Beta-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 beta-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 multidrug-resistant (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 > or = 4 microg/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 beta-lactam-resistant isolates.
Project description:A total of 133 Salmonella isolates recovered from retail meats purchased in the United States and the People's Republic of China were assayed for antimicrobial susceptibility, the presence of integrons and antimicrobial resistance genes, and horizontal transfer of characterized antimicrobial resistance determinants via conjugation. Seventy-three (82%) of these Salmonella isolates were resistant to at least one antimicrobial agent. Resistance to the following antibiotics was common among the United States isolates: tetracycline (68% of the isolates were resistant), streptomycin (61%), sulfamethoxazole (42%), and ampicillin (29%). Eight Salmonella isolates (6%) were resistant to ceftriaxone. Fourteen isolates (11%) from the People's Republic of China were resistant to nalidixic acid and displayed decreased susceptibility to ciprofloxacin. A total of 19 different antimicrobial resistance genes were identified in 30 multidrug-resistant Salmonella isolates. The bla(CMY-2) gene, encoding a class A AmpC beta-lactamase, was detected in all 10 Salmonella isolates resistant to extended-spectrum beta-lactams. Resistance to ampicillin was most often associated with a TEM-1 family beta-lactamase gene. Six aminoglycoside resistance genes, aadA1, aadA2, aacC2, Kn, aph(3)-IIa, and aac(3)-IVa, were commonly present in the Salmonella isolates. Sixteen (54%) of 30 Salmonella isolates tested had integrons ranging in size from 0.75 to 2.7 kb. Conjugation studies demonstrated that there was plasmid-mediated transfer of genes encoding CMY-2 and TEM-1-like beta-lactamases. These data indicate that Salmonella isolates recovered from retail raw meats are commonly resistant to multiple antimicrobials, including those used for treating salmonellosis, such as ceftriaxone. Genes conferring antimicrobial resistance in Salmonella are often carried on integrons and plasmids and could be transmitted through conjugation. These mobile DNA elements have likely played an important role in transmission and dissemination of antimicrobial resistance determinants among Salmonella strains.
Project description:Extended-spectrum ?-lactamase (ESBL)-producing Salmonella are one of the most important public health problems in developed countries. ESBL-producing Salmonella strains have been isolated from humans in Asian countries neighboring Japan, along with strains harboring the plasmid-mediated extended-spectrum cephalosporin (ESC)-resistance gene, ampC (pAmpC). However, only a few studies have investigated the prevalence of ESC-resistant Salmonella in chicken products in Japan, which are the main vehicle of Salmonella transmission. The aim of this study was to investigate the prevalence of ESBL-producing, pAmpC-harboring, or carbapenem-resistant Salmonella in chicken products in Japan. In total, 355 out of 779 (45.6%) chicken product samples collected from 1996-2010 contained Salmonella, resulting in 378 distinct isolates. Of these isolates, 373 were tested for resistance to ESCs, cephamycins, or carbapenems. Isolates that showed resistance to one or more of these antimicrobials were then examined by PCR and DNA sequence analysis for the presence of the bla(CMY), bla(CTX-M), bla(TEM), and bla(SHV) resistance genes. Thirty-five resistant isolates were detected, including 26 isolates that contained pAmpC (bla(CMY-2)), and nine ESBL-producing isolates harboring bla(CTX-M) (n = 4, consisting of two bla(CTX-M-2) and two bla(CTX-M-15 genes)), bla(TEM) (n = 4, consisting of one bla(TEM-20) and three bla(TEM-52) genes), and bla(SHV) (n = 1, bla(SHV-12)). All pAmpC-harboring and ESBL-producing Salmonella isolates were obtained from samples collected after 2005, and the percentage of resistant isolates increased significantly from 0% in 2004 to 27.9% in 2010 (P for trend = 0.006). This increase was caused in part by an increase in the number of Salmonella enterica subsp. enterica serovar Infantis strains harboring an approximately 280-kb plasmid containing bla(CMY-2) in proximity to ISEcp1. The dissemination of ESC-resistant Salmonella containing plasmid-mediated bla(CMY-2) in chicken products indicates the need for the development of continuous monitoring strategies in the interests of public health.
