Bacteriophage-resistant Acinetobacter baumannii are resensitized to antimicrobials

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. The authors characterize two phages against Acinetobacter baumannii, both in vitro and in vivo. A. baumannii strains develop resistance against both phages, but are in turn resensitized to different antimicrobial compounds.