Characteristics of Acquired beta-lactamase Gene in Clinical Isolates of Multidrug-resistant Pseudomonas aeruginosa / 대한임상미생물학회지

ABSTRACT

BACKGROUND: Recently, there have been reports of infections with multidrug-resistant Pseudomonas aeruginosa. To determine the mechanism of the resistance, we investigated the prevalence of Ambler class A and D beta-lactamases, their extended-spectrum derivatives, and class B and D carbapenemase in multidrug-resistant P. aeruginosa isolates. METHODS: During the period of March 2006 to May 2007, clinical isolates of multidrug-resistant P. aeruginosa were collected from patients in Chungnam National University Hospital, Daejeon, Korea. Inhibitor-potentiated disk diffusion tests were used for the screening of metallo-beta-lactamase (MBL) production. PCR and DNA sequencing were conducted for the detection of beta-lactamase genes. We also employed the enterobacterial repetitive intergenic consensus (ERIC)- PCR method for an epidemiologic study. RESULTS: A total of 37 consecutive, non-duplicate, multidrug-resistant P. aeruginosa were isolated. Twenty- nine of 37 isolates harbored blaOXA-10 (56.8%), blaOXA-2 (18.9%), and blaOXA-1 (5.4%). Only one isolate produced IMP-1, and it also harbored blaOXA-1. None harbored Ambler class A beta-lactamase or class D carbapenemase. The strains producing OXA type beta-lactamases showed a significantly higher resistance to aminoglycoside compared to non-producers. The ERIC-PCR pattern of the 19 OXA-10 producing strains indicated that the isolates were closely related in terms of clonality. CONCLUSION: OXA type beta-lactamases are the most prevalent among the acquired beta-lactamases produced by multidrug-resistant P. aeruginosa isolated at a university hospital in Chungcheong Province. Besides beta-lactam antibiotics, the strains harboring OXA type beta-lactamase showed a significantly higher resistance to aminoglycoside and qunolone.