Role of β−lactamase in the susceptibility of clinical isolates to β−lactam antibiotics

Abstract

Combination of βâlactam antibiotic with βâlactamase inhibitor has been proven to overcome resistance caused by βâlactamase production. An evaluation to the MIC of some βâlactam antibiotics to βâlactamase producing isolates will be reported. A. anitratus, E. coli, K. pneumoniae, Proteus sp, Pseudomonas sp, S. aureus, S. epidermidis, S. pneumoniae, S. viridans, and βâhemolytic Streptococcus, were challenged to Ampicillin/Sulbactam (AMS), Amoxicillin/Clavulanic acid (AMC), Cefoperazone (CFP), Cefoperazone/Sulbactam (CSL), Ceftriaxone (CRO), dan Cefotaxime (CTX) using ETest techniques. βâlactamase production was identified using Cefinase disk. Sixtyfour percent of isolates were capable of producing βâlactamase. All E. coli and K. pneumoniae tested were βâlactamase producer, none of Proteus sp, Pseudomonas sp, and S. epidermidis tested produced βâlactamase. In βâlactamase producing group, Sulbactam was able to reduce resistance to CFP from 25% to 5%. About 20% of βâlactamase producing isolates which were resistant to CFP, were susceptible to CSL. Susceptibility of S.viridans to AMS, AMC, CFP, and CSL was higher than 80%, but less than 50% to CRO and CTX. S. pneumoniae was less susceptible to tested antibiotics, 50 to 60% susceptibility was shown to AMC, CFP, and CSL. S.aureus was 60 to 70% susceptible, while βâhaemolytic Streptococcus showed good response to the tested antibiotics. Only 30% or less of K. pneumoniae and E. coli was susceptible to AMS and AMC. A. anitratus showed good susceptibility only to AMS (78%) and CSL (89%). Sixtyfour percent of isolate studied produced βâlactamase. βâlactamase inhibitor could reduce resistance of βâlactamase producing organism to βâlactam antibiotic from 25 to 5 percent. (Med J Indones 2004; 13: 140-5)

Keywords: Antibiotic Susceptibility, MIC, βâlactam antibiotic, βâlactamase inhibitor