Dataset Information

A Novel Transferable Resistance-Nodulation-Division Pump Gene Cluster, tmexCD2-toprJ2, Confers Tigecycline Resistance in Raoultella ornithinolytica.

ABSTRACT: We recently identified a novel plasmid-mediated resistance-nodulation-division (RND)-type efflux pump gene cluster, tmexCD1-toprJ1, in Klebsiella pneumoniae that conferred resistance to multiple antimicrobials, including tigecycline. While homologs of tmexCD1-toprJ1 were found encoded in many other bacterial species in GenBank, their functions and transfer mechanisms remain unknown. This study identified another mobile gene cluster, tmexCD2-toprJ2, co-occurring on both a plasmid (pHNNC189-2) and the chromosome of a clinical Raoultella ornithinolytica isolate, strain NC189, producing KPC-2, NDM-1, and RmtC. tmexCD2-toprJ2 shares high similarity at the nucleotide level with tmexCD1-toprJ1, with 98.02%, 96.75%, and 99.93% identities to tmexC1, tmexD1, and toprJ1, respectively. Phylogenetic analysis revealed that tmexCD2-toprJ2 may have originated from the chromosome of a Pseudomonas species. The expression of tmexCD2-toprJ2 in an Escherichia coli strain resulted in an 8-fold increase in the tigecycline MIC and decreased susceptibility to other antimicrobials. Genetic context analyses demonstrated that tmexCD2-toprJ2, together with the adjacent hypothetical site-specific integrase genes, was possibly captured and mobilized by a XerD-like tyrosine recombinase system, forming a putative transposition unit (xerD-like-int3-like-thf2-ybjD-umuD-ΔumuC1-int1-like-int2-like-hp1-hp2-tnfxB2-ISBvi2-tmexCD2-toprJ2-ΔumuC1), which was inserted into umuC-like genes in both the NC189 plasmid pHNNC189-2 and the chromosome. Since tmexCD1-toprJ1 and tmexCD2-toprJ2 could confer multidrug resistance, the spread of these gene clusters, associated with the new recombinase system, calls for more attention.

SUBMITTER: Wang CZ

PROVIDER: S-EPMC8097428 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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A Novel Transferable Resistance-Nodulation-Division Pump Gene Cluster, tmexCD2-toprJ2, Confers Tigecycline Resistance in Raoultella ornithinolytica.

Wang Cheng-Zhen CZ Gao Xun X Yang Qi-Wen QW Lv Lu-Chao LC Wan Miao M Yang Jun J Cai Zhong-Peng ZP Liu Jian-Hua JH

Antimicrobial agents and chemotherapy 20210318 4

We recently identified a novel plasmid-mediated resistance-nodulation-division (RND)-type efflux pump gene cluster, tmexCD1-toprJ1, in Klebsiella pneumoniae that conferred resistance to multiple antimicrobials, including tigecycline. While homologs of tmexCD1-toprJ1 were found encoded in many other bacterial species in GenBank, their functions and transfer mechanisms remain unknown. This study identified another mobile gene cluster, tmexCD2-toprJ2, co-occurring on bot ...[more]

