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Home , Actinomycosis, Lepromatous leprosy, Miliary tuberculosis, Nocardiosis, Tuberculoid leprosy

, , and – lecture Beata Sobieszczańska

Please, apart from this lecture read appropriate chapters from Murray.

Mycobacteria – most important characteristics of these include:

• cell wall containing a lot of lipids (many of them are toxic to human cells) such as mycolic acids and makes mycobacteria highly resistant to drying, disinfectants, and antimicrobials

• this specific structure of mycobacterial cell wall gives them the ability to survive within – only macrophages stimulated by interferon γ (IFNγ) released by Th1 cells can kill phagocytosed mycobacteria. Moreover, this specific structure of mycobacteria induces specific immune response limiting the spread of mycobacteria which is referred to as delayed hypersensitivity

• the hydrophobic cell wall is also responsible for the slow growth of mycobacteria as they clump together which inhibits the penetration of nutrients (they grow for weeks in contrast to other bacteria) – this causes tuberculosis is chronic disease developing for weeks to months to become apparent

Species of mycobacteria are divided into groups:

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Mycobacteria are acid-fast staining bacteria – that means they do not decolorize by acidic alcohol after staining with carbol fuchsin; better than acid-fast staining is fluorescent staining of mycobacteria with acridine orange

acid-fast staining (Ziehl-Neelsen technique) – mycobacteria appear as red slim rods on the blue background (all epithelial cells and mucins from respiratory secretions stain blue)

acridine orange staining – yellow-orange mycobacteria appear on the green background

Reservoirs, sources and ways of transmission of mycobacterial species pathogenic to humans:

tuberculous M. lepreae M. ulcerans MOTT mycobacteria

M. tuberculosis and M. africanum – humans Reservoir Humans Environment Environment M. bovis - animals

M. tuberculosis, M. africanum – diseased Environment persons Source of Diseased humans Environment (soil and water M. bovis – direct contaminated with contact with animals mycobacteria) and their products

Air-borne route Direct contact with Ways of transmission Food-borne route e.g. infected individuals or Traumatic inoculation Air-borne route to humans consumption of air-borne route unpasteurized milk

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Tuberculosis – steps of infection

1. Infected individual expels droplets nuclei = small particles of saliva containing 1-3 mycobacteria; the size of droplet nuclei allows them to get directly to the

2. In the , the droplet nucleus is phagocytosed by alveolar macrophages, but some mycobacteria are not destroyed within macrophages and multiply eventually killing the which releases enzymes together with mycobacteria into the environment - this attracts immune cells into the site of infection. Th1 cells release IFNγ that activates macrophages which become able to destroy phagocytosed mycobacteria. Cytokines released by macrophages and T cells induce specific cellular immune response referred to as delayed hypersensitivity1. This is primary tuberculosis. The primary sites of infection (tubercles) are present in the lung and in the mediastinal lymph nodes (as they are transported to the nearest lymph nodes by infected macrophages) of an infected individual.

3. Macrophages attracted to the site of infection transform into foamy macrophages – they and other immune cells surround the site of infection to prevent spreading of mycobacteria – eventually a granulomatous lesion is produced referred to as tubercle that in the center contains alive mycobacteria and from killed macrophages and damaged cells – this centre is described as caseous necrosis; since mycobacteria cannot proliferate in this hostile environment they become dormant = alive but unable to multiply. In this dormant state they can survive until the death of the host or can start to multiply (even 20-30 years after the primary infection) when the immune system is compromised. In immunosuppressed individuals (with decreased cellular immune response) mycobacteria do not fall into the dormant state but still multiply and disseminate first, in the lungs, then through the blood to the whole organism – mycobacteria can infect any site in the human body and any tissue, including bones and CNS

4. Disseminated form of tuberculosis is termed as as small lesions within the lung tissue resemble millet grains – as seen in the picture below. Miliary tuberculosis develops in primary infected individuals with decreased cellular immune response (this is primary progressive tuberculosis) or during reactivation of the primary infection.

small yellow lesions dispersed within the lung tissue are primary foci of tuberculosis

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5. With time, small lesions in the lung and lymph nodes may become calcified and disappear totally (become undetectable in the chest X-ray picture), however, larger lesions will persist until the host death.

6. In the case of decreased immunity, which happens in the elderly or because of acquiring other diseases that compromise the immune system e.g. HIV infection, primary lesions may reactivate – mycobacteria present within tubercles start to multiply leading to the rupture of the tubercle. Released mycobacteria spread within the lung, but may also get to the blood and spread to any system. This is the reactivation of tuberculosis (secondary tuberculosis) which is an endogenous infection. Thus, tuberculosis reactivates most commonly among elderly or HIV-infected patients.

7. Since during primary tuberculosis strong cellular immune response has developed, during the reactivation of tuberculosis, immune cells sensitized against mycobacterial antigens will appear in any site where mycobacterial will appear. These immune cells will destroy mycobacteria via releasing toxic enzymes – these enzymes apart from mycobacteria will destroy surrounding tissues leading to the development of cavitary lesions within affected organs.

8. The main differences between the primary tuberculosis and its reactivation are the presence of strong anti- mycobacterial cellular immune response and cavitary lesions present in secondary tuberculosis.

