SRP341169 PRJNA770908 Monitoring the seesaw effect in S. aureus grown in a bioreactor Over the past decade, daptomycin treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections has led to the emergence of daptomycin non-susceptible (DAP-NS) MRSA strains and a subsequent interest in combinatorial antibiotic therapies. The seesaw effect describes the correlation between daptomycin resistance and increased beta-lactam susceptibility in DAP-NS MRSA. In this study, we successfully produced the seesaw effect in MRSA strain N315 by exposure to incremental dosages of daptomycin followed by oxacillin in a bioreactor. WGS was employed to monitor the genomic changes that occurred following antibiotic treatment.