Acinetobacter baumannii is a Gram-negative bacterium that recently emerged as a life-threatening opportunistic pathogen responsible for outbreaks of nosocomial infections. It became one of the most challenging multi-drug resistant (MDR) microorganisms. A potential alternative approach to fight against bacterial infections is bacteriophage (phage) therapy. While widely used in Eastern countries, phage therapy is currently seen as very promising to treat MDR infections in the Occidental world.
We recently isolated 12 different A. baumannii phages from Georgian and Swiss environmental samples. They were all found to belong either to the Siphoviridae, the Myoviridae or the Podoviridae family. Full genome sequencing revealed DNA genomes of 41.8 to 193.3 kb in length. Despite phage classification tool set PHACTS predicted lysogenic life style for 6 phages, integrase genes were detected in the genome of 2 phages only. While 3 and 6 phages presented high homology (93% identity over 86% coverage to 99% homology over 100% coverage) and very limited homology (76% identity over 3% coverage to 79% identity over 20% coverage), respectively, 3 phages did not harbor significant homology to already known A. baumannii phages.
Tow phages named vB_AbaSLO and vB_phiAba10 revealed extended host range with >90% of sensible strains amongst a collection of 59 A. baumannii clinical isolates obtained from the University Hospital of Lausanne Switzerland (20% of MDR strains). The 10 other phages harboured narrower host ranges with 3% to 20% of sensible strains in the same collection.
This work is part of a Swiss/Georgian FNS SCOPES project aiming at developing a new anti- A. baumannii phage cocktail. In vivo tests of several combinations of the isolated phages are currently ongoing in a mouse model of bacteremia.