JAC Advance Access originally published online on November 30, 2005
Journal of Antimicrobial Chemotherapy 2006 57(1):24-30; doi:10.1093/jac/dki429
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CTX-M-15 extended-spectrum ß-lactamase from Nigerian Klebsiella pneumoniae
1 Department of Pharmaceutical Microbiology, University of Ibadan, Ibadan, Nigeria; 2 Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195, USA; 3 Johnson & Johnson Pharmaceutical Research and Development, L.L.C., Raritan, NJ, USA
Received 8 August 2005; returned 26 September 2005; revised 28 October 2005; accepted 1 November 2005
* Corresponding author. Tel: +1-206-543-8001; Fax: +1-206-543-3873; E-mail: marilynr{at}u.washington.edu
Objectives: In this study, extended-spectrum ß-lactamases (ESBLs) were characterized from 30 selected multidrug-resistant Klebsiella pneumoniae strains isolated from patients with community-acquired urinary tract infections from Southwest Nigeria.
Methods: The ß-lactamases were phenotypically characterized using isoelectric focusing, genotypically characterized using PCR assays and hybridization of the PCR products. Two of the blaCTX-M genes were completely sequenced. The location of the CTX-M-type genes was determined using transformation, DNA–DNA hybridization, PCR assays and hybridization of the PCR products from the Escherichia coli transformants.
Results: All 30 isolates produced at least one ß-lactamase. Seventeen of the isolates were resistant to cefotaxime, and had 
100-fold reduction in susceptibility with cefotaxime plus clavulanic acid (4 mg/L), indicating the presence of an ESBL. The 17 isolates were shown to have blaCTX-M genes that were associated with large plasmids (58 kb), which also carried a tetracycline resistance gene, tet(A), and various aminoglycoside resistance genes. Two CTX-M-type genes were sequenced and had amino acid sequences indistinguishable from previously sequenced CTX-M-15 ß-lactamases. The ISEcp1 element was located upstream of blaCTX-M-15 in the same position as previously described. In addition, 23 of the isolates produced TEM ß-lactamases, 27 produced SHV ß-lactamases and four produced AmpC ß-lactamases.
Conclusions: Thirty K. pneumoniae produced multiple ß-lactamases, with 57% producing CTX-M enzymes. This is the first characterization of CTX-M-15-positive K. pneumoniae in Western Africa.
Keywords: K. pneumoniae , ESBLs , CTX-M enzymes
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