A simple method for the primary isolation of Mycobacterium in a carbon dioxide atmosphere.

The stimulating effect of increased carbon dioxide on the growth of Mycobacterium has long been recognised.' Furthermore it has been shown' that many strains of tubercle bacilli from patients under continuous isoniazid treatment will not grow unless an atmosphere containing up to 10°0 carbon dioxide is provided. Opinions differ as to the percentage of Co., that would give optimum growth. Novy and Soule' reported welldeveloped growth in concentrations ranging from 5% to 50°;" CO,; Davies," Corper et al.: and Cohn et al." added CO, in amounts varying between 2~~ and 7,5~0; Gruft and Loder' used an atmosphere containing 8~0 CO" and Beam and Kubica' found that the presence of 10 I1 °0 of CO, gave the best results. It would appear that an atmosph~e containing from 5°0 to 10°0 CO, gives good results. At present incubation of cultures in an atmosphere of increased CO, tension can be carried out by one of the following methods: 1. In a CO, incubator-this apparatus is expensive, costly to operate and possibly beyond the reach of most small laboratories. In view of the fact that cultures must be kept for 6 8 weeks, such incubators must be large, or more than one must be acquired. 2. By use of gas-proof plastic bags in which the source of CO, is either M. ph/er·or a gas cylinder containing, under pressure, the required mixture of CO, and air. This method leaves much to be desired because the observation of cultures is hampered. 3. By use of McCartney bottles containing the required medium into which a mixture of air and CO, is injected." Disadvantages of this method include the danger of