Introduction: The criteria of Murray and Washington to rule out sputum culture may not be suitable for patients with non-cystic fibrosis bronchiectasis, due to their high pre-test probability of isolating potential pathogenic microorganisms (PPM) and the prognostic and therapeutic implications of these isolations.

Objectives: Analyze the profitability of growing sputum samples classified as “not valid” by Gram stain in patients with non-cystic fibrosis bronchiectasis and describe the PPM isolated.

Methods: We collected sputum samples from non-cystic fibrosis bronchiectasis patients from November 2016 to May 2017. We performed Gram stain and culture on plates of blood agar, chocolate agar and McConkey, incubated at 37ºC during 72 hours, in all the sputum samples. The predominant growth of a PPM was considered as a positive culture.

Results: We achieved 372 sputum samples. 112 of them were classified as "not valid" by Gram stain. The 112 "not valid" samples were obtained from 80 patients (40% ? 60% ?) with an average age of 70 S.D. 12 years. 71% were collected in stable phase and 29% during exacerbation. PPM were isolated in 42% of the 112 samples. The most frequent was P. aeruginosa (40% of the isolated PPM). There were no differences during exacerbation or stable phase.


1-The profitability of sputum culture of “not valid” samples by Gram stain in patients with non-cystic fibrosis bronchiectasis was 42%. The most frequently isolated PPM was P. aeruginosa.

2-The Murray and Washington criteria may not be an appropiate method to refuse the sample, since early detection of P. aeruginosa has an impact on the management.