title: Alternative Molecular Methods for Improved Detection of Meningococcal Carriage and Measurement of Bacterial Density.
abstract: Conventional methods for detecting pharyngeal carriage of Neisseria meningitidis are complex. There is a need for simpler methods with improved performance. We have investigated two alternative approaches. Three pharyngeal swabs were collected from 999 pupils aged 10 to 18 years in The Gambia. Carriage of N. meningitidis was investigated by 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 culture overnight, testing by PCR; and (iii) compression of the swab on filter paper and, after DNA concentration, testing by PCR. PCR after culture in THB was more than twice as sensitive as conventional methods in detecting N. meningitidis (13.2% versus 5.7%; P < 0.0001). PCR after DNA extraction from filter paper had a sensitivity similar to that of conventional methods (4.9% versus 5.7%; P = 0.33). Capsular genogroups detected by broth culture were genogroups W (21 isolates), B (12 isolates), Y (8 isolates), E (3 isolates), and X (2 isolates), and 68 meningococci had the capsule-null intergenic region. The distributions of genogroups and of capsule-null organisms were similar with each of the three methods. The carriage density in samples extracted from filter paper ranged from 1 to 25,000 DNA copies. PCR of broth cultures grown overnight doubled the yield of N. meningitidis carriage isolates compared with conventional methods. This approach could improve the efficiency of carriage studies. Collection on filter paper followed by quantitative PCR could be useful for density measurement and for carriage studies in areas with limited resources.
authors: Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom olivier.manigart@lshtm.ac.uk.|Medical Research Council Unit, Fajara, The Gambia.|Centre de Développement des Vaccins, Bamako, Mali.
authors: Olivier
authors: O
authors: Manigart
authors: Medical Research Council Unit, Fajara, The Gambia.
authors: Jacinta
authors: J
authors: Okeakpu
authors: Medical Research Council Unit, Fajara, The Gambia.
authors: Aderonke
authors: A
authors: Odutola
authors: Medical Research Council Unit, Fajara, The Gambia.
authors: Sheikh
authors: S
authors: Jarju
authors: Medical Research Council Unit, Fajara, The Gambia.
authors: Ebenezer
authors: E
authors: Foster-Nyarko
authors: Centre de Développement des Vaccins, Bamako, Mali.|Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors: Kanny
authors: K
authors: Diallo
authors: Medical Research Council Unit, Fajara, The Gambia.|Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors: Anna
authors: A
authors: Roca
authors: Medical Research Council Unit, Fajara, The Gambia.|Department of Paediatrics, Imperial College, London, United Kingdom.
authors: Beate
authors: B
authors: Kampmann
authors: Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|Medical Research Council Unit, Fajara, The Gambia.|Institute of Tropical Medicine, Antwerp, Belgium.
authors: Umberto
authors: U
authors: D'Alessandro
authors: Centre de Développement des Vaccins, Bamako, Mali.
authors: Samba
authors: S
authors: Sow
authors: Medical Research Council Unit, Fajara, The Gambia.
authors: Martin
authors: M
authors: Antonio
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors: Martin J
authors: MJ
authors: Maiden
authors: Vaccine Evaluation Unit, Public Health England, Manchester, United Kingdom.
authors: Ray
authors: R
authors: Borrow
authors: Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors: James M
authors: JM
authors: Stuart
authors: Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.
authors: Caroline L
authors: CL
authors: Trotter
authors: Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors: Brian M
authors: BM
authors: Greenwood
mesh_terms: D000293:Adolescent; D058491:Bacterial Load / Q000379:methods*; D002353:Carrier State / Q000175:diagnosis*; D002648:Child; D003430:Cross-Sectional Studies; D003470:Culture Media / Q000737:chemistry; D005260:Female; D005714:Gambia; D006801:Humans; D008297:Male; D008589:Meningococcal Infections / Q000175:diagnosis*; D009345:Neisseria meningitidis / Q000302:isolation & purification*; D010614:Pharynx / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D003470:Culture Media