Fig. 4: Dilution and clinical ultrasound to disperse aggregates.

a Metabolic activity, as indicated by Alamar blue fluorescence, of S. aureus in 20% TSB, 20% pSynF, or 20% SynF with or without UTMD. Both 20% pSynF and 20% SynF showed an approximate doubling of metabolic activity after UTMD and 2 h incubation. b Dispersion measured as change in CFUs after application of clinical ultrasound, with or without microbubbles, to undiluted or diluted pSynF containing S. aureus aggregates. No changes in dispersal were measured. c AMK sensitivity of MSSA in TSB or 20% SynF as a function of microbubble addition and UTMD. Whereas TSB had 5–6 log decreases in recovered counts, independent of treatments, AMK sensitivity in 20% SynF cultures increased from an ~1 log decrease to a 6-log decrease with the application of ultrasound. Data are presented as mean ± standard deviation. For each bar a n = 12, b, n = 12, c n = 10 (TSB, no insonation, no microbubbles, AMK) or 11 (20% SynF, no insonation, no microbubbles, no AMK) or 12. Individual data points are shown as open, colored symbols. Normality checked using Kolmogorov–Smirnov test. Comparisons done using (a, b (for pSynF, 20% pSynF)) Kruskal–Wallis test for multiple comparisons or (b (for TSB), c) Mann-Whitney tests for paired comparison on the basis of independent groups. ns, P > 0.05; *P < 0.05; ***P < 0.001; ****P < 0.0001.