Absence of Mycobacterium intracellulare and presence of Mycobacterium chimaera in household water and biofilm samples of patients in the United States with Mycobacterium avium complex respiratory disease

Abstract

Recent studies have shown that respiratory isolates from pulmonary disease patients and household water/biofilm isolates of Mycobacterium avium could be matched by DNA fingerprinting. To determine if this is true for Mycobacterium intracellulare, household water sources for 36 patients with Mycobacterium avium complex (MAC) lung disease were evaluated. MAC household water isolates from three published studies that included 37 additional MAC respiratory disease patients were also evaluated. Species identification was done initially using nonsequencing methods with confirmation by internal transcribed spacer (ITS) and/or partial 16S rRNA gene sequencing. M. intracellulare was identified by nonsequencing methods in 54 respiratory cultures and 41 household water/biofilm samples. By ITS sequencing, 49 (90.7%) respiratory isolates were M. intracellulare and 4 (7.4%) were Mycobacterium chimaera. In contrast, 30 (73%) household water samples were M. chimaera, 8 (20%) were other MAC X species (i.e., isolates positive with a MAC probe but negative with species-specific M. avium and M. intracellulare probes), and 3 (7%) were M. avium; none were M. intracellulare. In comparison, M. avium was recovered from 141 water/biofilm samples. These results indicate that M. intracellulare lung disease in the United States is acquired from environmental sources other than household water. Nonsequencing methods for identification of nontuberculous mycobacteria (including those of the MAC) might fail to distinguish closely related species (such as M. intracellulare and M. chimaera). This is the first report of M. chimaera recovery from household water. The study underscores the importance of taxonomy and distinguishing the many species and subspecies of the MAC.

Fig 1

16S rRNA gene multiplex PCR comparing M. intracellulare and M. chimaera (9). The two species are indistinguishable by this method. Lane 1, 100-bp ladder; lane 2, M. chimaera type strain DSM 44623^T; lane 3, M. chimaera isolate from household water sample; lane 4, M. intracellulare type strain ATCC 13950^T; lane 5, M. intracellulare patient isolate; lane 6, M. marseillense isolate from household water sample. Molecular weight markers are shown to the left.

Fig 2

PCR restriction enzyme analysis (PRA) of the 441-bp Telenti fragment of the hsp65 gene. The first five lanes include digests with BstEII (fragments of 235-115-100), and lanes 8 to 12 include the same isolates digested with HaeIII (fragments of 145-125-55). The digest patterns for M. marseillense, M. chimaera, and M. intracellulare are indistinguishable. Lanes 1 and 8, M. marseillense, household water; lanes 2 and 9, M. chimaera, household water; lanes 3 and 10, M. intracellulare, patient isolates; lanes 4 and 11, M. chimaera type strain DSM 44623^T; lanes 5 and 12, M. intracellulare type strain ATCC 13950^T; lane 6, 100-bp ladder (100, 200, 300, 400); lane 7, pGEM ladder (51, 65, 75, 126, 179, 222, 350). Molecular weight standard sizes are shown to the left and the right.