In addition to its documented antitumor effects, previous in vitro and in vivo infectivity experiments have shown that sulforaphane (SFN), an isothiocyanate compound found abundantly in broccoli and other cruciferous vegetables, inhibits the growth of the bacterial pathogen Helicobacter pylori. No recent evidence exists, however, on the possible microbial activity of SFN against a broader range of microorganisms, including those that may develop resistance to conventional antibiotics. The aim of this study was to determine the in vitro susceptibility patterns of SFN against a wide variety of bacterial and fungal pathogens. Sensitivity testing was done on 28 different microbial species using a modified Kirby-Bauer disk-diffusion method and results were interpreted based on guidelines established by the National Committee for Clinical Laboratory Standards. The broad-spectrum antibiotic, ceftriaxone (CTX), was used as a positive control for antimicrobial inhibition. It was found that 23 out of 28 different microbial species were inhibited by SFN with a minimal inhibitory concentration (MIC) ranging from 1-4 microg/mL. Five pathogens--Pseudomonas aeruginosa, 3 methicillin-resistant Staphylococcus aureus (MRSA) isolates and Candida albicans--were considered resistant to SFN, having MICs >or= 16-32 microg/mL. These findings suggest that, with the dual action of SFN against a select group of microorganisms and its ability to inhibit tumor growth, SFN (or the consumption of SFN-containing vegetables) might be especially helpful in preventing certain types of infections in both cancer and non-cancer patients.