In Vitro Susceptibility of Clinical and Carrier Strains of Staphylococcus aureus to STAFAL® Phage Preparation

The treatment of infections caused by <i>Staphylococcus aureus</i> is currently complicated by the increasing number of strains resistant to antimicrobial agents. One promising way to solve this problem is phage therapy. Due to the lack of data on the effectiveness and safety of phage preparations, STAFAL^® is the only registered phage preparation for the treatment of infectious diseases in the Slovak Republic and the entire European Union. The aim of this work was to determine the effectiveness of the STAFAL^® phage preparation against <i>S. aureus</i> strains of different origins with variable sensitivity to antimicrobial substances and with different genetic backgrounds. For this purpose, 111 carrier strains, 35 clinical isolates from bloodstream infections, and 46 strains from skin and soft tissue infections were analysed. The effectiveness of STAFAL^® was determined by the plaque forming method. STAFAL^® was effective against 74.0% of the strains tested. Susceptibility to this phage preparation was significantly higher in strains resistant to methicillin (MRSA), erythromycin and clindamycin (<i>p</i> < 0.05). The high efficiency of the STAFAL^® preparation was confirmed against spa types t003, t024 and t032, typical of the hospital environment. The in vitro results indicate high therapeutic potential of the STAFAL^® antistaphylococcal phage preparation, especially against MRSA strains.