SAN DIEGO – Veteran patients treated with ceftriaxone for methicillin-susceptible Staphylococcus aureus bacteremia were more likely to have treatment failure, compared with those who received cefazolin, a retrospective observational study found.
“To date, no study has specifically evaluated cefazolin versus ceftriaxone for MSSA bacteremia,” Dustin Carr, Pharm.D., said at an annual scientific meeting on infectious diseases. “The main design of this study was to inform our current site and give us additional antimicrobial stewardship opportunities to ensure appropriate selection, dosing, route, and duration.”
Dr. Dustin Carr
In a study conducted during Dr. Carr’s residency training at Louis Stokes Cleveland VA Medical Center, he and his colleagues retrospectively evaluated veteran patients with MSSA bacteremia from January 2009 to August 2014 who received at least 14 days of parenteral cefazolin or ceftriaxone. The use of concomitant anti-staphylococcal agents were excluded, as were patients with polymicrobial infections and those who received empiric antibiotics greater than 72 hours after cultures were finalized. Dr. Carr noted that infectious diseases clinicians are consulted for all cases of MSSA bacteremia at the Louis Stokes Cleveland VA Medical Center, which accounts for about 25% of all outpatient parenteral antimicrobial therapy cases.
Treatment failure was defined as unplanned extension of parenteral antimicrobial therapy, failure to complete a course of parenteral therapy, relapse or recurrence of infection within 90 days, addition of suppressive oral antimicrobial therapy, readmission or unanticipated surgical intervention within 90 days, and being lost to follow-up. Secondary outcomes were relapse and recurrence within 90 days of treatment, overall 90-day mortality, rate of Clostridium difficile infection within 90 days, adverse drug reactions, and cost of IV antimicrobials. The researchers used logistic regression to assess variables of treatment failure.
Dr. Carr, who is currently an infectious diseases specialty resident at Wake Forest Baptist Health, Winston-Salem, N.C., reported results from 71 patients: 38 who received cefazolin (the cefazolin group) and 33 who received ceftriaxone (the ceftriaxone group). Patients in the cefazolin group were more likely to be on dialysis, compared with those in the ceftriaxone group (24% vs. 0%, respectively; P = .003) and they were more likely to have a prosthesis (53% vs. 24%; P = .015).
The researchers observed no significant differences in the comorbidities between the two groups, but there was more IV drug use in the cefazolin group (13% vs. 0%). The primary source of infection did not differ between the groups, but SSTIs were more likely to be treated with ceftriaxone, compared with cefazolin (33% vs. 8%; P = .086).
Dr. Carr reported that 28.9% of patients in the cefazolin group experienced a treatment failure, compared with 54.5% of those in the ceftriaxone group, a difference that was statistically significant (P = .029). There were no significant differences in the rate of most secondary outcomes between the two groups, with the exception of cost and loss to follow-up. The mean cost of IV therapy per patient was $746.51 in the cefazolin group, compared with $60.30 in the ceftriaxone group, while 5.3% of patients in the cefazolin group were lost to follow-up, compared with 12.1% in the ceftriaxone group.
By setting of outpatient parenteral antibiotic therapy, treatment failure occurred most often in the community skilled nursing facility setting (71%), followed by home settings (41%) and the VA long-term care facility attached to Louis Stokes Cleveland VA Medical Center (17%).
On logistic regression, the only significant predictors of treatment failure among all patients were duration of IV therapy (OR 1.05; P = .015), having heart failure (OR 7.93; P less than .001), as well as being treated in an outside community skilled nursing facility, compared with being treated at the long-term care setting attached to Louis Stokes Cleveland VA Medical Center (P = .008).
Dr. Carr acknowledged certain limitations of the study, including its retrospective design and the fact that it lacked data on antimicrobial susceptibilities and minimum inhibitory concentrations. Other limitations, he said, were that patients were allowed to receive cefazolin prior to ceftriaxone use and that there were low frequencies of secondary outcomes.
IDWeek marks the combined annual meetings of the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America, the HIV Medicine Association, and the Pediatric Infectious Diseases Society. The researchers reported having no financial disclosures.