The surveillance cohort represented about 30 percent of the U.S. chronic dialysis population, the researchers reported.
Over the 5-year period, they found, the overall bloodstream infection rate was estimated to be 15.4 per 100 outpatient years, the rate for MSSA was 2.1 per 100 outpatient years, and the rate for methicillin-resistant S. aureus (MRSA) was 1.9 per 100 outpatient years.
Among those with MSSA, 56.1 percent were being treated with vancomycin a week after blood was taken for culture, compared with 16.7 percent of patients getting cefazolin (P<0.001), Chan and colleagues found.
And the preference for vancomycin became more marked over time—in 2006, the rate was 49.4 percent of MSSA patients on the drug, compared with 66.4 percent in 2010. Over the same time, rates of cefazolin use fell by 8 percent.
But in survival analyses, cefazolin was associated with a lower combined risk of hospitalization or death from MSSA bacteremia compared with vancomycin (HR 0.62, 95% CI 0.46 to 0.84).
In addition, the risk of sepsis was reduced by 48 percent (HR 0.52, 95% CI 0.33 to 0.89).
A large majority of patients with MRSA, 74.7 percent, were treated with vancomycin and outcomes were best with that drug, the researchers found.
The researchers cautioned that the study did not include inpatients, so they could not calculate an overall bacteremia rate among dialysis patients. Also, they noted that both unmeasured confounding and confounding by indication are possible.