Project description:Salmonella enterica serotype Newport isolates resistant to at least nine antimicrobials (including extended-spectrum cephalosporins), known as serotype Newport MDR-AmpC isolates, have been rapidly emerging as pathogens in both animals and humans throughout the United States. Resistance to extended-spectrum cephalosporins is associated with clinical failures, including death, in patients with systemic infections. In this study, 87 Salmonella serotype Newport strains were characterized by pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing and examined for the presence of class 1 integrons and bla(CMY) genes. Thirty-five PFGE patterns were observed with XbaI, and three of these patterns were indistinguishable among isolates from humans and animals. Fifty-three (60%) Salmonella serotype Newport isolates were identified as serotype Newport MDR-AmpC, including 16 (53%) of 30 human isolates, 27 (93%) of 29 cattle isolates, 7 (70%) of 10 swine isolates, and 3 (30%) of 10 chicken isolates. However, 28 (32%) Salmonella serotype Newport isolates were susceptible to all 16 antimicrobials tested. The bla(CMY) gene was present in all serotype Newport MDR-AmpC isolates. Furthermore, the plasmid-mediated bla(CMY) gene was transferable via conjugation to an Escherichia coli strain. The transconjugant showed the MDR-AmpC resistance profile. Thirty-five (40%) of the isolates possessed class 1 integrons. Sequence analyses of the integrons showed that they contained aadA, which confers resistance to streptomycin, or aadA and dhfr, which confer resistance to trimethoprim-sulfamethoxazole. One integron from a swine isolate contained the sat-1 gene, which encodes resistance to streptothricin, an antimicrobial agent that has never been approved for use in the United States. In conclusion, Salmonella serotype Newport MDR-AmpC was commonly identified among Salmonella serotype Newport isolates recovered from humans and food animals. These findings support the possibility of transmission of this organism to humans through the food chain.
Project description:Twenty-one Salmonella and 54 Escherichia coli isolates, recovered from food animals and retail ground meats, that exhibited decreased susceptibilities to ceftiofur and ceftriaxone were shown to possess a bla(CMY) gene. The bla(CMY-4) gene was identified in an E. coli isolate recovered from retail chicken and was further shown to be responsible for resistance to cephalothin, ampicillin, and amoxicillin-clavulanic acid and elevated MICs of ceftriaxone, cefoxitin, and ceftiofur.
Project description:Salmonella spp. producing extended-spectrum beta-lactamases (ESBLs) have been reported in many countries, but there is no information on their prevalence in Africa. ESBL-producing Salmonella enterica serotype Isangi and S. enterica serotype Typhimurium strains have been noted in South Africa since 2001. A total of 160 consecutive isolates of Salmonella spp. were collected from 13 hospitals located in different cities in South Africa over a 5-month period from December 2002 to April 2003. All strains were screened for production of ESBLs by the double disk diffusion test and for AmpC production by assessing resistance to cefoxitin. bla(SHV), bla(TEM), bla(CTX-M), and bla(CMY-2) were sought from all ESBL-positive and cefoxitin-resistant isolates. A total of 15.6% (25 of 160) isolates produced SHV or TEM ESBLs, and 1.9% (3 of 160) produced CMY-2. Nine S. enterica serotype Typhimurium, eight S. enterica serotype Isangi, and three S. enterica serotype Muenchen strains produced either TEM-63 or a derivative of TEM-63 designated TEM-131. Both TEM-63 and TEM-131 have an isoelectric point of 5.6, and their sequences have the following amino acid substitutions compared to the TEM-1 sequence: Leu21Phe, Glu104Lys, Arg164Ser, and Met182Thr. Additionally, TEM-131 has an Ala237Thr substitution. ESBL-producing Salmonella spp. have become a significant public health problem in South Africa with particular implications for the treatment of serious nontyphoidal Salmonella infections in children, for whom extended-spectrum cephalosporins were the preferred treatment.
