1, Shlomo Sela1, Yaira Chen1, Vladislav Volchinski1, Judith Kraut-Cohen1, Eddie Cytryn1, 1ARO, The Volcani Center, Rishon Le Zion, Israel.

Antibiotic resistance has become a major issue in health care treatment with the emergence of multidrug resistant pathogens, which is attributed to the excessive use of antibiotics in medicine and in agriculture. Accumulating evidence suggests that agricultural sources such as sewage effluents, biosolids and animal manure are potential sources of antibiotic resistant bacteria and resistance genes. The objective of the current study was to determine the magnitude of antibiotic resistance in lactobacilli and enterobacteria in commercial wheat and corn/sorghum silages in Israel. Mixed corn-sorghum silage and wheat silage were sampled at 2 commercial cattle feeding centers in Israel. Grab samples were taken at a depth of 10 cm from the center (pH = 3.9 in both silages) and shoulders (pH = 6.8 and 4.4, respectively) of each bunker silo. Isolates of Enterobacteriaceae and Lactobacillus were screened on ampicillin, tetracycline, ciprofloxacin, ceftriaxone, erythromycin kanamycin and vancomycin. Surprisingly, in both types of silage, the vast majority of lactobacilli isolates were resistant (based on EUCAST MIC clinical breakpoint values) to all the 7 tested antibiotics. These isolates are currently being screened for the presence of clinically relevant antibiotic resistance genes to determine the potential for horizontal-transfer to other bacteria. The resistance of the enterobacterial isolates was significantly lower than that of the lactobacilli, however all of the isolates were resistant to at least 2 of the 5 tested antibiotics, and some isolates were resistant to all 5. Interestingly, isolates from the corn-sorghum silage (sewage irrigation) were significantly more resistant than those isolated from the wheat silage (rain irrigated) (resistant to 3.25 of the screened antibiotics vs.2.5, respectively). This study demonstrates the vast scope of antibiotic resistance in silage, which may contribute to antibiotic resistance propagation through the food chain.

Key Words: silage, antibiotic resistance