[Prevalence of Class A Extended-Spectrum beta-Lactamases in Clinical Isolates of Acinetobacter baumannii and Pseudomonas aeruginosa.].
BACKGROUND
Prevalence of class A extended-spectrum beta-lactamases (ESBLs) has been investigated repeatedly in members of family Enterobacteriaceae in Korea, but only rarely in Acinetobacter baumannii and Pseudomonas aeruginosa. The aims of this study were to determine the prevalence of class A ESBL-producing A. baumannii and P. aeruginosa and to characterize the genotypes.


METHODS
During the period of June to September 2004, clinical isolates of A. baumannii and P. aeruginosa were collected from patients in Kosin University Gospel Hospital, Busan, Korea. Antimicrobial susceptibility was determined by the disk diffusion and the agar dilution methods, and ESBLproduction by the double-disk synergy test. Transferability of ceftazidime-resistance of ESBL-producers were tested by conjugation. The isoelectric points of ESBLs were determined by isoelectric focusing. Searches for bla(TEM), bla(SHV), bla(CTX-M), bla(PER-1), bla(VEB), and bla(GES/IBC) genes were performed by PCR amplification, and the genotypes of ESBLs were determined by a direct nucleotide sequence analysis of the amplified products.


RESULTS
A total of 58 clinical isolates of A. baumannii and 77 P. aeruginosa were collected. Three (5.2%) isolates of A. baumannii and four (5.2%) P. aeruginosa isolates showed positive results in the double-disk synergy test using ceftazidime and imipenem disks, and one (1.7%) A. baumannii and two (2.6%) P. aeruginosa isolates showed positive results in that test using ceftazidime and cefoxitin disks. The most prevalent class A ESBL genotype in A. baumannii isolates was bla(PER-1) (n=6), and bla(SHV-12) gene was also found in one P. aeruginosa isolate.


CONCLUSIONS
It is concluded that class A PER-1 ESBL-producing A. baumannii isolates are spreading, and SHV-12-producing P. aeruginosa has emerged in Korea. The spread of class A ESBLs could compromise the future usefulness of expanded-spectrum beta-lactam antibiotics for the treatment of A. baumannii and P. aeruginosa infections.