Inhibition of the clinical isolates of Acinetobacter baumannii by Pseudomonas aeruginosa: In vitro assessment of a case-based study

Abstract

Abstract Background: The global rise in nosocomial infections associated with gramnegative bacteria and the spread of multi-drug resistant Acinetobacter baumannii (MDR-AB) pose public health concerns. This study investigates the inhibitory effects and possible inhibitory mechanism of Pseudomonas aeruginosa (PA) on selected clinical strains of A. baumannii (AB) isolated from Taiwanese patients.Methods: Four and eight clinical strains of AB and PA, respectively, were randomly selected from the bacterial collection of Feng-Yuan Hospital, Taiwan. Antimicrobial-susceptibility was performed on the AB strains. Inhibition potential of the PA strains against AB was assessed by measuring the inhibition zones. In vitro analysis using phenazine-1-carboxamide (PCN) was conducted to assess the possible inhibitory mechanism of PA, which was later confirmed in the clinical isolates by liquid chromatography-mass spectrometry. Results: All the clinical AB strains showed resistance to the eleven antibiotics and were classified as MDR-AB. The nine PA strains exert either a high (PA3596, PA3681, PA3772, and ATCC27853) or a low (PA3613, PA3625, PA3712, PA3715, and PA3744) degree of inhibition against AB strains. 0.25 mg/ml PCN had a clearer inhibition zone than 0.05 mg/ml PCN, suggesting a dose-dependent inhibition of PCN on the AB strains. The four PA strains that demonstrated a high degree of inhibition had a relatively high amount of PCN. Conclusion: Selected strains of PA exert inhibitory actions on MDR-AB with PCN being a possible inhibitory agent. This finding raises the possibility of developing effective therapeutic antibiotics and disinfectant from specific components of PA for the treatment and control of Acinetobacter-associated infections in hospital settings.