Patterns of resistance associated with integrons, the extended-spectrum beta-lactamase SHV-5 gene, and a multidrug efflux pump of Klebsiella pneumoniae causing a nosocomial outbreak.
Multiresistant Klebsiella pneumoniae caused a nosocomial outbreak. Resistance patterns of the presumed outbreak isolates varied among and within patients. In order to control the outbreak, screening for extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae was commenced. A number of susceptible K. pneumoniae strains were stored to serve as controls in genetic strain typing. Typing by pulsed-field gel electrophoresis proved the clonality of the strains in the recognized outbreak patients. Typing of the control strains by pulsed-field gel electrophoresis showed that at least one patient had been missed by the ESBL screening procedure. Further genetic typing confirmed the presence of the SHV-5 ESBL gene in all but one of the outbreak strains. Variable presence of integrons that carried the aminoglycoside resistance genes aadB and aadA2 was found. A gyrA mutation in codon 83 was present in all outbreak strains tested, despite considerable differences in ciprofloxacin MICs. The MICs of ciprofloxacin and the chemically unrelated drug cefoxitin were correlated (r = 0.86, P < 0.01) and were compatible with the overexpression of an efflux pump in a subset of the outbreak strains. We conclude that outbreak strains that express an ESBL gene only at a low level may pass unnoticed in a screening procedure, when the laboratory is unaware of variable ESBL expression. In this particular outbreak, screening for strains for which ciprofloxacin MICs were > or =0.25 micro g/ml would in retrospect have been the most sensitive method for detection of the K. pneumoniae outbreak strain.
Gruteke
Paul
P
Municipal Public Health Laboratory, Amsterdam. Zuiderzee Hospital, Lelystad, The Netherlands. pgruteke@gggd.amsterdam.nl
Goessens
Wil
W
Van Gils
Jan
J
Peerbooms
Paul
P
Lemmens-Den Toom
Nicole
N
Van Santen-Verheuvel
Marga
M
Van Belkum
Alex
A
Verbrugh
Henri
H
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005260:Female; D006801:Humans; D032023:Integrons / Q000235:genetics*; D007710:Klebsiella Infections / Q000453:epidemiology*; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D013223:Statistics as Topic; D001618:beta-Lactamases / Q000378:metabolism*
D018435:ATP Binding Cassette Transporter, Subfamily B; D000900:Anti-Bacterial Agents; C117193:beta-lactamase SHV-5; D001618:beta-Lactamases; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase