Enhanced anti-biofilm activity of the minocycline-and-gallium-nitrate using niosome wrapping against Acinetobacter baumannii in C57/BL6 mouse pneumonia model

Acinetobacter baumannii is a worldwide health issue in terms of its high antibiotic resistance and ability to form biofilms. Nanoparticles (NPs) with high biocompatibility, high penetrating ability, and low medication dose can successfully treat the antibiotic-resistant infections. In this research, the anti-biofilm activity of niosomes containing minocycline and gallium nitrate (GaN) against A. baumannii biofilm was determined. In order to improve their anti-biofilm properties, minocycline and GaN were encapsulated in niosomes as biocompatible drug carriers. The niosomes' size, zeta potential, shape, stability, drug entrapment efficacy, drug release pattern and antibacterial activity were assessed. Several clinical samples were isolated from the lungs of patients hospitalized at Loghman hospital, Tehran, Iran. The biofilm formation of most lethal clinical isolates of A. baumannii was analyzed. The pneumonia model was generated by intranasally administering A. baumannii suspension to anesthetized mice whose immune systems was compromised twice by cyclophosphamide. Lung infection of the mouse with A. baumannii was confirmed using PCR. After treatment, the lungs were excised under sterile conditions and stained with hematoxylin and eosin (H&E) to determine histological symptoms, inflammation and intercellular secretions. The niosomes contained minocycline and GaN had an average size of 230 nm and a zeta potential of -40 mV, respectively. The percentage of drug entrapment and delayed drug release was both high in niosomal formulations. Niosomes containing minocycline and GaN dispersed 1, 3 and 5 day old biofilms. The mice given the combination of two compounds required less time to be treated than the animals given the single medication (minocycline). The minocycline& GaN-loaded niosomes could be considered as promising candidates to treat the infections caused by A. baumannii biofilm.