Phage-Derived Depolymerase as an Antibiotic Adjuvant Against Multidrug-Resistant Acinetobacter baumannii

Abstract

Bacteriophage-encoded depolymerases are responsible for degrading capsular polysaccharides (CPS), lipopolysaccharides (LPS), and exopolysaccharides (EPS) of the host bacteria during phage invasion. They have been considered as promising antivirulence agents in controlling bacterial infections, including those caused by multidrug-resistant (MDR) bacteria. This feature inspires hope of utilizing these enzymes to disarm the polysaccharide capsules of the bacterial cells, which then strengthens the action of antibiotics. Here we have identified, cloned, and expressed a depolymerase Dpo71 from a bacteriophage specific for the gram-negative bacterium Acinetobacter baumannii in a heterologous host Escherichia coli. Dpo71 sensitizes the MDR A. baumannii to the host immune attack, and also acts as an adjuvant to assist or boost the action of antibiotics, for example colistin. Specifically, Dpo71 at 10 μg/ml enables a complete bacterial eradication by human serum at 50% volume ratio. A mechanistic study shows that the enhanced bactericidal effect of colistin is attributed to the improved outer membrane destabilization capacity and binding rate to bacteria after stripping off the bacterial capsule by Dpo71. Dpo71 inhibits biofilm formation and disrupts the pre-formed biofilm. Combination of Dpo71 could significantly enhance the antibiofilm activity of colistin and improve the survival rate of A. baumannii infected Galleria mellonella. Dpo71 retains the strain-specificity of the parent phage from which Dpo71 is derived: the phage-sensitive A. baumannii strains respond to Dpo71 treatment, whereas the phage-insensitive strains do not. In summary, our work demonstrates the feasibility of using recombinant depolymerases as an antibiotic adjuvant to supplement the development of new antibacterials and to battle against MDR pathogens.

PYED-1 Overcomes Colistin Resistance in Acinetobacter baumannii

“…Instead, as shown in Figure 3, the combination of PYED-1 and colistin significantly inhibited biofilm formation by A. baumannii when compared with the untreated control and single-drug treatment groups. A few studies demonstrated that treatment with drug combinations inhibits A. baumannii biofilm formation [32,35,[43][44][45]. Noteworthily, our results showed that PYED-1 at 16 µg/mL in association with colistin at 0.25 µg/mL significantly inhibited A. baumannii biofilm formation on a polystyrene abiotic surface.…”

A thermosensitive hydrogel formulation of phage and colistin combination for the management of multidrug-resistant Acinetobacter baumannii wound infections

“…The IME-AB2 phage is a depolymerase-bearing phage and the capability of the encoded depolymerase in degrading the extracellular polysaccharide substances (EPS) has been previously reported. 68 We anticipated that the IME-AB2 phage could effectively degrade the EPS within the biofilm to facilitate the penetration of colistin into the biofilm to boost the antibiofilm capacity of the PAS combination. 39 Fig.…”

Proteomic Study of the Interactions between Phages and the Bacterial Host Klebsiella pneumoniae

“…In contrast, members of the Myoviridae family, which are included in the “larger phages” (>100 bp), did not present specific lysis blocks, and structural and morphogenesis-related proteins were repeated in several blocks throughout the genome ( 41 , 50 ). The genomes of all phages had endolysins and holins, proteins that are responsible for degradation of the bacterial cell wall during the infection by the host to facilitate the exit of the phage progeny ( 51 ).…”