Novel isolation and optimization of anti-MRSA bacteriophages using plaque-based biokinetic methods

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Background: MRSA (methicillin-resistant Staphylococcus aureus) is a global health problem. Many people are looking for new ways to combat MRSA, for example by using bacteriophages (phages). It has been extremely challenging to isolate a sufficient quantity of lytic anti-MRSA phages. Therefore, new techniques for separating, refining, and reworking anti-MRSA phages were sought in this study. Methods: Of 437 S. aureus isolates, nine clinical MRSA isolates were obtained from three hospitals in Baghdad, Iraq and two ATCC MRSA strains were used to separate wild anti-MRSA phages from sewage, filth, and hospital settings. The wild phage was optimized using plaque-based biokinetic methods. The resulting highly lytic and specific anti-MRSA phages were subjected to novel physico-chemical phage redesign protocols using agents to weaken the bacterial cell wall to allow phages to enter into host bacteria and acquire the specificity of the new host. Three protocols were tested using different combinations of benzethonium chloride (BZT-CH), alkaline ethanol, and chlorhexidine gluconate. Results: Five newly redesigned, transiently stable, anti-MRSA phages were produced using the BZT-CH and ethanol–alkali methods, albeit at varying rates. Conclusion: Although the resulting designed anti-MRSA phages are transiently stable, they represent a rare opportunity and an excellent endless source of lytic anti-MRSA phages from which a large number of permanent phage lysins can be separated and purified.