Frequency of oxacilinases in Pseudomonas aeruginosa clinical isolates

Abstract

Pseudomonas aeruginosa is an important opportunistic pathogen associated with serious nosocomial infections, especially in intensive care units. The therapeutic options are very limited against P. aeruginosa infections because these isolates possess intrinsic mechanisms of resistance and are able to acquire many others. Frequently, P. aeruginosa are resistant to multiple groups of antimicrobial agents, including b-lactams, aminoglycosides and fluoroquinolones. The production of b-lactamases enzymes is the main mechanism of b-lactam resistance in this pathogen. Cephalosporinases, carbapenemases and oxacillinases represent some of the b-lactamases produced by P. aeruginosa. The principal aim of this study is to estimate the frequency of ES²L OXA-type in P. aeruginosa clinical isolates recovered from patients assisted at Hospital São Paulo from January 1997 to August 2011. P. aeruginosa isolates showing discordant susceptibility profiles especially those resistant to cefepime but susceptible to ceftazidime will be screened for the OXA- encoding genes. The antimicrobial susceptibility profile will be confirmed by Etest. OXA-type-ESBL encoding genes will be searched by multiplex PCR following by DNA sequencing. The genetic similarity among the isolates will be evaluated by PFGE technique. The knowledge of the OXA type produced by P. aeruginosa is of fundamental importance for delineating adequate therapy and further control. (AU)