Pyruvate dehydrogenase activity and metronidazole susceptibility In Bacteroides fragilis

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Abstract
Pyruvate dehydrogenase activity was present and comparable (giving a colour change of 202–673 od units/min/g protein in our assay system) in two clinical strains of Bacteroides fragilis exhibiting reduced sensitivity to metronidazole (MIC 2–8 mg/1 at 48 h) in a resistant strain (Ingham's) of BacL fragilis (MIC 64/mg/l) and in two sensitive strains of Bact. fragilis (MIC 0–5 mg/1). Pyruvate dehydrogenase activity was not detected in a capnocytophaga strain (sensitive to 50 ug disc of metronidazole), in Escherichia coli or in ‘Bact. fragilis’strain (Britz) AM24s (MIC> 64 mg/1). Further testing of AM24s strain indicated that it was not Bact. fragilis but a facultatively anaerobic Gram-negative rod. Pyruvate dehydrogenase activity therefore, is similar in sensitive and resistant strains of Bact. fragilis and is unlikely to be related to the mechanism of resistance to metronidazole.