Mean^a (S.D.) frequency of spontaneous MRSA (n = 6) and <i>P. aeruginosa</i> (n = 6) mutants with increased fosfomycin (FOF), tobramycin (TOB) and F∶T MICs under aerobic and anaerobic conditions at 2×, 4× and 8× MIC.

aWhere the spontaneous mutation frequency was above or below the limit of detection, the limit of detection was used to calculate the mean e.g. if spontaneous mutation frequency was <4.4×10−8 then 4.4×10−8 was used.