Cough swabs should not be used to isolate non-tuberculous mycobacteria in children with cystic fibrosis.

Non-tuberculous mycobacterium (NTM) account for 13% of cystic fibrosis (CF)-related respiratory infections and present a major therapeutic challenge. There is increasing evidence to suggest an adverse prognostic significance of NTM, particularly for Mycobacterium abscessus. A recent large retrospective study of 1216 patients with CF found that growths of NTM were associated with progressive deterioration in lung function. Therefore, accurate microbiological diagnosis of NTM is important. In our centre, NTM cultures are collected routinely at annual assessment, on admission for a chest exacerbation, and when assessing patients for a progressive or unexplained respiratory deterioration (http://www.rbht. nhs.uk/childrencf). This is problematic in patients who are unable to produce sputum, particularly the very young in whom only cough swabs are easily and routinely available. We always send bronchoalveolar lavage (BAL) fluid for NTM culture if a child with Table 1 Comparison of NTM growth on different respiratory samples in six children with cystic fibrosis