Isolation and Characterization of a Bacteriophage ΦSU1 Active Against Multidrug-resistant Staphylococci

Pathogenic strains of Staphylococcus species are among the most important agents of nosocomial infections. In the present study, we isolated bacteriophages from hospital sewage of Kadapa, India, that can infect multidrug-resistant Staphylococcus aureus and Staphylococcus ureilyticus. Four phages were isolated, and FSU1 was chosen for further investigation because it had a wider host range. Transmission electron microscopy showed that the head of FSU1 was 44-45 nm in size with an icosahedral shape, while the tail was noncontractile with a length of 231 nm and adsorption efficiencies of 88.64 and 53.74% on S. ureilyticus and S. aureus, respectively. One-step growth experiments revealed latent periods and burst sizes of 35.02 min and 88.5 PFU/cell for S. ureilyticus and 38.77 min and 58.6 PFU/cell for S. aureus. FSU1 was stable at a pH of 4-8 and at a temperature of 28-50 °C, while a drop in titer was found at a pH of 9 and 4 °C, with complete inactivation at a pH of 3 and 10 and at 60 °C. Excess ZnCl2 inhibited FSU1 activity on S. ureilyticus. The results indicated that FSU1 was lytic and should be further studied.