Comparative growth rates of selected anaerobic species in four commonly used broth media

Generations times (g(t)) of selected anaerobic species were compared in four culture media commonly used for anaerobic bacteria to evaluate these media for growing inocula for anaerobic antibiotic susceptibility determinations. Twenty-two clinical isolates of Bacteroides fragilis, Fusobacterium spp., Clostridium perfringens, and Clostridium spp. were tested in Schaedler broth, supplemented Lombard-Dowell broth, supplemented thioglycolate broth, and supplemented peptone-yeast extract-glucose broth. Growth curves were performed in an anaerobic chamber; changes in cell density were followed by viable count procedures and, in some cases, turbidometric procedures. The clostridia did not appear to have significantly different g(t) values in different media. The g(t) values for the five clostridial species tested ranged from 18 to 45 min. The fusobacteria also showed no apparent differences in g(t) values in the four media; values ranged from 51 to 60 min. The two subspecies of B. fragilis tested showed no significant differences in g(t) values when compared with each other in the same media. The combined data, however, indicated that the growth rate in Schaedler broth was faster than in the other media (average g(t), 45.1 min), whereas the growth rate in peptone-yeast extract-glucose was slower (average g(t), 58.2 min). The growth rates in supplemented thioglycolate and supplemented Lombard-Dowell broth (average g(t), 53.6 min and average g(t), 51.0 min, respectively) were not significantly different.