FIG 2.

Phenotypic characterization of M. tuberculosis from the Lro outbreak and the restoration of the fadB4 gene. (A) The Lro isolate was compared with the school outbreak strain (CH), type strain (H37Rv), and lineage 2 strain (B65) for growth in liquid culture. The optical density and CFU/mL for Lro were significantly lower (P < 0.05) than those of the other strains at day 7 (data are means and standard deviations of 3 to 4 replicates). Lro with the fadB4 plasmid (Lro+fadB4) had significantly higher optical density and CFU/mL values at day 7 (P < 0.05). (B) Lro and CH bacilli each contained lipid bodies, indicated by arrows on the electron micrographs (scale bar of 500 nm). (C) Lro contained significantly more lipid bodies than CH, H37Rv, or B65: and the percentage of bacteria containing one or more lipid bodies was determined via Nile-red staining and fluorescence microscopy (mean and standard deviation of 300 cells for each strain; an asterisk indicates P < 0.05). (D) Lro, but not Lro+fadB4, was significantly more hydrophobic than the other strains (P < 0.05), as measured by the optical density change when bacteria moved into the hexadecane layer (mean and standard deviation of 3 experiments). The figure shows the microbiological profile of Lro M. tuberculosis that was isolated from one patient and then cultured in a common Mycobacterial growth medium (Sauton’s broth). Data were also gathered using the same isolate cultured in another common growth medium (Middlebrook 7H9) and using three other isolates from the Lro cluster (Fig. S1–S3).