Delayed hypersensitivity is a common immune response that occurs through direct action of sensitized T cells when stimulated by contact with antigen. It is referred to as a delayed response in that it will usually require 12–24 hours at a minimum for signs of inflammation to occur locally.

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Diagnosis of tuberculosis:

Skin test () allows detecting delayed hypersensitivity to mycobacterial antigens in persons with suspected tuberculosis. PPD (purified protein derivates) from M. tuberculosis is injected intradermally in the inner surface of the forearm. If the site becomes indurated after 48 to 72 hours, the reaction is positive (but only in countries where there is no obligatory vaccination against tuberculosis e.g. the USA. In countries where vaccination against tuberculosis is obligatory e.g. in Poland, if the diameter of the duration is > 15 mm the reaction is positive. Values < 15 mm suggest no contact with tuberculosis.

Culture and microscopy (sputum stained with acid-fast or acridine orange techniques). Since is fastidious for culture special media must be provided e.g. Löwenstein-Jensen medium – on this solid medium culture of mycobacteria lasts 10 weeks. Currently, special systems using fluid culture media allow to obtain the growth of Mycobacteria within a week. Identification is based on the growth characteristics and biochemical reactions.

Antimicrobial susceptibility testing is necessary as many mycobateria became resistant to common anti-tuberculous drugs.

Anti-mycobacterial drugs are divided into: a) first-line drugs (most powerful) b) second-line drugs (of much lower efficacy)

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MDR (MultiDrug Resistant Mycobacteria) are mycobacterial that are resistant to two of first-line drugs.

XDR (Extensively Resistant mycobacteria) are mycobacterial strains resistant to more than two first-line drugs e.g. resistant to , rifampin, and/or fluoroquinolones and resistant to at least one of the injectable second-line drugs (, kanamycin, capreomycin).

MOTT :

Infections caused by MOTT group of mycobacteria appear most commonly among immunosuppressed individuals and include – lower respiratory tract infections (lung diseases), skin infections or disseminated (similar to miliary tuberculosis). M. scrofulaceum produces cervical lymphadenitis among children; M. marinum produces skin infections after traumatic inoculation into skin. M. kansasii and MAI are associated with lung diseases and disseminated infections. 6

M. ulcerans produces ulcerative skin diseases like Buruli or long-lasting skin ulceration after traumatic inoculation into the skin.

Mycobacterium leprae causes leprosy (Hansen’s disease) – exclusively human disease. Leprosy is still present in endemic areas of Asia, South Americas, Pacific region, China, and North Africa. There are two different clinical forms of leprosy that depends on the cell mediated immunity:

a) tuberculoid – present in persons with strong cell mediated immunity; this form characterizes with few bacteria present in the patient body and positive skin test with lepromin (test similar to Mantoux test)

b) lepromatous – appear in persons with low cell mediated immunity and characterizes with great number of mycobacteria in histiocytes; lepromin skin test is negative in these individuals.

Leprosy primarily affects the nerves of the extremities, the skin, the lining of the nose, and the upper respiratory tract.

Students do not have to learn this classification !!!! This is an example of leprosy clinical classification

Clinical studies use the Ridley-Jopling system. It has five classifications based on severity of symptoms.

Classification Symptoms Disease response

Can heal on its own, persist, or may A few flat lesions, some large and numb; some nerve involvement progress to a more severe form

Borderline Lesions similar to tuberculoid but more numerous; more nerve May persist, revert to tuberculoid, or tuberculoid leprosy involvement advance to another form

Mid-borderline Reddish plaques; moderate numbness; swollen lymph nodes; more May regress, persist, or progress to leprosy nerve involvement other forms

Borderline Many lesions, including flat lesions, raised bumps, plaques, and May persist, regress, or progress nodules; more numbness

Many lesions with bacteria; hair loss; more severe nerve Lepromatous leprosy involvement with peripheral nerve thickening; limb weakness; Doesn’t regress disfigurement

Actinomyces

Actinomyces spp. colonizes oral cavity, a gastrointestinal and genitourinary tract of humans. Actinomyces are obligatory anaerobic GP rods that produce aerial hyphae while growing on nutrient-rich media making the similar to fungi (molds).

Actinomycosis is a chronic disease originating in the tissue adjacent to mucosal surfaces. Actinomycosis is an endogenous infection that appears is some individuals after tooth extraction, piercing, etc. Everyone can get actinomycosis although, oral hygiene is an important factor influencing its development!

There are clinical forms of actinomycosis: a) cervicofacial b) thoracic/pulmonary c) abdominal/pelvic/genital d) cerebral – very rare

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Diagnosis relies on microscopy (Gram-staining), culture in anaerobic conditions and identification using biochemical tests.

Nocardia brasiliensis, asteroides... They are GP rods, obligatory aerobic ubiquitous in soil and vegetation. They are worldwide distributed but most common in tropical countries. Humans can acquire nocardiosis via inhalation of dust contaminated with or via traumatic inoculation into the skin. Inhalation produces lung diseases (pulmonary nocardiosis with ) whereas traumatic inoculation leads to the cutaneous nocardiosis that runs as: a) mycetoma (Madura's foot) – ulceration of foots b) lymphocutaneous infections c) , subcutaneous abscesses In severe cases, secondary infections (caused by the spread of Nocardia via blood and lymph) like and brain abscesses may develop.

Diagnosis relies on microscopy and culture.

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