General characteristics and clinical significance of Nocardia and Gordonia genera

Abstract

Over the last years, an increasing attention in modern medical microbiology has been paid to examining Actinomycetaceae, Corynebacteriaceae, Mycobacteriaceae, Nocardiaceae, Gordoniaceae sps. Members of the Mycobacteriaceae family are increasingly examined in research and real-life practice, whereas bacteria belonging to families such as Nocardiaceae and Gordoniaceae remain poorly investigated despite novel methods emerging in practical microbiology that allow to more accurately identify microorganisms. According to the current classification, the genus Nocardia includes over 80 species, most of which rarely result in human disease development. Most often, members of the genus Nocardia cause lesions in bronchopulmonary system, which, however, may also cause development of pathological processes in other anatomical sites. Likewise, members of the genus Gordonia may also trigger infectious lesions in human, which were previously often incorrectly identified as other actinomycetes or mycobacteria. Owing to use of 16S rRNA sequencing, it substantially improved identification of these bacteria. Currently, an increasing number of microorganisms with potential clinical significance has been recorded. In addition, similar to nocardiosis, diverse primary and secondary immunodeficiencies play a primary role in gordonii-associated development of pathological processes. However, an additional risk factor may be represented by pathological conditions associated with ingestion of foreign bodies colonized by such microorganisms. Most often, members the genus Nocardia cause lesions in the bronchopulmonary system able, however, affect other anatomical areas. Half of all cases of pulmonary nocardiosis are accompanied by pathological processes of extrapulmonary localization, whereas as low as 20% of patients manifest with extrapulmonary form of the disease usually occurring when the pathogen spreads hematogenously or via other routes also highlighted by primary pulmonary lesion. Moreover, members of the genus Gordonia may result in similar infectious lesions. Currently, the number of aerobic actinomycetes of potential clinical significance is increasing that may be due to their role in diverse pathological processes of various etiologies, which have been more often reported in scientific publications. Few reports regarding infections caused by the genus Gordonia ara available which may be due to a paucity of microorganisms isolated from clinical material or false identification as mycobacteria or Nocardia. Similar to nocardiosis, diverse immunodeficiencies play a primary role in the development of pathological processes associated with Gordonia. However, an additional risk factor may be linked to pathological conditions associated with the ingestion of foreign bodies colonized by these microorganisms. Available publications allows to underline etiological significance of Gordonia in development of cholecystitis, granulomatous skin lesions, eyelid abscess of other soft tissues, granulomatous mastitis, brain abscess and meningitis, as well as external otitis, bronchitis, endocarditis and mediastinitis. In addition, all these microorganisms can cause bacteremia associated with use of a central venous catheter. Owing to emergence of new detection methods as well as elevated rate of immunocompromised patients, and subsequently increased amount of new cases caused by members of the Nocardiaceae and Gordoniaceae families, an interest they rise will grow progressively.