Development of extended-spectrum activity in TEM β-lactamases in hyper-mutable, mutS Escherichia coli |
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Authors: | M J Ellington D M Livermore T L Pitt L M C Hall N Woodford |
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Institution: | Antibiotic Resistance Monitoring and Reference Laboratory, Centre for Infections, Health Protection Agency, London, UK. matthew.ellington@hpa.org.uk |
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Abstract: | TEM-1 and TEM(pUC19)beta-lactamases can gain activity against ceftazidime and other expanded-spectrum cephalosporins via point mutation. The frequency of emergent resistance to ceftazidime at 4 x MIC was elevated >or= 250-fold in hyper-mutable, MutS-deficient Escherichia coli harbouring these beta-lactamase genes on high- or low-copy plasmids. Moreover, although ceftazidime-resistant mutants, or those with reduced susceptibility, were selected in both the wild-type and mutS hosts, many more mutants in the mutS host showed ceftazidimase-type extended-spectrum beta-lactamase (ESBL) activity. This correlated with a G-A point mutation at position 484 in the bla(TEM-1) and bla(TEM-pUC19) genes, conferring the Arg164His amino-acid substitution found in the TEM-29 ESBL. Non-ESBL mutants lacked changes in bla(TEM). |
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Keywords: | bla TEM ceftazidime Escherichia coli extended-spectrum β-lactamase hyper-mutator resistance |
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