TABLE 1.

MIC50s, MIC90s, and MIC ranges for various antimicrobial agents of P. aeruginosa isolates with hypermutable and nonhypermutable phenotypesa

PhenotypeMIC (μg/ml)
CeftazidimebPiperacillin-tazobactambAztreonambMeropenembTobramycinbColistinCiprofloxacinb
50%90%Range50%90%Range50%90%Range50%90%Range50%90%Range50%90%Range50%90%Range
Hypermutable2004001.6-40040040012.5-4004004000.8-400502000.4-40012.5251.6-500.850.4-40012.5250.4-50
Nonhypermutable6.22000.8-4001004000.8-40012.52000.4-4003.1500.1-2003.112.50.4-251.66.20.2-1001.66.20.05-12.5
  • a Hypermutable isolates had frequencies of mutations after exposure to rifampin and streptomycin of 1.6 × 10−6 and 1.4 × 10−6, respectively. For the nonhypermutable isolates, the frequencies were 9 × 10−9 and 3.3 × 10−8, respectively.

  • b Statistically significant difference (P < 0.001) between the MICs for the hypermutable and nonhypermutable isolates.