184. Channeling Alexander Fleming: Efficacy of Penicillin (PCN) to Treat Staphylococcus aureus (SA) Bacteremia

Background Up to 20% of SA isolates in the United States are penicillin-susceptible (PSSA); however, treatment with penicillin has been discouraged because of concern that routine testing may miss strains that have the capacity to produce clinically significant ß-lactamase in vivo. We performed a retrospective analysis to determine whether PCN therapy for the treatment of PSSA bacteremia was of comparable efficacy and safety to standard therapies. Methods We identified all episodes of SA bacteremia (March 18, 2010–July 23, 2018). SA penicillin susceptibility testing in our lab was performed by broth microdilution followed by nitrocefin ß-lactamase testing per CLSI guidelines on these isolates. A retrospective chart review was performed and our primary outcome was a composite endpoint of clinical success (no change in PSSA therapy due to persistent or worsening signs and symptoms, no PSSA bacteremia recurrence or persistence, and no infection‐related mortality). Microbiologic failure was defined as either failure to clear bacteremia/infection or recurrence after completion of therapy. Patients were followed until last contact with our medical system, the only tertiary center in the region. We compared our rates of success, mortality, and adverse drug reaction to historical SA bacteremia controls from the literature. Results PSSA accounted for 13% (130/971) of SA bloodstream episodes. Nineteen patients with PSSA (15%) were treated with PCN and 79% (15/19) achieved the primary endpoint of clinical success. Of the 4 patients who did not achieve the endpoint, 2 developed rash and were switched to a different antibiotic and 2 died from complications of sepsis. One of the patients died after clearing blood cultures but had DIC and a catastrophic intracranial hemorrhage, the other died of overwhelming sepsis after 4 days (2 days nafcillin, 2 days PCN) with continued bacteremia. Thus, our only microbiologic failure was due to early death from sepsis. Rates of success, mortality and drug reaction were similar to prior reports of alternative standard therapies (Table 1). Conclusion PCN is a viable treatment option for PSSA bacteremia as identified by routine laboratory testing. Further study will include characterizing the presence of ß-lactamase in these patient’s isolates. Disclosures All authors: No reported disclosures.