TABLE 1

Characteristics of MCR-1-producing E. coli strains and their E. coli J53 transconjugantsa

E. coli strainSTβ-Lactamase(s)PlasmidMIC (μg/ml)b
SAMAMCCFZCAZCTXFEPATMIMPMEMAMKGENCIPLVXMXFTZPSXTTETCHLCOL
CDA6167NDM-5, CMY-2, TEM-1ND>16/8>16/8>16>16>32>16≤2>8>8≤8<1>2>8>4>64/4>2/38≤28>2
BJ10156NDM-5, TEM-1ND>16/8>16/8>16>16>32>16>16>8>8≤8>8>2>8>4>64/4>2/38>8>16>2
BJ13457CTX-M-14, CMY-2, TEM-1ND>16/8>16/8>16>16>32>1616>84≤8>8>2>8>4>64/4≤0.5/9>88>2
CDA6-mcr-TNDIncX4≤4/2≤8/4≤4≤1≤1≤2≤2≤1≤1≤8≤2≤0.5≤1≤1≤4/2≤0.5/9≤2≤4>2
BJ13-mcr-TNDIncI2≤4/2≤8/4≤4≤1≤1≤2≤2≤1≤1≤8≤2≤0.5≤1≤1≤4/2≤0.5/9≤2≤4>2
CDA6-NDM-TNDNDM-5IncX3>16/8>16/8>16>16>32>16≤2>8>8≤8≤2≤0.5≤1≤1>64/4≤0.5/9≤2≤4≤0.5
BJ10-NDM-TNDNDM-5IncX3>16/8>16/8>16>16>32>16≤2>8>8≤8≤2≤0.5≤1≤164/4≤0.5/9≤2≤4≤0.5
  • a CDA6-mcr-T and BJ13-mcr-T, mcr-1 E. coli J53 transconjugants; CDA6-NDM-T and BJ10-NDM-T, blaNDM-5 E. coli J53 transconjugants. No mcr-1 transconjugant was obtained from BJ10. ND, not determined; —, negative by PCR.

  • b MICs were determined using a MicroScan WalkAway Plus system. SAM, ampicillin-sulbactam; AMC, amoxicillin-clavulanic acid; CFZ, cefazolin; CAZ, ceftazidime; CTX, cefotaxime; FEP, cefepime; ATM, aztreonam; IMP, imipenem; MEM, meropenem; AMK, amikacin, GEN, gentamicin; CIP, ciprofloxacin; LVX, levofloxacin; MXF, moxifloxacin; TZP, piperacillin-tazobactam; SXT, trimethoprim-sulfamethoxazole; TET, tetracycline; CHL, Chloramphenicol; COL, colistin.