title: Distinguishing the Signals of Gingivitis and Periodontitis in Supragingival Plaque: a Cross-Sectional Cohort Study in Malawi.
abstract: Periodontal disease ranges from gingival inflammation (gingivitis) to the inflammation and loss of tooth-supporting tissues (periodontitis). Previous research has focused mainly on subgingival plaque, but supragingival plaque composition is also known to be associated with disease. Quantitative modeling of bacterial abundances across the natural range of periodontal severities can distinguish which features of disease are associated with particular changes in composition. We assessed a cross-sectional cohort of 962 Malawian women for periodontal disease and used 16S rRNA gene amplicon sequencing (V5 to V7 region) to characterize the bacterial compositions of supragingival plaque samples. Associations between bacterial relative abundances and gingivitis/periodontitis were investigated by using negative binomial models, adjusting for epidemiological factors. We also examined bacterial cooccurrence networks to assess community structure. The main differences in supragingival plaque compositions were associated more with gingivitis than periodontitis, including higher bacterial diversity and a greater abundance of particular species. However, even after controlling for gingivitis, the presence of subgingival periodontitis was associated with an altered supragingival plaque. A small number of species were associated with periodontitis but not gingivitis, including members of Prevotella, Treponema, and Selenomonas, supporting a more complex disease model than a linear progression following gingivitis. Cooccurrence networks of periodontitis-associated taxa clustered according to periodontitis across all gingivitis severities. Species including Filifactor alocis and Fusobacterium nucleatum were central to this network, which supports their role in the coaggregation of periodontal biofilms during disease progression. Our findings confirm that periodontitis cannot be considered simply an advanced stage of gingivitis even when only considering supragingival plaque.
  
  
  
  Periodontal disease is a major public health problem associated with oral bacteria. While earlier studies focused on a small number of periodontal pathogens, it is now accepted that the whole bacterial community may be important. However, previous high-throughput marker gene sequencing studies of supragingival plaque have largely focused on high-income populations with good oral hygiene without including a range of periodontal disease severities. Our study includes a large number of low-income participants with poor oral hygiene and a wide range of severities, and we were therefore able to quantitatively model bacterial abundances as functions of both gingivitis and periodontitis. A signal associated with periodontitis remains after controlling for gingivitis severity, which supports the concept that, even when only considering supragingival plaque, periodontitis is not simply an advanced stage of gingivitis. This suggests the future possibility of diagnosing periodontitis based on bacterial occurrences in supragingival plaque.
authors: Institute for Child Health, UCL, London, United Kingdom Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, UCL, London, United Kingdom liam.shaw.13@ucl.ac.uk.
authors: Liam
authors: 0000-0001-7332-0820
authors: L
authors: Shaw
authors: Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere, Finland.
authors: Ulla
authors: U
authors: Harjunmaa
authors: Institute for Child Health, UCL, London, United Kingdom.
authors: Ronan
authors: R
authors: Doyle
authors: University of Malawi College of Medicine, Blantyre, Malawi.
authors: Simeon
authors: S
authors: Mulewa
authors: University of Malawi College of Medicine, Blantyre, Malawi.
authors: Davie
authors: D
authors: Charlie
authors: University of Malawi College of Medicine, Blantyre, Malawi.
authors: Ken
authors: K
authors: Maleta
authors: Institute for Child Health, UCL, London, United Kingdom.
authors: Robin
authors: R
authors: Callard
authors: MRC Clinical Trials Unit at UCL, London, United Kingdom.
authors: A Sarah
authors: AS
authors: Walker
authors: UCL Genetics Institute, UCL, London, United Kingdom.
authors: Francois
authors: F
authors: Balloux
authors: Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere, Finland Department of Paediatrics, Tampere University Hospital, Tampere, Finland.
authors: Per
authors: P
authors: Ashorn
authors: Institute for Child Health, UCL, London, United Kingdom.
authors: Nigel
authors: N
authors: Klein
mesh_terms: D000293:Adolescent; D000328:Adult; D001419:Bacteria / Q000145:classification; D018407:Bacterial Physiological Phenomena; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003773:Dental Plaque / Q000145:classification / Q000382:microbiology*; D005260:Female; D005891:Gingivitis / Q000145:classification / Q000382:microbiology*; D006801:Humans; D008295:Malawi; D010518:Periodontitis / Q000145:classification / Q000382:microbiology*; D012329:RNA, Bacterial / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D017423:Sequence Analysis, RNA; D055815:Young Adult
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S