Regional variation in the prevalence of extended-spectrum β-lactamase-producing clinical isolates in the Asia-Pacific region (SENTRY 1998-2002)

We examined the prevalence of extended-spectrum β-lactamase (ESBL)-producing strains of Klebsiella pneumoniae, Klebsiella oxytoca, Escherichia coli, Proteus mirabilis, Citrobacter koseri, and Salmonella spp. that were isolated as part of the SENTRY Asia-Pacific Surveillance Program between 1998 and 2002. During the study period, a total of 6388 strains were gathered from 17 medical centers in 7 countries and examined for ESBL production and hyperproduction of K. oxytoca chromosomal K1 β-lactamase enzyme. High rates of confirmed ESBL-producing isolates were found in K. pneumoniae strains from Singapore (35.6%), followed by those from mainland China (30.7%), South Africa (28.1%), and the Philippines (21.9%), whereas the rates were less than 10% in Japan and Australia. ESBL-producing E. coli strains were also prominent in mainland China (24.5%), Hong Kong (14.3%), and Singapore (11.3%). ESBL-producing K. oxytoca were common in the Philippines (38.5%), Singapore (33.3%), and China (30.0%). Hyperproduction of K. oxytoca chromosomal K1 β-lactamase enzyme was common in Australia and Japan. P. mirabilis strains from Singapore produced ESBL (17.9%) despite the low prevalence (0-8.1%) in other countries. Few ESBL-producing C. koseri and Salmonella spp. strains were found in Japan, Singapore, Taiwan, and South Africa. Although there was variation among countries in substrate preference, ceftazidime was more likely to detect presumptive ESBL phenotype in K. pneumoniae and aztreonam more likely in E. coli, whereas ceftriaxone was the best substrate for the confirmation of ESBL production. ESBL-producing strains showed high levels of coresistance to aminoglycosides, tetracycline, trimethoprim-sulfamethoxazole, and ciprofloxacin. Imipenem retained activity against all ESBL-producing strains. Organisms expressing ESBLs are widely distributed in the Asia-Pacific region, although prevalence rates vary significantly.