Abstract

The aim of this study is to investigate the antimicrobial susceptibility profile of Acinetobacter baumannii and the contribution of the insertion sequence upstream of ampC β-lactamase on the susceptibility profile of 64 A. baumannii clinical isolates collected from a Jordan hospital. A total of 64 consecutive clinical isolates of A. baumannii were recovered (between March 2005 and December 2006) at the King Abdullah University Hospital (KAUH). The antimicrobial susceptibility profile against 11 different antibiotics was determined by disk diffusion method. The minimum inhibitory concentration (MIC) of these antibiotics against all isolates was determined using Etest. Polymerase chain reaction (PCR) screening was carried out to identify the presence of ampC gene and its adjacent insertion sequence. A. baumannii showed high resistance profile to β-lactam antibiotics (cefotaxime 92.2%, cefuroxime 98.4%, ceftazidime 89.1%) and ciprofloxacin 89.1%. imipenem and meropenem showed increased resistant rates (70.1 and 71.6%, respectively) with nearly half of the isolates being resistant to amikacin (52.5%). All isolates were susceptible to colistin. AmpC gene was detected in all isolates and only β-lactam including carbapenems and β-lactamase inhibitor resistant isolates were found to carry the IS-AmpC gene. Our present study confirms the essential role of the insertion sequence which could represent a gene regulatory system, able to regulate various genes in A. baumannii. Finally, inappropriate infection control measures and inaccurate antibiotic usage are highly potential factors that might increase the prevalence and spread of antibiotic resistant A. baumannii isolates.

Key words: Acinetobacter baumannii, Antimicrobial susceptibility, IS-AmpC.