Mycobacterium kansasii infection

 

Mycobacterium kansasii infection

PKGhatak,MD

Mycobacterium kansasii is a harmless mycobacterium for healthy people. It is a different picture for people with long standing chronic lung diseases like cystic fibrosis, alpha1 antitrypsin deficiency and immune depressed people because of HIV infection, autoimmune diseases, or under medical treatment for cancer, etc.

Mycobacterium kasasii (M.kansasii) belongs to a group of mycobacteria known as NMB (non-mycobacteria tuberculosis) which is distinct from MTB responsible for Pulmonary tuberculosis.

Mycobacterium kansasii.

M.kanasasii are acid fast, slow growing NMB. The colony produces an orange colored smooth colony when grown on solid media and exposed to light. In the dark, the colony is colorless and rough. It tests negative for niacin and positive for catalase and has other similar biochemical features of NTBs. M.kansasii unlike other NTM is not universally present in soil and water, and colonization of the respiratory tract in healthy adults is a rare event. In addition to infection of the lungs, M.kansasii also infects vertebrae, bone marrow, spleen, liver, muscles and skin.

In the USA the incidences of new cases of M.kansasii are increasing as the mycobacteria tuberculosis infections are declining.

Texas recorded the most new cases of M.kansaii followed by Louisiana and Florida. As the name implies M.kansasii is prevalent in Kansas and also seen in the adjoining mid central states. White populations are more susceptible to M.kanasasii infection.

Globally - the miners in South Africa have high rates of new infections, and also in Wales, UK.

Two groups are commonly infected -adults with underlying conditions and children between 4 and 6 yr old along with young adults.

Pulmonary diseases due to M.kansasii.

Three distinct clinical presentations are recognized.1. Cavitary pulmonary tuberculosis, 2. Nodular bronchiectasis, 3. Disseminated infection.

The incidence of hemoptysis is 30%, weight loss is about 50%, and chest pain is seen in 25% of cases. Other symptoms like cough, production of sputum, fever, etc. have no specificity to this infection. Children and young adults present with cervical adenopathy in addition to pulmonary infections.

X-ray features. A single or multiple thin walled cavities in the apical portion of the lungs and hilar lymph node enlargement in association with bilateral pulmonary infiltrates are seen. In patients with severely depressed CD4 cell count then localization of the infection or cavity formation does not happen and dissemination of disease is usual. These findings along with a positive acid-fast organism in the sputum nearly clinch a clinical diagnosis of NMB infection.

Nodular bronchiectasis.

Inflammatory reactions and tissue destruction produce a weakened wall of smaller size bronchial tubes result in the development of multiple nodule shaped bronchiectasis in the central lung field. Frequent bouts of productive cough with streaks of blood along with other symptoms of infection are usually present. Secondary fungal and bacterial infections are frequent occurrences.

Disseminated infection.

Disseminated infection is mostly present in severely immunosuppressed patients. Bides lungs, bones, spleen, subcutaneous tissues, and kidneys are infected.

The sputum and bronchial washings should not be treated with KOH in the laboratory (a normal practice), because KOH kills M. kansasii and no growth will result in culture. Rapid liquid culture media should be used in growing M.kasasii, a growth in 2 weeks is expected. Newer techniques of species identification should be done. These tests are the Molecular hybridization test, PCR restriction analysis, Nucleic acid amplification test, Restriction fragment length polymorphism, Polymorphic tandem repeats, DNA genomics probe, etc.

Species identification not only speeds up identification but is also used as a guide in the selection of anti-tubercular drugs.

Non-pulmonary M.kasasii infection.

Cervical lymphadenitis in children is primarily due to M. tuberculosis followed by M.bovis. Of the NTM the M.avis complex infection predominates. M.kansasii cervical adenitis is the next common cause of childhood cervical adenopathy. The submandibular, submaxillary nodes are primarily involved but submantal, preauricular and periauricular glands are also infected. The skin over the enlarged glands appears glossy, glands feel rubbery to touch. Often the swollen glands rupture and produce chronic discharging sinus tracts. Many children have low grade fever, anorexia and fail to gain weight.

Osteomyelitis of the spine and sacroiliac.

The flat bones are susceptible to infection due to a rich blood supply. Often pain and fever are followed by abscess formation. In lower thoracic and lumbar vertebra osteomyelitis the abscess drains down the psoas fascia to the groin and can rupture producing a pus draining sinus tract.

When the spleen is infected generally an abscess forms and patients can present as fever of unknown origin. Liver, bone marrow granulomas and skin lesions are seen. Rarely, a meningoencephalitis develops.

Non-pulmonary infections are more common following a hematogenous spread and HIV infected people with CD4 cell counts below 50 are susceptible to these complications.

Diagnosis.

Biopsy tissues. All biopsied tissues should be stained for acid fast and cultured. Identification should be augmented by the newer methods listed above. Fungal and bacterial cultures are done at the same time.

Lymph nodes and bone marrow typically show several noncaseating granulomas with variable numbers of aid fast organisms.

In disseminated M.kasasii infection blood culture, urine and bone marrow cultures usually show growth in 2 weeks. All positive cultures are tested for drug resistance.

Treatment.

M.kansasii are resistant to pyrazinamide and resistance to INH & Rifampin is increasing. The initial anti-tubercular medications include INH, Rifampin, and Ethambutol. If M.kansasii is resistant to any 1^st line drugs then Azithromycin, Fluoroquinolones, Sulfamethoxazole and Streptomycin are added in various combinations.

Complications. Pleural effusion is a rarity, pneumothorax is occasionally seen.

Treatment of cervical adenitis.

Early surgery should be done and is a very effective way to cure. In advanced cases with draining sinus tracts treated with anti-tubercular medications for 3 to 6 months followed by surgery.

Mortality and morbidity vary according to the extent of the disease at the time of presentation and the immunological status of patients.

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