Bactericidal Effect of Anaerobic Broth Exposed to Atmospheric Oxygen Tested on Peptostreptococcus anaerobius

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Abstract
P. anaerobius strain VPI 4330-1 was used as the test organism in an evaluation of the bactericidal effect of anaerobic broth exposed to air. The test organism, grown under anaerobic conditions in Trypticase soy broth, was diluted in buffered salt solution, and about 2 .times. 104 cells were suspended in 10 ml of an aerated broth. Ninety percent of the cells were killed within 15 min in actinomyces broth and within 50 min in Trypticase soy broth. All cells survived for 2 h in fluid thioglycolate medium. Addition of DABCO [1,4-diazabicyclo(2.2.2)octane] or mannitol to Trypticase soy broth did not influence the death rate of the organism, whereas superoxide dismutase decreased the death rate. Addition of catalase or manganese dioxide to the broth kept all the cells viable for 2 h. Of the 3 broth media tested, actinomyces broth reduced O2 at the highest rate and Trypticase soy broth reduced it at the slowest rate. H2O2 could be demonstrated in actinomyces broth and in Trypticase soy broth but not in fluid thioglycolate medium. In addition to catalase, manganese dioxide also removed H2O2 from Trypticase soy broth, and superoxide dismutase significantly decreased the concentration of H2O2 in the broth. Apparently H2O2 mediated the toxic effect of atmospheric O2 in these broth media.