Analysis of penicillin-binding proteins (PBPs) in carbapenem resistant Acinetobacter baumannii

Abstract

Background & objectives: Acinetobacter baumannii is a Gram-negative, cocco-bacillus aerobic pathogen responsible for nosocomial infections in hospitals. In the recent past A. baumannii had developed resistance against β-lactams, even against carbapenems. Penicillin-binding proteins (PBPs) are crucial for the cell wall biosynthesis during cell proliferation and these are the target for β-lactams. Therefore, the present study was carried out to identify the PBPs in three (low, intermediate and high MICs) groups of carbapenem resistant isolates strains of A. baumannii. Methods: ATCC 19606 and 20 β-lactam resistant isolates of A. baumannii were obtained. Selective identification of the PBPs was done using Bocillin FL, a non-radioactive fluorescent derivative of penicillin. Results: The fluorescence emission from Bocillin-tag in SDS-PAGE gel of native strain identified eight PBPs, with apparent molecular weight of 94, 65, 49, 40, 30, 24, 22 and 17 kDa, however, these PBPs revealed alteration in carbapenem-resistant isolates. Interpretation & conclusions: A comparative analysis of PBPs in the resistant isolates with those of ATCC revealed a decreased expression of all PBPs except that of 65 and 17 kDa PBPs which were marginally downregulated, and simultaneous appearance of new 28 kDa PBP (in low and intermediate resistant isolates) and 36 kDa in high meropenem resistant group of A. baumannii. The present study indicated an association between alteration in PBPs and β-lactam resistance in A. baumannii.