Vanderbilt Summer Science Academy

The characterization Acinetobacter baumannii sensitivity to novel bacteriophages

Acinetobacter baumannii, a Gram-negative opportunistic pathogen, is an emergent threat as it is becoming increasingly antibiotic resistant. Bacteriophages, viruses that infect bacteria provide a mechanism for horizontal gene transfer and a potential alternative to traditional antibiotics via phage therapy. Recent work showed phage susceptibility can be transferred to phage-resistant strains in other bacteria. We hypothesize that outer membrane vesicles (OMVs) from a phage-susceptible strain will render a phage-resistant A. baumannii strain susceptible to phage infection. Here, we present the characterization of 17 lytic A. baumannii bacteriophages isolated from sewage. Each bacteriophage has a unique host range of clinical isolates that it can infect. Transmission electron microscopy was performed on four of the phages to determine capsid diameter and tail length. Genome sequencing and assembly of phage Ab-LH7 yielded a genome of about 21,000 base pairs. The genome aligns with several other A. baumannii strains, suggesting that phage Ab-LH7 is a prophage in some recent clinical isolates. The phage Ab-LH7 genome has 17 open reading frames that code for a variety of proteins, including a putative phage capsid protein. DNA sequencing and analysis will be applied to the rest of our phages. These phages will be used to investigate the potential for A. baumannii OMVs to broaden the bacterial range for phage therapy. Together, these studies will improve our understanding of how phages infect A. baumannii that could then be used to assist in genetic manipulation and improve phage therapies.