Project description:Extended-spectrum β-lactamases (ESBLs) confer resistance to clinically important third-generation cephalosporins, which are often used to treat invasive salmonellosis. In the United States, ESBLs are rarely found in Salmonella. However, in 2014, the US Food and Drug Administration found blaCTX-M-65 ESBL-producing Salmonella enterica serotype Infantis in retail chicken meat. The isolate had a rare pulsed-field gel electrophoresis pattern. To clarify the sources and potential effects on human health, we examined isolates with this pattern obtained from human surveillance and associated metadata. Using broth microdilution for antimicrobial susceptibility testing and whole-genome sequencing, we characterized the isolates. Of 34 isolates, 29 carried the blaCTX-M-65 gene with <9 additional resistance genes on 1 plasmid. Of 19 patients with travel information available, 12 (63%) reported recent travel to South America. Genetically, isolates from travelers, nontravelers, and retail chicken meat were similar. Expanded surveillance is needed to determine domestic sources and potentially prevent spread of this ESBL-containing plasmid.
Project description:Four Salmonella enterica serovar Virchow strains resistant to broad-spectrum cephalosporins were isolated from patients with gastroenteritis in 1997 and 1998 in Murcia and Barcelona, Spain. The isolates expressed a beta-lactamase with a pI of about 8 and a positive PCR when specific primers for CTX-M-9 were used. These results suggest the presence of a CTX-M-9 beta-lactamase in these strains.
Project description:We sequenced the genomes of 10 Salmonella enterica serovar Infantis isolates containing blaCTX-M-65 obtained from chicken, cattle, and human sources collected between 2012 and 2015 in the United States through routine National Antimicrobial Resistance Monitoring System (NARMS) surveillance and product sampling programs. We also completely assembled the plasmids from four of the isolates. All isolates had a D87Y mutation in the gyrA gene and harbored between 7 and 10 resistance genes [aph(4)-Ia, aac(3)-IVa, aph(3')-Ic, blaCTX-M-65, fosA3, floR, dfrA14, sul1, tetA, aadA1] located in two distinct sites of a megaplasmid (∼316 to 323 kb) similar to that described in a blaCTX-M-65-positive S Infantis isolate from a patient in Italy. High-quality single nucleotide polymorphism (hqSNP) analysis revealed that all U.S. isolates were closely related, separated by only 1 to 38 pairwise high-quality SNPs, indicating a high likelihood that strains from humans, chickens, and cattle recently evolved from a common ancestor. The U.S. isolates were genetically similar to the blaCTX-M-65-positive S Infantis isolate from Italy, with a separation of 34 to 47 SNPs. This is the first report of the blaCTX-M-65 gene and the pESI (plasmid for emerging S Infantis)-like megaplasmid from S Infantis in the United States, and it illustrates the importance of applying a global One Health human and animal perspective to combat antimicrobial resistance.
Project description:We characterized 9 New Delhi metallo-β-lactamase-producing Enterobacteriaceae (5 Klebsiella pneumoniae, 2 Escherichia coli, 1 Enterobacter cloacae, 1 Salmonella enterica serovar Senftenberg) isolates identified in the United States and cultured from 8 patients in 5 states during April 2009-March 2011. Isolates were resistant to β-lactams, fluoroquinolones, and aminoglycosides, demonstrated MICs ≤1 µg/mL of colistin and polymyxin, and yielded positive metallo-β-lactamase screening results. Eight isolates had blaNDM-1, and 1 isolate had a novel allele (blaNDM-6). All 8 patients had recently been in India or Pakistan, where 6 received inpatient health care. Plasmids carrying blaNDM frequently carried AmpC or extended spectrum β-lactamase genes. Two K. pneumoniae isolates and a K. pneumoniae isolate from Sweden shared incompatibility group A/C plasmids with indistinguishable restriction patterns and a common blaNDM fragment; all 3 were multilocus sequence type 14. Restriction profiles of the remaining New Delhi metallo-β-lactamase plasmids, including 2 from the same patient, were diverse.
