Objective To investigate the prevalence and plasmid size of qnrD determinant in Morganella morganii (M.morganii) isolates.Methods A total of 100 non-duplicated M.morganii clinical isolates were collected from inpatients.Standard ager dilution method was used to determine the minimum inhibitory concentrations (MICs) of fluoroquinolones against M.morganii isolates.PCR were performed to detect plasmid-mediated quinolone resistance determinants (PMQRs) in M.morganii isolates and the prevalence of extended-spectrum β-lactamase (ESBL) genes and AmpC β-lactamase genes in PMQRs-positive M.morganii strains.The homology analysis among qnrD-positive M.morganii strains were conducted by using pulsed-field gel electrophoresis (PFGE).The location of qnrD gene and the size of plasmid carrying it were determined by southern hybridization.The transferability of qnrD gene was determined by conjugation experiment.Results Thirty out of 100 M.morganii isolates (30％) were found carrying PMQRs including 17 qnrD-positive strains,14 aac (6')-Ib-cr-positive strains and 5 qepA-positive strains.PCR and sequencing confirmed that thirty PMQRs-positive isolates carried blaDHA-1.Among them,six isolates were positive for ESBLs genes (four for blaCTX-M-14,one for blaCTX-M-3 and one for blaCTX-M-24) and four isolates were positive for blaTEM-1.Almost all PMQRs-positive M.morganii isolates showed reduced susceptibility to fluoroquinolones.Moreover,seventeen qnrD-positive M.morganii isolates harbored blaDHA-1 including five (29.4％) harboring aac(6')-Ib-cr gene,four (23.5％) harboring blaCTX-M-14,two (11.8％) harboring blaTEM-1 and one harboring aac(6')-Ib-cr gene,blaCTX-M-14 and blaDHA-1.PFGE analysis showed that the 17 qnrD-positive M.morganii isolates were divergent from each other and not clone-related.Southern hybridization analysis showed that qnrD genes of all M.morganiiis isolates were mainly located in a 2.7 kb plasmid,but only a few of them were located in a size of 5.1 kb plasmid.M.morganiiis isolates failed to transfer qnrD gene to E.coli EC600 through conjugation.Conclusion PMQRs were widely distributed in M.morganiiis isolates.qnrD gene was the predominant determinants with a high prevalence rate of 17.0％,followed by aac(6')-Ib-cr gene.qnrD gene was located on a non-conjugative plasmid of approximately 2.7 kb or 5.1 kb.One qnrD-positive M.morganii isolate carrying aac(6')-Ib-cr gene,blaCTX-M-14 and blaDHA-1 was detected.

Objective To investigate the drug resistant genes against carbapenems,aminoglycosides and quinolones and the molecular epidemiology of clinical isolates of Acinetobacter baumannii.Methods Forty non-duplicate strains of Acinetobacter baumannii were collected from clinical specimens in First Affiliated Hospital of Wenzhou Medical University.The identification of strains was conducted by Vitek 2 Compact system.The susceptibilities to antimicrobials commonly used were determined by agar plate dilution method and broth microdilution method.The presence of class B metalloenzyme-encoding genes (blaIMP,blaVIM,blaNDM,blaSIM,blaGIM),class D cabapenemase-encoding genes (blaOXA-23,blaOXA-48,blaOXA-58),16S rRNA methylase genes (armA,rmtB) and quinolone resistance-determining regions (QRDR) in gyrA and parC were detected by polymerase chain reaction (PCR) and sequenced.Chromosomal or plasmid location of blaOXA-23 and armA genes were assessed by Southern blot.Multiple loci sequence classification (MLST) was performed to analyze the molecular epidemiology of these strains.Results All of the 40 isolates were multi-drug resistant Acinetobacterbaumannii (MDR-AB) and showed high level resistance to all of the tested antimicrobial agents excluding colistin and tigecycline.The positive rates of blaOXA-23 and armA were 90％ and 95％,respectively.All of the 40 isolates carried QRDR mutations in gyrA and parC genes,leading to the Ser83→ Leu and the Ser80→ Leu amino-acid substitutions,respectively.Southern blot showed the chromosomal location of blaOXA-23 and armA genes.Six different ST (ST191,ST381,ST373,ST426,ST208 and ST207) were assigned for these isolates by MLST and the most dominant clones were ST191 (23/40) and ST381 (10/40).Conclusions The predominant cabapenemase-encoding gene and 16S rRNA methylase gene of Acinetobacter baumannii isolates in First Affiliated Hospital of Wenzhou Medical University are blaOXA-23 and armA,respectively,which may be located on the chromosome and vertically transmit the drug resistance.ST191 MDR-AB with blaOXa-23 and armA gene clonally spread in this hospital.