Neil M. Ampel, MD

In a small, observational study, 60% of methicillin-susceptible Staphylococcus aureus isolates from blood were found to be resistant to ceftriaxone by Etest.

Although not a primary drug for treatment of methicillin-susceptible Staphylococcus aureus (MSSA) infections, ceftriaxone has pharmacologic properties that make it attractive for use when such infections require long-term therapy. In 2012, the Clinical and Laboratory Standards Institute recommended using oxacillin, cefoxitin, penicillin, and ceftaroline to determine antimicrobial susceptibility of MSSA isolates, under the assumption that other β-lactam antibiotics will have equivalent activity. In the literature, the reported ceftriaxone resistance rate for MSSA is <3%.

In a recent retrospective, observational study conducted at a community hospital in Pittsburgh, isolates from patients with MSSA bacteremia between January 2012 and February 2013 were tested for ceftriaxone susceptibility using the agar-diffusion Etest. Thirty-eight (60%) of the 63 isolates tested were found to be resistant to ceftriaxone (minimum inhibitory concentration, >32 µg/mL). Additional testing of eight of these isolates — as well as eight matched, ceftriaxone-susceptible ones — showed all to be susceptible to cefazolin, cefuroxime, ceftriaxone, cefepime, and ceftaroline. Pulsed-field gel electrophoresis did not find a predominant clone among the ceftriaxone-resistant organisms.

Citation(s):

Pickering A et al. The common occurrence of ceftriaxone-resistant methicillin sensitive Staphylococcus aureus at a community teaching hospital. Clin Infect Dis 2014 Mar 14; [e-pub ahead of print].