Identification of biodiversity of Nocardia spp. Isolated from clinical samples of the Tehran hospitals using phenotypic and molecular method

Nocardia is a germ-positive filamentous bacterium with relative acid-fast properties that ubiquitously exists as an environmental saprophyte. Nocardiosis is usually characterized as an acute or chronic illness associated with pus or granulomatosis, which can cause an aggressive disease both in healthy people and immunosuppressive patients. The aim of this study was to identify the biodiversity of Nocardia species isolated from Tehran hospitals via phenotypic and PCR molecular approaches.

200 samples were collected from Tehran hospitals. After being separated by paraffin baiting technique, the colonies were evaluated for their growth abilities in liquid lysozyme and at 45°C and based on other biochemical tests via macroscopic examinations and then microscopic gram and relative acid-fast staining practices. Ultimately, we designed a genus-specific primer set and performed the PCR reaction to compare both results.

From the 200 samples, 30 samples were identified as positive based on the culture and biochemical tests and molecular method.

Considering the species diversity of Nocardia genus and the existence of different conditions for performing phenotypic and biochemical tests, it is very probable that another genus relevant to the actinomycete family be mistakenly identified as Nocardia. Thus, molecular methods can provide confirmation of the phenotypic approach.