SELECTION AND CHARACTERISATION OF PHAGES ABLE TO DEGRADE BIOFILM PRODUCED BY CLINICAL ISOLATES OF E. FAECALIS

Phage therapy is a promising tool against infection sustained by antibiotic resistant bacteria. Recently, a further advantage has been envisaged, in what some phages infect bacteria inside the biofilms, where antibiotics are poorly active. We evaluated the activity of E. faecalis phage Φ1.1, a new Myoviridae virus of the Spounavirinae subfamily, on 15 isolates from inpatients admitted to the Careggi University Hospital of Florence, Italy. Results: Genomic analysis showed that Φ1.1 is characterized by a linear dsDNA of 143.5 Kb (%GC=35.8) ending with terminal repeats of 1911 bp. The closest homologue of ΦΦEF24C, a previously described broad-range, lytic phage of E. faecalis, to which Φ1.1 display a 98% nucleotide identity. A total of 203 ORFs can be observed in the Φ1.1 genome, with 4 of these that potentially encodes proteins related to digestion of bacterial cell wall. The phage infects 8 of the 15 strains that we tested. These strains were also infected in stationary phase of growth although with a lower efficiency. The production of biofilm by E.faecalis isolates was evaluated and its measured by Crystal-Violet staining after phage infection. Phage Φ1.1 was able to reduce the biofilm. This effect was observed also on the 7 strains that were not permissive for phage replication. The confocal microscopy biofilm analysis confirmed these results.