Abstract
For a better understanding of the multidrug resistant Pseudomonas aeruginosa (MDR-PA) epidemiology in mainland China, a nationwide surveillance network of 27 tertiary hospitals was established. Non-duplicate MDR-PA isolates from 254 cases of nosocomial infections, were collected during the period August 2011 to July 2012. Minimum inhibitory concentrations (MICs) of nine antimicrobial agents were determined by broth micro-dilution method according to the CLSI guidelines [M7-A10]. Genotyping analysis was performed by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). The presence of acquired carbapenemases was also determined by molecular approaches for 233 carbapenem-resistant isolates. Carbapenemase genes were detected in 19 (8.2%) isolates, with 13 of these isolates encoding IMP-type enzymes, five with VIM-2, and one with KPC-2. MLST analysis revealed significant genetic diversity among the MDR-PA isolates studied, and 91 STs (including 17 novel STs) were identified. However, a long-term outbreak of an emerging extensively drug-resistant (XDR) ST292/PFGE genotype A clone was detected in a hospital from Southwest China. This study has demonstrated that MDR-PA in mainland China have evolved from diverse genetic backgrounds. Evidence of clonal dissemination of the organism and nosocomial outbreaks in some regions, suggest a need to strengthen existing infection control measures.
Highlights
Carbapenems are important antimicrobial agents for the treatment of P. aeruginosa infections
The main clinical wards in which multidrug resistant Pseudomonas aeruginosa (MDR-PA) were isolated included surgical (99 patients, 39.0%) and ICU (68 patients, 26.8%), while the medical ward accounted for 18.9% (48 patients) and all other wards combined accounted for 15.4% (39 patients)
Except for the isolates collected in KM hospital, the MDR-PA isolates exhibited a high genetic diversity and varied resistant patterns
Summary
Carbapenems are important antimicrobial agents for the treatment of P. aeruginosa infections. The most common pattern was resistance to piperacillin/tazobactam, cefepime, aztreonam, imipenem, meropenem and ciprofloxacin, but susceptible to ceftazidime, amikacin and colistin (44 isolates, 17.3%). The MLST ST distribution of the 19 carbapenemase producing isolates was scattered, but three patients hospitalized in the same neurosurgery ward in HN hospital (Fig. 2), had urinary tract infection by IMP-9-producing P. aeruginosa each within 45 days, and shared the same resistance pattern and belonged to ST357.
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