Nocardia are aerobic and infectious (Nocardiosis), producing pulmonary disease, skin infections, lymphocutaneous lesions and brain abscesses (Mari et al, 2002; Shook & Rapini, 2006; Bennett et al, 2007). The genus contains approximately 15 known species.
The species identified in human pulmonary and systemic infections include asteroides, pseudobrasilenisis, otitidis-cavriarum, abscessus, farcinica, nova, transvalensis (Georghiou and Blacklock 1992; Groves; 1997; Yourke and Rouah, 2003; Bennett et al, 2007; Kennedy et al, 2007).
N. cyriacigeorgica recently was identified as an emerging pathogen in the U.S. and probably worldwide (Schlaberg et al, 2008).
Lymphocutaneous, subcutaneous mycetoma with sulfur granules and superficial skin infections also occur (Shook and Rapini, 2007). N. asteroides was identified with pneumonia and empyema (thoracis) in a healthy 40-day-old neonate after presumed inhalation exposure (Tantracheewathorn, 2004).
Nocardia are gram positive and stain partially with acid fast. Serological tests are not available.
Predisposing factors are immunocompromised individuals, pre-existing lung disease, corticosteroid therapy and diabetes mellitus (Georghiou and Blacklock, 1992; Mari et al, 2001; Bennett et aI, 2007).
As occurs with Streptomyces, the disease process can exhibit mimicry. Case reports of immunocompetent patients include brain abscesses (Chakrabarti et al, 2008; Kandasamy J et al, 2008; Dias et al, 2008), spinal cord abscess (Samkoff et al, 2008), mimicry of metastatic brain tumor (Kawakami et al, 2008), ventriculitis/choroid plexitis (Mongkolrattanothai et al, 2008), lymphangitis (Dinubile 2008), lung abscesses (Mari et al, 2001; Martinez et al, 2008 Tada et al, 2008), endophthalmitis (Ramakrishnan et al, 2008), and sternal osteomyelitis with mediastinal abscess (Baraboutis et al, 2008).
It is recommended that 16s rDNA sequencing should be used to identify infections of novel bacteria (Woo et al, 2008).
Mycobacteria are common in moisture-damaged building materials (ceramic, wood and mineral insulation), and their occurrence increases with the degree of mold damage (Rautiala et al, 2004; Torvinen, et al, 2006). They are environmental (soil, water, sewage), opportunistic gram positive bacteria capable of causing hypersensitivity pneumonitis as well as cervical lymphadenitis in children.
Mycobacteria have been isolated from water systems, spas, hot tubs, and humidifiers and are resistant to disinfection (Primm et al, 2004; Torvinen et al, 2007). The CDC has implicated Mycobacterium avium, terrae and immunogenum in outbreaks of hypersensitivity pneumonitis (Falkinham, 2003a, b).
M. terrae isolated from the indoor air of a moisture-damaged building induced a biphasic inflammatory response after intrathecal instillation into mouse lungs. There was an initial increase in TNF alpha and IL-6 at 6 hr. to 3 days, followed by a second phase at 7 to 28 days (Jussila et al, 2002a, b).
The genus Mycobacterium consists of approximately 117 species of which 20 are potential human pathogens. They cause nontuberculous mycobacteria (NTM) lung disease (American Thoracic Society, 2007).
Mycobacterium avium-intracellulare organisms are increasingly significant pathogens in North America causing a pulmonary infection named MAC (M. avium Complex). M. kansasii, chelonae and fortuitum are other important pathogens (Iseman et aI, 1985; Fujita et aI, 2002; Kuhlann and Woeltje, 2007; Fritz and Woeltje, 2007; Agrawal and Agrawal, 2007).
According to the American Thoracic Society (2007), "The minimum evaluation for NTM should include the following: 1) Chest radiograph or, in absence of cavitation, chest high-resolution computed tomography (HRCT) scan; 2) Three or more sputum specimens stained for acid-fast bacilli (AFG) analysis; and 3) Exclusion of other disorders such as tuberculosis. Clinical, radiographic and microbiologic criteria are equally important and all must be present to make a diagnosis of NTM lung disease.
The following criteria apply to symptomatic patients with radiographic opacities, nodular or cavitary, or HRCT scan that shows multifocal bronchiectasis with multiple nodules. These criteria fit best with Mycobacterium avium complex (MAC), M. kansasii, and M. abscessus. There is not enough known about NTM of other species to be certain that these diagnostic criteria are universally applicable to all NTM respiratory pathogens.
A microbiologic diagnosis includes one of the following: 1) Positive cultures from two separate expectorated samples; 2) Positive culture from at least one bronchial wash; 3) transbronchial or other lung biopsy with mycobacteria histopathologic features.
Patients suspected of having NTM lung disease but who do not meet the diagnostic criteria should be followed until the diagnosis is firmly established or excluded. NTM is on the rise worldwide. Mycobacteria have been isolated from water-damaged building materials from indoor environments. Finally, individuals treated with corticosteroids are at an increased risk.
M. ulcerans is a significant human pathogen that causes Buruli ulcer (BU). Cases of BU have been reported worldwide with the greatest burden of disease occurring in West and Central Africa. Its transmission source is not fully understood, but it may be waterborne. The disease is characterized by progressive, severe necrotizing skin lesions that do not respond to antimicrobial therapy and may either require either surgical excision or amputation as treatment. M. ulcerans is an intracellular pathogen. It produces a polyketide-derived macrolide, mycolactone.
Mycolactone is cytotoxic at 2 ng/ml, and is the organism’s virulence factor. Mycobacterium scrofulaceum and kansasii and other mycobacteria produce a less cytotoxic (33 to 1,000 ug/ml) lipid chemical when tested on fibroblast in vitro (Daniel et al, 2004; Yip et al, 2007).
The gram positive toxic organisms identified in indoor environments also include Bacillus spp, Nocardia spp. and Streptomyces spp. (Peltola et al, 2001a,b). Mycobacteria have been isolated from damp indoor environments (Jusilla et al, 2001, 2002a; Falkinham, 2003a, b).
Examples of additional gram positive bacteria are species of Atrhrobacter, Bacillus, Cellumonas, Gordona, and Paeniibacillus (Andersson et al, 1997). Bacillus simplex and Amyloliquefaciens isolated from moisture-damaged buildings produce surfactin (Iipopeptide) and peptides that adversely affect cell membranes and mitochondria (Mikkola et al, 2004, 2007).
Finally, there were elevated concentrations of Staphylococci and Actinomycetes in a water-damaged home in which a 3-month-old infant died from a Reye's-like syndrome with mitochondrial damage resulting in decreased enzymatic activity of complexes I-IV. Mitochondrial DNA mutation testing of the infant resulted in negative findings for known mitochondrial diseases. This home also contained several species of Aspergillus, Penicillium and S. chartarum (Gray et al, in preparation).