Distribution and drug-resistance of 3 500 gram-negative bacteria in Guangzhou

Objective: To investigate the distribution and drug-resistance of the common gram-negative bacteria in Guangzhou.

Methods: From July 2001 to August 2003, the resistance of 3 500 strains of common gram-negative bacteria isolated from 13 hospitals in Guangzhou to 15 to 21 antibiotics was determined by standard Kirby-Bauer method according to the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS, 2000). WHONET-5 software was used to analyze the data.

Results: Totally 3 500 gram-negative bacterial strains were isolated from 13 hospitals in Guangzhou in the past two years, and the top 3 most common pathogens of them were Escherichia coli (1 244 strains, 35.5%), Klebsiella pneumoniae (900 strains, 25.7%), and Pseudomonas aeruginosa (547 strains, 15.6 %). The total prevalence of extended-spectrum beta-lactamases (ESBLs)-producing strains was 31.0% (1 084/3 500). The prevalences of ESBLs-producing strains in the Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter cloacae, Acinetobacter SP., other Enterobacter SP., Stenotrophomonas maltophilia, and Proteus SP. in Guangzhou were 38.7%, 37.9%, 5.3%, 55.2%, 8.2%, 27.7%, 33.3% and 9.2%, respectively. Among them, 1 463 (41.8%) strains was isolated from the respiratory tract and 943 (26.9%) from the urinary tract. According to our surveillance, the clinical antibacterial drug with the lowest total drug-resistance rates of Gram-negative bacteria was imipenem (8.7%) followed by Cefoperazone/sulbactam (13.3%), while that with the highest resistance was ampicillin (90.9%) followed by nalidixic acid (69.3%). Imipenem was the most effective agents against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Acinetobacter SP., other Enterobacter SP., and Proteus SP. isolated from 13 hospitals in Guangzhou, with drug-resistant rates of 1.1%, 0.5%, 0.6%, 3.2%, 0.8% and 0%, respectively, whereas the most effective agents against Pseudomonas aeruginosa and Stenotrophomonas maltophilia was cefoperazone/sulbactam, with the drug-resistance rates of 10.8% and 15.9%, respectively. Most of the isolates were multi-drug resistant. The resistance rates of ESBLs-producing strains to 15 to 21 antimicrobial agents were much higher than those of non-ESBLs-producing strains (P<0.05).

Conclusions: Drug resistance of the clinical isolates is a serious problem in Guangzhou, and the increasing prevalence of ESBLs-producing strains of other bacteria should be given full attention. An unanimous and effective strategy for controlling this problem is urgently needed. Imipenem and cefoperazone/sulbactam are the most effective antibiotics against the gram-negative bacteria isolated from the 13 hospitals in Guangzhou.