The relationship between phoH and colistin-heteroresistant in clinical isolates of Acinetobacter baumannii

Abstract

Heteroresistant phenotype is defined as a subpopulation of major bacteria with a minimum inhibitory concentration (MIC) higher than the original population. The molecular mechanisms of this phenotype have not yet been fully described. Therefore, finding its molecular mechanisms to control infection and prevent disease recurrence in the world is of great importance.This study investigated the relationship between phoH and heterogeneity to colistin in A. baumannii clinical isolates. A total of sixty A. baumannii isolates were isolated from the burn ward of Tehran hospitals and identified by biochemical test, and confirmed by molecular methods. The MIC values of the isolates relative to colistin were determined using the broth micro dilution method, and then heteroresistant isolates were identified using the modified population analysis profile (PAP) method. Finally, phoH gene expression in heteroresistant isolates and non-heteroresistant isolates was compared by RT-qPCR. All isolates were intermediate to colistin (MIC <2), and out of 60 confirmed isolates, seven isolates were heteroresistant (11.66%). Quantitative real-time PCR results showed that phoH expression was high in the heteroresistant group, while phoH expression was the lowest in Non-heteroresistant. This study indicates that the phoH gene can be considered an anti-heteroresistant target against colistin in A. baumannii isolates, although further studies are needed.