Species spectrum of pathogenic Nocardia isolated from patients

Aim and Traditionally Nocardia asteroides was considered the predominant species of causing nocardiosis. The improved identification of isolates using molecular techniques have shown that the genus exhibits considerable taxonomic complexity and phenotypic base identification can be ambiguous. The aim of this study was to assess the species distribution of Nocardia strains mostly recovered from patients suspected of having tuberculosis, during three years period (2009-2012).The clinical isolates were identified to species level using conventional tests and genotypic methods using single and multi locus sequence analysis (MLSA) of 16S rRNA, gyrB and secA1 genes. Nocardiosis was diagnosed in 46 patients.The most frequent underlying condition were organ transplantation (6 patients; 13%), cancer (6 patients; 13%), human immunodeficiency virus (HIV) (6 patients; 13%), non-infectious chronic lung disease (5 patients; 10.8%) and tuberculosis (4 patients; 8.7%). Nocardia species was recovered from 46 different clinical specimens, the most common of which was bronchoalveolar lavage (BAL) (43.5%). Eleven different Nocardia species were identified: N. asteroides (n=12), N. cyriacigeorgica (n=9), N. farcinica (n=7), N. wallacei (n=6), N. carnea (n=3), N. otitidiscaviarum (n=3), N. abscessus (n=1), N. arthritidis (n=1), N. kruczakiae (n=1), N. nova (n=2) and N. veterana (n=1).In conclusion, infection caused by Nocardia species appears to be more common than is generally appreciated. The current study provides further evidence that Nocardia species are capable of causing a wide range of human diseases in healthy and immunocompromised patients. MLSA is a reliable method for accurate species identification of Nocardia isolates and would be more feasible for routine use in clinical laboratories.