Outbreak of multi-resistant Klebsiella oxytoca involving strains with extended-spectrum beta-lactamases and strains with extended-spectrum activity of the chromosomal beta-lactamase.
OBJECTIVE
This study was conducted to analyse broad-spectrum cephalosporin-resistant Klebsiella oxytoca strains.


METHODS
The 57 isolates studied were recovered from clinical specimens (n=23) or from rectal swabs (n=34) during a 26-month period. Antibiotic susceptibility patterns were determined using standard agar diffusion and dilution methods including the synergy test between extended-spectrum cephalosporins and clavulanic acid. ERIC-2 PCR and pulsed-field gel electrophoresis (PFGE) methods were used to study the clonal relatedness of the strains. Plasmid-mediated and chromosomal beta-lactamases were characterized by mating and specific bla gene amplification and sequencing.


RESULTS
Four different antibiotic resistance patterns were identified whereas ERIC-2 PCR and PFGE revealed six main profiles. Extended-spectrum beta-lactamases (ESBLs) were found in 32 strains: TEM-7 (n=26), TEM-129 (n=1), TEM-3 (n=4), SHV-2 (n=1). The new TEM-type beta-lactamase, TEM-129, differed from TEM-7 by one mutation (Glu-104-->Lys). All TEM-7 or TEM-129 producers were genetically related. Twenty-five other strains with identical ERIC-2 PCR and PFGE profiles harboured a bla(OXY-2) gene different from the reference gene: 24 strains displayed one substitution (Ala-237-->Ser) in the KTG motif and one strain, highly resistant to ceftazidime, showed an additional substitution (Pro-167-->Ser).


CONCLUSIONS
The study demonstrated that the majority of strains (n=52) harbouring the OXY-2-type beta-lactamase corresponded to two clones. The first clone (n=27) corresponded to ESBL-producing strains. The second clone (n=25) displayed extended-spectrum activity of the chromosomal beta-lactamase.
Decré
Dominique
D
UPRES n EA2392, Faculté de Médecine, UFR Saint-Antoine, Université Paris 6. dominique.decre@chusa.jussie.fr
Burghoffer
Béatrice
B
Gautier
Valérie
V
Petit
Jean-Claude
JC
Arlet
Guillaume
G
D002876:Chromosomes, Bacterial; D003227:Conjugation, Genetic; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D016521:Electrophoresis, Gel, Pulsed-Field; D041121:Klebsiella oxytoca / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000378:metabolism*
D001618:beta-Lactamases