[Special position of strongly haemolytic strains of the genus Listeria].

The special status of the strongly haemolytic strains of serovar (sv) 5 of Listeria monocytogenes is reviewed. Besides some biochemical reactions sv 5 strains are characterized by their excessive haemolysis on sheep blood agar and by a positive result of the CAMP test with R. equi. The haemolysis is caused by a soluble thermolabile protein which stimulates the formation of antibodies and which is inhibited by cholesterol. Sv 5-strains are less virulent than strains of sv 1/2a and sv 4b. The antibiotic sensitivity patterns characteristic for listeriae and for the principles of treating Listeria infections, are valid for sv 5-strains, too. The special position of sv 5 versus the other serovars of L. monocytogenes - with particular reference to its biochemical activity, its haemolytic properties, its lysosensitivity and its pathogenicity - calls for a reconsideration of its taxonomic position within the genus Listeria.