Blood and charcoal added to acidified agar media promote the growth of Mycobacterium genavense

Tell different agar media were tested for the in vitro growth of Mycobacter ium genavense in primary cultures and in subcultures from BACTEC vials. The se agar media were based on Middlebrook 7H9, 7H10 and 7H11, and supplemente d with additives: mycobactin I, yeast extinct, charcoal, or defibrinated sh eep blood. Some media were acidified with phosphoric acid to a final pH of 6.2 +/- 0.2. Fourteen M. genavense strains from nude mouse organs as well a s one decontaminated clinical specimen (from a bird) were tested. The optim al medium for primary cultures of M. genavense was Middlebrook 7H11 acidifi ed to pH 6.2 +/- 0.2 and supplemented with charcoal and sheep blood: on thi s medium, all strains produced colonies within 6-12 weeks of incubation in numbers approaching the number of bacilli inoculated. Ii was also the only medium to support the growth of the decontaminated clinical specimen. Added blood and charcoal appeared not as essential for subcultures as for primar y cultures. Three media supported the growth of all strains within month in cubation: they were acidified, and were supplemented with yeast extract or pancreatic digest of casein, and with either blood or charcoal. (C) 1999 El sevier Science Inc.