Adjunctive daptomycin confers no benefit in MSSA bloodstream infections

For patients with methicillin-susceptible Staphylococcus aureus (MSSA) bloodstream infections (BSIs), the use of daptomycin as an adjunct to standard treatment does not help shorten the duration of bacteraemia and, hence, should be done away with, as suggested in a study.

A total of 115 adult patients treated with either cefazolin or cloxacillin were randomized to undergo a 5-day course of adjunctive daptomycin or placebo. Of these, 104 patients (median age, 67 years; 34.5 percent female) were included in the final analysis.

Endovascular infection (39.4 percent) was the most common cause of bacteraemia, followed by skin and soft tissue infections (24.0 percent), osteomyelitis (7.7 percent), and pneumonia (6.7 percent). Most patients were treated with cefazolin (73.1 percent) and had a complicated bloodstream infection (78.8 percent).

There was no significant difference in the primary outcome of duration of MSSA BSI between daptomycin and placebo (median, 2.04 vs 1.65 days, respectively; absolute difference, 0.39 days; p=0.40). Likewise, adjunctive daptomycin did not result in substantial reduction in 90-day mortality compared with placebo (18.9 percent vs 17.7 percent; p=1.0).

Daptomycin was well tolerated, and no serious adverse events were reported. The proportion of patients who developed renal failure, hepatotoxicity, or rhabdomyolysis was similar in the active treatment and placebo groups.

The findings oppose evidence from in vitro studies suggesting that adding daptomycin to an anti-staphylococcal beta-lactam (ASBL) results in synergistic activity against S. aureus, researchers said. Instead, the combination yields null effects in the management of patients with MSSA BSIs. [Antimicrob Agents Chemother 2004;48:2871-2875]

Therefore, daptomycin should not be added to ASBL in this population, as indicated in current treatment guidelines, they added. [JAMA 2018;320:1249-1258; JAMA 2014;312:1330-1341]