The genotypes of extended-spectrum β-lactamases in 119 clinical isolates of Proteus mirabilis

Objective To investigate the prevalence of ESBLs and resistance genes in the 119 strains of Proteus mirabilis isolated in Renji Hospital between January 2007 and June 2008. Methods Susceptibility was determined by K-B method for the 119 Proteus mirabilis strains. Screening and confirmatory tests were done to identify ESBLs-producing strains. Sequencing analysis was conducted to characterize TEM,CTX-M -1 group,CTX-M-2 group,CTX-M-9 group and SHV genes in ESBLs positive strains. Results The prevalence of ESBLs in 119 Proteus mirabilis strains was 20.2%. All ESBLs positive strains were highly resistant to cephalosporin antibiotics and completely resistant to cefuroxime and cefazolin. However,resistance to cefotaxime,gentamicin and ciprofloxacin was 95.5%,95.2% and 86.4%,respectively. TEM gene,CTX-M-1 group,and CTX-M-2 group were identified in 70.8%,54.2% and 33.3% of the 24 ESBLs-positive strains,respectively. No CTX-M-9 group or SHV gene was identified. Sequencing analysis results indicated that all the 17 TEM-positive Proteus mirabilis strains were TEM-1 type. The 13 strains carrying CTX-M-1 group ESBLs belonged to CTX-M-3 subtype. The 8 strains harboring CTX-M-2 group ESBLs belonged to CTX-M-2 subtype. Conclusions The prevalence of ESBLs is high in Proteus mirabilis isolates. ESBLs-producing strains are resistant to multiple antibiotics,including penicillins,cephalosporins,quinolones,sulfonamides and aminoglycosides.