Molecular epidemiology of OHIO-1 beta-lactamase

Salmonella serovars are important reservoirs of antimicrobial resistance. Recently, we reported on multidrug-resistant (MDR) Salmonella enterica serovar Typhimurium strains among pigs with resistance to ampicillin, kanamycin, streptomycin, sulfamethoxazole, and tetracycline (resistance [R] type AKSSuT) and resistance to amoxicillin-clavulanic acid, ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (R type AxACSSuT). In the present study, 67 isolates (39 from humans and 28 from pigs) of clinically important Salmonella serovar Muenchen were characterized. Among the porcine isolates, 75% showed resistance to seven antimicrobials: ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, amoxicillinclavulanic acid, and kanamycin (R type ACSSuTAxK). One isolate from humans showed resistance to 10 of the 12 antimicrobials: ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, amoxicillin-clavulanic acid, kanamycin, gentamicin, cephalothin, and ceftriaxone (R type ACSSuTAxKGCfCro). Pulsed-field gel electrophoresis revealed no clonality between the porcine and the human strains. The porcine and the human MDR strains carried class 1 integrons of 2.0 and 1.0 kb, respectively. Genes specific to the porcine strain included aadA2, aphA1-Iab, and tetA(B). DNA sequencing revealed that the porcine isolates carried bla OXA-30 on a class 1 integron. Genes specific to the human strain included bla TEM , strA, strB, cmlA, tetA(A), and aadA2. No bla CMY-2 gene was detected. Serovar Muenchen strains of porcine and human origin were able to transfer resistance genes to laboratory strain Escherichia coli MG1655 by conjugation. Plasmid restriction with four restriction enzymes, EcoRI, BamHI, HindIII, and PstI, showed that the conjugative plasmids from porcine Salmonella serovar Muenchen and Typhimurium R-type MDR strains isolated from the same farms at the same time were similar on the basis of the sizes and the numbers of bands and Southern hybridization. The plasmid profiles among the Salmonella serovar Muenchen isolates from the two host species were different. This is the first report to show a high frequency of MDR Salmonella serovar Muenchen strains from pigs and a human strain that is similar to the MDR isolates with the AmpC enzyme previously reported among Salmonella serovars Newport and Typhimurium strains. The MDR strains from the two host species independently represent public health concerns, as Salmonella serovar Muenchen is among the top 10 causes of salmonellosis in humans.

Section: Vol 49 2005supporting

confidence: 62%

Multidrug-Resistant Salmonella enterica Serovar Muenchen from Pigs and Humans and Potential Interserovar Transfer of Antimicrobial Resistance

Gebreyes

Thakur

2005

“…Within three years of its discovery, conjugative plasmids encoding OHIO-1 were found disseminated in virtually all species of the family Enterobacteriaceae on at least one ward in our medical center (28). We later showed that all of these plasmids, regardless of origin, were derived from a single progenitor (17). These observations were consistent with the lack of observable transposition of OHIO-1 (D. M. Shlaes and G. Jacoby, unpublished observations).…”

Section: Methodssupporting

confidence: 73%

“…OHIO-1 has a pI similar to that of LEN-1 but is plasmid mediated. OHIO-1 appears to have been geographically restricted within the state of Ohio (17,28,29). To better understand the evolution of this restricted resistance mechanism, we have sequenced the structural gene and its flanking sequences.…”

