reported as important in virulence. Diagnosis Isolation Traditionally, culture methods for the isolation of E. rhusiopathiae involve the use of selective and enrichment media. Commercially available blood culture media are satisfactory for primary isolation from blood, since E. rhusiopathiae is not particularly fastidious. A number of selective media for the isolation of Erysipelothrix have been described, also. A commonly used medium is Erysipelothrix selective broth (ESB), a nutrient broth containing serum, tryptose, kanamycin, neomycin, and vancomycin. Modified blood azide medium (MBA) is a selective agar containing sodium azide and horse blood or serum. Packer's medium is a selective medium for grossly contaminated specimens, which contains sodium azide and crystal violet. Bohm's medium uses sodium azide, kanamycin, phenol, and water blue. Shimoji's selective enrichment broth contains tryptic soy broth, Tween 80, tris-aminomethane, crystal violet, and sodium azide. Species identification Conventional species identification is based on colony morphology, Gram-staining and biochemical tests. Colonies are small with a narrow zone of alpha hemolysis on blood agar plates. Laboratory smears show Gram-positive rods (though Gram stain has low sensitivity for this microbe). It is nonmotile, catalase-negative, microaerophilic, capnophilic, and non-spore-forming. It can also produce H2S (gas), which is a unique characteristic for a Gram-positive bacillus. Acid is produced from glucose, fructose, galactose, and lactose, but not from maltose, xylose, and mannitol. Sucrose is fermented by most strains of E. tonsillarum, but not by E. rhusiopathiae. Hydrogen sulfide H2S is produced by 95% of strains of Erysipelothrix species as demonstrated on triple sugar iron (TSI) agar. E. rhusiopathiae can be differentiated from other Gram-positive bacilli, in particular, from Arcanobacterium (Corynebacterium) pyogenes and Arcanobacterium (Corynebacterium) haemolyticum, which are hemolytic on blood agar and do not produce hydrogen sulfide in TSI agar slants, and from Listeria monocytogenes, which is catalase positive, motile, and sensitive to neomycin. Rapid identification of E. rhusiopathiae can be achieved with the API Coryne System. It is a commercial strip system based on a number of biochemical reactions for the identification of coryneform bacteria and related genera, including E. rhusiopathiae. The system permits reliable and rapid identification of bacteria and has been considered to be a good alternative to traditional biochemical methods. Other assays Several polymerase chain reaction (PCR) based methods have also been developed for detection of E. rhusiopathiae. Laboratory investigations of humans may reveal leucocytosis, slightly increased serum c-globulins, and an increase in inflammatory markers (erythrocyte sedimentation rate, C-reactive protein, and