Clinical significance and taxonomy of Actinobacillus hominis

Clinical findings in 36 immunosuppressed patients with lower respiratory tr act infection or bacteremia,vith Actinobacillus hominis are described. Anim al contact was only recorded for three patients; nine patients died despite appropriate antimicrobial treatment. Although infections with this microor ganism seem to be rare, the fact that 37 of 46 strains characterized in thi s study have been found in Copenhagen indicates that under-reporting may oc cur. A. hominis is phenotypically relatively homogeneous but can be difficu lt to differentiate from other Actinobacillus species unless extensive bioc hemical testing is performed. Mannose-positive strains of A. hominis are es pecially difficult to differentiate from A. equuli, Attempts to identify A. hominis by automatic identification systems may lead to misidentifications . Ribotyping and DNA-DNA hybridization data show that A. hominis is a homog eneous species clearly separated from other species within the genus Actino bacillus.