ANTIGENIC RELATIONSHIPS BETWEEN LISTERIA MONOCYTOGENES AND STAPHYLOCOCCUS AUREUS

The antigenic relationships between the different serotypes of Listeria monocytogenes and Staphylococcus aureus were investigated by means of agglutination, agglutinin-absorption, precipitation, and complement fixation tests. Reciprocal cross-reactions were demonstrated with serotypes 1, 2, and 3 of L. monocytogenes and many S. aureus strains, but not with serotypes 4a and 4b, using O suspensions of L. monocytogenes and autoclaved suspensions of S. aureus. Soluble heat-stable polysaccharide extracts, on the contrary, were quite specific in precipitin tests. Antisera against L. monocytogenes type 3 cross-precipitated unilaterally extracts of most S. aureus strains. In the absence of clear-cut serological species specificity in these two microorganisms, in their reactions with rabbit antisera, and with human sera from suspected cases of listeriosis, there is need for caution in the interpretation of positive serological tests as an aid to diagnosis.