How does efflux pump activation affect tigecycline susceptibility?

How does efflux pump activation affect tigecycline susceptibility?

Efflux pumps are membrane proteins that actively remove tigecycline from bacterial cells before it can bind ribosomes and inhibit protein synthesis. When these pumps turn on, they reduce the amount of drug that reaches its target, raising the minimum inhibitory concentration and lowering susceptibility.

What pumps specifically drive resistance to tigecycline?

The Tet(A) and Tet(B) efflux pumps confer low-level resistance in E. coli and K. pneumoniae. The adeABC efflux system dominates in Acinetobacter baumannii. The mef(A) and mreA pumps operate in streptococci and enterococci. These system-specific pumps explain why susceptibility varies between species.

How does regulatory gene mutation trigger efflux activation?

Mutations in repressors such as acrR, marR, or ramR derepress the global efflux regulon. Once freed from repression, the pumps reach high levels and eject multiple drug classes, including tigecycline. Clinical isolates often show these mutations paired with reduced susceptibility.

What happens when multiple pumps operate simultaneously?

Concurrent activation of two or more efflux systems produces higher MICs than single-pump cases. For example, A. baumannii isolates that carry both adeABC and adeIJK show fourfold higher resistance than isolates with only adeABC. Overlapping coverage of drug expulsion explains the er<|eos|>