Background : In recent years, Acinetobacter baumannii isolates acquired resistance to cefepime have increased significantly. The aim of this study was to survey the prevalence of PER-1 extendedspectrum β-lactamase (ESBL)-producing A. baumannii isolates in a University Hospital, Busan, Korea.

Methods :Antimicrobial susceptibilities were tested by the disk diffusion method, and double disk synergy test was performed for screening of ESBL-production. MICs were determined by agar dilution method. The isoelectric points of β-lactamases were determined by isoelectric focusing. Transferability of cefepime-resistance were tested by conjugation. bla_PER-1 and bla_PER-2 alleles were detected by PCR, and the DNA sequences of amplified products were determined by using the dideoxy-chain termination method.

Results :Among 51 clinical isolates of A. baumannii intermediate or resistant to cefepime, 10 isolates (19.6%) showed positive results in double disk synergy test. PCR-based experiments detected bla_PER-1 gene in all the 10 isolates. All the isolates contained three β-lactamase bands: pI 5.3, 7.9, and 9.4. MICs of ampicillin, piperacillin, cephalothin, cefoxitin, cefoperazone, ceftazidime, cefotaxime, cefepime, and aztreonam were >256 mg/L, respectively, and them of imipenem were 8-16 mg/L.

Conclusion :The prevalence of PER-1-producing  strains in Busan was less than that of in Seoul. But an outbreak of infection caused by this strain in an intensive care unit shows that spread of PER-1-producing A. baumannii strains can be anticipated in a near future. Prevention of hospital infection by these resistant microorganisms are needed. (Korean J Clin Microbiol 2004;7(1):20-26)