Prostaglandin E2 attenuates synergistic bactericidal effects between COX inhibitors and antibiotics on Staphylococcus aureus.

PGE2 is found to attenuate the bactericidal effects of kanamycin or ampicillin in Staphylococcus aureus, as well as the methicillin-resistant S. aureus (MRSA). Co-treatment with cyclooxygenase (COX) inhibitors (celecoxib, aspirin or naproxen) synergistically enhances kanamycin or ampicillin-induced cell death of S. aureus and MRSA. COX inhibitors repressed bacterial multidrug resistance through down-regulating efflux pump activity in antibiotics-treated S. aureus and MRSA. However, this synergistic bactericidal effects are reduced by the treatment with PGE2. PGE2 restores the efflux pump activity as well as increases biofilm formation in S. aureus and MRSA. Collectively, the enhancement of efflux pump activity and biofilm formation with PGE2 might partially explain the resistance to synergistic bactericidal effects between COX inhibitors and antibiotics in PGE2-treated S. aureus.