Isolation, characterisation and potential applications of a novel bacteriophage targeting beta-lactam-resistant Staphylococcus saprophyticus

Staphylococcus saprophyticus is a gram-positive commensal characteristically resistant to novobiocin. Clinically, it is associated with urinary tract and other opportunistic infections. But reports on phages against them are scanty, which underlines the importance of the study. We isolated a Staphylococcus saprophyticus strain from soiled socks. The strain was characterised through biochemical tests and 16S rDNA ribotyping. Furthermore, the antibiogram revealed that the strain is resistant to penicillinase-resistant beta-lactam antibiotics. A double-stranded DNA temperate phage, ØPh_SS01, was isolated against S. saprophyticus from a mixed sewage sample. The phage is stable over a wide range of temperatures, including pH and salt, with 67.08 ± 25 virions/cell following adsorption within 14 min. The potential of ØPh_SS01 was established in Mannitol Salt broth with a 7-log reduction of S. saprophyticus over a period of 24 h. Moreover, it inhibited and disrupted biofilm at efficiencies of 77% and 69%, respectively, at an MOI of 100. Studies on adherent immortalised human keratinocytes and urethral cell lines did not result in any significant change in viability. Sequence analysis of ØPh_SS01 depicted a genome size of 47 Kb with 37.36% GC content. A similarity of 91.5% to related entries indicated its novelty. The textile matrices immobilised with phages could reduce the bacterial load by about 7-log, which shows the potential of the phage in infection control.