Korean J Clin Microbiol.  2004 Sep;7(2):124-129.

Isolation of Klebsiella Oxytoca Clinical Isolate Producing AmpC beta-lactamase, DHA-1

• Song W
• Kim JS
• Kim HS
• Lee TJ
• Park MJ
• Park IH
• Lee KM

Abstract

BACKGROUND: Klebsiella oxytoca strain exhibiting an unusual inducible beta-lactam resistance phenotype was isolated from a wound specimen of a patient at a university hospital in August 2002. The isolate was resistant to ampicillin, ampicillin-sulbactam, cephalothin, cefoxitin, and demonstrated reduced inhibition zone diameters for ceftazidime in combination with clavulanate versus those for ceftazidime when tested alone.
METHODS
Antimicrobial susceptibilities were tested using the Etest and disk diffusion method. AmpC beta-lactamase production was determined by modified Hodge test. The disk antagonism method was used to detect inducibility of beta-lactamase. Conjugation experiments were performed by the filter mating method using the recipient Escherichia coli J53 Azir strain. PCR and DNA sequencing of DHA-specific PCR products were tested.
RESULTS
The double disk synergy test was negative and the modified Hodge test was positive for the K. oxytoca isolate. Antagonism was observed between cefoxitin and oxyimino-cephalosporins. Sequence analysis of the DHA-specific PCR products revealed that they were identical to the amino acid sequence of the DHA-1 beta-lactamase. Transfer of the resistance by conjugation experiments was successful.
CONCLUSIONS
We found a plasmid-mediated DHA-1 beta-lactamase-producing K. oxytoca possessing an unusual inducible beta-lactam resistance phenotype was found in a university hospital in Korea. The resistance phenotype was conferred by DHA-1 encoded by a self-transferable plasmid.

Keyword

Klebsiella oxytoca; inducible; AmpC beta-lactamase; DHA-1

MeSH Terms

Amino Acid Sequence
Ampicillin
beta-Lactam Resistance
beta-Lactamases*
Cefoxitin
Ceftazidime
Cephalothin
Clavulanic Acid
Diffusion
Escherichia coli
Humans
Klebsiella oxytoca*
Klebsiella*
Korea
Phenotype
Plasmids
Polymerase Chain Reaction
Sequence Analysis
Sequence Analysis, DNA
Wounds and Injuries
Ampicillin
Cefoxitin
Ceftazidime
Cephalothin
Clavulanic Acid
beta-Lactamases