Radiometric studies with gas-liquid and thin-layer chromatography for rapid demonstration of hemin dependence and characterization of Mycobacterium haemophilum

Abstract

Eight isolates of Mycobacterium haemophilum were evaluated by radiometric methods to determine whether this test system could support the growth of these organisms as well as demonstrate their growth requirements for iron complexes such as hemin, ferric ammonium citrate, and blood. In addition, gas-liquid and thin-layer chromatography were evaluated to determine whether these procedures could further differentiate M. haemophilum from other mycobacteria. During the initial 24 to 48 h, there was no significant difference between the radiometric test broths containing iron complexes and control broths without iron supplementation. After 48 h, the test growth index readings rapidly increased, and control broth readings leveled off and declined. The mean growth index reading of the test broths after 6 days of incubation was 100 times that of the controls. The mean incubation time with supplemented 7H10 agar was 17 days. The use of radiometric media resulted in the demonstration of hemin dependence by M. haemophilum significantly earlier than with 7H10 agar. Of the three supplements studied, whole blood provided the greatest growth rate, followed by ferric ammonium citrate and hemin. When 12 species of mycobacteria other than M. haemophilum were radiometrically evaluated, no isolate demonstrated an iron complex requirement. Gas-liquid and thin-layer chromatography procedures were able to rapidly differentiate M. haemophilum from the other 12 Mycobacterium species.