Comparison of Cloxacillin and Benzylpenicillin in Penicillin Susceptible S. Aureus Bacteraemia

The overall research idea of is a RCT is to test the hypothesis that benzylpenicillin is superior to cloxacillin in the treatment of PSSA bacteraemia.

Population: Adult patients (>18 years) with PSSA bacteraemia will be eligible for enrolment in the study. Exclusion criteria are allergy to penicillin, inability to give informed consent, and concomitant growth of other clinically significant bacteria in blood cultures. We are planning a nation-wide study.

Intervention: Benzylpenicillin treatment of PSSA bacteraemia will be evaluated. As soon as S. aureus has been identified in blood cultures and the susceptibility testing indicates penicillin susceptibility (Two-three days from start of treatment), patients will be randomized to continue therapy with either cloxacillin or benzylpenicillin. The duration of treatment depends on the type of infection, and details about length of therapy and dosage will be decided by the specific patient diagnosis (i.e., endocarditis, arthritis). Repeated blood cultures and echocardiography are important in the diagnostic work-up of S. aureus bacteraemia and will be included in the study protocol. Patients will also be monitored regarding adverse events, such as liver and renal impairment, rash, diarrhoea, thrombophlebitis et c., and treatment failure, relapse, and mortality.

Control: The study drug (benzylpenicillin) will be compared to cloxacillin, which is the current drug of choice for methicillin susceptible S. aureus in Sweden. Both drugs will be used at clinically recommended doses, with appropriate adjustments for renal impairment if needed. Outcome: Primary outcome is; to be alive for 90 days without any complications. Complications are defined as having any of relapse (90 days after antibiotic finished), need of change or addition of antibiotics due to side effects or treatment failure or adverse events.

Inclusion criteria

Aged ≥18 with penicillin susceptible S. aureus bacteraemia (PSSA), and able to provide written informed consent.

Exclusion criteria

• allergy to penicillin,
• inability to give informed consent,
• concomitant growth of other clinically significant bacteria in blood cultures
• neutropenia

-≥ 96h with prior antibiotics

• When the per oral follow up medication can not be flukloxacillin or penicillinV/Amoxicillin (ie prosthetic joint infection)
• Patients in terminal palliation, where death is expected within 7 days.
• Where the treating physician believes cloxacillin is not a first-line treatment.