A-062. Variation in the Effect of Exposure to Gatifloxacin on the Metabolic Activities of Different Strains of Clostridium perfringens

F. Rafii, M. Park, G. Gamboa da Costa;
US FDA, Natl. Ctr. for Toxicological Res., Jefferson, AR.

Clostridium perfringens, a member of the normal colonic bacteria, is also a major pathogen that can cause food poisoning, gas gangrene, and antibiotic-associated diarrhea. It produces toxins that are involved in pathogenicity, fermentation products that affect colonic mucosal health, and enzymes that are involved in the activation and detoxification of different compounds. Antibiotic resistance in C. perfringens may develop during treatment of infectious diseases. Strains of Clostridium species resistant to newer fluoroquinolones, such as gatifloxacin, have been found. The effect of exposure to gatifloxacin on toxin production, fermentative activities, and reductive enzymes was evaluated in five different gatifloxacin-resistant gyrase mutants of C. perfringens compared with the five parent wild-type strains. The bacteria were grown under anaerobic conditions in brain heart infusion broth. The amounts of alpha-toxin and theta-toxin produced by the wild type and mutant strains were compared by measuring the lecithin hydrolysis of egg yolk and hemolysis of sheep red blood cells. Reductive enzymes in the mutant and wild type strains were compared by measuring the reduction of 4-nitrobenzoic acid and Direct Blue 15. Acetic acid and butyric acid production was measured by GC-MS with isotopic dilution of labeled internal standards. Comparison of alpha-toxin and theta-toxin production in different strains showed an increase in production of both toxins in one of the gatifloxacin-resistant mutants. RT-PCR showed that there was higher expression of mRNA for the alpha toxin in this mutant than its wild type strain. The concentration of short chain fatty acids in the filter-sterilized supernatant was the same in mutant and wild type for two strains, decreased in the mutants of two strains, and increased in the mutant of one strain. Similar variations were observed in the reductive enzymes as shown by the reduction of the dye and nitro compounds. Our result show that, in addition to the mutations in target genes, exposure to gatifloxacin results in strain-specific physiological changes in C. perfringens that affect activity and pathogenicity.

228/A. Experimental Therapeutics

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