Project description:A total of 136 <i>Salmonella</i> isolates from chicken feces and meat samples of the top 12 integrated chicken production companies throughout Korea were collected. Among the 17 ESC-resistant <i>Salmonella</i>; <i>bla</i><sub>CTX-M-15</sub> was the most prevalent gene and two strains carried <i>bla</i><sub>TEM-1</sub>/<i>bla</i><sub>CTX-M-15</sub> and <i>bla</i><sub>CMY-2</sub>, respectively. The transferable <i>bla</i><sub>CTX-M-15</sub> gene was carried by IncFII plasmid in three isolates and the <i>bla</i><sub>CMY-2</sub> gene carried by IncI1 plasmid in one isolate. <i>bla</i><sub>CMY-2</sub> gene-harboring strain was selected as the donor based on the high frequency of <i>bla</i><sub>CMY-2</sub> gene transfer in vitro and its transfer frequencies were determined at 10<sup>-3</sup> transconjugants per recipient. The transfer of <i>bla</i><sub>CMY-2</sub> gene-harboring plasmid derived from chicken isolate into a human pathogen; enteroinvasive <i>Escherichia coli</i> (EIEC), presented in mouse intestine with about 10<sup>-1</sup> transfer frequency without selective pressure. From the competition experiment; <i>bla</i><sub>CMY-2</sub> gene-harboring transconjugant showed variable fitness burden depends on the parent strains. Our study demonstrated direct evidence that the <i>bla</i><sub>CMY-2</sub> gene harboring <i>Salmonella</i> from chicken could frequently transfer its ESC-resistant gene to <i>E. coli</i> in a mouse intestine without antimicrobial pressure; resulting in the emergence of multidrug resistance in potentially virulent EIEC isolates of significance to human health; which can increase the risk of therapeutic inadequacy or failures.
Project description:A chloramphenicol-resistant strain of Salmonella enterica serovar Typhi was first noted in Korea in 1992, when a resistant isolate was detected in a returned traveler. Continued isolation of multidrug-resistant (MDR) strains thereafter in other settings prompted a retrospective analysis of laboratory records and phenotypic and genotypic analyses of 12 chloramphenicol-resistant isolates. Among these, one isolate was resistant only to chloramphenicol, and the other isolates were also resistant to ampicillin and co-trimoxazole. MDR was transferred by conjugation from 9 of the 11 isolates. PCR showed that all isolates had an incompatible group HI1 plasmid, and oriT was detected in 10 isolates, which included strains with an unsuccessful transfer of resistance. All of the ampicillin-resistant isolates had a beta-lactamase band of pI 5.4 and bla(TEM) alleles. A PCR amplicon from an isolate showed that the sequences were identical to those of bla(TEM-1), suggesting that all isolates had a TEM-1 beta-lactamase. All isolates had class 1 integrons: 10 isolates had integrons of ca. 1.2 kb with dhfr7 gene cassettes, and 1 isolate had an integron of ca. 2.3 kb with aacA4 and bla(OXA-1)-like gene cassettes. The pulsed-field gel electrophoresis patterns of 7 of 11 MDR isolates were identical and indistinguishable from those reported for isolates in India and Indonesia. In conclusion, some of the MDR strains in Korea are related to those in other Asian countries. Susceptibility testing became necessary for selection of antimicrobial agents for the optimal treatment of patients with the emergence of MDR Salmonella serovar Typhi in Korea.
Project description:Molecular evolution of multiresistance in nontyphoid Salmonella spp. was investigated with 155 isolates obtained in Argentina from 1984 to 1998. In 74 isolates obtained from 1984 to 1988 resistance was associated with the presence of Tn3, Tn9, class I (In0) and II (Tn7) integrons, and the aac(3)-IIa gene. Extended-spectrum cephalosporin (ESC) resistance in Salmonella spp. emerged in 1989, and 81 isolates resistant to at least one ESC and one aminoglycoside were collected thereafter. Among these, two patterns of antimicrobial resistance mechanisms were found: from 1989 to 1992, resistance was related to the spreading of Tn1331 and bla(CTX-M-2), in addition to the persistence of In0 and Tn7. From 1993 to 1998, several integrons were added to the first pattern and three integron groups (IG), namely, IG1 (38% of the isolates), IG2 (51%), and IG3 (11%), were identified. At least two beta-lactamase genes were detected in 65% of the isolates (after 1989) by PCR analysis. Furthermore, five beta-lactamase genes, bla(CTX-M-(2)), bla(OXA-9), bla(OXA-2), bla(TEM-1), and bla(PER-2), were found in two isolates. The bla(CTX-M-2) gene was found in several complex sulI-type integrons with different rearrays within the variable region of class I integrons, suggesting evolution of these integrons in nontyphoid Salmonella. In conclusion, progressive acquisition and accumulation of plasmid-mediated resistance determinants occurred from 1984 to 1998 in nontyphoid Salmonella isolates of the most prevalent serovars from Argentina. It is suggested that antimicrobial resistance mechanisms in these bacteria may have been the consequence of plasmid exchange between Salmonella enterica serovar Typhimurium and Escherichia coli or Shigella flexneri and/or spreading of mobile elements from the nosocomial environment.
