Table 1.
Specimen details, colistin susceptibilities and presence of mcr-1 in colistin resistant isolates
| Species | Isolate | Specimen type | Date of collection | Hospital | Vitek MIC (μg/ml) | Etest MIC (μg/ml) | mcr-1 PCR | Additional antibiotic resistance |
|---|---|---|---|---|---|---|---|---|
| E. coli | CEC1 | Urine | 25/01/2016 | A | 4 (R) | 4 (R) | + | SXT, |
| CEC2 | Urine | 16/01/2016 | F | 4 (R) | 4 (R) | + | SXT, CIP, CXM(I) | |
| CEC3 | Urine | 15/01/2016 | D | 16 (R) | 4 (R) | + | none | |
| CEC4 | Urine | 16/01/2016 | E | 8 (R) | 4 (R) | + | SXT, AMP, CXM(I) | |
| CEC5 | Urine | 01/02/2016 | H | 16 (R)c | 0.5 (S) | - | AMI(I) | |
| CEC7 | Superficial abdominal swab | 27/01/2016 | D | 8 (R) | 4 (R) | + | SXT, AMP, AMC(I), CIP, CXM(I), TZP(I) | |
| CEC8 | Urine | 12/02/2016 | A | 8 (R) | 4 (R) | + | SXT, AMP, CIP | |
| CEC9 | Urine | 16/02/2016 | B | 4 (R) | 2 (S) | + | SXT, AMP, CIP | |
| CEC10 | Urine | 16/02/2016 | C | 4 (R) | 2 (S) | + | AMP, AMC(I), CIP, CXM, CTX, CAZ, FEP, AMI(I), TZP(I) | |
| CEC11 | Urine | 03/03/2016 | B | 8 (R) | 4 (R) | + | SXT, AMP, | |
| CEC12a | Urine | 23/05/2016 | A | 4 (R) | 4 (R) | - | SXT, AMP, AMC(I) | |
| CEC13 | Urine | 10/06/2016 | G | 4 (R) | 4 (R) | + | SXT, AMP, CIP, CXM(I), FOX(I) | |
| CEC14 | Urine | 27/07/2016 | A | 4 (R)c | 0.5 (S) | - | none | |
| CEC15a | Urine | 23/07/2016 | A | 4 (R) | 4 (R) | - | SXT, AMP | |
| K. pneumoniae | CK1b | Urine | 20/05/2016 | E | 4 (R) | 2 (S) | + | AMP, AMC, CIP, CXM, CTX, CAZ, FEP, TZP(I) |
| CK2 | Sputum | 17/06/2016 | A | 16 (R) | 4 (R) | + | SXT, AMP, AMC, CIP, CXM, FOX, CTX, CAZ, FEP, GEN, AMI, TZP, ETP, IPM, MEM | |
| CK5 | Urine | 17/07/2016 | C | 4 (R) | 0.5 (S) | + | AMP, CXM | |
| CK6 | Urine | 26/07/2016 | A | 16 (R) | Isolate lost during culture | SXT, AMP, AMC, CIP, CXM, FOX, CTX, CAZ, FEP, GEN, AMI(I), TZP | ||
| CK7b | Urine | 12/08/2016 | E | 16 (R) | 4 (R) | - | SXT, AMP, AMC, CIP, CXM, CTX, CAZ, FEP, GEN, TZP(I) | |
| CK8 | Sputum | 02/07/2016 | C | 4 (R) | 0.5 (S) | + | AMP, GEN(I), AMI(I) | |
| K. oxytoca | CK3 | Superficial skin swab | 21/06/2016 | B | 16 (R) | 0.25 (S) | + | AMP |
aSuccessive E. coli isolates obtained from the same patient. bSuccessive K. pneumonia isolates obtained from the same patient. cRepeat Vitek susceptibility testing redefined the colistin MIC as 0.5 μg/mL; both these isolates were excluded from further analysis. R resistant, I intermediate, S susceptible, SXT trimethoprim-sulfamethoxazole, CIP ciprofloxacin, CXM cefuroxime, AMP ampicillin, AMI amikacin, AMC amoxicillin-clavulanic acid, TZP piperacillin-tazobactam, CTX cefotaxime/ceftriaxone, CAZ ceftazidime, FEP cefepime, GEN gentamicin, ETP ertapenem. IPM imipenem, MEM meropenem