β-Lactam Resistance in Salmonella Strains Isolated from Retail Meats in the United States by the National Antimicrobial Resistance Monitoring System between 2002 and 2006

Abstract

Ampicillin-resistant (Amp r ) Salmonella enterica isolates (n ‫؍‬ 344) representing 32 serotypes isolated from retail meats from 2002 to 2006 were tested for susceptibility to 21 other antimicrobial agents and screened for the presence of five beta-lactamase gene families (bla CMY , bla TEM , bla SHV , bla OXA , and bla CTX-M ) and class 1 integrons. Among the Amp r isolates, 66.9% were resistant to five or more antimicrobials and 4.9% were resistant to 10 or more antimicrobials. Coresistance to other ␤-lactams was noted for amoxicillin-clavulanic acid (55.5%), ceftiofur (50%), cefoxitin (50%), and ceftazidime (24.7%), whereas less than 5% of isolates were resistant to piperacillin-tazobactam (4.9%), cefotaxime (3.5%), ceftriaxone (2%), and aztreonam (1.2%). All isolates were susceptible to cefepime, imipenem, and cefquinome. No Salmonella producing extended-spectrum beta-lactamases was found in this study. Approximately 7% of the isolates displayed a typical multidrugresistant (MDR)-AmpC phenotype, with resistance to ampicillin, chloramphenicol, streptomycin, sulfonamide, tetracycline, plus resistance to amoxicillin-clavulanic acid, cefoxitin, and ceftiofur and with decreased susceptibility to ceftriaxone (MIC > 4 g/ml). Pulsed-field gel electrophoresis results showed that several MDR clones were geographically dispersed in different types of meats throughout the five sampling years. Additionally, 50% of the isolates contained bla CMY , 47% carried bla TEM-1 , and 2.6% carried both genes. Only 15% of the isolates harbored class I integrons carrying various combinations of aadA, aadB, and dfrA gene cassettes. The bla CMY , bla TEM , and class 1 integrons were transferable through conjugation and/or transformation. Our findings indicate that a varied spectrum of coresistance traits is present in Amp r Salmonella strains in the meat supply of the United States, with a continued predominance of bla CMY and bla TEM genes in ␤-lactam-resistant isolates.

Comparison of the Prevalences and Antimicrobial Resistances of Escherichia coli Isolates from Different Retail Meats in the United States, 2002 to 2008

“…The resistance of chicken isolates to ß-lactams AMC, FOX, AXO, and TIO was significantly greater than that of other meat isolates, whereas the turkey isolates were more resistant to KAN, AMP, FIS, CIP, and TET compared to other meat isolates (P Յ 0.05). Similar results were observed with Salmonella isolates from retail poultry meat monitoring (40). Although, in general, the pork isolates had lower resistance than the poultry isolates, their resistance to KAN, STR, AMP, FIS, and TET was significantly higher than that of the beef isolates (P Յ 0.05).…”

“…In the last 10 years, this resistance phenotype has emerged in both humans and food animals in the United States (12,40,44). TIO is the only cephalosporin approved for systemic use in food animals in the United States.…”

First study of Salmonella in meat in Romania

“…Resistance to tetracycline (80.53%) and streptomycin (81.20%) tended to occur at relatively high frequencies, higher than reported by Thong and Modaressi in 2011 (73.8% and 57.9%) [11], Yildirim et al in 2011 (67.6% and 61.7%) [13], and Zhao et al in 2009, who observed resistance of S. Typhimurium to streptomycin (63%) and tetracycline (61%) [23]. A higher resistance rate to tetracycline was reported by Mahmud et al in 2011 (93%) [14].…”

Comparative Genomics of 28 Salmonella enterica Isolates: Evidence for CRISPR-Mediated Adaptive Sublineage Evolution

“…The bla CMY-2 gene encodes a cephalomycinase that exhibits extended resistance to many ␤-lactams, including narrow-, expanded-, and broad-spectrum cephalosporins, whereas SugE has been shown to confer decreased susceptibility to quaternary ammonium compounds, including common disinfectants such as cetylpyridinium chloride (14,81). The close physical proximity of sugE to the bla CMY-2 ␤-lactamase gene is of particular public health significance, as it points to the potential coselection of linked CDS carried by extrachromosomal elements and their role in the spread of MDR phenotypes among veterinary and human pathogens.…”