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Mycobacterium tuberculosis complex (MTBC)

Mycobacterium leprae

  • the main organism responsible for leprosy (Hansen's disease).
  • It was discovered in 1873 by the Norwegian physician Gerhard Armauer Hansen, who was searching for the bacteria in the skin nodules of patients with leprosy. It was the first bacterium to be identified as causing disease in humans.
  • Leprosy is not highly infectious, as approximately 95% of people are immune and sufferers are no longer infectious after only a couple of days on treatment.
  • Effective treatment for leprosy appeared in the late 1930s with the introduction of dapsone and its derivatives.
  • The search for more effective anti-leprosy drugs than dapsone led to the use of clofazimine and rifampicin in the 1960s and 1970s.
  • two to three million people are estimated to be permanently disabled because of Leprosy. India has the greatest number of cases, with Brazil second and Burma third.
  • Brazil, Madagascar, Mozambique, Tanzania and Nepal as having 90% of new cases.

Mycobacterium avium complex (MAC)

  • formerly Mycobacterium Avium Intracellulare Scrofulaceum (MAIS) and consists of M. avium and M. intracellulare
  • these are ubiquitous and can be found in:
    • aerosolized water (fresh water or salt water, especially hot water systems which have had temperature lowered)
    • house dust
    • soil, birds, ruminant farm animals (esp. deer)
    • cigarette components (tobacco, filters, paper)
  • apparently, there is no human-to-human transmission
  • presents in 3 forms:
    • unilateral chronic cervical lymphadenopathy/lymphadenitis in children
    • disseminated disease with diarrhoeal illness in patients with HIV / AIDS with low CD4 counts who have not been treated with highly active antiretroviral therapy.
    • pulmonary MAC infection in immunocompetent hosts
      • non-TB mycobacteria (NTM) such as M. avium, M. abscessus, M. lentiflavum, M fortuitum and M. kansasii can be spread by water supplies, particularly if hot water system temperatures have been lowered to save energy costs
      • Lady Windermere syndrome:
        • mainly thin, healthy, middle aged or elderly women who tend to avoid expectorating sputum to reduce the bacterial load, and who may have thoracic skeletal abnormalities such as pectus excavatum, scoliosis, straight back, or mitral valve prolapse.
        • chronic infection, mainly of the R. middle or L. lingula lobes, and chronic cough, leading to bronchiectasis over period of months-years
      • fibrocavity form:
      • hot tub lung disease:
        • mainly young and middle aged who frequently use poorly maintained indoor hot tubs
        • diffuse interstitial and nodular infiltrates mimicking hypersensitivity pneumonitis
      • in 2014, it was found that of the 200 cases per year in Brisbane, 40% were due to the water supply
    • less common presentations:
    • these cases require Rx with 2 or 3 anti-mycobacterial drugs for 12 - 18 months

Mycobacterium ulcerans

  • in 1948, in Melbourne, Australia, this organism was found to be the cause of chronic skin ulcers in Bairnsdale, Victoria and endemic in Buruli, Uganda.
  • the skin ulcers have been called Bairnsdale ulcers, Daintree ulcers in Qld, ulcerans, Buruli ulcers, Kumusi ulcer, ‘sik bilong Sepik’ in Papua New Guinea, the ‘Tora ulcer’, in the Congo and also known as the ‘Mexican ulcer’ in Latin America.
  • whilst primarily occurring in Bairnsdale region in Victoria, it has migrated westwards, appearing in Philip Island and Mornington Peninsula in the 1990s, then in early 2000's, cases have been found in Victoria's Bellarine Peninsula region and as far north as Sandringham by 2019
  • reported severe cases in Port Philip region (particularly in Rye and surrounding townships of Sorrento, Blairgowrie and Tootgarook) have been doubled in the 5 years from 2012-2017
  • diagnoses in Victoria have increased from 89 in 2014 to 336 in 2018 1)
  • in 2019, cases were also being reported in Belmont and in Airey's Inlet
  • in 2021, cases were reported in the Essendon, Moonee Ponds and Brunswick West areas from an apparently common source
  • little is known of where it resides (presumably in the soil, appears to be associated with swampy or stagnant water, and/or coastal vegetation, and outbreaks tend to occur following flooding) or how it is contracted (perhaps via mosquito bites), or how it is spreading, although it is known that it can also infect koalas and possums which may be a reservoir
  • incubation period 4wks-9 months (median 4-5 months)
  • appears to have a higher risk in those aged > 60yrs or those under 15 years
  • diagnoses in Victoria peak June-Nov but occur all year
  • not transmissible from person to person unless ulcers with large numbers of organisms contact broken skin

Image from Better Health Victoria 2019

mycobacterium.txt · Last modified: 2021/02/23 16:42 by gary1