The usefulness of surveillance cultures becomes questionable when the pathogen causing the infectious episode is distinct from the colonizing pathogen. In fact, then the surveillance cultures can be misleading. In a clearly presented and precisely conducted retrospective analysis of data from a single, large medical center in this issue of CHEST (see page 625), Cline et al4 studied this question in children with tracheostomy tubes. They found that, more often than not, the pathogen isolated at the acute infectious episode was different from the colonizing pathogen. Furthermore, studies in patients with COPD have also revealed a similar phenomenon, whereby new strain acquisition rather than changes in bacterial load of the colonizing pathogen have been clearly shown to underlie exacerbations.5 Although surveillance cultures have not been studied as a guide to antibiotic treatment in exacerbations of COPD, they would be of limited value and potentially detrimental in guiding antibiotic choice. Mechanisms of infections are poorly understood in non-CF bronchiectasis, so it still remains a question whether surveillance cultures would be of value in that population.