Year | No. of isolates | Colistin MIC50,* µg/mL | Colistin MIC90,† µg/mL | % susceptible‡ | % resistant‡ |
---|---|---|---|---|---|
2008 | 1130 | 0.5 | 1.0 | 99.9 (1129/1130) | 0.1 (1/1130) |
2009 | 1097 | 0.25 | 0.5 | 99.9 (1096/1097) | 0.1 (1/1097) |
2010 | 1013 | 0.25 | 0.5 | 99.5 (1008/1013) | 0.5 (5/1013) |
2012 | 499 | 0.25 | 0.5 | 100.0 (499/499) | 0.0 (0/499) |
2013 | 655 | 0.25 | 0.5 | 99.7 (653/655) | 0.3 (2/655) |
2014 | 618 | 0.25 | 0.5 | 100.0 (618/618) | 0.0 (0/618) |
2015 | 559 | 0.25 | 0.5 | 99.5 (556/559) | 0.5 (3/559) |
Note: MIC = minimum inhibitory concentration.
*MIC at or below which 50% of isolates are inhibited.
†MIC at or below which 90% of isolates are inhibited.
‡European Committee on Antimicrobial Susceptibility Testing breakpoints for colistin v. Enterobacteriaceae: an MIC of 2 µg/mL or less is defined as susceptible; an MIC of 4 µg/mL or more is defined as resistant.20