Complete Nucleotide Sequence of a 92-Kilobase Plasmid Harboring the CTX-M-15 Extended-Spectrum Beta-Lactamase Involved in an Outbreak in Long-Term-Care Facilities in Toronto, Canada

Abstract

A major outbreak involving an Escherichia coli strain that was resistant to expanded-spectrum cephalosporins occurred in Toronto and surrounding regions in 2000 to 2002. We report the complete sequence of a plasmid, pC15-1a, that was found associated with the outbreak strain. Plasmid pC15-1a is a circular molecule of 92,353 bp consisting of two distinct regions. The first is a 64-kb region that is essentially homologous to the non-R-determinant region of plasmid R100 except for several point mutations, a few small insertions and deletions, and the absence of Tn10. The second is a 28.4-kb multidrug resistance region (MDR) that has replaced the R-determinant region of the R100 progenitor and consists mostly of transposons or partial transposons and five copies of the insertion element IS26. All drug resistance genes found in pC15-1a, including the beta-lactamase genes bla CTX-M-15 , bla OXA-1 , and bla TEM-1 , the tetracycline resistance gene tetA, and aminoglycoside resistance genes aac(6)-Ib and aac(3)-II, are located in the MDR. The bla CTX-M-15 gene was found downstream of ISEcp1as part of a transposition unit, as determined from the surrounding sequence. Examination of the plasmids from CTX-M-15-harboring strains isolated from hospitals across Canada showed that pC15-1a was found in several strains isolated from a site in western Canada. Comparison of pC15-1a and pCTX15, found in an E. coli strain isolated in India in 1999, revealed that the plasmids had several features in common, including an R100 backbone and several of the resistance genes, including bla CTX-M-15 , bla TEM-1 , bla OXA-1 , tetA, and aac(6)-Ib.Plasmid-mediated extended-spectrum beta-lactamase (ESBL) enzymes are most commonly of the TEM, SHV, or CTX-M type (8). To date more than 120 TEM enzymes, more than 50 SHV enzymes, and more than 30 CTX-M enzymes have been reported (www.lahey.org/studies/). Members of these groups are class A enzymes and, for the most part, are inhibited by clavulanic acid.The CTX-M-type beta-lactamases are increasingly found in enterobacterial species throughout the world; more than half have been reported within the last 4 years (7, 28). They are generally most active against cefotaxime and show little activity against ceftazidime. Phylogenetically, they are grouped into five clusters based on their amino acid identities: the CTX-M-1 cluster etc.), the CTX-M-2 cluster etc.), the CTX-M-8 cluster (CTX-M-8), the CTX-M-25 cluster , and the CTX-M-9 cluster

Dissemination of Clonally RelatedEscherichia coliStrains Expressing Extended-Spectrum β-Lactamase CTX-M-15

“…Although the isolates in our study do not belong to clone CgA, they were isolated mainly from urine samples, and an association of ST131 E. coli isolates with urinary tract infections might be inferred. Although most CTX-M-15 isolates studied were recovered from hospitalized patients, these microorganisms are now widely spread in the community setting, including long-term care facilities in the countries from which isolates included in this study originated (2,5,14,33). Our study has increased knowledge of the number of epidemic E. coli clonal complexes causing urinary tract infections.…”

Toxin Kid uncouples DNA replication and cell division to enforce retention of plasmid R1 in Escherichia coli cells

“…Moreover, other observations indicate that our past experiments may have been inappropriate to conclude that Kid does not kill Escherichia coli cells (30,31). Importantly, Kid, Kis, and other elements that we found essential for R1 rescue are conserved in plasmids conferring resistance to extended-spectrum β-lactamases, a worrying threat to human health (1,(6)(7)(8)(9)(10)32). Therapeutic options to fight pathogens carrying these plasmids are limited, and activation of Kid may be perceived as a good antibiotic alternative.…”

“…kis-kid and all other elements required for R1 rescue (i.e., UUACU-positive copB-repA and UUACU-free repA mRNAs) are present in plasmids encoding extended-spectrum β-lactamases, which is a major clinical concern worldwide for which therapeutic alternatives are scarce (1,3,(6)(7)(8)(9)(10), suggesting that the system also operates there. Worth noting, plasmids conferring vancomycin resistance to enterococci also encode fairly conserved Kid and Kis homologs, and their pharmacological activation has also been proposed as a strategy for tailored therapy against these worrisome pathogens (11).…”

“…TA pairs are common in plasmids disseminating antibiotic resistance in bacterial pathogens worldwide (2,(6)(7)(8)(9)(10). The link of these systems to PSK and the exiguous list of alternatives in the pipeline have led some to propose that chemicals activating these TA pairs may constitute a powerful antibiotic approach against these organisms (5,(11)(12)(13).…”

Emergence of blaCTX-M-15 Gene and Its Transferability in Enterobacter spp. Isolated From the Hospitals of Tehran, Iran

“…In clinical strains, CTX-M-encoding genes are commonly located on plasmids which vary in size from 7 -200 kb (5). Many of these plasmids are conjugative with transfer frequencies ranging from 10 -2 -10 -7 (6). To date, more than 60 types CTX-M ESBLs belonging to five evolutionary groups are described.…”