Abstract
Introduction Pseudomonas aeruginosa is an important pathogen in cystic fibrosis (CF) due to its ability to colonise the airway by adhering to mucins within stagnant mucus. However, what remains to be elucidated is how pathogens survive in the airway.
Aims and objectives To investigate the growth of Pseudomonas laboratory strains, PA01 and PA14, in medium supplemented with paediatric/adult CF sputum and purified mucin. This is in order to elucidate whether CF mucin provides a nutrient source for Pseudomonas.
Methods Sputum samples were solubilised in 6M guanidine hydrochloride and purified via caesium chloride/4M guanidine hydrochloride density gradient centrifugation. Fractions containing mucins were dialysed, lyophilised, re-suspended, and sterilised via autoclaving. Strains were grown in samples with M9 medium. Growth was assessed via Colony Forming Unit counts (Miles, A.A. et al. The Journal of Hygiene 1938; 38: 732-749). Specific growth rates were calculated at log growth phase.
Results PA01 and PA14 have an increased growth rate in adult (n = 5) compared to paediatric (n = 5) CF sputum (p<0.0001, one-way ANOVA) whilst PA01 has an increased growth rate of 1.336 m (hour-1) in adult vs. 0.8320 m (hour-1) in paediatric mucin (p<0.05, one-way ANOVA).
Conclusions This is the first report of a difference in growth rate of Pseudomonas aeruginosa strains in adult vs. paediatric CF sputum. Currently the mechanism remains to be defined. Growth rate differences could be due to differences in mucin metabolism or sputum composition, such as the presence of growth promoting factors. It is therefore necessary to discover whether decline in lung function due to respiratory infection is partly due to an alteration in composition with age.
- Copyright ©the authors 2016
