Fig. 1

Initial observation of MAC SCVs phenotype from patients with MAC-pulmonary disease. Each primary stock of the MAC strain was inoculated onto both 7H10 agar and 7H10-CRE agar (containing clarithromycin at 2 µg/ml, rifampicin at 1 µg/ml, and ethambutol at 2 µg/ml) and incubated at 37 °C for 3 weeks. On 7H10 agar, the MAC strain exhibited a mixed colonial morphology, with dominant large and opaque colonies, as well as small, translucent colonies. In contrast, on 7H10-CRE agar, small, translucent colonies were predominant, except for the M. avium subsp. avium #476 strain, which displayed mixed colonial morphology. Large, opaque colonies are indicated by black arrows, and small, translucent colonies are indicated by red arrows