Absence of serotype-specific surface antigen and altered teichoic acid glycosylation among epidemic-associated strains of Listeria monocytogenes.

Outbreaks of food-borne listeriosis have often involved strains of serotype 4b. Examination of multiple isolates from three different outbreaks revealed that ca. 11 to 29% of each epidemic population consisted of strains which were negative with the serotype-specific monoclonal antibody c74.22, lacked galactose from the teichoic acid of the cell wall, and were resistant to the serotype 4b-specific phage 2671.