DWS microbiologists, Andrew Pridmore and Charlotte Austin recently had their work published by the Microbiology Society’s Open Access Journal. The poster, which was originally presented at Anaerobe 2021: the microbiota and beyond, examined the variability in oxygen tolerance among the anaerobic bacteria associated with the human intestinal tract. With the overall aim of comparing potential pathogens with the normal microbiota.
The effects of oxygen were studied using two different Whitley Workstations: an A35 to provide strictly anaerobic “reference” conditions and an H35 to provide precisely controlled atmospheric oxygen concentrations in increments of 0.1%.
In initial experiments with high bacterial inoculum densities, the potential pathogens Bacteroides fragilis and Clostridioides difficile grew in the presence of up to 2.4% v/v oxygen, while common “normal microbiota” species of Bifidobacterium, Fusobacterium and Finegoldia tolerated 0.5 – 1.0% and Eggerthella lenta tolerated 0.1%. Potentially therapeutic species of Roseburia, Alistipes, Blautia and Faecalibacterium grew only in strictly anaerobic conditions and were unable to grow when incubated in 0.1% oxygen.
Using the bacterial strains that tolerated at least 0.1% oxygen, quantitative experiments were then performed to determine the percentage recoveries of smaller inocula (100 – 300 cfu on surface spread plates) in the presence of increasing oxygen, in comparison with strictly anaerobic colony counts. In 2.0% v/v oxygen, inoculum recovery for two B. fragilis strains and one C. difficile was >80%. In contrast, recovery of an F. magna strain decreased from 83% in 0.1% oxygen to <1% in 0.5% oxygen.
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