TABLE 1.
Characterization of mcr-1-carrying E. coli isolates and plasmids
| Isolate | Isolation date | Market | MLSTa | Resistance patternb | Colistin (mg/liter) | Other resistance genes | Location and plasmid size (kb) | Conjugation frequency (cells per recipient) | Genetic context |
|---|---|---|---|---|---|---|---|---|---|
| GDP6F1 | Sep 2016 | A | ST48 (ST10 Cplx) | AMP, STR, NEO, CHL, FLR, SXT, TET, DOX | 4 | aadA2, aadA1, aph(3′)-Ic, blaTEM-176, blaOXA-10, blaCARB-2, mcr-1, qnrS1, oqxB, oqxA, cmlA1, floR, arr-2, sul2, sul3, tet(A), dfrA14, dfrA16 | IncP, 50.4 | 5.0 × 10−4 | IncP-mcr-1-hp-IncP |
| GDT6F13 | Apr 2016 | B | ST4014 | AMP, CTX, FOS, STR, GEN, NEO, CHL, FLR, SXT, TET, DOX | 8 | strA, strB, aph(3′)-Ic, aac(3)-IId, blaCTX-M-55, mcr-1, oqxA, oqxB, fosA3, erm(B), mph(A), floR, sul2, tet(A), dfrA17 | chromosome | ISApl1-mcr-1-hp-ISApl1 | |
| GDT6F36 | May 2016 | C | ST7508 | STR, CHL, FLR, TET | 8 | strA, strB, mcr-1, qnrS1, floR, sul2, tet(A) | IncP, 52.7 | 1.4 × 10−4 | ISApl1-mcr-1-hp-ISApl1 |
| GDT6F38 | May 2016 | C | ST101 (ST101Clpx) | AMP, NEO, CHL, FLR, SXT, TET, DOX | 8 | aadA1, aph(3′)-Ia, aadA2, mcr-1, floR, cmlA1, sul2, sul3, tet(M), tet(A), dfrA12 | chromosome | ISApl1-mcr-1-hp-IS1294- ISApl1 | |
| GDT6F49 | May 2016 | C | ST2040 | AMP, CTX, STR, CHL, FLR, SXT, TET, DOX | 8 | aadA1, blaOXA-10, blaCTX-M-65, mcr-1, qnrS1, cmlA1, floR, arr-2, tet(A), tet(A), dfrA14 | IncX4, 33.3 | 5.5 × 10−4 | IncX4-mcr-1-IncX4 |
| GDT6F93 | July 2016 | D | ST7013 | AMP, CL, STR, CHL, FLR, CIP, SXT, TET, DOX | 4 | strA, strB, mcr-1, aadA5, aadA1, blaOXA-10, blaTEM-1A, qnrS1, cmlA1, floR, arr-2, sul2, tet(A), dfrA17, dfrA14 | IncI2, 60.8 | 1.7 × 10−3 | IncI2-mcr-1-IncI2 |
| GDT6F97 | July 2017 | D | ST156 | AMP, CTX, FOS, STR, GEN, NEO, CHL, FLR, CIP, SXT, TET, DOX | 4 | tet(A), aac(3)-Iid, fosA3, dfrA12, floR, strB, tet(M), aadA22, strA, aph(3′)-Iia, oqxA, oqxB, erm(B), sul2, blaCTX-M-14 | IncI2, 60 | 4.8 × 10−4 | IncI2-mcr-1-IncI2 |
a
MLST, multilocus sequence type.
b
Antimicrobial susceptibility was determined and evaluated according to CLSI document no. M100-S27 (https://clsi.org/standards/products/microbiology/documents/m100/). Resistance to florfenicol (>16 mg/L) and neomycin (>8 mg/L) was interpreted according to EUCAST clinical breakpoints and epidemiological cutoff values (http://mic.eucast.org/Eucast2/). AMP, ampicillin; CTX, cefotaxime; FOS, fosfomycin; STR, streptomycin; GEN, gentamicin; NEO, neomycin; CHL, chloramphenicol; FFC, florfenicol; CIP, ciprofloxacin; SXT, sulfamethoxazole/trimethoprim; TET, tetracycline; DOX, doxycycline.