Cefazolin and ertapenem combination therapy was used successfully to salvage 11 cases (6 endocarditis) of persistent methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia, including immediate clearance (≤24 hours) in 8 cases. While in vitro synergy was modest, cefazolin plus ertapenem exhibited synergistic action in a rat model of MSSA endocarditis. The combination of cefazolin and ertapenem provides potent in vivo activity against MSSA beyond what is predicted in vitro and warrants further clinical study in the treatment of refractory MSSA bacteremia and endocarditis.
Eleven patients with persistent MSSA bacteremia had rapid blood-stream clearance after changing to the combination drug treatment, and all survived.
No guidance is available regarding the management of patients with persistent bacteremia due to methicillin-susceptible Staphylococcus aureus (MSSA). Researchers previously described in vitro and in vivo synergism of cefazolin and ertapenem against MSSA. They now describe a case series using this treatment.
Eleven patients with persistent MSSA bacteremia lasting from 4 to 9 days despite antibiotic therapy were given a combination of cefazolin and ertapenem. Initial antibiotic regimens included vancomycin, piperacillin/tazobactam, ceftriaxone, and nafcillin, alone or in various combinations. Six patients had confirmed endocarditis. In the 8 of 9 (89%) instances with relevant measurements, blood cultures were negative within 24 hours after the change to combined cefazolin and ertapenem. All patients survived. In an animal model of MSSA endocarditis, the geometric mean bacterial concentration in vegetations was approximately 4-log lower with the combination than with cefazolin alone.