CERCETÃRI PRIVIND PRODUCEREA DE BETA-LACTAMAZE CU SPECTRU EXTINS LA TULPINI DE ENTEROBACTERII

Abstract

Aim: To evaluate the susceptibility
of extended spectrum beta-lactamase (ESBL) producing organisms among Escherichia coli and
Klebsiella pneumoniae, isolated between January-October 2009 from hospital and community.
Materials and methods: From 611 enterobacteria strains, for 112 strains (E. coli, n=84 and
K. pneumoniae, n=28), the ESBL phenotypic confirmation was performed with double disk
test (DDT) and the replacement disk method. The minimum inhibitory concentrations (MICs)
for next antimicrobial agents tested: ceftazidime, cefotaxime, ceftriaxone, cefepime, cefpirome,
imipenem, meropenem, ertapenem, moxifloxacin, gatifloxacin, levofloxacin, ofloxacin were
performed by agar dilution method. Resistance rates were reported using the Clinical Laboratory
Standard Institute (CLSI) breakpoints for the fully susceptible category; moderately
susceptible isolates were classified as resistant. K. pneumoniae ATCC 700603 and E. coli
ATCC 25922 were used for quality control. Results: Resistance rates for ceftazidime,
cefotaxime, ceftriaxone and aztreonam among tested strains were very high: 84.5%, 100%,
100% and 96.4% for E. coli and 98.8%, 98.8%, 97.6% and 89.2% for K. pneumoniae, with
the MIC90 values > 256 mg/L for either antimicrobial tested agent. The MICs for fourth
generation cephalosporins ranges from 4 mg/L to 512 mg/L. The MICs for tested quinolones
were > 2 mg/L for 89.2% strains. Using breakpoint for susceptibility, all isolates were
sensitive to ertapenem, imipenem and meropenem. Conclusions: We noticed a high resistance
rate for ceftazidime, cefotaxime, ceftriaxone and aztreonam. In this study, carbapenems demonstrated
the highest degree of activity