A method for determining in-vitro drug susceptibilities of some Nocardiae and Actinomadurae: results with 17 antimicrobial agents.

A simple timesaving method for determining drug susceptibilities in vitro of isolates of Nocardia and Actinomadura is reported. An isolate is considered "susceptible" when the quantity of drug required for inhibition of growth is that concentration which might be obtained in serum by conventional therapy. Sulfonamides remain the drugs of choice for treating disease due to Nocardia species. Although doxycycline and minocycline appear to be very effective against Nocardia species, susceptibility testing may be desirable when a physician is considering substitution of an antibiotic for a sulfonamide. Susceptibility testing also may be desired before a drug is selected for treating disease due to Actinomadura madurae.