Effect of atmosphere of incubation on the growth of Neisseria meningitidis in a blood culture medium.

Seven strains of Neisseria meningitidis have been grown in a commercial blood culture medium (supplemented peptone broth, Beckton-Dickinson) under five different atmospheric conditions (anaerobic, transiently vented, permanently vented in air, in 5% CO2 in air, and in air with agitation). Macroscopic evaluation was not a quick and reliable method to discover growth with this medium. With transient venting and under anaerobic conditions macroscopic growth was not detected at all and a loss in viability was observed. It is therefore recommended that frequent subcultures should be performed if meningococcal bacteraemia is suspected. Preliminary data indicate that agitation in air induces a more rapid growth than stationary incubation.