Mycopathologia 143: 151–154, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. 151 A study of the enzymatic profile of soil isolates of Nocardia asteroides Z.U. Khan 1 , T.D. Chugh 1 , R. Chandy 1 , F. Provost 2 & P. Boiron 2 1 Department of Microbiology, Faculty of Medicine, Kuwait University, Kuwait; 2 Mycology Unit, National Reference Center for Human Mycoses, Antifungal Agents and Actinomycetes, Pasteur Institute, Paris, France Received 24 June 1998; accepted in revised form 22 December 1998 Abstract In this study, using the API-ZYM system, we have reported the enzyme profile of 42 soil strains and 2 clinical strains of Nocardia asteroides isolated locally. Of the 19 enzymes tested, only 7 were demonstrable in over 90% of the soil isolates. These included alkaline phosphatase, esterase lipase, leucine arylamidase, acid phosphatase, phosphohydrolase, α-glucosidase and β -glucosidase. In addition, β -galactosidase activity was demonstrated in all the strains by the O-nitrophenyl-β -D-galactopyranoside (ONPG) test. The enzymes which were not demonstrable in >95% of the strains included valine arylamidase, cystine arylamidase, trypsin, chymotrypsin, α-galactosidase, β -glucoronidase, N -acetyl-β -glucosaminidase, α-mannosidase and α-fucosidase. With the exception of valine arylamidase, which was lacking in all but one isolate, the enzyme profiles of the soil isolates were comparable with the clinical isolates of N. asteroides reported in previous studies. The reasons for this difference in the two sets of isolates is not clear. The study reinforces the view that specific differences in the enzymatic profiles of Nocardia species could be used for their rapid identification. However, more extensive studies are needed to establish the reproducibility of this method. To the best of our knowledge, this is the first study of the enzymatic profile of soil isolates of N. asteroides originating from a single geographic region. Key words: API-ZYM system, enzymatic profile, Nocardia identification, Nocardia in Kuwait, Nocardia in soil Introduction Nocardia species are Gram-positive, aerobic actino- mycetes with a world-wide distribution in soil. They may enter the body via inhalation of contaminated dust particles or via wounds contaminated with dust or soil. Nocardia species have emerged as an important cause of mortality and morbidity in severely immunocom- promised patients [1] including patients with human immunodeficiency virus infection [2]. Pathogenic no- cardiae are capable of causing a wide spectrum of infections with pulmonary, central nervous system, and cutaneous manifestations [3]. For the diagnosis and effective management of nocardiosis, it is im- portant to isolate and identify the etiologic species. Identification of nocardiae to a species level is a time- consuming process that involves performance of a number of biochemical tests such as hydrolysis of ca- sein, tyrosine and hypoxanthine, production of urease and resistance to lysozyme [4, 5]. Some of the strains of Nocardia may take more than two weeks to hy- drolyze the above substrates [5]. With the recognition of two new species within the Nocardia asteroides taxon, namely N. farcinica and N. nova, additional biochemical and antimicrobial susceptibility tests are required to confirm their identification [6]. Enzymatic profile studies of Nocardia and other clinically impor- tant actinomycetes have been reported to be helpful for rapid identification of these groups of microorganisms [7–13] In this paper, using the API-ZYM system, we present results of enzyme profiles of soil isolates of N. asteroides and examine reproducibility of this method for identification of pathogenic Nocardia species. Materials and methods Nocardial strains and preparation of inoculum Forty-two strains of N. asteroides isolated from soil samples collected from different locations in Kuwait