Mycobacterium kansasii

Non-tuberculous (atpyic) mycobacterium found in soil, dust, and water.

Genetic variability has been described in M. kansasii strains. Six subspecies are distinguished, with human pathogenic strains belonging predominantly to subspecies I. M. kansasii belongs to the photochromogenic species. The germ grows at 31 and 37 °C in dry, large colonies and only forms a typical yellow pigment when exposed to light.

It should be noted that, as with M. marinum, M. flavescens and M. szulgai, IGRA tests for M. kansasii can be positive (Quantiferon-TB Gold ^Plus®), so they cannot be used to rule out tuberculosis (Hauer B et al. 2006).

Pulmonary infections with M. kansasii resemble infections with M. tuberculosis in their clinical presentation. In rare cases, M. kansasii is also the etiologic agent of infantile lymphadenitis.

Skin involvement is rare; disseminated granulomatous nodules, including eroded or ulcerated nodules, may occur in immunocompromised patients in the setting of a systemic infectious event. Their clinical morphology is usually uncharacteristic, comparable to systemizations of other nontuberculous mycobacterioses. Dermatologically relevant is the infection event in the context of TNF-alpha therapy of psoriasis (Brunasso AMG et al. 2021).

Disease due to M. kansasii is usually well treatable with a triple combination of INH, RMP, and EMB. The MIC values of isoniazid in vitro are 1.0 µg/ml for most strains, which is within the range of readily achievable serum and tissue levels at normal dosing (3 - 5 mg/kg body weight). Alternatively, therapy with clarithromycin, EMB, and RMP may be recommended, as all antibiotics here have low MIC values. The duration of therapy should be sufficiently long, i.e., until 12 months after sputum conversion. For pathogens resistant to RMP, clarithromycin/azithromycin, moxifloxacin, EMB, trimethoprim/sulfamethoxazole, or SM may be considered, depending on the results of susceptibility testing (Griffith DE et al. 2007).

1. Brunasso AMG et al. (2021) Mycobacterium kansasii infection in a psoriasis patient treated with adalimumab and switch to apremilast: First report and literature review. Dermatol Reports 13:8797.
2. Griffith DE et al (2007) Am J Respir Crit Care Med 175: 367-416.
3. Han SH et al (2010) Disseminated Mycobacterium kansasii infection associated with skin lesions: a case report and comprehensive review of the literature. J Korean Med Sci. 25:304-308.
4. Hauer B et al. (2006) Interferon-gamma assays - description and assessment of a new tool in the diagnosis of tuberculosis. Pneumology 60: 29-44