Clinical Significance and Epidemiologic Analyses of Mycobacterium avium and Mycobacterium intracellulare among Patients without AIDS

Abstract

The clinical significance and prevalence of Mycobacterium avium and Mycobacterium intracellulare were analyzed in a cohort of 7,472 patients who, from 1999 to 2003, sought care at the University of Texas M.D. Anderson Cancer Center, Houston, and had cultures performed for mycobacteria. Patients were stratified for age, sex, and underlying diseases, and bacteria were identified by 16S rRNA gene sequencing. M. avium was isolated in 62 (0.83%) of 7,472 patients and M. intracellulare in 65 (0.87%). Clinically, only 10 of the 62 (16.2%) patients with M. avium had probable to definite evidence of infection, whereas the majority (83.8%) had weak evidence of infection. Sex and age did not affect the isolation or infection of M. avium. Hematological tumors predisposed to M. avium colonization but not infection. In contrast, 41 of the 65 (63.1%) patients with M. intracellulare had probable to definite infection, a level much higher than those with M. avium (P < 0.001). M. intracellulare was more prevalent in women (1.33% of 3,311) than in men (0.50% of 4,161) (P < 0.001), and underlying diseases had no effect in women. Men with lung cancer had a higher prevalence (1.37%) than men without (0.34%) (4.0-fold; P < 0.001), but it was similar to that in women. A marked age trend for the isolation of M. intracellulare among women was noted: 0.27% (1-fold) for ages of <50 years, 0.85% (3.1-fold) for ages 50 to 59 years, 1.50% (5.6-fold) for ages 60 to 69 years, and 3.74% (13.9-fold) for ages >70 years (trend, P < 0.001). The combined rate for women >50 was 1.86% (95% confidence interval [1.30 to 2.42%]) (6.9-fold). Together, these results suggest that, among non-AIDS patients, M. intracellulare is more pathogenic and tends to infect women increasingly beyond menopause (age >50 years) regardless of underlying disease. The prevalence rate of 1.86% in postmenopausal women suggests the need to further investigate the public health significance of M. intracellulare.Mycobacterium avium and Mycobacterium intracellulare are slow-growing, nontuberculous mycobacterial (NTM) species that, due to similar biochemical characteristics, are usually grouped in the Mycobacterium avium-M. intracellulare complex (MAIC). The organisms are probably the most significant NTM associated with human diseases, causing disseminated infection in patients with AIDS, nodular bronchiectasis and other pulmonary infections, lymphadenitis, and skin infection (10).Although infrequently differentiated in the literature, M. avium and M. intracellulare exhibit significantly different pathogenicity and biology, as suggested by the following. First, the vast majority (Ͼ95%) of AIDS-related MAIC infections are due to M. avium, not M. intracellulare, and the M. avium infection typically occurs when the CD4 cell count falls to less than 0.05 ϫ 10 9 /liter (7, 10). Thus, deficiency in cellular immunity is an infection risk for M. avium but not for M. intracellulare. From a microbiology standpoint, the term MAIC in AIDS is obsolete (9). Second, nodular bronchiectasis caused b...

Association between 16S-23S Internal Transcribed Spacer Sequence Groups of Mycobacterium avium Complex and Pulmonary Disease

“…(3,19), is better able to invade and replicate inside macrophages than M. intracellulare (14), and has been associated with more invasive forms of MAC disease (3,10,21,27). Our data differ from the findings of a recent study by Han et al, who found that M. avium (identified by 16S rRNA sequencing) isolated from clinical specimens was actually less likely to be associated with pulmonary disease than was M. intracellulare (9). In that study, M. avium isolation was strongly associated with hematologic malignancy but did not often cause clinical disease (16.1% of isolates), while 63.1% of patients with M. intracellulare had clinical disease.…”

Pulmonary disease caused by nontuberculous mycobacteria

“…For example, within the MAC, M. intracellulare is more pathogenic than M. avium and some strains demonstrate hypervirulence leading to progressive lung disease and poor prognosis [36][37][38]. Many NTM infect humans via adherence to the respiratory mucosa.…”

Subspecies Identification and Significance of 257 Clinical Strains of Mycobacterium avium

“…In our earlier study (34), we noted that the frequent isolation of M. avium from patients with cancer was mainly due to the use of more diagnostic bronchoscopy procedures instead of being due to true infections. In fact, only 16.2% of all 62 patients with M. avium isolation showed evidence of definite or probable infection in that study whereas 63.1% of 65 patients with M. intracellulare exhibited such evidence of infection.…”

“…The isolation sources of the M. avium strains were categorized as tissue, respiratory tract, abdominal source, and others. The clinical significances were categorized as definitive, probable, or possible infection or contaminant based on the American Thoracic Society criteria (35) and our previous experience (34). Objective criteria, such as sterile specimens, radiographic abnormalities, and multiple isolations, were emphasized.…”

“…In view of common isolation of MAIC from patients with cancer in our institution, we performed a study earlier to differentiate M. avium and M. intracellulare and to compare the clinical significances and epidemiologic features of those infections (34). The present study was an expansion of the previous study to focus on M. avium and its subspecies.…”