Project description:A CTX-M-65‒producing Salmonella enterica serovar Infantis clone, probably originating in Latin America and initially reported in the United States, has emerged in Taiwan. Chicken meat is the most likely primary carrier. Four of the 9 drug resistance genes have integrated into the chromosome: blaCTX-M-65, tet(A), sul1, and aadA1.
Project description:We analyzed the resistance to cefotaxime of a Salmonella enterica serovar Enteritidis isolate from a stool culture of a 4-year-old boy. It produced a beta-lactamase CTX-M-14, encoded by two related R plasmids. The region surrounding the blaCTX-M-14 gene had an original mosaic structure containing insertion sequences (IS26 and IS903D).
Project description:At a children's hospital in Riga, Latvia, isolates identified as Salmonella typhimurium were found to be resistant to expanded-spectrum cephalosporins. Two of the resistant strains were analyzed for the mechanism of cephalosporin resistance. Isoelectric focusing revealed a common beta-lactamase with a pI of 8.8. In addition, one of the strains produced a pI 7.6 beta-lactamase. A transconjugant producing only the pI 7.6 enzyme was susceptible to expanded-spectrum cephalosporins; therefore, this enzyme was most likely SHV-1. Transformants producing only the pI 8.8 beta-lactamase were resistant to cefotaxime and aztreonam but were susceptible or intermediate to ceftazidime. A substrate profile determined spectrophotometrically with purified enzyme revealed potent activity against cefotaxime, with a relative kcat value of 95 (benzylpenicillin equal to 100). The enzyme showed lower relative kcat values for ceftazidime (3.3) and aztreonam (9.3). In addition, the enzyme was inhibited by clavulanate, sulbactam and tazobactam, with 50% inhibitory concentrations of 19, 100, and 3.4 nM, respectively. These results indicated the presence of an unusual extended-spectrum beta-lactamase. The gene expressing the pI 8.8 beta-lactamase was cloned. Nucleotide sequencing revealed a beta-lactamase gene that differs from the gene encoding CTX-M-2, which also originated from S. typhimurium, by 11 nucleotides, 4 of which result in amino acid substitutions: Ala27Thr, Val230Gly, Glu254Ala, and Ile278Val. These results indicated the presence of a novel extended-spectrum beta-lactamase, designated CTX-M-5, that specifically confers resistance to cefotaxime.
Project description:Salmonella enterica resistance to extended-spectrum cephalosporins (ESC) conferred by cefotaximases (blaCTX-M) is a growing concern in the United States. Among food-producing animals, poultry are a major reservoir of ESC-resistant Salmonella. A retrospective study was carried out to further characterize 38 ceftiofur-resistant clinical Salmonella enterica isolates obtained from poultry during 2007-2018. Of the isolates tested, 31 displayed resistance to ceftriaxone and harbored blaCMY-2, whereas 7 isolates demonstrated resistance or reduced susceptibility to cefepime in addition to ceftriaxone resistance. These 7 isolates displayed extended-spectrum ?-lactamase activity, harbored blaCTX-M-1, and were recovered only from recent poultry diagnostic submissions made in 2011-2018 as opposed to the 31 isolates that were recovered in 2007-2018. Further characterization of the blaCTX-M-1 gene determined that it was located on conjugative IncN/ST1 and IncI1/ST87 plasmids in the isolates from commercial turkeys and broilers, respectively. These plasmids have been responsible for extensive spread of blaCTX-M-1 in livestock, poultry, and humans in Europe. Potential transfer of IncN and IncI1 plasmids and/or nontyphoidal Salmonella carrying these plasmids through the food chain, or by other means to humans, may result in treatment failures. Our study demonstrates the importance of further characterization of ceftiofur-resistant S. enterica isolates detected by veterinary diagnostic laboratories to identify the sources of blaCTX-M-1 and to mitigate the spread of ESC-resistant Salmonella in the poultry production pyramid.