Background: Acinetobacter baumannii is one of the most common causes of nosocomial infections. The
knowledge about resistance and susceptibility of this bacterium to antibiotics is mandatory in every region. This
study evaluated the susceptibility of A. baumannii strains to ampicillin-sulbactam and colistin in a total of 100
samples of A. baumannii obtained from intensive care unit (ICU) patients with nosocomial infections.
Methods: After identification of A. baumannii, susceptibility to ampicillin-sulbactam and colistin was assessed
using Epsilometer test (E-test).
Results: Regarding the resistance to ampicillin-sulbactam, sensitivity, resistance, and intermediate resistance of
A. baumannii strains were 62%, 16%, and 22%, respectively. The distribution of resistance among A. baumannii
strains was not significantly different regarding the gender, age, duration of ICU stay, background diseases,
and type of interventional procedure. The obtained strains of A. baumannii from the patients who had taken
β-lactam, aminoglycoside, anti-methicillin resistant Staphylococcus aureus (anti-MRSA), and colistin were
significantly resistant to ampicillin-sulbactam (P value <0.05). Overall, 16% of
Conclusion: Acinetobacter baumannii strains showed resistance to ampicillin-sulbactam and only one strain
was detected with colistin resistance. It is suggested that a local antibiotic resistance regarding A. baumannii
infection be defined in order to improve final outcome of antimicrobial treatment and prevent further resistance.