Comparative Growth Rates of Selected Anaerobic Species in Four Commonly Used Broth Media

Abstract

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.