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Journal of Clinical Microbiology, July 2005, p. 3273-3277, Vol. 43, No. 7
0095-1137/05/$08.00+0 doi:10.1128/JCM.43.7.3273-3277.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Laboratory of General Biology, Faculty of Science, University of Yaoundé I, P.O. Box 812 Yaounde, Cameroon,1 A Stampor "School of Public Health" Medical School, University of Zagreb, Croatia,2 Faculty of Medicine and Biomedical Sciences, University of Yaounde I, P.O. Box 1364 Yaounde, Cameroon,3 Laboratory of Bacteriology, Yaounde Central Hospital, Yaounde, Cameroon,4 Institute of Medical Microbiology, University of Zürich, P.O. Box, CH-8028 Zürich, Switzerland,5 NENT/NANT, Institute of Veterinary Bacteriology, University of Berne, Länggassstrasse 122, P.O. Box, CH-3001 Berne, Switzerland6
Received 28 December 2004/ Returned for modification 18 February 2005/ Accepted 22 March 2005
Organisms producing extended-spectrum ß-lactamases (ESBLs) have been reported in many countries, but there is no information on the prevalence of ESBL-producing members of the family Enterobacteriaceae in Cameroon. A total of 259 Enterobacteriaceae strains were isolated between 1995 and 1998 from patients at the Yaounde Central Hospital in Cameroon. Enterobacterial isolates resistant to extended-spectrum cephalosporin and monobactam were screened for ESBL production by the double-disk (DD) synergy test. Thirty-one (12%) of these Enterobacteriaceae strains were shown to be positive by the DD synergy test, suggesting the presence of ESBLs. Resistance to oxyimino-cephalosporins and monobactams of 12 (38.7%) of the 31 strainsi.e., 6 Klebsiella pneumoniae, 4 Escherichia coli, 1 Citrobacter freundii, and 1 Enterobacter cloacae strainwas transferred to E. coli HK-225 by conjugation. Resistance to gentamicin, gentamicin plus trimethoprim-sulfamethoxazole, or trimethoprim-sulfamethoxazole was cotransferred into 6, 2, and 1 of these transconjugants, respectively. All 12 transconjugants were resistant to amoxicillin, piperacillin, all of the cephalosporins, and aztreonam but remained susceptible to cefoxitin and imipenem. Crude extracts of ß-lactamase-producing transconjugants were able to reduce the diameters of inhibition zones around disks containing penicillins, narrow- to expanded-spectrum cephalosporins or monobactams when tested against a fully susceptible E. coli strain but had no effect on such zones around cefoxitin, imipenem, and amoxicillin-clavulanate disks. The ß-lactamases produced by the 12 tranconjugants turned out to be SHV-12 by DNA sequencing. Therefore, the ESBL SHV-12 is described for the first time in Cameroon.
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