At a dose of 10 mg/kg given twice daily, daptomycin reduces the number of organisms per kidney significantly compared with that in infected untreated controls within 48 h after the initiation of therapy. At 20 mg/kg given once a day, daptomycin is less effective but reduces colony counts significantly after 4 days of therapy, and its activity is comparable to that of vancomycin or vancomycin-gentamicin given twice daily[2].
In Vitro
Daptomycin has excellent in-vitro inhibitory and bactericidal activity against nafcillin-susceptible and resistant staphylococci (MIC90 less than or equal to 0.5 mg/L) and against enterococci (MIC90 less than or equal to 2.0 mg/L). Daptomycin is more active than vancomycin against the majority of isolated tested. With the exception of trimethoprim-sulphamethoxazole, daptomycin is the most active agent in vitro against enterococci, and is the most active against nafcillin-resistant staphylococci. Daptomycin and vancomycin show a marked increase in MIC when the inoculum is increased from 105 to 107 cfu/mL[1]. Daptomycin is effective within a very narrow range of drug concentrations (from 0.125 to 2.0 tLg/mL) and is more active than other agents tested against S. faecalis[2]. Daptomycin inhibits the formation of these nucleotide-linked intermediates[3].
Kinase Assay
Cell Assay
Animal Administration
Inocula containing 109 CFU/mL are prepared from an 18-h brain heart infusion broth culture. The exact number in each inoculum is subsequently determined by the standard serial 10-fold dilution agar pour plate technique. Animals are challenged intravenously with a 1.0-mL inoculum. This inoculum is known to infect the renal medulla of normal rats. Twenty-four hours later the animals are divided into eight groups and are given either saline only (controls) or antibiotic therapy initiated with Daptomycin at 10 mg/kg (Daptomycin10), Daptomycin at 20 mg/kg (Daptomycin20), Daptomycin10 plus gentamicin at 1.5 mg/kg, vancomycin at 20 mg/kg, vancomycin at 20 mg/kg plus gentamicin at 1.5 mg/kg, ampicillin at 30 mg per rat per injection, and ampicillin at 30 mg per rat plus gentamicin at 1.5 mg/kg. Animals receive Daptomycin20 once daily; all other drugs are administered twice daily. Vancomycin and Daptomycin are given subcutaneously; ampicillin and gentamicin are given intramuscularly. Drugs are administered for up to 13 days.
References
[1]. Benson CA, et al. Comparative in-vitro activity of LY146032 a new peptolide, with vancomycin and eight other agents against gram-positive organisms. J Antimicrob Chemother. 1987 Aug;20(2):191-6.
[2]. Miniter PM, et al. Activity of LY146032 in vitro and in experimental enterococcal pyelonephritis. Antimicrob Agents Chemother. 1987 Aug;31(8):1199-203.
[3]. Allen NE, et al. Inhibition of peptidoglycan biosynthesis in gram-positive bacteria by LY146032. Antimicrob Agents Chemother. 1987 Jul;31(7):1093-9.
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