Molecular cha ratce irs it cs of the extended-spectrum β-lactamase and/or AmpC enzyme-producing Proteus mirabilis strains prevelant in Shenzhen People′s Hospital

Abstract

Objective To investigate the prevalence and molecular characteristics of the extended -spectrum β-lactamase （ ESBL） and AmpC enzyme-producing Proteus mirabilis （ P.mirabilis） strains isolated in Shenzhen People′s Hospital.Methods The production of ESBLs and AmpC enzymes by P.mirabilis isolates were detected by a screening and confirmatory test for ESBLs and AmpC disk test , respectively .The PCR assays followed by DNA sequencing of the products were employed to analyze the multiple genes including the ESBLs genes, AmpC genes, insertion sequences （ISs） upstream of the ESBLs or AmpC genes, plasmid -mediated quinolone resistance （ PMQR ） determinants , quinolone resistance-determining region （QRDR） genes , the integrase genes, and class1 integron cassette.The epidemiological analysis of the isolates was performed by pulsed field gel electrophoresis .Results There were 130 P.mirabilis clinical isolates collected from Shenzhen People′s Hospital in China during the year 2004 to 2010.Among them, 13 isolates （10%） produced ESBLs, that accounted for 0%-9.1%in the year 2004-2009 and up to 29.4%in 2010, and 3 isolates （2.3%） produced AmpC enzymes.The predominant genotype of ESBLs -producing isolateswas b al CTX-M-14（n=7）, followed by blaCTX-M-65（n=3）, blaCTX-M-55（n=1）, blaCTX-M-24（n=1） and blaPER-1 （n =1）.The clinical isolate of PER-1-producing P.mirabilis was reported for the first time in China.Twoisolates carried an AmpC β-lactamase gene of blaCMY-2 and one isolate carried an unidentified AmpC gene .ISEcp1 located upstream of blaCTX-M and blaCMY-2 were detected in 91.7% （11/12） of CTX-M-producing isolatesand one CMY-2-producing isolate, respectively.ISPa12 was present upstream of blaPER-1 in one studiedisolate.Approximately 66.7% （10/15） of ESBL and /or AmpC-producing isolates harbored PMQR genes including2 carrying qnrD, 5 carrying aac-Ib-cr and 3 carrying both qnrD and aac-Ib-cr.Twelve ESBL and /orAmpC-producers with high level of resistance to ciprofloxacin carried the similar mutation profiles of S 83I inGyrA, S80I or S80R in ParC and among them, six strains showed E466D mutation in GyrB.Approximately86.7% （13/15） of ESBL and/or AmpC-producing isolates carried class 1 integron.Fourteen PFGE typeswere observed among 15 ESBL and/or AmpC-producers.Conclusion The prevalence of CTX-M β-lactamasesin P.mirabilis isolates contributed to the increased resistance to extended -spectrum cephalosporins.The qnrD and/or aac-Ib-cr genes were detected among the most of ESBL and /or AmpC-producing P.mirabilis clinical isolates. Key words: qnrD; Proteus mirabilis; Extended-spectrum β-lactamase; AmpC enzyme; qnrD; Pulsed-field gel electrophoresis