Figure 2. The majority of lesions in monkeys are initiated by a single bacterium.

(a) 79% of granulomas (n = 37) contained a single barcode, although all eight barcodes were represented in each animal. When multi-focal lesions (lesions with histologic evidence of being comprised of two or more granulomas, n = 22) were analyzed separately, many (64%) contained only a single barcode, suggesting these lesions arose through localized spreading as opposed to coalescence of nearby lesions. In contrast, thoracic lymph nodes contained as many as six barcodes (n = 13), reflecting draining of infecting bacilli from lungs to lymph nodes. Bacterial load was similar in these two animals to the four other animals analyzed at 4 weeks post-infection (Supplemental Figure 1b). (b) A linear regression of total bacterial load in individual granulomas (n=37) indicates no relationship between CFU and the number of barcodes recovered, such that initial bacterial load did not influence later bacterial load (Spearman’s • = 0.2404, slope = 0.1510 +/− 0.1919, p = 0.4372, Kruskal-Wallis, p = 0.1120). (c) A range of bacterial load per lesion is present in individual lesions, in clustered lesions, and lymph nodes. Bacterial load in lesions visible at 2 weeks p.i. by PET-CT (n = 16) is significantly higher than those not visible until 3 weeks (n = 36, p < 0.05), with substantial overlap, suggesting that the timing of lesion formation can affect bacterial burden. Bars represent medians.