FIG 4.

Usnic acid in combination with colistin inhibits the growth of A. baumannii resulted in multiple morphological changes. (A) Chemical structure of USN and a hypothesis diagram showing that CST facilitates the entry of USN into the A. baumannii cell, resulting in detectable cell profile. (B) Time-kill assay of A. baumannii treated with 0.25× MIC CST alone, 250 μM USN alone and in combination, compared with untreated cells. (C) Representative cell images of CST+USN-treated cells showing multiple morphological changes compared with untreated cells. Cells were treated with 0.25× MIC CST and 250 μM USN for 1 h. Scale bar represents 1 μm.