Nocadiae

Nocard 1888; Eppinger 1890;

Worldwide, sporadically occurring (in the USA more frequently, in Europe very rarely) gram-positive, aerobic rods, which in their morphology show great similarities with the actinomycetes (Nocardia were formerly assigned to the fungi like the actinomycetes, but differ from these by their aerobic way of life), which are distributed in the soil. Especially Nocardia asteroides, also Nocardia brasiliensis, Nocardia madurae and Nocardia pelletieri are of medical interest and causative agents of the nowadays very rare nocardiosis in humans. According to the natural occurrence in the soil, nocardioses are exogenous infections.

Nocardioses are common worldwide, occur sporadically (not epidemically) and are rather rare overall. Presumably due to the increasing number of immunosuppressed patients, the number of cases is rising. In the USA, the number of nocardioses is estimated at about 500-1,000 cases per year; for Germany, there is only vague information suggesting about 100 cases per year. The male sex is preferred (about 1.5-3:1).

Host range / reservoir: Nocardia are environmental germs and are found in soil, dust, water and sewage. Infections can also occur in animals. Examples include mastitis in cows, lymphangitis farciminosa bovis, and mycetoma following injury. In fish farms, diseases caused by Nocardia seriolae have been described.

Inoculation of the pathogen in the presence of wounds (skin nocardiosis, mostly Nocardia brasiliensis) or by inhalation of the pathogen (pulmonary nocardiosis, mostly Nocardia asteroides). There is no human-to-human transmission. About 85% of affected patients are immunocompromised (HIV/AIDS, neoplasms, collagenoses, pre-existing chronic lung diseases) - (Hémar V et al. 2018). After invasion of the human organism, e.g. by inhalation of dust containing nocardia or by skin lesions, the host defense initially consists of phagocytes (neutrophil granulocytes, macrophages). If the nocardia escape killing by phagocytes (e.g. by preventing phagosome-lysosome fusion), further multiplication and then local or systemic spread occurs. Abscesses or granulomas are formed, which determine the course of the disease.

Rare, chronic granulomatous bacterial infectious disease caused by pathogens of the genus Nocardia (aeroactinomycetes). Mostly occurring in immunosuppressed patients (after organ transplantation, HIV infection) or severe underlying diseases (e.g. lupus erythematosus, systemic). Depending on the localization, a distinction is made:

• Pulmonary nocardiosis: lung abscesses, pneumonias
• Surface nocardiosis: granulomas and abscesses along the lymphatic tract.
• Systemic nocardiosis: abscesses of internal organs, sepsis

Pathogen detection in pus or sputum. Cultural detection is possible on universal culture media or media for tuberculosis diagnostics (e.g. Löwenstein-Jensen medium).

In addition to the actual nocardia, other gram-positive, aerobic rods of this bacterial group are also subsumed under the collective term "nocardiaform bacteria".

Further information Reference centres / expert laboratories 5 Consiliary laboratory for actinomycetes, Prof. Dr. K. P. Schaal, Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Sigmund-Freud-Str. 25, 53105 Bonn Web addresses 5 National consiliary laboratory: http://mibi03.meb. uni-bonn.de/~groups/schaal

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