Molecular characterization and resistance profile of nosocomial Acinetobacter baumannii in intensive care unit of tertiary care hospital in Bangladesh

Abstract

This study was designed to investigate the resistance profile along with the genetic background of resistance to beta-lactam antibiotics among the nosocomial A. baumannii in Bangladesh. A. baumannii was confirmed by detecting blaOXA-51-like. Antibiotic susceptibility was determined by disk diffusion method. Agar dilution method was used to determine MIC of ceftazidime and imipenem. All A. baumannii were phenotypically screened for ampC, ESBL and MBL production. Genetic markers of antibiotic resistance such as blaampC, blaOXA-51,23,40,58and143, blaKPC, blaIMP, blaVIM and blaNDM-1, genetic environment around blaADC and ISAba1 upstream of blaOXAs were evaluated by PCR. Twenty-four (96%) A. baumannii were considered as MDR. 96% A. baumannii were resistant to amoxiclav, ceftazidime, ciprofloxacin and cefoxitin, 92% to cefotaxime and piperacillin-tazobactam, 88% to cefepime, amikacin and imipenem, 52% to sulbactamcefoperazone and 40% were resistant to aztreonam. All were sensitive to colistin. The distribution of several beta-lactamase genes such as blaOXA-51 (100%), blaADC-like (92%), blaNDM-1 (92%), EBC group (84%), blaOXA-23 (76%), blaVIM (72%), blaKPC (44%), DHA group (24%), blaOXA-58 (16%), ACC group (8%) and CIT group (4%) were observed among the 25 A. baumannii. This is the first reported plasmid mediated ampC beta-lactamases in A. baumannii. blaOXA-51 was positive in 100%, blaNDM-1 in 95.45%, blaOXA-23 in 77.27%, blaVIM in 72.73%, blaKPC in 50% and blaOXA-58 in 18.18% of imipenem resistant isolates. MDR profile of nosocomial A. baumannii would highlight the importance of standard guideline of antimicrobials use and infection control policy in the hospitals of Bangladesh.