Isolation and identification the Nocardia species from clinical specimens

The genus Nocardia is a Gram-positive aerobic bacterium and has mycolic acid, peptidoglycan, and phospholipid components in cell wall structure. The gold standard for nocardiosis identification is the isolation and culture of Nocardia. This bacterium causes pulmonary and extra pulmonary nocardiosis in human and isolated of Bronchoalveolar lavage (BAL), Sputum, Abscesses, Blood, Cerebrospinal fluid (CSF), and etc. Decontamination methods such as sodium hydroxide and N-acetyl-L-cysteine are toxic for the genus Nocardia. There are various methods and media for Nocardia isolation of clinical specimens such as paraffin baiting method, paraffin agar, media with antimicrobial agents such as Thayer-Martin agar and Buffered charcoal yeast extract (BCYE), Ogawa agar, conventional media such as blood agar, nutrient agar, brain-heart infusion agar (BHI). There are various phenotypic tests [colony morphology, pigment production, specific and conventional staining methods such as Gram, acid-fast and partial acid-fast, growth to lysozyme broth, aerial hyphae production, Growth at 45 °C, enzyme production, carbohydrate utilization, hydrolysis of amino acids, matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and etc.] and molecular methods [technique polymerase chain reaction (PCR) base sequencing, PCR-restriction fragment length polymorphism (RFLP), Whole genome sequencing (WGS), and DNA-DNA hybridization] for Nocardia identification at the genus and species level. The most common species such as Nocardia asteroides complex, Nocardia nova complex, and Nocardia otitidiscaviarum have been isolated from clinical specimens from Iran.

Keywords:

Nocardia , Isolation , Identification