Investigating the Effect of Ampicillin-Sulbactam and Colistin on Acinetobacter baumannii Strains by Epsilometer Test: An In Vitro Study

  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. After identification of A. baumannii, susceptibility to ampicillin-sulbactam and colistin was assessed using Epsilometer test (E-test). 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 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.