Virulence and transferability of resistance determinants in a novel Klebsiella pneumoniae sequence type 1137 in China.

A study was designed to characterize three carbapenemase-producing Klebsiella pneumoniae isolated from pediatric patients in China. Molecular characterization was done using polymerase chain reaction and sequencing for blaVIM, blaNDM, blaIMP, blaKPC, blaCTX-Ms, blaOXAs, blaTEMs, and blaSHV; plasmid-mediated quinolone resistance determinants; aminoglycoside resistance determinants; multilocus sequencing typing; plasmid replicon typing; addiction; and virulence factors. Kp32 belonged to the newly described sequence type 1137, were positive for aac(6')-Ib-suzhou, qnrA1, qnrB4, qnrS1, aac(6')-Ib, rmtB, armA, blaSHV-12, blaCTX-M-15, blaKPC-2, and blaIMP-4; contained IncA/C plasmids that tested positive for K1 capsular antigens, the ccdAB (coupled cell division locus) addiction system and the wabG, ureA, rmpA, magA, allS, fimH, and the aerobactin virulence factors. However, the others belonged to clone ST11, and were positive for aac(6')-Ib-cr, qnrB4, blaCTX-M-14, blaSHV-11, aac(6')-Ib, rmtB, and blaKPC-2; contained IncFIA plasmids that tested positive for K2 capsular antigens, the vagCD addiction system and the uge, wabG, ureA, kfuBC, rpmA, and fimH virulence factors. ST1137 had more virulence factors than the comparative strains ST11. The blaKPC-2 gene was located on the IncFIA and IncA/C replicon groups of plasmids. An analysis of the genetic environment of blaKPC-2 gene has demonstrated that the blaKPC-2 gene was always associated with one of the Tn4401 isoforms (a or b). Our study suggested that K. pneumoniae carbapenemases being found in virulent K. pneumoniae should be emphasized, as this will eventually become a global health threat.

Efflux system overexpression and decreased OprD contribute to the carbapenem resistance among extended-spectrum beta-lactamase-producing Pseudomonas aeruginosa isolates from a Chinese university hospital.

The aim of this study was to investigate, for the first time, the combinations of carbapenem resistance mechanisms in clinical isolates of extended-spectrum beta-lactamase (ESBL)-producing Pseudomonas aeruginosa in a Chinese hospital. Pulsed-field gel electrophoresis revealed the presence of eight clonal types among the 15 ESBL producers. Multilocus sequence typing of two isolates harboured blaIMP-1 identified the clonal strain as ST325. All these genes were found either alone or simultaneously in the strains in the following five different arrangements:; ; ; ; . Regarding mutation-driven resistance, all, but four of the isolates had a relevant decrease of oprD expression. In addition, 73.3% of the isolates overexpressed mexB, 40% mexD, and 33.3% mexY. A specific combination of overexpressed mexB or mexY and alteration in loop L710 of OprD were significantly associated with meropenem resistance. In conclusion, combination of several mutation-driven mechanisms leading to OprD inactivation and overexpression of efflux systems was the main carbapenem resistance mechanism among the ESBL-producing P. aeruginosa isolates, but acquisition of a transferable resistance determinant such as metallo-ß-lactamase could be problematic in clinical settings in China.

Acquisition of carbapenem resistance in multiresistant Klebsiella pneumoniae isolates of sequence type 11 at a university hospital in China.

Four closely related KPC-producing Klebsiella pneumoniae strains, which were isolated from the patients with neonatal sepsis, harbored bla(CTX-M-14), bla(TEM-1), bla(CTX-M-15), bla(SHV-11),bla(SHV-12), class 1 integron, qnrS1, acc(6')-Ib-cr, and rmtB genes. Multilocus sequence typing experiments showed that all isolates but Kp122 were proven to share the same sequence type (ST), ST11. These isolates have not yet been previously reported in a university-affiliated children's hospital or in the city of Wenzhou.

Molecular characterization of the bla(KPC-2) gene in clinical isolates of carbapenem-resistant Klebsiella pneumoniae from the pediatric wards of a Chinese hospital.

The present study was conducted to confirm the presence of Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae associated with a nosocomial outbreak in a Chinese pediatric hospital. From July 2009 to January 2011, 124 nonduplicated K. pneumoniae isolates were collected from specimens from patients of pediatric units in the hospital. Twelve of the 124 isolates possessed the bla(KPC-2) gene and showed 7 different pulsed-field gel electrophoresis (PFGE) patterns. Meanwhile, 16S rRNA methylase, acc(6')-Ib-cr, and several types of ß-lactamases were also produced by the majority of the KPC-producing isolates. Class 1 integron-encoded intI1 integrase gene was subsequently found in all strains, and amplification, sequencing, and comparison of DNA between 5' conserved segment and 3' conserved segment region showed the presence of several known antibiotic resistance gene cassettes of various sizes. The conjugation and plasmid-curing experiments indicated some KPC-2-encoding genes were transmissible. In addition, conjugal cotransfer of multidrug-resistant phenotypes with KPC-positive phenotypes was observed in KPC-producing strains. Restriction endonuclease analysis and DNA hybridization with a KPC-specific probe showed that the bla(KPC-2) gene was carried by plasmid DNA from K. pneumoniae of PFGE pattern B. The overall results indicate that the emergence and outbreak of KPC-producing K. pneumoniae in our pediatric wards occurred in conjunction with plasmids coharboring 16S rRNA methylase and extended-spectrum ß-lactamases.