Affiliation:
1. Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
2. Center for Phage Technology, Texas A&M University, College Station, Texas, USA
3. Department of Chemistry, Texas A&M University, College Station, Texas, USA
4. Department of Animal Science, Texas A&M University, College Station, Texas, USA
Abstract
ABSTRACT
The increased prevalence of drug-resistant, nosocomial
Acinetobacter
infections, particularly from pathogenic members of the
Acinetobacter calcoaceticus-baumannii
complex, necessitates the exploration of novel treatments such as phage therapy. In the present study, we characterized phage Petty, a novel podophage that infects multidrug-resistant
Acinetobacter nosocomialis
and
Acinetobacter baumannii
. Genome analysis reveals that phage Petty is a 40,431-bp ϕKMV-like phage, with a coding density of 92.2% and a G+C content of 42.3%. Interestingly, the lysis cassette encodes a class I holin and a single-subunit endolysin, but it lacks canonical spanins to disrupt the outer membrane. Analysis of other ϕKMV-like genomes revealed that spaninless lysis cassettes are a feature of phages infecting
Acinetobacter
within this subfamily of bacteriophages. The observed halo surrounding Petty's large clear plaques indicated the presence of a phage-encoded depolymerase capable of degrading capsular exopolysaccharides (EPS). The product of gene 39, a putative tail fiber, was hypothesized to possess depolymerase activity based on weak homology to previously reported phage tail fibers. The 101.4-kDa protein gene product 39 (gp39) was cloned and expressed, and its activity against
Acinetobacter
EPS in solution was determined. The enzyme degraded purified EPS from its host strain
A. nosocomialis
AU0783, reducing its viscosity, and generated reducing ends in solution, indicative of hydrolase activity. Given that the accessibility to cells within a biofilm is enhanced by degradation of EPS, phages with depolymerases may have enhanced diagnostic and therapeutic potential against drug-resistant
Acinetobacter
strains.
IMPORTANCE
Bacteriophage therapy is being revisited as a treatment for difficult-to-treat infections. This is especially true for
Acinetobacter
infections, which are notorious for being resistant to antimicrobials. Thus, sufficient data need to be generated with regard to phages with therapeutic potential, if they are to be successfully employed clinically. In this report, we describe the isolation and characterization of phage Petty, a novel lytic podophage, and its depolymerase. To our knowledge, it is the first phage reported to be able to infect both
A. baumannii
and
A. nosocomialis
. The lytic phage has potential as an alternative therapeutic agent, and the depolymerase could be used for modulating EPS both during infections and in biofilms on medical equipment, as well as for capsular typing. We also highlight the lack of predicted canonical spanins in the phage genome and confirm that, unlike the rounding of lambda lysogens lacking functional spanin genes,
A. nosocomialis
cells infected with phage Petty lyse by bursting. This suggests that phages like Petty employ a different mechanism to disrupt the outer membrane of
Acinetobacter
hosts during lysis.
Funder
HHS | National Institutes of Health
Texas AgriLife Research
MoSTR | National Science Foundation
Texas A and M University
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
Cited by
53 articles.
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