Growth Inhibition of a Spectrum of Bacterial and Fungal Pathogens by Sulforaphane, an Isothiocyanate Product Found in Broccoli and Other Cruciferous Vegetables

Abstract

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 μg/mL. Five pathogens - Pseudomonas aeruginosa, 3 methicillin-resistant Staphylococcus aureus (MRSA) isolates and Candida albicans - were considered resistant to SFN, having MICs ≥ 16 - 32 μg/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.

Sulforaphane - isothiocyanate - broccoli - cruciferous vegetables - antimicrobial effects - Brassica oleracea Italica - Brassicaeae

References

• 1 Zhang Y, Kensler T W, Cho C G, Posner G H, Talahay P. Anticarcinogenic activities of sulphoraphane and structurally related synthetic norbornyl isothiocyanates.  Proc Natl Acad Sci USA. 1994;  91 3147-50
• 2 Fahey J W, Haristoy X, Dolan P M, Kensler T W, Scholtus I, Stepehenson K K. et al . Sulforaphane inhibits extracellular, intracellular, and antibiotic-resistant strains of Helicobacter pylori and prevents benzo[a]pyrene-induced stomach tumors.  Proc Natl Acad Sci USA. 2002;  99 7610-15
• 3 Verhoeven D TH, Goldbohm R A, van Poppel G, Verhagen H, van den Brandt P A. Epidemiological studies on Brassica vegetables and cancer risk.  Cancer Epidemiol Biomarkers Prev. 1996;  5 733-48
• 4 Lin H J, Probst-Hensch N M, Louie A D, Kau I H, Witte J S, Ingles S A. et al . Glutathione transferase null genotype, broccoli, and lower prevalence of colorectal adenomas.  Cancer Epidemiol Biomarkers Prev. 1998;  7 647-52
• 5 Chiao J W, Chung F L, Kancherla R, Ahmed T, Mittelman A, Conaway C C. Sulforaphane and its metabolite mediate growth arrest and apoptosis in human prostate cancer cells.  Int J Oncol. 2002;  20 631-6
• 6 Dornberger K, Bockel V, Heyer J, Schonfeld C H, Tonew M, Tonew E. Investigations of the isothiocyanates erysolin and sulforaphan of Cardaria draba L.  Pharmazie. 1975;  30 792-6
• 7 Haristoy X, Fahey J W, Scholtus I, Lozniewski A. Evaluation of the antimicrobial effects of several isothiocyanates on Helicobacter pylori.  Planta Med. 2005;  71 326-30
• 8 Winn W C, Allen S D, Janda W M, Koneman E W. Koneman’s color atlas and textbook of diagnostic microbiology, 6th edition. Philadelphia; Lippincott Williams & Wilkins 2006
• 9 Bauer A W, Kirby W MM, Sherris J C, Turck M. Antibiotic testing by a standardized single disk method.  Am J Clin Pathol. 1966;  45 493-6
• 10 National Committee for Clinical Laboratory Standards. Methods for disk susceptibility tests for bacteria that grow aerobically - 7th edition: Approved Standard M2-A7. Wayne; NCCLS 2000
• 11 National Committee for Clinical Laboratory Standards. Performance standard for antimicrobial disk susceptibility tests - 8th edition: Approved Standard M2-A8. Wayne; NCCLS 2003
• 12 Moellering R C, Graybill J R, McGowan J E, Corey L. Antimicrobial resistance prevention initiative - an update: proceedings of an expert panel on resistance.  Am J Med. 2007;  120 S4-25
• 13 Jones R N, Kirby J T, Beach M I, Biedenbach D J, Pfaller M A. Geographic variations in activity of broad-spectrum beta-lactams against Pseudomonas aeruginosa: summary of the worldwide SENTRY Antimicrobial Surveillance Program.  Diagn Microbiol Infect Dis. 2002;  43 239-43
• 14 Maheo K, Morel F, Langout S, Kramer H, Le Ferrec E, Ketterer B. et al . Inhibition of cytochromes P-450 and induction of glutathione S-transferases by sulforaphane in primary human and rat hepatocytes.  Cancer Res. 1997;  57 3649-52
• 15 Gamet-Payrastre L, Li P, Lumeau S, Cassar G, Dupont M A, Chevolleau S. et al . Sulforaphane, a naturally occurring isothiocyanate, induces cell cycle arrest and apoptosis in HT29 human colon cancer cells.  Cancer Res. 2000;  60 1426-33
• 16 Fahey J W, Zalcman A T, Talat P. The chemical diversity and distribution of glucosinolates and isothiocyanates among plants.  Phytochemistry. 2001;  56 5-51