mentioning

confidence: 99%

OHIO-1 beta-lactamase is part of the SHV-1 family

Shlaes

Currie-McCumber

Hull

et al. 1990

Self Cite

The 011IO-1 ,B-lactamase gene was subcloned in a 1.16-kilobase TaqI fragment in the 2.4-kilobase chimeric plasmid pSK04. After directional subcloning into M13, the DNA sequence of this fragment was determined. The results showed an open reading frame of 858 base pairs (bp) encoding a protein of 286 amino acids. The structural gene showed 95, 87, and 60% DNA sequence identity with SHV-1, LEN-1, and TEM-1, respectively, and 93, 85, and 62% predicted amino acid sequence identity, respectively. The 87 bp upstream of the OHIO-i structural gene had 96% identity with the upstream flanking sequence of SHV-1, including the -35 and -10 consensus sequences and the putative ribosomal binding site. A 223-bp DNA probe derived from a Psfi-HaeHl fragment in the C-terminal sequence of OHIO-1 had predicted 96, 88, and 61% sequence identity with SHV-1, LEN-1, and TEM-1, respectively. This probe hybridized to SHV-1 and poorly to LEN-1, but not to TEM-1 or a variety of other plasmid-mediated I-lactamase genes, under stringent conditions. Screening of plasmid DNA derived from 40 ampicillin-resistant clinical isolates by Southern hybridization with the 223-bp probe uncovered no strains encoding OHIO-1. Isoelectric focusing of the same collection did identify two strains producing enzymes resembling SHV-1, however. We have also performed a kinetic comparison of OHIO-1, SHV-1, and TEM-1. OHIO-1 and SHV-1 were indistinguishable from each other but could be distinguished from TEM-i. These data clearly place OHIO-1 within the SHV-1 family of 13-lactamases.The OHIO-1 P-lactamase is a group 2b enzyme with a substrate and inhibitor profile resembling those of TEM-1 and SHV-1 (8, 28). Recent immunochemical data (34) and inhibitor profiling data (A. A. Medeiros, personal communication) suggest that OHIO-1 belongs within the SHV-1 family of P-lactamases. LEN-1 is a ,B-lactamase encoded on the chromosomes of some strains of Klebsiella pneumoniae with a pI of 7.0 and a nucleotide sequence resembling that of SHV-1 (2, 22). OHIO-1 has a pI similar to that of LEN-1 but is plasmid mediated. OHIO-1 appears to have been geographically restricted within the state of Ohio (17,28,29). To better understand the evolution of this restricted resistance mechanism, we have sequenced the structural gene and its flanking sequences. To arrive at a better understanding of structure and function among P-lactamases, we have searched for differences in substrate specificities among these enzymes and compared these with differences in their sequences. Finally, we have developed an intragenic DNA probe from the OHIO-1 gene sequence.

“…Additionally, the RFLP patterns identified many highly conserved restriction fragments among each of the plasmids, suggesting that the plasmids may be genetically similar but that they may have evolved over time. Previous studies have shown that plasmid DNA can change rapidly (24,40). DT104 isolates of Salmonella typically carry a chromosomal integron that encodes all or a subset of the antimicrobial resistance genes (11,37).…”

Section: Discussionmentioning

confidence: 99%

Animal and Human Multidrug-Resistant, Cephalosporin-Resistant Salmonella Isolates Expressing a Plasmid-Mediated CMY-2 AmpC β-Lactamase

Winokur

Brueggemann

DeSalvo

et al. 2000

274

220

Salmonella spp. are important food-borne pathogens that are demonstrating increasing antimicrobial resistance rates in isolates obtained from food animals and humans. In this study, 10 multidrug-resistant, cephalosporin-resistant Salmonella isolates from bovine, porcine, and human sources from a single geographic region were identified. All isolates demonstrated resistance to cephamycins and extended-spectrum cephalosporins as well as tetracycline, chloramphenicol, streptomycin, and sulfisoxazole. Molecular epidemiological analyses revealed eight distinct chromosomal DNA patterns, suggesting that clonal spread could not entirely explain the distribution of this antimicrobial resistance phenotype. However, all isolates encoded an AmpC-like ␤-lactamase, CMY-2. Eight isolates contained a large nonconjugative plasmid that could transform Escherichia coli. Transformants coexpressed cephalosporin, tetracycline, chloramphenicol, streptomycin, and sulfisoxazole resistances. Plasmid DNA revealed highly related restriction fragments though plasmids appeared to have undergone some evolution over time. Multidrug-resistant, cephalosporin-resistant Salmonella spp. present significant therapeutic problems in animal and human health care and raise further questions about the association between antimicrobial resistance, antibiotic use in animals, and transfer of multidrug-resistant Salmonella spp. between animals and man.Salmonella spp. are important zoonotic pathogens in humans and animals. In the United States it is estimated that over 1.4 million cases of salmonellosis occur each year, 95% of which are the result of food-borne transmission (28). Large outbreaks have been associated with ingestion of poultry, meat, and milk and other dairy products (6). Although the majority of infections result in asymptomatic or self-limited diarrheal illness, severe, life-threatening bacteremias and other deep-seated infections do occur, particularly in immunocompromised hosts, neonates, and the elderly (7,14).