(632) Clinical Outcomes Using Standard-Dose Cefazolin for MSSA Bacteremia in Patients With Obesity

Introduction: Cefazolin is commonly used for a variety of infections, including methicillin-sensitive staphylococcus aureus (MSSA) bacteremia. Some evidence suggests patients with obesity may require higher doses of cefazolin, such as 3 grams IV every 8 hours, to attain therapeutic levels. Doses of up to 9 grams per day have been well tolerated. Additionally, 3 gram doses of cefazolin are indicated pre-operatively in patients weighing ≥ 120 kg. We sought to determine if there are differences in clinical outcomes using standard-dose cefazolin in patients with obesity compared to patients without obesity.

Methods: This was a multicenter, retrospective, observational study of adult patients admitted between October 2018 and October 2023. Patients were excluded if they received > 48 hours of empiric antibiotics or cleared blood cultures the same day as initiation of cefazolin. The primary efficacy outcome was days to blood culture clearance, defined as time from first dose of cefazolin until blood culture clearance. Obesity was defined as a body mass index (BMI) of at least 30 kg/m2.

Results: Out of 69 patients included, 22 (31.9%) were considered obese. There was no statistically significant difference in days to culture clearance, in-hospital mortality, or overall mortality in obese vs. non-obese patients. After controlling for deep-seated infections and appropriately dosed cefazolin based on renal function using multivariable linear regression, there was no significant difference in days to culture clearance. There was a numerically longer time to culture clearance, in days, in the obesity group (2.4 days) compared to the non-obesity group (1.6 days, p=0.08).

Conclusions: There was no significant difference in clinical outcomes in obese vs. non-obese patients with MSSA bacteremia treated with standard-dose cefazolin. Dosing should be based on therapeutic drug monitoring when possible to ensure adequate target attainment.