Saturday, June 15, 2024

Pediatric Nocardiosis

Background

Nocardia are weakly gram-positive, filamentous bacteria found worldwide in soils. Human disease from this microbe was first described by Eppinger in 1890, after bovine disease was described by Nocard in 1888. Pathogenic Nocardia are members of the family Nocardiaceae, the aerobic actinomycetes. Nocardia asteroides is the principal cause of systemic nocardiosis in the United States. Nocardia pseudobrasiliensis,Nocardia otitidis-caviarum (formerly Nocardia caviae), Nocardia farcinica,Nocardia nova, and Nocardia transvalensis have also been rarely associated with human systemic disease.

A recent report of infections with Nocardia carnea, Nocardia elegans, Nocardia paucivorans, Nocardia puris, and Nocardia takedensis has come from Japan.
Nocardia brasiliensis is a common cause of localized chronic mycetoma. A total of approximately 30 strains of Nocardia have been associated with human disease.

Two newly described species have been associated with disease in humans: Nocardia abscessus, from soft-tissue abscesses,
and Nocardia africana, from respiratory secretions of patients with pneumonia in the Sudan.
Most recently, Nocardia ignorata, a new agent of human nocardiosis, was isolated from respiratory specimens in Europe and soil samples from Kuwait.
Case reports of Nocardia cyriacigeorgica occurring in the United States have been published, with several infections being retrospectively identified from stored samples.

Molecular DNA hybridization techniques (usually involving the 16S ribosomal RNA [rRNA]) have better characterized the Nocardia species; this identification is useful in identifying antibiotic resistance patterns. Several of the species mentioned above (N nova, Nfarcinica, Nabscessus, N cyriacigeorgica) had been considered as N asteroides isolates in some reports.

Nocardiosis is an acute, subacute, or chronic suppurative infection caused by Nocardia. It has a pronounced tendency to remission and exacerbation. Infections are localized or disseminated. Localized cutaneous or lymphocutaneous infections usually occur after contamination of an abrasion, resulting in cutaneous or lymphocutaneous abscess. In children with immunocompetence, systemic spread from the primary skin site is extremely rare.

Disseminated and fulminant disease mainly occurs in immunocompromised hosts (among persons with deficient cell-mediated immunity) with underlying illnesses, such as chronic granulomatous disease or human immunodeficiency virus (HIV) infection, and in children undergoing cytotoxic chemotherapy, bone marrow transplantation, or prolonged glucocorticoid treatment.

Nocardiosis has also been associated with pulmonary alveolar proteinosis, tuberculosis and other mycobacterial diseases, and interleukin 12 deficiency. Inhalation of the free-living organism is the likely route of infection. The primary disease occurs in the pulmonary system and may mimic tuberculous, staphylococcal, or mycotic infections. Hematogenous dissemination may occur to all organs of the body. The brain, kidneys, and liver are the most common metastatic sites.

Interestingly, Nocardia species have been found to produce effective antibacterial agents, including one agent (nargencin) that shows promise against methicillin resistant Staphylococcus aureus.
Nocardia lactamdurans has also been found to produce a cephamycin under the right conditions.

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