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.