Molecular Identification of Nocardia Isolates from Clinical Samples and an Overview of Human Nocardiosis in Brazil

Abstract

Background Nocardia sp. causes a variety of clinical presentations. The incidence of nocardiosis varies geographically according to several factors, such as the prevalence of HIV infections, transplants, neoplastic and rheumatic diseases, as well as climate, socio-economic conditions and laboratory procedures for Nocardia detection and identification. In Brazil the paucity of clinical reports of Nocardia infections suggests that this genus may be underestimated as a cause of human diseases and/or either neglected or misidentified in laboratory specimens. Accurate identification of Nocardia species has become increasingly important for clinical and epidemiological investigations. In this study, seven clinical Nocardia isolates were identified by multilocus sequence analysis (MLSA) and their antimicrobial susceptibility was also determined. Most Nocardia isolates were associated to pulmonary disease.Methodology/Principal FindingsThe majority of Brazilian human isolates in cases reported in literature were identified as Nocardia sp. Molecular characterization was used for species identification of Nocardia nova, Nocardia cyriacigeorgica, Nocardia asiatica and Nocardia exalbida/gamkensis. Data indicated that molecular analysis provided a different Nocardia speciation than the initial biochemical identification for most Brazilian isolates. All Nocardia isolates showed susceptibility to trimethoprim-sulfamethoxazole, the antimicrobial of choice in the treatment nocardiosis. N. nova isolated from different clinical specimens from one patient showed identical antimicrobial susceptibility patterns and two distinct clones.Conclusions/SignificanceAlthough Brazil is the world's fifth-largest country in terms of land mass and population, pulmonary, extrapulmonary and systemic forms of nocardiosis were reported in only 6 of the 26 Brazilian states from 1970 to 2013. A least 33.8% of these 46 cases of nocardiosis proved fatal. Interestingly, coinfection by two clones may occur in patients presenting nocardiosis. Nocardia infection may be more common throughout the Brazilian territory and in other developing tropical countries than is currently recognized and MLSA should be used more extensively as an effective method for Nocardia identification.

DIFFERENTIATION BETWEEN Nocardia spp. AND Mycobacterium spp.: CRITICAL ASPECTS FOR BACTERIOLOGICAL DIAGNOSIS

“…BAIO et al 3 identified seven isolates by 31 different phenotypic tests and analyzed profiles using six identification systems. Two isolates were identified as Nocardia sp.…”

Nocardia nova identification in a transtracheal wash of a horse with recurrent airway obstruction

“…More recent studies in domestic animals and humans have revealed that speciation of Nocardia require confirmation using molecular methods, including analysis of 16S rRNA gene, 65-kDa heat shock protein gene (hsp65), essential secretory protein A (secA1), gyrase B (gyrB) or DNA-DNA hybridisation. The molecular methods have showed a reliable and rapid means of speciation, and provided a number of taxonomic changes as well inclusion of new species of Nocardia (Baio et al 2013, Condas et al 2013.…”

PCR-RFLP Methodology to Identify <i>Nocardia</i> Isolates in Cuba

“…In 1891, the first case of human nocardiosis was described in a patient with pseudotuberculosis syndrome and brain abscesses. Since then, approximately 30 species have been recognized as human pathogens [2].…”

“…Although cases of infection have been reported in the central nervous system, skin, and eyes (keratitis and endophthalmitis), pulmonary disease is usually the most characteristic and frequent clinical manifestation of nocardiosis [2].…”

“…The clinical features and radiological findings presented by nocardiosis patients are nonspecific. The features can be confused with other pulmonary infections with different etiologies [2]. The serological techniques tested to date are not sufficiently sensitive, and these techniques present a large number of cross-reactions with other actinomycetes.…”