Effects of natural products on several stages of the spore cycle of Clostridium difficile in vitro.

Abstract

To investigate the effect of natural products on the spore cycle of Clostridium difficile invitro. Twenty-two natural products were investigated using four C. difficile strains. Effects on sporulation, determined using microscopy and a conventional spore recovery assay, showed that fresh onion bulb extract (6·3% vv-1 ) and coconut oil (8% vv-1 ) inhibited sporulation in all four isolates by 66-86% and 51-88%, respectively, compared to untreated controls. Fresh ginger rhizome extract (25% vv-1 ) was also inhibitory, although to a lesser extent. Using a standard spore germination and outgrowth assay, germination was unaffected by the 22 products, whereas outgrowth was significantly reduced by artichoke extract (18·8mgml-1 ), fresh onion bulb extract (25% vv-1 ), Leptospermum honeys (8% wv-1 ) and allicin (75mgml-1 ; P<0·01). Sporicidal activity, investigated using a standard plate recovery assay, was minimal. Three of the 22 natural products (13%) showed inhibitory effects on sporulation of C. difficile and six products (27%) reduced vegetative outgrowth of C. difficile. This study shows the potential of natural products to inhibit different stages of C. difficile sporulation and encourages further investigation in this field.