Epidemiological evaluation of mycobacteria isolates in one city hospital: reports from the hospital microbiology laboratory

Abstract

The frequency of mycobacteria isolated from patient's specimens at Showa University Fujigaoka Hospital was investigated. By fitting a polynominal curve (degree = 3) of the annual frequency of culture-positive Mycobacterium tuberculosis (1977 through 1995), it was noted that the frequency had not changed since 1977. The patients in the 40s or older and 60s or older comprised 74 and 38%, respectively. Of 104 patients diagnosed as tuberculosis (between 1993 and 1995), 43 (41%) were compromised hosts with the following underlying diseases: kidney disease; diabetes mellitus; malignant tumor; respiratory disease; Behçet's disease; ophthalmosarcoidosis; multiple arthritis; Hashimoto's disease. This suggested that these compromised hosts are at high risk of onset and relapse of tuberculosis, and occasionally the doctor's or patient's delay was seen during the diagnostic process. By fitting a polynominal curve (degree = 3) of the annual frequency of culture-positive atypical mycobacteria (1977 through 1995), it was noted that the frequency had increased since 1981. The patients in the 40s or older and 60s or older comprised 88 and 60%, respectively. Between 1982 and 1994, we encountered 46 cases of atypical mycobacteriosis of the lung: 37 M. avium complex (MAX) diseases; 7 M. kansasii diseases; one M. chelonae disease; one unidentified disease involving Runyon Group II mycobacterium. Eight involved patients with bronchiectasia (5 cases), diabetes mellitus (2 cases), or leukaemia (one case). Haemophilus influenzae, Pseudomonas aeruginosa, and Moraxella catarrhalis at more than 10(7) CFU per ml of sputum were isolated from 6 patients diagnosed with MAC or M. kansasii lung diseases, suggesting the possibility of mixed infections. M. tuberculosis and atypical mycobacterium (15 cases), and two different atypical mycobacteria (16 cases) were isolated from the same or different specimens of the same patients at the same or different times. However, the pathogenicity of these mycobacteria remained unknown, because atypical mycobacteria are non-pathogenic in many cases. The above findings suggested that the environment fit for the mycobacteria growth in human body has gradually been formed associating with aging, lung-lesion, and decline of immune capacity.