IN-VITRO ACTIVITIES OF PAROMOMYCIN AND LASALOCID EVALUATED IN COMBINATION AGAINST CRYPTOSPORIDIUM-PARVUM

Using a chemiluminescence immunoassay, paromomycin and lasalocid were shown to inhibit Cryptosporidium parvum growth in Madin-Darby canine k idney cells in a concentration-dependent manner. The median effective concentrations (EC(50)s) for paromomycin and lasalocid were 1184 mg/L and 0.4 mg/L, respectively. Neither drug was cytotoxic to host cells a t concentrations up to five times their EC(50)s. Drug combination stud ies were conducted and the resulting data were analysed by the median- effect principle and combination index method. Statistically significa nt synergy was observed when combinations of paromomycin and lasalocid were used at ratios of 5000:1 and 2500:1. A possible mechanism for sy nergy is discussed.