ABSTRACT
Objective To study the main types and their distribution of molecular typing of carbapenem-resistant Acinetobacter baumannii (CRAB)in Beijing.Methods Seventy-eight non-repeated CRAB strains were isolated and collected from patients aged over 60 years in hospitals in Beijing from 2010 to 2014.The drug susceptibilities of 11 antimicrobial agents were tested by microdilution method.A modified Hodge assay was used to preliminarily screen the carbapenemases.A multiplex PCR assay was used for detection of the carbapenemases genes:OXA-23-like,OXA-24-like,OXA-51-like,OXA-58-like,IMP-1,and VIM-2 of Acinetobacter baumannii.We also detected the insertion sequence IsAbal of OXA-23-like and OXA-51-like,and the preliminary classification of homology of carbapenem-resistant Acinetobacter baumannii (CRAB)was conducted by 3LST technique.According to the drug susceptibility,carbapenemases gene typing,3LST primary screen,and hospital distribution,22 strains were selected to conduct MLST classification.Results The test of OXA enzyme gene in 78 strains of CRAB showed that all the strains(100％)carried oxa-51-like,and 74/78 strains(94.8％)carried oxa-23-like.Additionally,all products of ISAbal-oxa-23 were positive in OXA-23-like positive strains.In the examined five β-lactamase genes,74 strains(94.8％)showed positive AmpC gene;50 strains (64.1％) showed positive TEM-1 gene;5 strains (6.4％) showed positive PER-1 gene;48 strains(61.5％)showed positive genes of TEM-1 and AmpC and 3 strains showed positive genes of TEM-1,Amp C,and PER-1.By using 3LST technique for preliminary classification,we found 74 strains were in type Ⅰ of group types belonging to the European Ⅱ cloning spectrum.Of the six ST types found in MLST classification,the ST195,ST208,ST218 and ST368 belonged to the clone complex 92(CC92);the ST103 and ST500 were two newly discovered types in Chinese population.Conclusions CC92 clone cluster is the major epidemic strain of CRAB in Beijing,which belongs to the classic European Ⅱ cloning spectrum,and its insertion sequence,Abalinduced OXA-23-like carbapenemases is the major molecular of carbapenem resistant Acinetobacter baumannii(CRAB) in Beijing.Both AmpC and TEM-type 1 β-lactamase genes are detected to be positive in most of strains.The newly discovered two types are mainly CC103 clone complex.
ABSTRACT
Objective To investigate the antimicrobial resistance ,molecular phenotypes ,virulence gene profiles of Salmonella A gona (S .A gona) isolated from patients with acute diarrhea ,and to better understand its epidemic trend ,prevention and treatment .Methods Clinical data and stool samples of patients with acute diarrhea during April to October in 2013 and 2014 from the Second Hospital of Tianjin Medical University were collected .Enrichment culture ,biochemical identification and serotyping analysis were used to isolate and identify S .A gona strains .The isolated strains were further analyzed with antibiotics susceptibility test ,pulsed field gel electrophoresis (PFGE) ,multiple locus sequence typing (MLST ) , Quinolone resistance determining region (QRDR) .Plasmid-mediated quinolone resistance (PMQR) and β-lactamases genes (TEM ,SHV ,OXA ,and CTX-M) were amplified by polymerase chain reaction (PCR) and sequencing .The representative genes carried by Salmonella pathogenicity islands (SPI) 1 — 6 ,9 — 12 and virulence plasmids were amplified by PCR .And the clinical characteristics of S .Agona infection were analyzed .Results Among 119 non-repetitive (non-typhoidal salmonella ,NTS) isolates during the two years ,eight isolates (6 .7％ ) of S .A gona were identified . The resistance rate of S .A gona strains to streptomycin was 100 .0％ , those to ampicillin and gentamicin were 62 .5％ ,to levofloxacin ,ciprofloxacin and nalicixic acid were 25 .0％ ,to chloramphenicol ,amoxillin/clavulanic acid and piperacillin tazobactam were 12 .5％ .The strains were susceptible to other drugs .All 8 isolates had the identical ST13 genotype .PFGE showed 5 clones ,and 4 out of 5 isolates had the exact same patterns of PFGE and drug susceptibility .Two (fluoroquinolones ,FQ) resistant strains carried gyrA mutation leading to amino acid substitutions at position 87 in GyrA ,and no PMQR genes was detected ,while one of which was sensitive to ciprofloxacin by K-B method .All five ampicillin-resistant isolates were positive for TEM-1b gene and one isolate of them was resistant to β-lactam/β-lactamase inhibitor complex .The representative genes carried by SPI 1 — 6 , 9 ,11 ,12 (hilA ,sseL ,mgtC ,siiE ,sopB ,pagN ,bapA ,pagC and sspH2) were 100 .0％ positive ,while the genes carried by SPI10 (sef A ) virulence plasmids (spvB , prot6E) were negative . Two patients with FQ resistant strains infection were clinically diagnosed with bacillary dysentery ,and the remaining six cases with FQ susceptible strains infection were clinically diagnosed with acute gastroenteritis .Conclusions FQs-resistant and multi-drug resistant S .A gonaisolates have emerged in clinical settings .These isolates carry a variety of virulence genes .Resistance to FQ of S .Agonamay cause more severe illness .ST13 might be the dominant genotype of S . A gona in China ,and we should try to prevent the infection outbreak of S .A gona .
ABSTRACT
Multiple locus sequence typing (MLST) was undertaken to extend the genetic characterization of 29 isolates of Bacillus cereus and Bacillus thuringiensis previously characterized in terms of presence/absence of sequences encoding virulence factors and via variable number tandem repeat (VNTR). Additional analysis involved polymerase chain reaction for the presence of sequences (be, cytK, inA, pag, lef, cya and cap), encoding putative virulence factors, not investigated in the earlier study. MLST analysis ascribed novel and unique sequence types to each of the isolates. A phylogenetic tree was constructed from a single sequence of 2,838 bp of concatenated loci sequences. The strains were not monophyletic by analysis of any specific housekeeping gene or virulence characteristic. No clear association in relation to source of isolation or to genotypic profile based on the presence or absence of putative virulence genes could be identified. Comparison of VNTR profiling with MLST data suggested a correlation between these two methods of genetic analysis. In common with the majority of previous studies, MLST was unable to provide clarification of the basis for pathogenicity among members of the B. cereus complex. Nevertheless, our application of MLST served to reinforce the notion that B. cereus and B. thuringiensis should be considered as the same species.