Treatment outcome with pencillin G or cloxacillin in penicillin susceptible Staphylococcus aureus bactearemi

An increasing proportion of penicillin-susceptible Staphylococcus aureus (PSSA) has been reported over the last years. The aim of this retrospective study was to compare penicillin G with cloxacillin in the treatment of PSSA bloodstream infections. The primary outcome was the mortality rate after 90 days and the secondary outcome was the development of treatment complications of varying severity. Medical records from patients with PSSA bacteraemia during 2018–2020 were reviewed. Patient outcome was ranked on an ordinal scale according to severity: (i) alive at 90 days without any complications; (ii) adverse events not requiring treatment; (iii) change or addition of antibiotics owing to treatment failure or adverse events; (iv) relapse within 90 days; and (v) death within 90 days. The outcome ranking scale was dichotomised at every level and was analysed by logistic regression and a propensity score-weighted analysis. A total of 316 patients received cloxacillin and 68 patients received penicillin G as final treatment. Mortality rates did not differ significantly between the treatment groups (cloxacillin 19% vs. penicillin G 13%; P = 0.24), but patients treated with cloxacillin had an increased odds of having any complication compared with patients treated with penicillin G (odds ratio = 2.43, 95% confidence interval 1.30–4.53; P = 0.005). A propensity score analysis confirmed the results. Mortality rates in PSSA bacteraemia did not differ between treatment groups but cloxacillin treatment increased the overall odds of treatment complications.