Efficient differentiation of Nocardia farcinica, Nocardia cyriacigeorgica and Nocardia beijingensis by high-resolution melting analysis using a novel locus

Abstract

Accurate identification of Nocardia species remains a challenge due to the complexities of taxonomy and insufficient discriminatory power of traditional techniques. We report the development of a molecular technique that utilizes real-time PCR-based high-resolution melting (HRM) analysis for differentiation of the most common Nocardia species. Based on a novel fusA-tuf intergenic region sequence, Nocardia farcinica, Nocardia cyriacigeorgica and Nocardia beijingensis were clearly distinguished from one another by HRM analysis. The limit of detection of the HRM assay for purified Nocardia spp. DNA was at least 10 fg. No false positives were observed for specificity testing of 20 non-target clinical samples. In comparison to established matrixassisted laser desorption/ionization-time of flight MS, the HRM assay improved the identification of N. beijingensis. Additionally, all the products of PCR were verified by direct sequencing. In conclusion, the developed molecular assay allows simultaneous detection and differentiation of N. farcinica, N. cyriacigeorgica and N. beijingensis with high sensitivity and specificity.

Successful control of scleritis caused by Nocardia farcinica: A case report

“…Compared with traditional culturing method, it can be more rapid and precise to identify pathogenic bacteria and thus play a major role in the diagnosis of infectious eye diseases. [ 15 , 16 ]…”

“…Compared with traditional culturing method, it can be more rapid and precise to identify pathogenic bacteria and thus play a major role in the diagnosis of infectious eye diseases. [15,16] Infectious scleritis caused by N. farcinica should be differentiated from the following diseases. First, scleral infection caused by N. farcinica lacks specific clinical manifestations.…”

Treatment of Nocardial Brain Abscess in a Patient With Systemic Lupus Erythematosus and Idiopathic Thrombocytopenic Purpura: Case Report and a Review of the Literature

“…Nocardia species are aerobic gram-positive, catalase-positive, acid-fast bacteria, which produce branched, aerial hyphae up to 2 μm in diameter that often fragment into coccobacilli-shaped elements [1,4]. The diagnosis is challenging due to the non-specific presentation, the requirement for invasive diagnostic procedures, and the difficulty in the isolation and identification of the Nocardia species [3]. There are no serodiagnostic tests, and 16SrRNA may not definitively distinguish between different species of Nocardia, which exhibit different antibiotic susceptibilities [5][6][7].…”

“…The hyphae were then identified with a 99.9% certainty as Nocardia farcinica using matrix-assisted laser desorption/ionization-time-of-flight spectrometry and partial sequencing of 16S rDNA. A 100% certainty was not possible due to a 99% sequence homology between Nocardia farcinica and Nocardia kroppenstedtii [ 3 ]. Tests for acid-fast bacilli, human immunodeficiency virus, hepatitis B, and toxoplasma were all negative.…”