Identification of Nocardia Species Isolated from Soil Samples of the City of Tehran, Iran, Using Phenotypic Tests

Abstract

Background: Nocardia are Gram-positive, aerobic and partially acid-fast and cause dangerous infectious disease, nocardiosis, by entering the respiratory tract or damaged skin. In this study, we used various biochemical tests for identificating Nocardia species in soil samples of the city of Tehran, Iran. Methods: After isolation of Nocardia using paraffin baiting method, for detection and identification of various species, some phenotypic tests including growth in lysozyme broth, hydrolysis of amino acids such as hypoxanthine, xanthine, tyrosine, casein, gelatin and urea, production of nitrate reductase, growth at 35 °C and 45 °C, and utilization of some carbohydrates were used. Findings: The analysis of phenotypic tests presented that 12 isolates of Nocardia asteroides (63.15%), 5 isolates of Nocardia cyriacigeorgica (26.31%), and 1 isolate of Nocardia otitidiscaviarum (5.26%) were identified. Only 1 isolate (5.26%) remained undetected after phenotypic tests. Conclusion: In this study, several Nocardia species isolated from the soil samples of Tehran which were phenotypically similar to the well-known species. However, further identification tests are required to confirm the heterogeneity of the isolates and to identify the exact phenotype and genotype of the Nocardia species.

Keywords

• Nocardia
• Soil
• Phenotypic test
• Iran