Molecular epidemiology of KPC-2-producing Proteus mirabilis

Abstract

Objective To investigate the molecular epidemiology and resistance mechanism of reduced carbapenem susceptibility of Proteus mirabilis from intensive care unit (ICU). Methods Nineteen carbapenem resistance or reduced carbapenem susceptibility of Proteus mirabilis were isolated from two ICUs in Second Affiliated Hospital of Zhejiang University from August 2010 to October 2010.Pulsed-field gel electrophoresis (PFGE) was performed to analyze the molecular epidemiology of isolates.Antibiotic susceptibilities were determined by agar dilution method.Conjugation experiments were carried out in mixed broth cultures.Plasmid DNAs were obtained by using an alkalinelysis technique.Specific polymerase chain reaction （PCR） and DNA sequencing were preformed to confirm the genotype of β-1actamases. Results Nineteen Proteus mirabilis showed resistance or reduced carbapenem susceptibility, and were resistant or susceptible to cephalosporins.PFGE analysis indicated that nineteen carbapenem-non-susceptible Proteus mirabilis belonged to 3 clones, named as clone A (14 isolates), clone B (2 isolates of subclone B1 and 2 isolates of subclone B2) and clone C (1 isolate).Fourteen clone A isolates were indistinguishable, and subclone B1 and subclone B2 were closely related with only one fragment disparity.Escherichia coli (EC600) acquired an approximately 45 000 bp，54 000 bp and 45 000 bp plasmids from clone A, subclone B1 and subclone B2 isolates separately by conjugation studies.PCRs and DNA sequence analysis confirmed that all Proteus mirabilis isolates and their transconjugants produced the KPC-2 carbapenemase. Conclusion Carbapenem-non-susceptible Proteus mirabilis were epidemic in two ICUs in our hospital，and were clonally disseminated.（Chin J Lab Med,2012,35:349-353） Key words: Proteus infections; Proteus mirabilis; Disease outbreaks; Carbapenems; beta-lactamases