Antimicrobial susceptibility and extended-spectrum beta-lactamases of Hong Kong isolates of enterobacteriaceae.

High levels of resistance to extended-spectrum cephalosporins have been reported in the Western Pacific area but data on the prevalence of extended-spectrum beta-lactamases (ESBLs) is more scanty. 370 Hong Kong blood culture isolates of Enterobacteriaceae isolated in the years 1990 and 1995 were evaluated for resistance to 15 antibiotics and the presence of ESBLs. 1995 isolates showed increased levels of resistance for beta-lactams, trimethoprim, ciprofloxacin and aminoglycosides. The proportion of E. coli harbouring ESBLs was 1/61 (1.6%) in 1990 and 2/77 (2.6%) in 1995. The prevalence in Klebsiella spp. rose from 1/36 (2.8%) in 1990 to 5/49 (10.2%) in 1995. ESBLs were found most frequently in Enterobacter spp. and were present in 7/29 (24.1%) of 1990 isolates and 5/22 (22.7%) of 1995 isolates. ESBLs may not be detectable in routine susceptibility testing and appropriate screening methods such as double disc screening tests are necessary to accurately determine ESBL prevalence.