The carbon dioxide requirements of anaerobic bacteria

Some clinically significant anaerobic bacteria were incubated in pure culture in anaerobic jars containing a range of atmospheric concentrations of CO2. Growth of Clostridium perfringens, C. sporogenes and C. septicum was independent of the amount of CO2. Small supplements of CO2 (0.25%) allowed good growth of the majority of anaerobes studied--an observation contrary to established teaching. The exceptions were Fusobacterium necrophorum which showed an absolute requirement for CO2 of at least 1% and B. melaninogenicus which needed an atmospheric content of 10--40% CO2 for optimal growth. The inclusion of CO2 in the anaerobic jar at a final concentration of 10% is to be recommended for all routine isolation procedures.