FIG 5.
MGAS2221ΔfabT shows increased resistance to polymyxin B. (A) Spot dilution assay of wild-type strain MGAS2221 and the fabT deletion mutant on THY plates containing either 0, 20, 50, or 100 μg/ml polymyxin B. Shown from left to right are undiluted and 10−1- to 10−5-diluted samples of a mid-logarithmic phase culture grown in THY medium. (B) Spot dilution assay of wild-type strain MGAS2221 and strains MGAS1253 and MGAS25770 on THY plates containing 0, 30, 80, or 150 μg/ml polymyxin B. The last two strains were isolated from patients with invasive disease and contain single nucleotide insertions within the fabT gene: MGAS1253, A15 insertion, SF370-like strain isolated around 1920 (12); MGAS25770, A106 insertion, 5005-like strain isolated in 2006 (12).