In vitro evaluation of cefepime and other broad-spectrum β-lactams for isolates in Malaysia and Singapore medical centers

Abstract

The degree of activity of several β-lactam antimicrobial agents was assessed in Malaysia (four medical centers) and Singapore (two medical centers) tested against 570 clinical isolates. The organisms were tested locally by the Etest (AB BIODISK, Solna, Sweden) method, validated by concurrent use of quality assurance strains (94.1% accurate performance overall). Ten groups of bacteria were tested against cefepime, cefpirome, ceftazidime, ceftriaxone, piperacillin/tazobactam, oxacillin, and imipenem. Among the tested Escherichia coli and Klebsiella spp., the occurrence of extended spectrum β-lactamase-producing phenotypes was 5.6–7.0% and 36.7–38.0%, respectively. These strains remained most susceptible (97.5–100.0%) to cefepime and imipenem. Ceftazidime-resistant Enterobacter spp. (21.4% resistant), Citrobacter spp. (15.0%), indole-positive Proteus spp. (6.0%), and Serratia spp. (9.7%) were not resistant to cefepime, and only one strain was resistant to imipenem. Imipenem was generally most potent against nonfermentative Gram-negative bacilli such as Acinetobacter spp. and Pseudomonas aeruginosa. All tested β-lactams were active against the oxacillin-susceptible staphylococci, except ceftazidime (MIC 90, 12 μg/mL; 63.2–84.8% susceptibility rates). Overall spectrums of activity (rank by % resistance) favored imipenem (3.5%) > cefepime (7.7%) > cefpirome (8.9%) > piperacillin/tazobactam (13.2%) > ceftriaxone (14.7%) > ceftazidime (16.9%). No significant differences in resistance patterns were noted between monitored nations, and these results indicate emerging, elevated rates of resistance versus the studied broad-spectrum β-lactams in Malaysia and Singapore. Results provide benchmark data for future studies using quantitative methods to determine antimicrobial resistance in these geographic areas.