Mycobacterium avium Complex Infection in an Immunocompetent Young Adult Related to Hot Tub Exposure

The insertion sequence IS1245 is a novel mycobacterial repetitive element identified in Mycobacterium avium. It encodes a transposase which exhibits a 64% amino acid similarity with IS1081, an insertion element present in the M. tuberculosis complex. The host range of IS1245 appears limited to M. avium as this element was not identified in M. intracellulare or in any other of 18 mycobacteria species tested. When IS1245 was used for restriction fragment length polymorphism (RFLP) analysis, human isolates characteristically presented a high number of copies (median, 16; range, 3 to 27) and a diversity of RFLP patterns comparable to that found by pulsed-field gel electrophoresis. Isolates from nonhuman sources differed both in number of copies and in RFLP pattern diversity: while swine isolates shared the characteristics of human strains, those from several avian sources exhibited a very low copy number of IS1245 and appeared clonal on the basis of RFLP.

Pulmonary disease caused by Mycobacterium avium complex usually occurs in patients with chronic lung disease or deficient cellular immunity, and its prevalence is increasing. We describe 21 patients (mean age, 66 years) with such infection without the usual predisposing factors, representing 18 percent of the 119 patients surveyed. Seventeen women and 4 men were given a diagnosis of M. avium complex from 1978 to 1987, with a stable incidence over the decade, on the basis of pulmonary symptoms, abnormalities on chest films, positive cultures, and in 14, biopsy evidence of invasive disease. Most of the patients (86 percent) presented with persistent cough and purulent sputum, usually without fever or weight loss. The cough was present for a mean of 25 weeks before the correct diagnosis was made. Radiographic patterns of slowly progressive nodular opacities predominated (71 percent); only five patients had cavitary disease at presentation. All patients responded initially to antimycobacterial therapy, but eight eventually relapsed when it was stopped. Four patients died of progressive pulmonary infection caused by M. avium complex. The extent of the initial pulmonary involvement was greater in patients with progressive disease than in those whose condition improved. We conclude that pulmonary disease caused by the M. avium complex can affect persons without predisposing conditions, particularly elderly women, and that recognition of this disease is often delayed because of its indolent nature.

Disseminated infection with Mycobacterium avium complex developed in 67 patients with the acquired immunodeficiency syndrome (AIDS) who were followed at Memorial Sloan-Kettering Cancer Center. Twenty-nine patients were treated with two or more antimycobacterial drugs for a mean of 6 weeks, and 7 patients received therapy for less than 1 month. Most patients received ansamycin, clofazimine, and ethionamide or ethambutol. Clinical improvement did not occur in treated patients, and microbiologic cure was never obtained. Mycobacterial bacteremia persisted in 24 of 26 treated patients. Colony counts of M. avium complex in sequential blood cultures decreased in 3 patients. Every autopsied patient with M. avium complex infection diagnosed before death, whether treated or not, had disseminated M. avium complex infection at autopsy.