ABSTRACT
We characterized two bacteriophages, ΦFG02 and ΦCO01, against clinical isolates of Acinetobacter baumannii and established that the bacterial capsule is the receptor for these phages. Phage-resistant mutants harboured loss-of-function mutations in genes responsible for capsule biosynthesis, resulting in capsule loss and disruption of phage adsorption. The phage-resistant strains were resensitized to human complement, beta-lactam antibiotics and alternative phages and exhibited diminished fitness in vivo. Using a mouse model of A. baumannii infection, we showed that phage therapy was effective.
Subject(s)
Acinetobacter Infections/microbiology , Acinetobacter Infections/therapy , Acinetobacter baumannii/virology , Anti-Bacterial Agents/pharmacology , Bacteriophages/physiology , Phage Therapy , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/genetics , Animals , Bacterial Capsules/virology , Complement System Proteins/pharmacology , Disease Models, Animal , Drug Resistance, Bacterial , Female , Humans , Loss of Function Mutation , Mice , Mice, Inbred BALB C , Microbial Sensitivity Tests , beta-Lactamase Inhibitors/pharmacologyABSTRACT
This work reports the self-assembly of a sparingly soluble antibiotic (ciprofloxacin) and a hydrophobic tripeptide ((D)Leu-Phe-Phe) into supramolecular nanostructures that yield a macroscopic hydrogel at physiological pH. Drug incorporation results in modified morphology and rheological properties of the self-assembled hydrogel. These changes can be correlated with intermolecular interactions between the drug and the peptide, as confirmed by spectroscopic analysis (fluorescence, circular dichroism, IR). The drug appears bound within the hydrogel by non-covalent interactions, and retains its activity over a prolonged release timescale. Antimicrobial activity of the ciprofloxacin-peptide self-assembled hydrogel was evaluated against Staphylococcus aureus, Escherichia coli, and a clinical strain of Klebsiella pneumoniae. Interestingly, the peptide hydrogel alone exhibited a mild anti-bacterial activity against Gram-negative bacteria. While toxic to bacteria, no major cytotoxicity was seen in haemolysis assays of human red blood cells or in mouse fibroblast cell cultures. This new approach of drug incorporation into the nanostructure of a simple tripeptide hydrogel by self-assembly may have important applications for cost-effective wound dressings and novel antimicrobial formulations.
