|ANDERSON, PHELUE - Texas Veterinary Medical Diagnostics Laboratory|
|Crippen, Tawni - Tc|
|CALDWELL, DAVID - Texas A&M University|
|Byrd Ii, James - Allen|
Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2010
Publication Date: 5/1/2011
Citation: Beier, R.C., Anderson, P.N., Hume, M.E., Poole, T.L., Duke, S.E., Crippen, T.L., Sheffield, C.L., Caldwell, D.J., Byrd II, J.A., Anderson, R.C., Nisbet, D.J. 2011. Characterization of Salmonella enterica isolates from turkeys in commercial processing plants for resistance to antibiotics, disinfectants, and a growth promoter. Foodborne Pathogens and Disease. 8:593-600.
Interpretive Summary: Many different kinds of disinfectants are used on farms, in food processing plants, in hospitals, and in homes. Also, growth promotants are used on the farm to help increase the growth of animals. In each of these places there is also widespread use of a variety of antibiotics. Little is known about the impact of disinfectants or growth promotants on the spread of antibiotic resistance. Certain bacteria named Salmonella are a major health hazard from poultry, eggs, and produce. We found that Salmonella isolated from turkeys in commercial processing plants had a low incidence of multiple-resistance to antibiotics, and a low level of resistance to disinfectants used on the farm. High levels of growth promotant resistance were found in some Salmonella and may affect the type of bacterial strains present in these treated poultry. This information is important in understanding the way antibiotic-resistant bacteria are affected by disinfectants and growth promotants and may help in pathogen control during food processing.
Technical Abstract: Salmonella enterica serovars isolated from turkeys in commercial processing plants were characterized for susceptibility to antibiotics, disinfectants, disinfectant components, and the organoarsenical growth promotant 4-hydroxy-3-nitrophenylarsonic acid (3-NHPAA) and its metabolites NaAsO2 (As[III]) and Na2HAsO4 7H2O (As[V]). The 130 Salmonella serovars tested demonstrated a low incidence of resistance to gentamicin (GEN), kanamycin (KAN), sulfamethoxazole (SMX), streptomycin (STR), and tetracycline (TET). Isolates that demonstrated resistance to antibiotics were most often multiply-resistant. Salmonella enterica serovar Hadar was resistant to KAN, STR, and TET, and S. enterica serovar Typhimurium was resistant to GEN, SMX, and STR. No cross-resistance was observed between the antibiotics and disinfectants tested. The Salmonella had a MIC distribution for chlorhexidine of 1–8 mug/mL, which is considered resistant to chlorhexidine. All isolated Salmonella serovars were susceptible to triclosan. The benzyldimethylammonium chloride component of DC&R*R was primarily responsible for its disinfection activity. The didecyldimethylammonium chloride (C10AC) component of disinfectant P-128 was primarily responsible for its disinfecting activity, and the C10AC component was the most active ammonium chloride tested. These Salmonella serovars appeared to be on the border of having low resistance to benzalkonium chloride, with MICs of 16–32 mug/mL. The MICs for the organoarsenical, 3-NHPAA, remained relatively consistent between processing Plant 1 and Plant 2 at primarily 4096 mug/mL. However, MICs for the 3-NHPAA metabolites (As[III] and As[V]) were higher in Plant 1 compared to Plant 2. In Plant 1, 76% of the isolates had MICs >256 mug/mL for As(III), and 92% of the isolates had MICs >1024 mug/mL for As(V). In Plant 2, all of the isolates had MICs less than or equal to 256 mug/mL for As(III), and 90% of the isolates had MICs less than or equal to 1024 mug/mL for As(V). Only 4 different Salmonella serovars were isolated from Plant 1, but 10 serovars were isolated from Plant 2. Salmonella enterica serovar Derby isolates from Plant 1 were highly resistant to As(III) and As(V), with MIC values >1024 mug/mL and >8192 mug/mL, respectively. These levels could have been high enough to kill the Salmonella serovars that were observed in Plant 2, but not observed in Plant 1, namely, S. enterica serovars Agona, S. Anatum, S. Brandenburg, S. Meleagridis, S. Reading, and S. Typhimurium.