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Characterization of Salmonella enterica isolates from turkeys in commercial processing plants for resistance to antibiotics, disinfectants, and a growth promoter

Beier, Ross C., Anderson, Phelue N., Hume, Michael E., Poole, Toni L., Duke, Sara E., Crippen, Tawni L., Sheffield, Cynthia L., Caldwell, David J., Byrd, James A., Anderson, Robin C., Nisbet, David J.
Foodborne pathogens & disease 2011 v.8 no.5 pp. 593
Salmonella enterica subsp. enterica serovar Derby, Salmonella enterica subsp. enterica serovar Hadar, Salmonella enterica subsp. enterica serovar Typhimurium, ammonium chloride, antibiotic resistance, arsenic, benzalkonium chloride, chlorhexidine, cross resistance, disinfectants, gentamicin, growth promotion, kanamycin, meat processing plants, metabolites, minimum inhibitory concentration, multiple drug resistance, roxarsone, serotypes, streptomycin, sulfamethoxazole, tetracycline, turkeys
Salmonella enterica isolates from turkeys in two commercial processing plants (1 and 2) were characterized for susceptibility to antibiotics, disinfectants, and the organoarsenical growth promoter, 4-hydroxy-3-nitrophenylarsonic acid (3-NHPAA, roxarsone), and it’s metabolites, NaAsO2 (As(III)) and Na2HAsO4 7H2O (As(V)). The 130 Salmonella serovars tested demonstrated a low incidence of resistance to the antibiotics gentamicin (GEN), kanamycin (KAN), sulfamethoxazole (SMX), streptomycin (STR), and tetracycline (TET). Isolates resistant to antibiotics were most often multidrug resistant. Serovars Hadar and Typhimurium were resistant to KAN, STR, and TET and GEN, SMX, and STR, respectively. All isolated Salmonella serovars were resistant to the disinfectant chlorhexidine with minimum inhibitory concentrations (MICs; 1–8 mg=mL), and they were susceptible to triclosan and benzalkonium chloride. The didecyldimethylammonium chloride component was the most active ammonium chloride tested. No cross-resistance was observed between antibiotics and disinfectants. The MICs for 3-NHPAA (4096 mg=mL) were consistent between processing Plant 1 and Plant 2, but MICs for the 3-NHPAA metabolites (As(III) and As(V)) were higher in Plant 1 than in Plant 2. In Plant 1, 76% of the isolates had MICs >256 mg=mL for As(III) and 92% of the isolates had MICs >1024 mg=mL for As(V). In Plant 2, all of the isolates had MICs 256 mg=mL for As(III) and 90% of the isolates had MICs 1024 mg=mL for As(V). Only 4 Salmonella serovars were isolated from Plant 1, but 10 serovars were isolated from Plant 2. S. enterica serovar Derby from Plant 1 was highly resistant to As(III) and As(V) with MICs >1024 and >8192 mg=mL, respectively, suggesting previous exposure to high arsenic metabolite concentrations. These levels may have been high enough to kill other Salmonella serovars, thus possibly explaining the lack of serovar diversity observed in Plant 1. The application of a growth promoter may affect the serovar diversity in treated birds.