Project description:BACKGROUND:Salmonella and Shigella cause significant morbidity and mortality among children worldwide. Increased antimicrobial resistance results in greater burden of disease. MATERIALS AND METHODS:From 2005 to 2011, Salmonella and Shigella isolates collected from ill children at a major hospital in Yucatan, Mexico, were subjected to serotyping and antimicrobial susceptibility testing by disk diffusion and agar dilution. The identification of bla CTX, bla CMY, bla SHV, bla TEM, and bla OXA and qnr resistance genes was conducted by PCR and sequencing. RESULTS:Among 2344 children with acute gastroenteritis, salmonellosis decreased from 17.7% in 2005 to 11.2% in 2011 (p < 0.001). In contrast, shigellosis increased from 8.3% in 2010 to 12.1% in 2011. Compared to children with Salmonella, those with Shigella had significantly more bloody stools (59 vs 36%, p < 0.001), dehydration (27 vs 15%, p = 0.031), and seizures (11 vs 3%, p = 0.03). In Salmonella (n = 365), there was a significant decrease in resistance to ampicillin (43 to 16%, p < 0.001), trimethoprim-sulfamethoxazole (44 to 26%, p = 0.014), and extended-spectrum cephalosporins (27 to 10%, p = 0.009). Reduced susceptibility to ciprofloxacin in Salmonella rose from 30 to 41% (p < 0.001). All ceftriaxone-resistant isolates harbored the bla CMY-2 gene. qnr genes were found in 42 (36%) of the 117 Salmonella isolates with a ciprofloxacin MIC ? 0.125 ?g/ml. Four were qnrA1 and 38 were qnrB19. Resistance to ampicillin (40%) and trimethoprim-sulfamethoxazole (58%) was common in Shigella (n = 218), but isolates remained fully susceptible to ceftriaxone and ciprofloxacin. CONCLUSION:Illness from Salmonella has decreased while severe Shigella infections have increased among children with gastroenteritis in the Yucatan Peninsula. While Shigella resistance to clinically important antibiotics remained unchanged, resistance to most of these, except ciprofloxacin, declined in Salmonella. bla CMY-2 and qnr genes are common in Salmonella isolates.
Project description:The National Antimicrobial Resistance Monitoring System monitors susceptibility among Enterobacteriaceae in humans in the United States. We studied isolates exhibiting decreased susceptibility to quinolones (nalidixic acid MIC >32 microg/mL or ciprofloxacin MIC > or =0.12 microg/mL) and extended-spectrum cephalosporins (ceftiofur or ceftriaxone MIC > or =2 microg/mL) during 1996-2004. Of non-Typhi Salmonella, 0.19% (27/14,043) met these criteria: 11 Senftenberg; 6 Typhimurium; 3 Newport; 2 Enteridis; and 1 each Agona, Haifa, Mbandaka, Saintpaul, and Uganda. Twenty-six isolates had gyrA mutations (11 at codon 83 only, 3 at codon 87 only, 12 at both). All Senftenberg isolates had parC mutations (S801 and T57S); 6 others had the T57S mutation. The Mbandaka isolate contained qnrB2. Eight isolates contained bla(CMY-2); 1 Senftenberg contained bla(CMY-23). One Senftenberg and 1 Typhimurium isolate contained bla(SHV-12); the Mbandaka isolate contained bla(SHV-30). Nine Senftenberg isolates contained bla(OXA-1) contained bla(OXA-9). Further studies should address patient outcomes, risk factors, and resistance dissemination prevention strategies.