Detection of Efflux mediated drug resistance in clinical isolates of Acinetobacter baumannii in a tertiary care hospital.

PURPOSE: The increased efflux activity among the clinical isolates of Acinetobacter baumannii is considered as one of the emerging resistance mechanisms. This study focuses on role of efflux pump and their inhibitors in multidrug resistant Acinetobacter baumannii.

METHODOLOGY: The presence of Efflux pump was determined in 198 isolates of multi/pandrug resistant Acinetobacter baumannii. Additionally, the MICs of Imipenem was assessed using Micro broth dilution (MBD) method in the presence and absence of Efflux pump inhibitors (EPI) i.e., Phenylalanine arginine Beta Naphthylamide (PAβN) and Carbonyl Cyanide chlorophenyl hydrazone (CCCP). Molecular characterization (adeABC gene) of AdeABC efflux pump which belong to Resistance Nodulation Division (RND) superfamily was determined by conventional PCR.

RESULT: Among 198 clinical isolates of multi/pandrug resistant A.baumannii, the efflux activity observed were 81% (160 isolates) and 58% (114 isolates) at the concentration of 0.5mg/L and 2.5mg/L respectively. In addition, 59% (117 isolates) showed significant reduction in the MIC of Imipenem in the presence of EPIs - PAβN whereas 54% (107 isolates) also showed significant reduction in the MIC of Imipenem in the presence of EPIs - CCCP. The most prevalent gene of AdeABC efflux pump family among these isolates was the combination of adeB and adeC gene (19%) followed by adeB gene (10%)

CONCLUSION

Our study determined the presence of efflux pump as one of the resistance mechanisms which multi/pandrug resistant A.baumannii use to defend themselves from antibiotics. Efflux pump Inhibitors (PAβN& CCCP) showed the potential in restoring the activity of Imipenem against A.baumannii by significant reduction in their MICs.