Culture-independent multilocus sequence typing of Pseudomonas aeruginosa for cross-infection screening.

The genotyping of pathogens within cystic fibrosis cohorts is an important process, enabling the detection of transmissible and clinically-important strains. Traditionally this has been via culture-dependent processes. However, culture-independent investigation of respiratory samples is becoming more common, with such approaches highlighting the limitations of culture-based methods. In this study we describe the culture-independent application of multilocus sequence typing (MLST) for Pseudomonas aeruginosa, performed on DNA extracted from the sputa of cystic fibrosis patients. We compare the output to conventional culture-dependent MLST applied to the same samples and demonstrate high concordance. Culture-independent MLST enabled genotyping of culture-negative samples in patients from whom P. aeruginosa was intermittently isolated, and revealed the hidden presence of transmissible strains. Culture-independent MLST is also capable of highlighting samples containing multiple strains, albeit inconsistently. We conclude that culture-independent MLST can be a useful genotyping tool for screening cohorts and identifying patients that warrant further detailed investigation.