[Effect of broad spectrum beta-lactamases on in vitro sensitivity of clinical isolates of Klebsiella pneumoniae to oral cephalosporins].
Extended-spectrum beta-lactamases which confer resistance to oxymino cephalosporins, are derived from common TEM-1, TEM-2 and SHV-1. beta-lactamases by mutations which alter the configuration of active site and expand their spectrum of activity. The aim of this investigations was to determine the effect of these enzymes on in vitro susceptibility of clinical isolates of Klebsiella pneumoniae to oral cephalosporins. beta-lactamases were characterised by isoelectric focusing and polymerase chain reaction. The susceptibility of K. pneumoniae isolates harboring these enzymes to oral cephalosporins was determined by broth-microdilution method and the stability of these antibiotics to enzyme degradation was tested by macroiodometric method. Based on the isoelectric point beta-lactamases were assigned into three groups: SHV-2 type (pI 7.6), SHV-5 type (pI 8.2) and TEM-1 derivates (pI 5.4). All types of beta-lactamases described in this investigation were associated with high level of resistance to older cephalosporins like cephalexin, cefaclor, cefuroxime, cefotiam, cefprozil and cefadroxil and to amoxycillin too. Third generation oral cephalosporins like ceftibuten and cefetamet were more stable in the presence of beta-lactamases but some of the strains were resistant to these antibiotics too. SHV-5 beta-lactamases producers displayed higher level of resistance to most of oral cephalosporins compared to SHV-2 and TEM producing strains. According to the results of this investigation oral cephalosporins cannot be considered as a therapeutic option for the treatment of infections caused by ESBL producing K. pneumoniae isolates.
Zavod za mikrobiologiju, SNZ A. Stampar, Medicinski fakultet, Zagreh.
B
B
Bedenić
S
S
Singer
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000096:biosynthesis*
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D001618:beta-Lactamases