Isolation and Characterization of Lytic Bacteriophages Targeting Clinical Staphylococcus Other Than S. aureus

Staphylococcus spp., other than S. aureus (SOSA, formerly CoNS), are opportunistic pathogens often linked to biofilm infections on indwelling devices. Their rising antibiotic resistance highlights the need for novel therapies. Bacteriophages are promising due to their specificity and ability to inhibit cell growth and biofilm formation. In this study, lytic phages isolated from swab pools were characterized against six clinical S. epidermidis and S. warneri isolates. Two distinct groups were identified via their host range, transmission electron microscopy, and genome sequencing. Group 1 phage ΘBRJ9 belongs to genus Sepunavirus (Myoviridae), while Group 2 phage ΘBRJ18 belongs to genus Andhravirus (Podoviridae). Both showed rapid adsorption, short latent periods (20 min), and high burst sizes (79 and 60 PFU/cell). They strongly inhibited planktonic SOSA growth at MOI 10, with efficacy comparable to or better than vancomycin, and their genomes lacked lysogeny, virulence, or resistance genes. These phages display a lytic lifestyle and are candidates for targeted SOSA therapies. Future work will assess biofilm efficacy, antibiotic synergies, and in vivo performance.