Interplay of efflux, impermeability, and AmpC activity contributes to cefuroxime resistance in clinical, non-ESBL-producing isolates of Escherichia coli.
Cefuroxime resistance in Escherichia coli strains susceptible to extended-spectrum cephalosporins is not uncommon, but the resistance mechanisms have so far not been elucidated. Therefore, 14 clinical non-extended-spectrum beta-lactamase isolates of E. coli were examined, 11 of which were cefuroxime resistant. Quantitative RT-PCR was used to examine the transcription levels of the genes acrA (encoding AcrA, part of the AcrAB-TolC efflux pump system) and ompF (encoding the porin OmpF). Isoelectric focusing was used for detection of beta-lactamases, and a spectrophotometric assay was used to measure AmpC activity. Among the 11 cefuroxime-resistant isolates, 7 had increased acrA transcription (from 2.4 to 38 times the ATCC strain), 3 isolates had very low ompF transcription levels (<or=0.01 times the ATCC strain), and 2 isolates showed increased AmpC activity (confirmed by 3-aminophenylboronic acid inhibition). We suggest that efflux, impermeability, and increased AmpC activity all contribute to cefuroxime resistance in E. coli.
Clinical Microbiology, MTC, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden. owe.kallman@karolinska.se
Owe
O
Källman
Christian G
CG
Giske
Ørjan
Ø
Samuelsen
Bengt
B
Wretlind
Mats
M
Kalin
Barbro
B
Olsson-Liljequist
D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001897:Boronic Acids / Q000494:pharmacology; D002444:Cefuroxime / Q000493:pharmacokinetics*; D002463:Cell Membrane Permeability; D024881:Drug Resistance, Bacterial; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D008074:Lipoproteins / Q000096:biosynthesis / Q000235:genetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D008826:Microbial Sensitivity Tests; D018272:Porins / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000378:metabolism*
C083497:AcrA protein, E coli; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001897:Boronic Acids; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; C109237:OmpF protein; D018272:Porins; D065093:beta-Lactamase Inhibitors; C028592:3-aminobenzeneboronic acid; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; D002444:Cefuroxime