Effect of growth stage on mycolic acid structure in cell walls of Nocardia asteroides GUH-2

Systemic nocardiosis in a Mediterranean population of cultured meagre, Argyrosomus regius Asso (Perciformes: Sciaenidae)

Marine cultured meagre, Argyrosomus regius Asso, in central and western Greece were affected by an outbreak of systemic granulomatous disease subsequently demonstrated to be nocardiosis. The fish were originally imported as juveniles from hatcheries in France and Italy and on-grown in Greece, the latter also providing broodstock for a small number of local Greek hatcheries for the production of second-generation juveniles. The disease in cage reared fish had been present throughout the year, particularly in the 1+ and 2+ year old fish with a low to variable morbidity and 1-4% total mortality. Multiple lesions were visible externally on the skin of affected fish, with severe ulcerations and necrosis. Internally, multifocal yellowish-white nodules, 0.1-0.5 cm in diameter, were visible on the surface of several internal organs. Histopathology revealed systemic granulomatous inflammation. Fite-Faraco staining clearly demonstrated the presence of Nocardia-like organisms which were Gram-positive, long, rod to beaded filamentous bacteria. Nocardia genus-specific 16s RNA primers NG1 and NG2 were used to generate a 600 bp fragment recovered from affected tissue, confirming the diagnosis of Nocardia spp. To our knowledge, this is the first report of nocardiosis in meagre.

Ocular nocardia infections with special emphasis on the cornea

Nocardia are aerobic, gram-positive, nonmotile and branching filamentous bacteria. Corneal infection by Nocardia is rare. Trauma is the most common predisposing factor. Isolated case reports of nocardial infection associated with contact lens wear and laser in situ keratomileusis (LASIK) have been reported. The clinical picture usually consists of superficial patchy infiltrates, which may be arranged in a wreath pattern. Presence of gram-positive, branching, beaded filaments that stain with 1% acid-fast stain (using 1% sulfuric acid, modified Kinyoun's method) in smears of corneal scrapings is suggestive of nocardial infection. Nocardia grow on commonly used media as tiny, white, dry colonies. Available knowledge and clinical experience suggest that although sulfacetamide eyedrops can be tried as the initial drug, trimethoprim-sulfamethoxazole and amikacin are effective drugs. Once therapy is initiated, the infiltrate responds promptly and resolves, forming a corneal scar with or without vascularization, and good visual recovery can be expected.

Acid-fastness of Nocardia asteroides GUH-2 cultured in brain heart infusion broth supplemented with paraffin

Nocardia asteroides GUH-2 was not acid-fast when grown in brain heart infusion (BHI) broth. When grown in BHI broth supplemented with paraffin, many filamentous cells showed acid-fastness after treatment with 1% acid-alcohol as the decolorizing agent. When treated with 3% acid-alcohol, filamentous cells were not acid-fast. In addition to the acid-fast filamentous cells of nocardiae, unknown acid-fast spherical bodies were observed in the paraffin-supplemented BHI broth cultures.

Nocardia species: host-parasite relationships

The nocardiae are bacteria belonging to the aerobic actinomycetes. They are an important part of the normal soil microflora worldwide. The type species, Nocardia asteroides, and N. brasiliensis, N. farcinica, N. otitidiscaviarum, N. nova, and N. transvalensis cause a variety of diseases in both normal and immunocompromised humans and animals. The mechanisms of pathogenesis are complex, not fully understood, and include the capacity to evade or neutralize the myriad microbicidal activities of the host. The relative virulence of N. asteroides correlates with the ability to inhibit phagosome-lysosome fusion in phagocytes; to neutralize phagosomal acidification; to detoxify the microbicidal products of oxidative metabolism; to modify phagocyte function; to grow within phagocytic cells; and to attach to, penetrate, and grow within host cells. Both activated macrophages and immunologically specific T lymphocytes constitute the major mechanisms for host resistance to nocardial infection, whereas B lymphocytes and humoral immunity do not appear to be as important in protecting the host. Thus, the nocardiae are facultative intracellular pathogens that can persist within the host, probably in a cryptic form (L-form), for life. Silent invasion of brain cells by some Nocardia strains can induce neurodegeneration in experimental animals; however, the role of nocardiae in neurodegenerative diseases in humans needs to be investigated.

Nocardia species: host-parasite relationships

The nocardiae are bacteria belonging to the aerobic actinomycetes. They are an important part of the normal soil microflora worldwide. The type species, Nocardia asteroides, and N. brasiliensis, N. farcinica, N. otitidiscaviarum, N. nova, and N. transvalensis cause a variety of diseases in both normal and immunocompromised humans and animals. The mechanisms of pathogenesis are complex, not fully understood, and include the capacity to evade or neutralize the myriad microbicidal activities of the host. The relative virulence of N. asteroides correlates with the ability to inhibit phagosome-lysosome fusion in phagocytes; to neutralize phagosomal acidification; to detoxify the microbicidal products of oxidative metabolism; to modify phagocyte function; to grow within phagocytic cells; and to attach to, penetrate, and grow within host cells. Both activated macrophages and immunologically specific T lymphocytes constitute the major mechanisms for host resistance to nocardial infection, whereas B lymphocytes and humoral immunity do not appear to be as important in protecting the host. Thus, the nocardiae are facultative intracellular pathogens that can persist within the host, probably in a cryptic form (L-form), for life. Silent invasion of brain cells by some Nocardia strains can induce neurodegeneration in experimental animals; however, the role of nocardiae in neurodegenerative diseases in humans needs to be investigated.

Composition and toxicity of diethyl ether soluble lipids from Nocardia asteroides GUH-2 and Nocardia asteroides 10905

Virulent Nocardia asteroides GUH-2 and avirulent N. asteroides 10905 contained 8.2% and 10.6% of diethyl ether soluble lipids (DESL) per dry cell mass, respectively. Intraperitoneal (i.p.) inoculation of 250 micrograms of DESL from GUH-2 dissolved in mineral oil was toxic to mice, resulting in weight loss and death of 100% of the animals (20/20) within 20 days. In contrast, DESL from 10905 had very little toxicity, and only one mouse (1/10) died within 30 days. Three fractions resulted from DESL by silicic acid column chromatography: (1) neutral lipids and fatty acids (NFA); (2) glycolipids (GL); and (3) phospholipids (PL). Each fraction dissolved in mineral oil was inoculated into mice as described above. The NFA and PL were not toxic. GL from 10905 had low toxicity (30% of the animals died, 3/10) whereas GL from GUH-2 expressed high toxicity (100% of the animals became cachetic and died, 10/10). GL from 10905 represented a minor component (0.6% of dry cell weight) whereas GL from GUH-2 was more prominent (1.5% of dry cell wt.). Approximately 95% of GL from GUH-2 had properties of an authentic trehalose-6,6'-dimycolate standard. Infrared spectrum of the major glycolipid (GUH-2 GL) had characteristic absorptions in the fingerprint region between 800 cm-1 and 1500 cm-1. Upon alkaline hydrolysis GUH-2 GL released 76% mycolic acids in the C50 size range plus 24% trehalose.(ABSTRACT TRUNCATED AT 250 WORDS)