Application of the API YeastIdent system in determining the enzymatic profiles of Nocardia asteroides isolates

Glucose represses production of ammonium in many clinical isolates of Nocardia asteroides growing on bromcresolpurple casein glucose agar. Strains exhibiting this property are designated as group A, while group B represents isolates showing a high degree of proteolytic activity and a resulting rapid increase in pH. Twenty isolates of N. asteroides were characterized as group A or B. Enzymatic profiles obtained using the API YeastIdent system showed significant enzymatic variation between 12 group B and 8 group A isolates. Proteolytic enzymes which most varied in activity between groups were glycine aminopeptidase, histidine aminopeptidase and leucyl glycine aminopeptidase. As some of the N. asteroides isolates were isolated from asymptomatic patients, it is of interest to consider the possibility of one group being of low virulence while the other is more strongly associated with infection.