Comparison of Various Methods for Isolation of Nocardia from Soil

Background: The genus Nocardia is Gram-positive, aerobic filamentous bacilli and saprophytic micro-organisms that can be isolated from freshwater, salt water, dust and decaying vegetation especially the soil. This study aimed to investigate the several media for to determine a suitable culture media with the ability to better for the isolation of Nocardia from soil. Methods: In this study, 400 soil samples were collected from different areas from Iran. The soil samples were then cultured on the four culture media such as Humic acid vitamin B agar, Paraffin agar, Sabouraud dextrose agar supplemented whit cycloheximide and carbon-free broth containing paraffin rods and incubated at 35°C. All of culture media investigated every 3 days for a month. Colonies suspicious to Nocardia were stained with Gram-stain, acid-fast and partially acid-fast and evaluated for resistance to lysozyme. Results: From 400 soil samples, the number of 62, 10, 28 and 19 strains of Nocardia were isolated by paraffin rods, Humic Acid Vitamin B agar, Paraffin agar and Sabouraud dextrose agar whit cycloheximide, respectively. Most Nocardia strains were isolated using paraffin bait technique. Conclusions: Isolation of Nocardia spp. is enhanced by using the paraffin baiting technique that relies on the selective ability of this micro-organism to metabolize paraffin.