Naturally Occurring Biofilms On Alfalfa and Other Types of Sprouts

NaturallyOccurring Biofilms on Alfalfa and Other Types of Sprouts

Journal of Food Protection
Vol. 63, No. 5, pp. 625-632
William F. Fett

ABSTRACT — Scanningelectron microscopy was used to examine the cotyledons, hypocotyls, and roots ofalfalfa, broccoli, clover, and sunflower sprouts purchased from retail outletsas well as alfalfa sprouts grown in the laboratory using a tray system equippedwith automatic irrigation. Biofilms were observed on all plant parts of the fourtypes of commercially grown sprouts. Biofilms were also commonly observed onalfalfa sprouts grown in the laboratory by 2 days of growth. Rod-shaped bacteriaof various sizes were predominant on all sprouts examined both as free-livingcells and as components of biofilms. Occasionally, cocci-shaped bacteria as wellas yeast cells were also present in biofilms. The microbes contained in thebiofilmsappeared to be attached to each other and to the plant surface by a matrix, mostlikely composed of bacterial exopolysaccharides. Biofilms were most abundant andof the largest dimensions on cotyledons, sometimes covering close to the entirecotyledon surface (approximately 2 mm in length). Naturally occurring biofilmson sprouts may afford protected colonization sites for human pathogens such asSalmonella and Escherichia coli O157:H7, making their eradication withantimicrobial compounds difficult.