Mycobacterium Leprae: Transmission, Types, Diagnosis, and Prevention Explained

Introduction of mycobacterium leprae

Mycobacterium leprae is a bacterium that causes leprosy, also known as Hansen’s disease. It is an intracellular, pleomorphic, acid-fast, pathogenic bacterium. M. leprae is an aerobic bacillus (rod-shaped bacterium ) with parallel sides and round ends, surrounded by the characteristic waxy coating unique to mycobacteria. It occurs in large numbers within the lesions of lepromatous leprosy that are usually grouped together like bundles of cigars or arranged in a palisade. Due to its thick waxy coating, M. leprae stains with a carbol fuchsin rather than with the gradational gram stain. 

What is mycobacterium leprae?

Obligate intracellular bacillus.  Still has not been cultivated on artificial medium or tissue culture. Produces no known toxins and is well adapted to penetrate and reside within macrophages. M. leprae grows best in cooler tissues the skin, peripheral nerves, anterior chamber of the eye, upper respiratory tract, and testes), sparing warmer areas of the skin (the axilla, groin, scalp, and midline of the back).M. leprae  causes Hansen’s disease / leprosy in man, which affects mainly the mucous membrane of the nose, skin and nerve fibers.

Transmission of mycobacterium leprae

The route of transmission of leprosy remains uncertain and may be multiple: Nasal droplet infection, Contact with infected soil, Even insect vectors have been considered the prime candidates and Direct dermal inoculation (e.g., during tattooing) may transmit M. leprae. Casual contact does not cause leprosy.  Prolonged contact with the person is necessary.  This contact may be direct (e.g. skin to skin) or indirect (e.g. contact with soil, and fomites such as contaminated clothes and linen).  Leprosy has a long incubation period, an average of about three to five years.  The nose is a major portal of exit of organisms of a person affected by leprosy.M. leprae can be transmitted Aerosol inhalation, intimate contact with lerpomatius leprosy patient, incubation period 5 to 7 years.

What is leprosy?

Leprosy is a chronic bacterial infection, it affects the skin and various nervous systems of the body, particularly the peripheral nerves. Leprosy is more common in tropical and subtropical areas. Leprosy is infectious disease caused by obligate intracellular bacteria mycobacterium leprae and mycobacterium lepromotosis. It is transmitted from untreated and infected patent’s nasal secretions and skin lesions. Contact with armadillos of the species dasypus novemcintus. Leprosy caused by M. leprae   localized skin lesions, raised or flat, Light or pigmented, thickened peripheral nerves, ulnar nerve in the upper limb and fibular nerve in the lower limbs, and sensory loss in lesion.

What are the symptoms of leprosy

• Sensory nerve damage

• Aye nerve damage

• Motor nerve damage

• Autonomic nerve damage

• Loss of sensation

• Tingling and numbness

• Leprosy bacilli can take months or years to develop any symptoms

• Loss of temperature sensation on skin

• Light patches on the skin

• Painful nerves swelling or lumps on the face or earlobes

• Risk of kidney failure

Risk factors

• Close contact

• Age

• Genetics: NOD2 variants

• Immunosuppression: chemotherapy, HIV positive  

Types of mycobacterium leprae

1. Tuberculoid leprosy:

Areas of skin and peripheral nerves are infiltrated with lymphocytes, the Nerve involvement is characteristic with loss of sensation. CMI is intact & lepromin skin test is positive.  The organism is found in small number in the lesion. Tuberculoid leprosy is associated with the most strinking immune response and manifests as very dry, scaly, hypopigmented patches or plaques with very sharply defined edges. The plaques are usually anesthetic except those on the face. The number of lesions ranges from one to five. The main presenting features: hypopigmented anesthetic firm rash in which healing often occur at the Centre. loss of thermal sensation, touch and pain and this occurs early compared to ll. 

2. Lepromatous leprosy:

A patient with features of polar lepromatous leprosy: multiple nodular skin lesions, particularly of the forehead, and loss of eyebrows involvement in lepromatous leprosy results in a characteristic leonine appearance. The course is progressive & severe with continuous bacteremia and CMI is deficient and lepromin test is negative.

Haw to diagnosis mycobacterium leprae

Clinical signs and histologic examination of biopsy specimens taken from lepromas or other skin lesions.

Modified Z-N staining.

A consistent pattern of inflammation plus the presence of acid-fast bacilli is presumptive evidence of infection with M. leprae.

IGM Abs found in 95% of untreated lepromatous leprosy patients: the decreases with effective therapy: little diagnostic utility in tuberculoid leprosy.

PCR of skin specimen for M.leprae: positive in LL and BL leprosy. Negative results in 50% of tuberculoid leprosy cases .

Lepromin skin test .

Treatment of M.leprae

Sulphones - e.g. Dapsone (DDS) and rifampicin, are used for treatment. Clofazimine is given to sulphone resistant cases. Drugs of choice are rifampicin, dopsone, and clofazimine. 

Haw to prevention M.leprae

• No vaccine is available.

• Chemoprophylaxis may be used to contacts of case.

Conclusion

Mycobacterium leprae causes leprosy, a chronic disease affecting skin and nerves, but it is curable with early diagnosis and multidrug therapy.