Transposition of the gene encoding a TEM-12 extended-spectrum beta-lactamase.
An isolate of Klebsiella oxytoca from the blood culture of a child with leukemia was found to produce two beta-lactamases, at least one of which conferred resistance to ceftazidime. Genes encoding both enzymes were located on a single self-transmissible 100-kb plasmid, pOZ201. This plasmid was introduced into Escherichia coli UB5201 (pACYC184), and the gene encoding one beta-lactamase was transposed onto plasmid pACYC184 by exploiting a gene dosage effect. The transposable gene was found to encode a TEM-12 enzyme as determined by nucleotide sequencing. This gene was subsequently transposed onto plasmid pUB307. The transposable element encoding the TEM-12 enzyme has been designated Tn841. Both plasmids pACYC184::Tn841 and pUB307::Tn841 were shown to encode a beta-lactamase with the same isoelectric point and substrate profile as the TEM-12 beta-lactamase. Transposon Tn841, at approximately 7 kb, is larger than TnA (4.8 kb) and transposes at a lower frequency. Although it produced a resolvase which can complement the resolvase of Tn3, its transposase function was not able to complement the transposition of a TnA element which lacked transposase. The occurrence of a gene encoding an extended-spectrum beta-lactamase on a transposable element in a clinically significant bacterium is potentially a cause for concern for the spread of resistance to the extended-spectrum cephalosporins.
Heritage
J
J
Department of Microbiology, University of Leeds, United Kingdom.
Hawkey
P M
PM
Todd
N
N
Lewis
I J
IJ
D001483:Base Sequence; D004251:DNA Transposable Elements / Q000502:physiology; D004269:DNA, Bacterial / Q000096:biosynthesis; D007525:Isoelectric Focusing; D007709:Klebsiella / Q000235:genetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D001618:beta-Lactamases