Adaptation of acinetobacter baumannii tocolistin exposure: laboratory mimicking of a clinical case

Abstract

Colistin resistance is an emerging threat. Here, we presented the development of colistin resistance in A. baumannii after colistin use on a disease course of a patient. To mimic the effects of colistin in laboratory conditions, three colistin susceptible A.baumannii isolated from the patient were exposed daily to colistin for up to 40 days. The colistin MICs and pmrABC expressions of each generation were studied. After 25 days of colistin treatment, colistin-resistant A. baumannii was isolated from the intra-abdominal fluid of the patient. During the in vitro study, the expressions of pmrCAB reached the highest level at the generation that corresponds to the duration of colistin therapy on the isolation day of the isolate. In conclusion, the duration of colistin exposure is critical for the development of colistin resistance. A. baumannii can develop a stable colistin-resistant phenotype with elevated MICs and upregulated pmrCAB operon after three weeks of colistin exposure.