Alternative molecular methods for improved detection of meningococcal carriage and measurement of bacterial density

Background: Conventional methods for detecting pharyngeal carriage of Neisseria meningitidis (Nm) are complex. There is a need for simpler methods with improved performance. We have investigated two alternative approaches. Methods: Three pharyngeal swabs were collected from 999 pupils aged 10 to 18 years in The Gambia. Carriage of Nm was investigated using three different methods: (i) plating on Thayer-Martin selective medium and testing by conventional microbiological methods followed by PCR testing, (ii) seeding in Todd Hewitt broth (THB) and, after overnight culture, testing by PCR, (iii) compression of the swab on filter paper and, after DNA concentration, testing by PCR. Results: PCR after culture in THB was more than twice as sensitive as conventional methods in detecting Nm (13.2% versus 5.7%; p