Contamination and deterioration of alfalfa sprouts caused by a seedborne isolate of Erwinia herbicola

A Gram negative, rod-shaped, yellow-pigmented bacterium was recovered from beneath the seed coats of surface-sterilized alfalfa seed from three seed lots used for the commercial production of sprouts. This bacterium was responsible for the deterioration of alfalfa sprouts marketed in film-wrapped plastic containers. Identity of the isolate was confirmed as Erwinia herbicola (Lohnis) Dye (synonym Pantoea agglomerans comb. nov.). The level of contamination by this bacterium in nonsurface-sterilized seed was 34.7% while in surface-sterilized seed it was 13.2%. No other microorganisms were consistently recovered from surface-sterilized seed samples from these lots, or from other alfalfa seed samples assayed as controls. The bacterium was able To survive for more than three years beneath the seed coats of contaminated seed. We recommend that alfalfa sprout companies routinely assay samples for seedborne microorganisms from lots intended for sprouting.