SAN DIEGO, CA—Cefazolin offers reduced mortality and similar recurrence rates vs. the penicillinase-stable penicillins (PSPs) nafcillin or oxacillin in patients with methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia, a retrospective cohort study from records of US Veterans Health Administration (VHA) hospitals reported at IDWeek 2015 has found.

In the large, multicenter study, 30-day and 90-day morality were “less likely to occur in patients receiving definitive therapy with cefazolin compared with nafcillin or oxacillin,” said lead study author Jennifer McDanel, PhD, of CADRE Iowa City Veterans Affairs Medical System and Carver College of Medicine, University of Iowa, Iowa City, Iowa.

The Infectious Diseases Society of America recommends switching therapy to a beta-lactam if a patient is infected with MSSA. Cefazolin is often prescribed instead of PSPs partly because it is less expensive and because PSPs are associated with toxicities such as drug-induced fever, rash, renal dysfunction, and liver function abnormalities. However, cefazolin is administered less often than nafcillin or oxacillin, she said, and treatment failures have been reported in patients with deep-seated infections.

To compare the effectiveness of cefazolin with nafcillin or oxacillin for definitive therapy of MSSA infections complicated by bacteremia, Dr. McDanel and colleagues reviewed records for patients admitted to 120 VHA hospitals from 2003– 2010 with blood culture-positive MSSA who had undergone definitive cefazolin or PSP therapy with nafcillin or oxacillin 4–14 days after the first MSSA blood culture was collected.

A total of 1,337 patients had received cefazolin and 2,146, nafcillin or oxacillin. Patients who received cefazolin had a 30-day mortality rate of 10%, compared with 15% of patients who had received the PSPs (P<0.001); 90-day mortality was 20% vs. 25% (P=0.002), respectively.

Cox proportional hazard regression and ordinal logistic regression analyses were used to assess associations between definitive pharmacotherapies, death, and recurrence. When adjusted for skin and soft tissue infections, endocarditis, osteomyelitis, diabetes, APACHE III score, age, Charlson comorbidity score, admission to the intensive care unit, and hospital-onset infection, the regression model showed that “patients who received definitive therapy with cefazolin had a 36% lower 30-day mortality compared with patients receiving nafcillin or oxacillin,” with 90-day mortality 22% lower with cefazolin, she said.

Recurrent MSSA bacteremia 45–365 days following treatment (n=2,890) was similar for patients who received either cefazolin or nafcillin/oxacillin (adjusted odd ratio 1.13, 95% CI: 0.94–1.35; P=0.188).

“Providers might consider cefazolin for MSSA bacteremia,” Dr. McDanel concluded.