Salmonella, including antibiotic-resistant Salmonella, from flies captured from cattle farms in Georgia, U.S.A

• Published in: The Science of the total environment 2018-03, Vol.616-617, p.90-96
• Main Authors: Xu, Yumin, Tao, Sha, Hinkle, Nancy, Harrison, Mark, Chen, Jinru
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents; Antibiotic resistance; Cattle; Diptera - microbiology; Drug Resistance, Multiple, Bacterial; Farms; Fly; Georgia; Microbial Sensitivity Tests; Salmonella; Salmonella - isolation & purification
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.10.324

Flies can be transmission vehicles of Salmonella from cattle to humans. This study determined the prevalence of Salmonella in/on flies captured from 33 cattle farms, including 5 beef and 28 dairy farms, in Georgia, USA, and characterized antibiotic resistance profiles of the isolated Salmonella. Twenty-six out of the 33 cattle farms (79%) and 185 out of the 1650 flies (11%) tested positive for Salmonella in the study. The incidence of Salmonella-positive flies varied from farm to farm, ranging from 0 to 78%. Among the 185 Salmonella isolated from flies, 29% were resistant to ampicillin, 28% to tetracycline, 21% to amoxicillin/clavulanic acid, 20% to cefoxitin, and 12% to streptomycin. Incidences of resistance against other tested antibiotics were low, ranging from 0 to 3%. Furthermore, 28% of the Salmonella isolates were multidrug resistant, demonstrating resistance to 3 or more antibiotics. The minimal inhibitory concentrations of ampicillin, cefoxitin, streptomycin, and tetracycline against the Salmonella isolates ranged from 32 to >2048, 64 to 2048, 128 to 1024, and 32 to 1024μg/mL, respectively. These data suggest that flies could be effective vehicles of transmitting antibiotic resistant Salmonella and disseminating antibiotic resistance genes on cattle farms, posing risks to human and animal health. [Display omitted] •The prevalence of fly-borne Salmonella from cattle farms in the U.S.A. was studied.•Prevalence of fly-borne Salmonella varied from farm to farm, ranging from 0 to 78%.•Salmonella resistance to tetracycline, β-lactams, and streptomycin was common.•Salmonella resistance to gentamicin and nalidixic acid was rare.•Twenty-eight percent of the Salmonella of fly origin were multidrug resistant.