Mechanisms of bacterial resistance

Type of resistanceCauseResulting phenotype
Acquired [29]Mutations, horizontal gene transferAcquired antibiotic resistance in MDR and XDR strains (β-lactamase production, colistin resistance, polymyxin resistance…)
Adaptive [27, 28]Temporary change in phenotype due to environmental causes, quickly reversibleEfflux pump upregulation
Intrinsic [30]Resistance not caused by acquired or adaptive abilitiesOuter membrane, efflux pump, biofilm