Clinical and Epidemiological Study of Disease Caused by Mycobacterium kansasii in the Metropolitan Area of Bilbao, Spain

Changing epidemiology of nontuberculous mycobacterial lung disease over the last two decades in a region of the Basque country

Recent studies suggest an increasing prevalence of nontuberculous mycobacteria (NTM) lung disease. The aim of the present study was to describe incidence rates of NTM lung disease and trends therein in our area over a 20-year period. This was a retrospective study of all cases of NTM lung disease between 1997 and 2016 that met the 2007 American Thoracic Society criteria. We analysed the annual incidence rates, species of mycobacteria isolated, trends over time and annual mortality in 327 patients. Mycobacterium kansasii was the most common mycobacterium isolated (84%), followed by Mycobacterium avium complex (MAC) (13%). We compared two periods: 1997-2006 (257 cases, 79%) and 2007-2016 (70 cases, 21%). The incidence rates tended to decrease across these years, with a peak of incidence in 2000 with 10.6 cases per 100 000. There was a clearly decreasing trend in M. kansasii infection, not only in the first period (incident rate ratio (IRR) 0.915, 95% CI 0.88-0.90; p<0.0001) but also in the second (IRR 0.869, 95% CI 0.780-1.014; p=0.080), reaching 1.8 per 100 000 in 2016. In contrast, MAC infection tended to increase across the two periods (IRR 1.251, 95% CI 1.081-1.447; p=0.003). In our region, the incidence of NTM lung disease has notably decreased in recent years. M. kansasii had high incidence rates in the first decade but clearly decreased in the second decade.

Chronic laryngitis caused by Mycobacterium Kansasii in a traveler

Chronic laryngitis commonly presents with dysphonia, and infectious causes include tuberculosis and endemic mycoses. We present a 58-year-old female with laryngitis for 5 years, fevers, chills, fatigue, malaise, myalgias, anterior neck pain, and night sweats after multicontinent exposure. Bronchoscopy cultures were negative. Bilateral microflap excision of vocal fold lesions demonstrated thickened epithelium and a deep vocal fold mass. Biopsy showed necrotizing granulomatous inflammation with acid-fast bacilli. Mycobacterium kansasii was identified. Treatment led to improvement in dysphonia, systemic symptoms, and vocal fold irritation. To our knowledge, this is the first case of isolated nontuberculous mycobacterial vocal fold infection. Laryngoscope, 129:2534-2536, 2019.

Mycobacterium kansasii

The incidence of Mycobacterium kansasii varies widely over time and by region, but this organism remains one of the most clinically relevant isolated species of nontuberculous mycobacteria. In contrast to other common nontuberculous mycobacteria, M. kansasii is infrequently isolated from natural water sources or soil. The major reservoir appears to be tap water. Infection is likely acquired through the aerosol route, with low infectivity in regions of endemicity. Human-to-human transmission is thought not to occur. Clinical syndromes and radiological findings of M. kansasii infection are mostly indistinguishable from that of Mycobacterium tuberculosis, thus requiring microbiological confirmation. Disseminated disease is uncommon in HIV-negative patients and usually associated with severe immunosuppression. The majority of patients with M. kansasii pulmonary disease have underlying pulmonary comorbidities, such as smoking, chronic obstructive pulmonary disease, bronchiectasis, and prior or concurrent M. tuberculosis infection. Surveys in Great Britain, however, noted higher rates, with 8 to 9% of M. kansasii infections presenting with extrapulmonary disease. Common sites of extrapulmonary disease include the lymph nodes, skin, and musculoskeletal and genitourinary systems. The specificity of gamma interferon release assays (IGRAs) for M. tuberculosis may be reduced by M. kansasii infection, as M. kansasii encodes CFP-10 and ESAT-6, two antigens targeted by IGRAs. A study conducted to evaluate the therapy in rifampin-resistant disease found that patients with acquired rifampin resistance were treated with daily high-dose ethambutol, isoniazid, sulfamethoxazole, and pyridoxine combined with aminoglycoside therapy. Given the potential toxicities, particularly with aminoglycoside therapy, clarithromycin and/or moxifloxacin therapy could be considered as alternatives.

Short communication: subtyping of Mycobacterium kansasii by PCR-restriction enzyme analysis of the hsp65 gene

Mycobacterium kansasii is one of the most common causes of pulmonary disease resulting from nontuberculous mycobacteria (NTM). It is also the most frequently isolated NTM species from clinical specimens in Poland. The aim of this study was to investigate the distribution of M. kansasii subtypes among patients suspected of having pulmonary NTM disease. Fifty clinical isolates of M. kansasii recovered from as many patients with suspected mycobacterial lung disease between 2000 and 2010 in Poland were genotyped by PCR-restriction enzyme analysis (PCR-REA) of partial hsp65 gene. Mycobacterium kansasii subtype I was the only genotype to be identified among the isolates, both disease-associated and non-disease-associated. Isolation of M. kansasii subtype I from clinical specimens may be indicative of infection but may also merely represent colonization.