Nontuberculous Mycobacteria in Cystic Fibrosis

Abstract

Background-The clinical significance of the presence of non-tuberculous mycobacteria in the sputum of patients with cystic fibrosis is unclear. A retrospective case-control study was performed to assess possible risk factors for nontuberculous mycobacteria and its impact on clinical status in patients with cystic fibrosis. Methods-The records of all patients attending the Leeds cystic fibrosis clinics who were positive for non-tuberculous mycobacteria were examined. Each case was matched with two controls for sex, age, and respiratory function at the time of the first non-tuberculous mycobacteria isolate. Details of respiratory function, nutritional status, antibiotic and corticosteroid therapy, Shwachman-Kulczycki (S-K) score, Northern chest radiographic score, and the frequency of isolation of other bacteria and fungi were collected from two years before to two years after the first non-tuberculous mycobacteria isolate. The patients' genotype and the presence of diabetes mellitus were also recorded. Results-Non-tuberculous mycobacteria were isolated from 14 patients out of a cystic fibrosis population of 372 (prevalence = 3.8%). No significant eVect of nontuberculous mycobacteria was seen on respiratory function, nutritional status, or S-K score. There was a significant association with the number of intravenous antibiotic courses received before the first isolate with cases receiving, on average, twice as many courses as controls (cases 6.64, controls 2.86, 95% CI for diVerence 1.7 to 5.9). No significant diVerence was seen between cases and controls for Northern scores, previous steroid therapy, or the incidence of diabetes mellitus. Conclusions-Non-tuberculous mycobacteria infection in patients with cystic fibrosis is uncommon and its clinical impact appears to be minimal over a two year period. Frequent intravenous antibiotic usage is a possible risk factor for colonisation with non-tuberculous mycobacteria.

Update on host-pathogen interactions in cystic fibrosis lung disease

“…The underlying host-pathogen interaction mechanisms regulating the CF-characteristic microbial “switch” from S. aureus and H. influenzae to P. aeruginosa remain, however, controversial and incompletely understood, but probably involve pathogen-derived factors, such as pyocyanin and host-derived immune factors as well as environmental influences. In the era of commonly and early used inhaled antibiotics and prolonged patient survival, new “emerging” pathogens are increasingly detected in CF airway fluids, particularly fungi, such as Aspergillus fumigatus [ 2 , 26 ], Candida albicans [ 9 , 10 ], and Scedosporium species [ 22 ], and the bacteria Stenotrophomonas maltophilia [ 13 ], Achromobacter xylosoxidans [ 12 , 15 ], methicillin-resistant S. aureus (MRSA) [ 14 ], Burkholderia cepacia [ 11 , 25 ], and atypical mycobacteria (nontuberculous mycobacteria, NTMs) [ 1 , 23 ], which are often hard to treat in the clinics due to antibiotic resistance patterns [ 7 , 8 , 31 , 33 , 34 ]. Whereas the prevalence (or at least the detection rate) of these microbial species increases in most CF centers, their pathophysiological disease relevance for the outcome of CF lung disease remains controversial and poorly defined.…”

“…Whereas the prevalence (or at least the detection rate) of these microbial species increases in most CF centers, their pathophysiological disease relevance for the outcome of CF lung disease remains controversial and poorly defined. MRSA [ 14 ], B. cepacia , and NTMs [ 23 ] are broadly accepted as harmful CF pathogens, while for other rare species (such as S. maltophilia [ 13 , 30 , 32 ]), this is less clear.…”

Nontuberculous mycobacteria

“…5 One interpretation of these increasing numbers is that the true prevalence of NTM is rising in the CF population. 19,20 On the other hand, heightened surveillance practices in conjunction with laboratory techniques that have substantially improved the recovery of NTM organisms could potentially confound this hypothesis. Surveillance protocols that now call for multiple rather than single culture specimens and the implementation of “double-processing” of sputum samples to prevent bacterial overgrowth have enhanced our ability to detect NTM in CF patients.…”

“…56 Standard therapy for NTM based on these guidelines includes the concurrent use of three or more drugs to prevent the development of drug resistance and the continuation of therapy for one year of consistently negative sputum cultures after conversion from culture positivity. 19,22 A joint US/European committee sponsored by the US CF Foundation and the European CF Society has recently drafted guidelines for the diagnosis and management of NTM infections in the setting of CF. These draft guidelines were presented at the 2013 European CF Society conference in Lisbon and excerpts of the treatment recommendations for specific NTM species were incorporated into Table 1.…”