Emerging role of bacteria in oral carcinogenesis: a review with special reference to perio-pathogenic bacteria

Figures & data

Table 1. Summary of epidemiological studies that assessed the association between bacteria and oral cancer

Study	N	Technology used	Case sample	Control sample	Taxa associated with oral cancer
Nagy et al., 1998 (50)	21	Cultivation; biochemical identification	Tumour surface swabs	Contagious mucosa surface swabs	Fusobacterium, Porphyromonas, Actinomyces, Propionibacterium spp. and Candida albicans
Katz et al., 2011 (51)	15	Immunohistochemical staining	FFPE gingival carcinoma tissue	FFPE normal tissue	Porphyromonas gingivalis
Tateda et al., 2000 (55)	270	Cultivation, PCR and Southern-blot	Tumour tissue, gingival smears & oropharyngeal swabs	None	Streptococcus anginosus
Sasaki et al., 2005 (56)	49	PCR	Fresh tumour tissue, dental plaque & saliva	Fresh tissue, leukoplakia, lymphoma & rhabdomyosarcoma	S. anginosus
Morita et al., 2003 (57)	63	Real-time PCR	Fresh tumour tissue	Fresh non-cancerous tissue	Association with S. anginosus ruled out
Mager et al., 2005 (60)	274	Checkerboard DNA–DNA hybridisation	Unstimulated saliva	Unstimulated saliva	Capnocytophaga gingivalis, Prevotella melaninogenica and S. mitis
Hooper et al., 2006 (61)	51	Cultivation; 16S rRNA gene sequencing	Fresh tumour tissue	Fresh contagious tissue	Micrococcus luteus, P. melaninogenica, Exiguobacterium oxidotolerans, Fusobacterium naviforme, Staphylococcus aureus and Veillonella parvula
Hooper et al., 2007 (59)	20	16S rRNA metagenomics (Sanger sequencing)	Fresh tumour tissue	Fresh contagious tissue	Ralstonia insidiosa, Fusobacterium naviforme, Peptostreptococcus micros, Clavibacter michiganensis subsp. tessellarius, Capnocytophaga sp. oral strain S3 and Prevotella sp. oral clone BE073
Pushalkar et al., 2012 (58)	20	16S rRNA metagenomics (Sanger sequencing) & DGGE	Fresh tumour tissue	Fresh contagious tissue	Parvimonas sp. oral taxon 110, Eubacterium infirmum, Eubacterium brachy, Gemella haemolysans, Gemella morbillorum, Gemella sanguinis, Johnsonella ignava, Peptostreptococcus stomatis, S. gordonii, S. parasanguinis I and S. salivarius
Pushalkar et al., 2011 (62)	05	16S rRNA metagenomics (NGS; Roche's 454) & DGGE	Stimulated saliva	Stimulated saliva	Genera Streptococcus, Rothia, Gemella, Peptostreptococcus, Lactobacillus, Micromonas and Porphyromonas
Schmidt et al., 2014 (63)	94	16S rRNA metagenomics (NGS; Illumina)	Tumour surface swabs	Surface swabs: contra-lateral normal; healthy and pre-cancer subjects	Genus Fusobacterium and phylum Bacteriodetes (Streptococcus and Rothia showed inverse association)
Al-Hebshi et al., 2015 (64)	03	16S rRNA metagenomics (NGS; Roche's 454)	Fresh tumour tissue	None	Bacteroides fragilis

PCR: polymerase chain reaction; FFPE: formalin-fixed, paraffin-embedded; DGGE: denaturing gradient gel electrophoresis; NGS: next-generation sequencing.

Fig. 1.  The possible mechanisms by which oral bacteria contribute to oral carcinogenesis. ROS, reactive oxygen species; RNI, reactive nitrogen intermediates, MMPs, matrix metalloproteinases; PAR, protease-associated receptor; EMT, epithelial to mesenchymal transition.

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