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 / 中华微生物学和免疫学杂志

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 isola-ted 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 inclu -ding 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 iso-lates was performed by pulsed field gel electrophoresis .Results There were 130 P.mirabilis clinical iso-lates 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.