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Polyxeni Potter

Author affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Prevalence of Nontuberculous Mycobacteria in Cystic Fibrosis Clinics, United Kingdom, 2009

Paul Seddon

, Katy Fidler, Sundhya Raman, Hilary Wyatt, Gary Ruiz, Caroline Elston, Felicity Perrin, Khin Gyi, Diana Bilton, Francis Drobniewski, and Melanie Newport

Author affiliations: Royal Alexandra Children’s Hospital, Brighton, UK (P. Seddon, K. Fidler); Brighton and Sussex Medical School, Brighton (K. Fidler, S. Raman, M. Newport); Kings College Hospital, London, UK (H. Wyatt, G. Ruiz, C. Elston, F. Perrin); Royal Brompton Hospital, London (K. Gyi, D. Bilton); Barts and the London School of Medicine and Dentistry, Queen Mary, University of London, London (F. Drobniewski)

Abstract

Incidence of pulmonary infection with nontuberculous mycobacteria (NTM) is increasing among persons with cystic fibrosis (CF). We assessed prevalence and management in CF centers in the United Kingdom and found 5.0% of 3,805 adults and 3.3% of 3,317 children had recently been diagnosed with NTM. Of those, 44% of adults and 47% of children received treatment.

Nontuberculous mycobacteria (NTM) are ubiquitous environmental organisms (1), broadly classifiable into “slow” and “rapid” growers. Many species, especially the slow-growing Mycobacterium avium complex (MAC), are known to cause disseminated disease in immunodeficient persons (2,3). Rapid growers include the phylogenetically similar M. abscessus and M. chelonae, referred to as M. abscessus complex (MABSC). Such organisms have emerged as pathogens in immunocompetent adults, for example, after traumatic limb injuries sustained during the 2004 tsunami in the Indian Ocean (4). NTM have been identified as pulmonary pathogens in immunocompetent middle-aged women with nodular bronchiectasis (5) and older men who smoke with upper lobe cavitation (6). Since the 1990s, NTM have been increasingly isolated from the sputum of patients with cystic fibrosis (CF) (7,8).
CF is the most frequent lethal genetic disorder of White persons, affecting >8,000 persons in the United Kingdom and 30,000 in the United States. Early death is mainly from chronic lung disease caused by persistent lower airway infection and inflammation. Important airway pathogens include Staphylococcus aureus and Pseudomonas aeruginosa, but others, such as NTM, are playing an increasingly recognized role.
A multicenter prospective study of CF patients in the United States (9) found the prevalence of NTM in sputum to be 13%; MAC was the most common species (72%), and M. abscessus was the next most common (16%). Older age was the most significant predictor for a positive sputum culture. A multicenter CF study in France reported a prevalence of 6.6%, showing MABSC to be the most common; MAC was the next most prevalent (10). Single-center studies in Europe have found variable NTM prevalences, from 13.3% in a center in Germany (7) to 3.8% in a center in the United Kingdom (8).
It is often difficult to determine whether isolation of NTM represents colonization or disease that requires treatment. Current American Thoracic Society guidelines (1) are helpful, but application lacks uniformity, and management is complicated by inducible resistance to antibiotics (11).
To determine the optimal management of NTM in CF, we first need to define the extent of the problem and characterize current practice. The aim of this study was to establish the prevalence of NTM infection in the UK CF community, how it is screened for, and how it is managed.

The Study

A single-page questionnaire (Technical Appendix

[PDF - 83 KB - 2 pages]) was sent to the lead CF physician in all UK pediatric and adult CF centers identified by the principal UK CF charity, the Cystic Fibrosis Trust, in 2009. Nonresponders were followed up with by email or telephone. The local research ethics committee deemed the study did not require ethical approval.
Results were tabulated and basic statistical analysis performed by using Microsoft Excel 2007 (Microsoft, Redmond, WA, USA). Because M. chelonae and M. abscessus have common phenotypic characteristics and not all samples were fully sequenced by a reference laboratory, we combined these for reporting as MABSC.