Alternative Medication May Be More Favorable Choice for MSSA Bacteremia

The findings, coupled with the cost savings involved with using cefazolin, make it an appealing first line agent for most MSSA bloodstream infections.

SAN DIEGO  — A retrospective comparison of clinical outcomes between patients receiving nafcillin and cefazolin for treatment of methicillin-susceptible staphylococcus aureus (MSSA) bacteremia showed cefazolin was just as effective and resulted in significantly less side effects, according to study results released Saturday at ASM’s 55th ICAAC 2015.

The findings, coupled with the cost savings involved with using cefazolin, make it an appealing first line agent for most MSSA bloodstream infections, Maggie Monogue,clinical pharmacy fellow at Hartford Hospital Center for Anti-Infective Research and Development, said at a media event here.

Laboratory experiments have suggested that high-density MSSA infections, such as infections of the bone and heart, treated with cefazolin may result in higher rates of antibiotic failure due to the presence of certain enzymes. When present, the enzymes breakdown the antibiotic’s structure, which could make cefazolin ineffective against MSSA infections.

However, this recent 142 patient study conducted at Parkland Health and Hospital System in Dallas from August 2011 to August 2014 without funding, shows cefazolin may be a viable treatment option. The patients were broken into two groups of 71, with one cohort  receiving nafcillin and the other receiving cefazolin. The failed treatment rate for patients receiving nafcillin was 14 percent and the failure rate for the cefazolin cohort was 8.4%.

“The number of high burden infections was similar between the two arms, which suggests that the effect of the antibiotic destroying enzymes may not be as significant in clinical practice,” Monogue said. “Additionally there were significantly more adverse events observed in the nafcillin arm (19.7%  versus 7%). The study showed adverse events were driven largely by the high proportion of patients receiving nafcillin who developed some degree of kidney injury during treatment (16.9% versus 2.8%).

“The results are important to the health care system because nafcillin can be up to ten times the cost of cefazolin,” Monogue said. “With continually rising healthcare costs and tight budgets, cheaper alternatives are necessary.”

Cefazolin is often a more tolerable option and dosed less frequently, making it a beneficial option for both patients and hospitals, said study coauthor Jessica Ortwine, PharmD, clinical infectious disease pharmacist at Parkland Health and Hospital System.


1. Monogue ML. Nafcillin vs. cefazollin for the treatment of methicillin-susceptible Staphylococcus bacteremia. Presented at: ICAAC/ICC 2015; Sept. 17-21, 2015; San Diego.