Table 3.
Examples of chromosomal and plasmid-encoded polymyxin resistance mechanisms described in Enterobacteriaceae, Pseudomonas, and Acinetobacter.
| Chromosomal Resistance | Plasmid-Encoded Resistance | ||||
|---|---|---|---|---|---|
| Two-component systems [ref] | Additional mechanisms [ref] | mcr type | Ref | ||
| Enterobacteriaceae | Klebsiella pneumoniae | PhoPQ [103] PmrAB [147] |
Shedding of capsular polysaccharide capable of trapping polymyxins [148] Overexpression of the efflux pump kpnEF [149] |
mcr-1 | [108] |
| mcr-2 | [108,150] | ||||
| mcr-7 | [133] | ||||
| mcr-8 | [134] | ||||
| E. coli | PhoPQ [151] PmrAB [112] |
Modification of Kdo (3-deoxy-D-manno-octulosonic acid) [152] | mcr-1 | [123] | |
| mcr-2 | [153] | ||||
| mcr-3 | [129] | ||||
| mcr-4 | [154] | ||||
| mcr-5 | [154] | ||||
| Salmonella | PhoPQ [155] PmrAB [156] |
Inhibition of expression of outer membrane proteins OmpF and/or OmpC [157] | mcr-4 | [130] | |
| mcr-5 | [158] | ||||
| Pseudomonas | PhoPQ [159] PmrAB [160] CprRS [161] ColRS [110] ParRS [162] |
Efflux pump MexXY/OprM [163] Lipid A diacylation [164] Chromosomal mcr-5 [165] |
mcr-1 | [166] | |
| Acinetobacter | PmrAB [167] | Expression of the efflux pump EmrAB [168] | mcr-1 | [166] | |
| mcr-4.3 | [169] | ||||