[Clinical and epidemiological study of disease caused by Mycobacterium kansasii in the metropolitan area of Bilbao, Spain].
OBJECTIVE: Epidemiological description of individuals from whom Mycobacterium kansasii isolates were obtained in respiratory samples, and analysis of the isolates using molecular biological techniques. MATERIAL AND METHODS: A descriptive retrospective/ prospective study was carried out from January 1994 to April 2002 in Basurto Hospital and Santa Marina Hospital and from January 2000 to April 2002 in Cruces Hospital, Galdakao Hospital, and San Eloy Hospital. Diagnosis of the disease was performed according to American Thoracic Society criteria; other definitions were also applied to allow inclusion of all cases. Disease caused by M. kansasii in patients who were not infected with the human immunodeficiency virus (HIV) was compared with disease caused by Mycobacterium tuberculosis in a control group. Polymerase chain reaction was applied with analysis of restriction fragment length polymorphisms to differentiate between species of mycobacteria and classify them into genotypes. Amplified fragment length polymorphisms were used to recognize clones within each genotype. RESULTS: The patient charts of 334 patients in which an isolate of M. kansasii had been recorded were reviewed. We considered 220 patients to be suffering from disease caused by M. kansasii (American Thoracic Society criteria along with probable disease according to established definitions). The disease was more frequent in male patients (n=185; 84.1%) and in individuals who were not HIV positive (n=184; 83.6%). The highest incidence of disease in the Bizkaia region was found in Margen Izquierda-Encartaciones, where the rate was 8.05 per 100 000 inhabitants. In the Bilbao area, the highest rate was found in the districts lying on the outskirts. The underlying diseases were tuberculosis (20.5%), chronic obstructive pulmonary disease (25.9%), pulmonary neoplasia (7.7%), silicosis (0.9%), chronic liver disease (11.4%), and duodenal ulcer (8.6%). The most frequent constitutional symptoms were fever (39.1%), loss of appetite (23.2%), and weight loss (33.3%). Among the respiratory symptoms, the most outstanding were cough (70.9%) and expectoration (62.3%). The most frequent radiographic patterns were cavitation and pulmonary infiltration. The most common treatment regimen was rifampicin, isoniazid, and ethambutol (43.4%), and the average duration was 12 months in patients who were HIV negative. Analysis of antibiotic sensitivity, performed on 56 strains, revealed that 100% were resistant to isoniazid, while none displayed rifampicin resistance. Thirty-four cases of disease caused by M. kansasii were compared with 68 cases of tuberculosis, all of them without HIV infection. The comparison revealed a predominance of smokers, respiratory symptoms, and cavitation in patients with disease caused by M. kansasii. The majority of the isolates (98.5%) corresponded to genotype I. A total of 8 clones were obtained; the clones designated 1 and 3 were more common in HIV-positive and HIV-negative individuals respectively. CONCLUSIONS: In recent years, there has been an increase in the number of patients with disease caused by M. kansasii in the province of Bizkaia. The disease is more frequent in male patients, individuals who are HIV negative, and in urban areas. In addition, more respiratory symptoms and a higher incidence of cavitation were found in patients with disease caused by M. kansasii than in those with tuberculosis. Genotype I is the most common isolate, and clones 1 and 3 affect 80% of patients suffering from the disease.