Jingyong Sun

Resistance trends among clinical isolates in China reported from CHINET surveillance of bacterial resistance, 2005-2014

With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22,774 and 84,572 annually. Rates of extended-spectrum β-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.

High prevalence of CTX-M β-lactamases in faecal Escherichia coli strains from healthy humans in Fuzhou, China

Abstract Background: The community could be a reservoir of antibiotic resistance genes. The aim of this study was to investigate the prevalence and genetic environments of blaCTX-M among faecal Escherichia coli obtained from healthy persons in a region of China. Methods: Bacteria in stool specimens were screened for extended-spectrum β-lactamase (ESBL) production on 2 MacConkey agars, one with cefotaxime and one with ceftazidime. blaCTX-M and their genetic environments, as well as phylogenetic analysis and detection of the O25b-ST131 clone of E. coli, were characterized by polymerase chain reaction and sequencing. Pulsed field gel electrophoresis and conjugation assays were performed by standard procedures. Results: A surprisingly high number (50.5%, 55/109) of faecal samples showed the presence of ESBL-producing E. coli. blaCTX-M genes were detected in all of these strains. The CTX-M-9 group (41/55, 74.5%) was found most frequently, followed by the CTX-M-1 group (16/55, 29.1%). CTX-M-14 (n = 39) was the predominant CTX-M enzyme in this study. However, the genes for the CTX-M-2 and CTX-M-8 groups were not observed. ISEcp1 was detected in 90.9% of the strains, while IS26 was observed upstream from blaCTX-M in only 1 strain. Phylogenetic groups A and D were found to predominate in commensal E. coli. High clonal diversity was observed and most blaCTX-M genes were transferable. The O25b-ST131 clone was found in 4 strains. Conclusions: This study reveals the wide dissemination of CTX-M ESBL-producing E. coli in the gut flora of healthy individuals in China.

Plasmid-mediated 16S rRNA methylases in aminoglycoside-resistant Enterobacteriaceae isolates in Shanghai, China.

ABSTRACT High-level resistance to aminoglycosides produced by 16S rRNA methylases in Enterobacteriaceae isolates was investigated. The prevalences of armA in Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were 0.6%, 3.0%, and 10%, respectively. rmtB was more prevalent than armA. Pulsed-field gel electrophoresis patterns indicated that armA and rmtB have spread horizontally and clonally.

First Report of Klebsiella oxytoca Strain Coproducing KPC-2 and IMP-8 Carbapenemases

ABSTRACT The study shows for the first time the presence of the Klebsiella oxytoca strain fp10 coproducing plasmid-mediated KPC-2 and IMP-8 carbapenemases. The strain was obtained from the fecal sample of an inpatient and showed high-level resistance to imipenem and ertapenem (MICs > 32 μg/ml). Conjugation experiments demonstrated the transferability of the carbapenem-resistant determinants. The results of plasmid analysis and Southern hybridization revealed that the blaKPC-2 gene was located on transferable plasmid pFP10-1 (∼54 kb), whereas the blaIMP-8 gene was on transferable plasmid pFP10-2 (∼180 kb). Analysis of the genetic environment of these two genes has demonstrated that ISKpn6 and ISKpn8 are involved in the spread of the blaKPC-2 gene, while the transposable elements IS26, intI1, and tniC might contribute to the dissemination of the blaIMP-8 gene. The chimera of several transposon-associated elements indicated a novel genetic environment of IMP-type metallo-β-lactamase gene in Enterobacteriaceae from China.

Plasmid-mediated carbapenem-hydrolyzing enzyme KPC-2 and ArmA 16S rRNA methylase conferring high-level aminoglycoside resistance in carbapenem-resistant Enterobacter cloacae in China.

The emergence and spread of carbapenem-resistant Enterobacteriaceae in the world are a major concern. We investigated 5 isolates of Enterobacter cloacae that were resistant to all clinically available antimicrobial agents, except polymyxin B. The MICs of imipenem and aminoglycosides were >32 and >256 mg/L, respectively. All of the isolates produced 5 extended-spectrum beta-lactamase (ESBLs) with pIs of 5.4 (TEM-1), 6.7 (KPC-2), 8.2 (SHV-12), 8.4 (CTX-M-14), and ArmA 16S rRNA methylase. bla(KPC-2) was located on a large nonconjugative plasmid, whereas armA was located on another conjugative plasmid. Although carbapenem-resistant Enterobacteriaceae remains rare, the emergence of this group of organism merits monitoring.

Phylogenetic Groups and Pathogenicity Island Markers in Fecal Escherichia coli Isolates from Asymptomatic Humans in China

ABSTRACT The study of phylogenetic groups and pathogenicity island (PAI) markers in commensal Escherichia coli strains from asymptomatic Chinese people showed that group A strains are the most common and that nearly half of all fecal strains which were randomly selected harbor PAIs.

