Nocardia Nova

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A Microbial Biorealm page on the genus Nocardia Nova

Classification

Bacteria

Higher order taxa

Bacteria; Actinobacteria; Corynebacteriales; Nocardiaceae; Nocardia

Species

N. aerocolonigenes, N. africana, N. argentinensis, N. asteroides, N. blackwellii, N. brasiliensis, N. brevicatena, N. carnea, N. cerradoensis, N. corallina, N. cyriacigeorgica, N. dassonvillei, N. elegans, N. farcinica, N. nigiitansis, N. opaca, N. otitidis-cavarium, N. paucivorans, N. pseudobrasiliensis, N. rubra, N. seriolae, N. transvelencesis, N. uniformis, N. vaccinii, N. veteran

NCBI: Taxonomy


Description and significance

Nocardia nova is a gram positive aerobic microbe often found living in soil and other plant materials [3]. It was previously thought to be a fungus because of its branched filamentous appearance. The bacteria forms hyphae structures that break up into rods and cocci when disturbed. N. nova is responsible for causing 500-1000 cases of nocardiosis each year [1]. Nocardiosis is a diseased caused by the systemic or localized infection of a Nocardia genus bacteria. Laboratory identification of the organism can be difficult because the gram stain can produce variable results. The organism is also acid fast, and this can be used to identify clinically significant microbes when the gram stain fails.

Genome structure

One strain of N. nova has been studied more in depth then any other, strain SH22a [4]. It has a large genome made up of 8,348,532 base pairs and is contained within one circular chromosome. The genome is predicted to contain 7,583 protein-coding genes, of which 5,494 could be assigned definitive functions. The genome of this strain contained no plasmids. Interestingly, the genome of SH22a contained 14 coding genes for ATP dependent mammalian cell entry transporters, which have previously been associated with virulence [4].

Cell and colony structure

The bacteria forms hyphae structures that break up into rods and cocci when disturbed [2]. It was originally though to be a fungus because of its morphology, but because of its growth on selective medias it is a true bacterium. When observed using light microscopy colonies may look like long branching groups of both cocci and bacillus [5]. When N. nova is growing within infected tissue it can be visualized using the Gomori methenamine silver stain.

Metabolism

N. nova is an extremely fastidious aerobic organism that sometimes evades laboratory detection because of its slow growth. It is able to utilize fructose, glucose, and glycerol, but no other carbohydrates. Some unusual features of the microbe are that it has high amounts of esterase enzymes and that it possesses enzymes to catabolize hydrocarbons and naturally occurring rubber compounds [4].

Ecology

Members of the Nocardia genus live in soil and stagnant water in the environment. It is often found living near the rhizosphere, directly adjacent to the roots of plants [6]. Recent research also indicates that N. nova is capable of both oxidizing very long hydrocarbons into higher alcohols to prepare them for catabolism and breaking down aromatic compounds. The organism is also able to degrade the organic rubber polyisoprene down to propionyl CoA and acetyl CoA which it can then use as a source of energy in the absence of a carbohydrate. All of the metabolic pathways allow N. nova to remove potentially toxic substance from the environment.

Pathology

N. nova is a potent pathogen especially to the immunocompromised. Because of its slow growth it often evades detection when it infects the central nervous system, leading to brain abscesses. The primary pathological finding of the organism is in patients with pulmonary disease [5]. Inoculation occurs through inhalation. Because the organism is exceptionally hard to identify many infections develop into nocardiosis, a systemic infection of the patient. Because of a lack of clinical research there are not well defined treatment guidelines for nocardiosis. Common treatments include sulfonamides including sulfadiazine and trimethoprim-sulfamethoxazole, sometimes in combination with carbapenems or third-generation cephalosporins like ceftriaxone. Duration of treatment lasts between 6 and 12 months based on the severity of infection and brain involvement. Some severe brain abscesses may require surgical treatment. Cure rates varies based on the severity from 100% in skin and soft tissues to less then 50% in patients with brain abscesses [5].

References

[1]Arora, Geeta, Mark Friedman, and Richard P. Macdermott. "Disseminated Nocardia Nova Infection." Southern Medical Journal 103.12 (2010): 1269-271.

[2]Wallace, R. J., et al. "Clinical and laboratory features of Nocardia nova." Journal of clinical microbiology 29.11 (1991): 2407-2411.

[3]Munoz, J., et al. "Clinical and microbiological features of nocardiosis 1997–2003." Journal of medical microbiology 56.4 (2007): 545-550.

[4] Luo, Quan, et al. "Insights into the microbial degradation of rubber and gutta-percha by analysis of the complete genome of Nocardia nova SH22a." Applied and environmental microbiology 80.13 (2014): 3895-3907.

[5] Kurdgelashvili, George, MD, Michael S. Bronze, MD, and Thomas J. Marrie, MD. "Nocardiosis : Background, Pathophysiology, Epidemiology. Medscape, 12 Jan. 2015.

[6] https://gold.jgi.doe.gov/project?id=12769


Edited by Peter Kyros of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio