Evaluating the effect of different temperatures and culture media on the production of methicillin-resistant Staphylococcus aureus (MRSA) bacteriophages

Abstract

Background: Staphylococcus aureus is a common pathogen that causes various infections. The emergence of methicillin-resistant S. aureus (MRSA) has made treatment more challenging, necessitating the exploration of new therapeutic approaches. In this regard, the study investigated the optimal conditions for phage production and activity. Objective: Evaluating the effect of different temperatures and culture media on    the production of methicillin-resistant Staphylococcus aureus (MRSA) bacteriophages. Methodology: This was cross-sectional hospital-based study carried out in Baghdad Governorate, Iraq, from the beginning of October 2022 to November 2024 on S. aureus isolates. A total of 3 isolate from S. aureus bacteria which were taken from, Al-Kadhimiya Hospital and the isolate of phage (Rih21) Bacteriophage. Three different media used in the experiments (Luria broth, Mueller Hinton, and Nutrient broth). And three different temperatures (37, 40, 45 ^◦C). The results recorded by counting plaque number and phage titer calculated.   Results: In the study, the effect of media composition on Staphylococcus aureus phage production was investigated using a double agar overlay method. The plaque morphology of the phage was observed to vary in different culture media, with sizes ranging from small to large and appearances ranging from clear to turbid. Among the tested media, Luria Broth was identified as the optimal medium for phage production. A temperature of 37°C was determined to be the ideal temperature for phage production. Additionally, Phage Rih21 exhibited lytic activity against MRSA isolates in vitro, suggesting its potential as a therapeutic option for combating MRSA infections. These findings support the use of phage therapy as a promising strategy against MRSA infections. Conclusion: Storing phages at 4°C in a 50% glycerol medium provided the best preservation and density of phages.A temperature range of 28-37°C was identified as optimal for bacteriophage production.The Rih21 bacteriophage exhibited lytic activity at temperatures ranging from 37-45°C, with the ideal temperature for activity being 37°C.The optimal temperature for phage production varied based on the specific phage and its host.