Further Spread of blaNDM-5 in Enterobacteriaceae via IncX3 Plasmids in Shanghai, China

One hundred and two carbapenem-resistant Enterobacteriaceae (CRE) strains were isolated in a teaching hospital in Shanghai, China from 2012 to 2015. In a follow-up study, four New Delhi metallo-β-lactamase-5 (NDM-5)-producing strains were identified after screening these CRE strains, including 1 Klebsiella pneumoniae strain (RJ01), 1 Proteus mirabilis strain (RJ02), and 2 Escherichia coli strains (RJ03 and RJ04). All K. pneumoniae and E. coli isolates were resistant to carbapenems, third-generation cephalosporins, and piperacillin-tazobactam, but were susceptible to amikacin. No epidemiological links for either E. coli isolate were found by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). However, MLST revealed a novel sequence type, ST2250, of the K. pneumoniae RJ01 strain. Inc types and sizes of blaNDM-5-carrying plasmids differed among the four isolates, although in P. mirabilis RJ02 and E. coli RJ03, blaNDM-5 was carried by conjugative IncX3 plasmids of nearly the same size (∼40 kb). Investigation of the genetic background of sequences flanking the blaNDM-5 gene showed that all four isolates shared the same genetic content (IS3000-ΔISAba125-IS5-blaNDM-5-ble-trpF-dsbC-IS26-ΔumuD), which was identical to that of the pNDM_MGR194 plasmid circulating in India. This is the first identification of blaNDM-5 in P. mirabilis, which suggests its further spread to Enterobacteriaceae, and indicates that IncX3 plasmids may play an important role in potentiating the spread of blaNDM.

Molecular characterization of ISCR1-mediated blaPER-1 in a non-O1, non-O139 Vibrio cholerae strain from China

ABSTRACT We report the detection of PER-1 extended-spectrum β-lactamase (ESBL) in a clinical non-O1, non-O139 Vibrio cholerae strain from China. ISCR1-mediated blaPER-1 was embedded in a complex In4 family class 1 integron belonging to the lineage of Tn1696 on a conjugative IncA/C plasmid. A free 8.98-kb circular molecule present with the ISCR1-blaPER-1–truncated 3′-conserved sequence (CS) structure was detected in this isolate. These findings may provide insight into the mobilization of blaPER-1.

High prevalence of vanM in vancomycin-resistant Enterococcus faecium isolates from Shanghai, China

ABSTRACT The vanM gene was first found in a vancomycin-resistant Enterococcus faecium (VREm) isolate in Shanghai in 2006. In this study, we found that, in 70 VREm strains isolated in nine Shanghai hospitals from 2006 to 2014, vanM was more prevalent than the vanA gene (64.3% [45/70] versus 35.7% [25/70]). The vanM-type isolates showed similar antimicrobial susceptibility patterns with the vanA types. The vanM-type VREm emerged and disseminated in Shanghai.

Coexistence of blaOXA-48 and Truncated blaNDM-1 on Different Plasmids in a Klebsiella pneumoniae Isolate in China

Objectives: To describe the genetic environment, transferability, and antibiotic susceptibility of one clinical Klebsiella pneumoniae isolate harboring both blaOXA-48 and blaNDM-1 on different plasmids from a Chinese hospital. Methods: The isolate was subjected to antimicrobial susceptibility testing and multilocus sequence typing using Etest and PCR. The plasmids harboring blaOXA-48 and blaNDM-1 were analyzed through conjugation experiments, S1-nuclease pulsed-field gel electrophoresis, and hybridization with specific probes. Plasmid DNA was sequenced using Pacbio RS II and annotated using RAST. Results: K. pneumoniae RJ119, carrying both blaOXA-48 and blaNDM-1, was resistant to almost all carbapenems, cephalosporins, fluoroquinolone, and aminoglycosides and belonged to ST307. blaOXA-48 was located on a 61,748-bp IncL/M conjugative plasmid, which displayed overall nucleotide identity (99%) to pKPN-E1-Nr.7. blaNDM-1 was located on a 335,317-bp conjugative plasmid, which was a fusion of a blaNDM-1-harboring InA/C plasmid pNDM-US (140,825 bp, 99% identity) and an IncFIB plasmid pKPN-c22 (178,563 bp, 99% identity). The transconjugant RJ119-1 harboring blaNDM-1 was susceptible to carbapenem, and there was an insertion of IS10 into the blaNDM-1 gene. Conclusion: This is the first report of the coexistence of blaOXA-48 and blaNDM-1 in one K. pneumoniae clinical isolate in China. OXA-48 in RJ119 contributed to the majority to its high resistance to carbapenems, whereas NDM-1 remained unexpressed, most likely due to the insertion of IS10. Our results provide new insight for the relationship between genetic diagnosis and clinical treatment. They also indicate that increased surveillance of blaOXA-48 is urgently needed in China.