In vitro evaluation of the cyclic lipopeptide LY 146032 (daptomycin)

In vitro activity of the new cyclic lipopeptide LY 146032 (daptomycin, Eli Lilly) was evaluated against 67 clinical isolates of Staphylococcus aureus, 15 clinical isolates of S. epidermidis and 80 clinical isolates of Streptococcus faecalis. Activity was best against methicillin-resistant S. epidermidis (minimal inhibitory concentrations of LY 146032 0.25-0.5 mg/l). Minimal inhibitory concentrations and minimal bactericidal concentrations were of similar value. LY 146032 requires physiological concentrations of Ca++ ion for the expression of antibacterial activity. Results of the time-kill curves indicated that exposure to a concentration of the antibiotic equivalent to the minimal inhibitory concentration abolished recovery in the strains of S. aureus and S. epidermidis investigated. Response by S. faecalis was less predictable although most S. faecalis strains were killed in vitro by LY 146032 concentrations of less than or equal to 8 mg/l which is within the predicted clinically achievable range.