Naslov
Effect of Amount Of Beta-lactamase On The Post Beta-lactamase Inhibitor Effect of Clavulanic Acid Against Isogenic Escherichia coli Strains Producing SHV Extended-Spectrum Beta-lactamases.

Autori
Bedenić, Branka

Izvornik
Clinical microbiology and infection (1198-743X) 10 (2004), Suppl. 3; 564-565

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, kongresno priopcenje, znanstveni

Ključne riječi
Post-beta-lactamase inhibitor effect; Escherichia coli; SHV Extended-Spectrum Beta-lactamases

Sažetak
Objectives Post-beta-lactamase inhibitor effect (PLIE)is a phenomenon which enables beta-lactam/inhibitor combinations to remain active in vivo throughout the interval between two consecutive doses, even when inhibitor serum concentrations decrease to values below those active in vitro. The aim of this investigation was to determine the effect of increased amount of SHV -extended-spectrum beta-lactamases (ESBLs) on the duration of the postantibiotic effect (PAE) and post-beta-lactamase-inhibitor effect (PLIE). Methods The experiments were performed on isogenic Escherichia coli strains with strong and weak promoters which produce SHV-2, SHV-3 and SHV-5 beta-lactamases. The strains with weak promoter produced low amount of beta-lactamase (mpb strains) while strains with strong promoter hyperproduce the enzyme (mpa strains). The minimum inhibitory concentrations (MICs) of beta-lactams alone and combined with clavulanic acid were determined by broth microdilution method. The determination of PAE and PLIE was performed by viable counting method. PAE was calculated as PAE=T-C, where T is the time necessary for viable bacteria in the test culture to grow by 1 log10 and C is time necessary for viable bacteria in the control culture to grow by 1 log10. PLIE was calculated as PLIE= total delay-(DG-delay of growth due to experimental conditions + PAE) Results The PLIE lasted 1.4 h for the SHV-2 mpb strain, 2.2 h with SHV-3 -mpb strain and 0.9 h for SHV-5 mpb strain. The strains with strong promoter had shorter duration of PLIE. It ranged from 0.3 h for SHV-3 mpa strain to 0.8 h for SHV-2 mpa strain. No PLIE was detected for SHV-5-mpa strain. The PAE was also of shorter duration in the strains which hyperproduce beta-lactamase. It was not observed with SHV-3-mpa and SHV-5- mpa strains. Mpb strains with lower amount of beta-lactamase had a duration of PAE which ranged from 0.62 to 1.4h. Conclusions The hyperproduction of SHV- ESBL shortened the duration of PAE and PLIE in isogenic E. coli strains. This phenomenon could be responsible for the resistance of some SHV-ESBL-producing Enterobacteriaceae with high level enzyme production to beta-lactam/inhibitor combinations and for in- vivo therapeutic failures of such combinations.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti, Kliničke medicinske znanosti

POVEZANOST RADA