[Plasmid-mediated cephalosporinase among extended-spectrum-beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae].
OBJECTIVE
To investigate the prevalence and genotype of plasmid-mediated cephalosporinase (AmpC) beta-lactamase in extended-spectrum-beta-lactamase-producing (ESBL) Escherichia coli and Klebsiella pneumoniae.


METHODS
24 strains of cefoxitin-resistant ESBL-producing E. coli and 8 strains of K. pneumoniae were collected from January to December 2001 at Beijing Chaoyang Hospital. Analytical isoelectric focusing electrophoresis was used to measure the pI of the beta-lactamase. Conjugation experiment was used to study the transfer of cefoxitin resistance. The homology of the isolates was determined by pulsed field gel electrophoresis (PFGE). Plasmid-mediated AmpC enzyme genes were amplified and sequenced by using multiplex PCR.


RESULTS
The prevalence of ESBL-producing E. coli and K. pneumoniae were 16.8% (49/292) and 16.5% (35/212), respectively. The prevalence of AmpC enzyme among ESBL-producing E. coli and K. pneumoniae isolates were 2.0% (1/49) and 17.1% (6/35), respectively. These 7 isolates produced DHA-1 AmpC enzyme. One strain of K. pneumoniae could transfer cefoxitin resistance to the recipient. Among 7strains, 5 strains produced CTX-M-3 and 2 produced SHV-12 ESBL. These 7 strains also produced TEM-1 broad-spectrum enzymes. These strains harbored 2 - 5 plasmids and one of them were 33 - 36 kb. PFGE showed these strains came from a variety of clones.


CONCLUSIONS
In this hospital, 7 strains of the ESBL-positive E. coli and K. pneumoniae produced both DHA-1AmpC enzyme and CTX-M-3/SHV-12 ESBL. These 7 strains were from different clones.
Wang
Qing-tao
QT
Department of Clinical Laboratory, Beijing Chaoyang Hospital, Capital University of Medical Sciences, Beijing 100020, China.
Liu
Ying-mei
YM
Wang
Hui
H
Sun
Hong-li
HL
Chen
Min-jun
MJ
Du
Xiao-ling
XL
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002440:Cefoxitin / Q000494:pharmacology; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D005838:Genotype; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D016133:Polymerase Chain Reaction; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002440:Cefoxitin; C048795:AmpC beta-lactamases; D001618:beta-Lactamases