PMID: 33495220

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Project description:Transporters belonging to the chromosomally encoded resistance-nodulation-division (RND) superfamily mediate multidrug resistance in Gram-negative bacteria. However, the cotransfer of large gene clusters encoding RND-type pumps from the chromosome to a plasmid appears infrequent, and no plasmid-mediated RND efflux pump gene cluster has yet been found to confer resistance to tigecycline. Here, we identified a novel RND efflux pump gene cluster, designated tmexCD1-toprJ1, on plasmids from five pandrug-resistant Klebsiella pneumoniae isolates of animal origin. TMexCD1-TOprJ1 increased (by 4- to 32-fold) the MICs of tetracyclines (including tigecycline and eravacycline), quinolones, cephalosporins, and aminoglycosides for K.pneumoniae, Escherichia coli, and Salmonella TMexCD1-TOprJ1 is closely related (64.5% to 77.8% amino acid identity) to the MexCD-OprJ efflux pump encoded on the chromosome of Pseudomonas aeruginosa In an IncFIA plasmid, pHNAH8I, the tmexCD1-toprJ1 gene cluster lies adjacent to two genes encoding site-specific integrases, which may have been responsible for its acquisition. Expression of TMexCD1-TOprJ1 in E. coli resulted in increased tigecycline efflux and in K. pneumoniae negated the efficacy of tigecycline in an in vivo infection model. Expression of TMexCD1-TOprJ1 reduced the growth of E. coli and Salmonella but not K. pneumoniaetmexCD1-toprJ1-positive Enterobacteriaceae isolates were rare in humans (0.08%) but more common in chicken fecal (14.3%) and retail meat (3.4%) samples. Plasmid-borne tmexCD1-toprJ1-like gene clusters were identified in sequences in GenBank from Enterobacteriaceae and Pseudomonas strains from multiple continents. The possibility of further global dissemination of the tmexCD1-toprJ1 gene cluster and its analogues in Enterobacteriaceae via plasmids may be an important consideration for public health planning.IMPORTANCE In an era of increasing concerns about antimicrobial resistance, tigecycline is likely to have a critically important role in the treatment of carbapenem-resistant Enterobacteriaceae, the most problematic pathogens in human clinical settings-especially carbapenem-resistant K.pneumoniae Here, we identified a new plasmid-borne RND-type tigecycline resistance determinant, TMexCD1-TOprJ1, which is widespread among K. pneumoniae isolates from food animals. tmexCD1-toprJ1 appears to have originated from the chromosome of a Pseudomonas species and may have been transferred onto plasmids by adjacent site-specific integrases. Although tmexCD1-toprJ1 still appears to be rare in human clinical isolates, considering the transferability of the tmexCD1-toprJ1 gene cluster and the broad substrate spectrum of TMexCD1-TOprJ1, further dissemination of this mobile tigecycline resistance determinant is possible. Therefore, from a "One Health" perspective, measures are urgently needed to monitor and control its further spread. The current low prevalence in human clinical isolates provides a precious time window to design and implement measures to tackle this.

Project description:Bacterial efflux pumps in the resistance-nodulation-cell division (RND) family of Gram-negative bacteria contribute significantly to the development of antimicrobial resistance by many pathogens. In this study, we selected the MtrD transporter protein of Neisseria gonorrhoeae as it is the sole RND pump possessed by this strictly human pathogen and can export multiple antimicrobials, including antibiotics, bile salts, detergents, dyes, and antimicrobial peptides. Using knowledge from our previously published structures of MtrD in the presence or absence of bound antibiotics as a model and the known ability of MtrCDE to export cationic antimicrobial peptides, we hypothesized that cationic peptides could be accommodated within MtrD binding sites. Furthermore, we thought that MtrD-bound peptides lacking antibacterial action could sensitize bacteria to an antibiotic normally exported by the MtrCDE efflux pump or other similar RND-type pumps possessed by different Gram-negative bacteria. We now report the identification of a novel nonantimicrobial cyclic cationic antimicrobial peptide, which we termed CASP (cationic antibiotic-sensitizing peptide). By single-particle cryo-electron microscopy, we found that CASP binds within the periplasmic cleft region of MtrD using overlapping and distinct amino acid contact sites that interact with another cyclic peptide (colistin) or a linear human cationic antimicrobial peptide derived from human LL-37. While CASP could not sensitize Neisseria gonorrhoeae to an antibiotic (novobiocin) that is a substrate for RND pumps, it could do so against multiple Gram-negative, rod-shaped bacteria. We propose that CASP (or future derivatives) could serve as an adjuvant for the antibiotic treatment of certain Gram-negative infections previously thwarted by RND transporters. IMPORTANCE RND efflux pumps can export numerous antimicrobials that enter Gram-negative bacteria, and their action can reduce the efficacy of antibiotics and provide decreased susceptibility to various host antimicrobials. Here, we identified a cationic antibiotic-sensitizing peptide (CASP) that binds within the periplasmic cleft of an RND transporter protein (MtrD) produced by Neisseria gonorrhoeae. Surprisingly, CASP was able to render rod-shaped Gram-negative bacteria, but not gonococci, susceptible to an antibiotic that is a substrate for the gonococcal MtrCDE efflux pump. CASP (or its future derivatives) could be used as an adjuvant to treat infections for which RND efflux contributes to multidrug resistance.

Dataset Information

A Novel Transferable Resistance-Nodulation-Division Pump Gene Cluster, tmexCD2-toprJ2, Confers Tigecycline Resistance in Raoultella ornithinolytica.

Publications

A Novel Transferable Resistance-Nodulation-Division Pump Gene Cluster, <i>tmexCD2-toprJ2</i>, Confers Tigecycline Resistance in Raoultella ornithinolytica.

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