Bibliometric analysis of subject trends and knowledge structures of gut microbiota

Table 1 Temporal distribution of gut microbiota related publications in PubMed (during the periods of 2004-2008, 2009-2013 and 2014-2018)

Period	Rank	Country	Publications, n (%)	Top journal	Publications, n (%)	Author, number of papers
2004-2008	1	United States	406 (37.3)	The Journal of Nutrition	35 (3.2)	Isolauri E (27)
	2	England	307 (28.2)	The British Journal of Nutrition	30 (2.7)	Salminen S (25)
	3	Netherlands	73 (6.7)	Journal of Clinical Gastroenterology	25 (2.2)	Gibson GR (20)
	4	Russia (Federation)	45 (4.1)	Applied and Environmental Microbiology	23 (2.1)	Doré J (17)
	5	Germany	40 (3.6)	Zhurnal Mikrobiologii, Epidemiologii, I immunobiologii	20 (1.8)	Knol J (14)
	6	Switzerland	31 (2.8)	Journal of Agricultural and Food Chemistry	19 (1.7)	Blaut M (13)
	7	France	27 (2.4)	Journal of Pediatric Gastroenterology and Nutrition	19 (1.7)	Gordon JI (13)
	8	Japan	26 (2.3)	Alimentary Pharmacology and Therapeutics	15 (1.3)	Boehm G (11)
	9	China	18 (1.6)	The American Journal of Gastroenterology	12 (1.0)	Shanahan F (11)
	10	Italy	12 (1.1)	Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology	12 (1.0)	Kim DH (10)
	Total		985 (90.5)		210 (19.2)
2009-2013	1	United States	1174 (40.4)	PLoS One	145 (4.9)	de Vos WM (44)
	2	England	884 (30.4)	Gut Microbes	57 (1.9)	O′Toole PW (34)
	3	Netherlands	177 (6.1)	The British Journal of Nutrition	53 (1.8)	Doré J (32)
	4	Switzerland	125 (4.3)	Journal of Agricultural and Food Chemistry	48 (1.6)	Knight R (28)
	5	Germany	99 (3.4)	Anaerobe	38 (1.3)	Gordon JI (25)
	6	Russia (Federation)	49 (1.6)	Proceedings of the National Academy of Sciences of the United States of America	36 (1.2)	Gibson GR (25)
	7	France	46 (1.5)	Inflammatory Bowel Diseases	33 (1.1)	Shanahan F (24)
	8	China	32 (1.1)	Digestive Diseases (Basel, Switzerland)	31 (1.0)	Raoult D (24)
	9	United Arab Emirates	26 (0.8)	Current Opinion in Gastroenterology	31 (1.0)	Salminen S (24)
	10	Spain	26 (0.8)	Nature Reviews. Gastroenterology and Hepatology	27 (0.9)	Isolauri E (23)
	Total		2638 (90.9)		499 (17.1)
2014-2018	1	United States	3013 (39.4)	PLoS One	247 (3.2)	Wang J (87)
	2	England	2394 (31.3)	Scientific Reports	149 (1.9)	Li J (80)
	3	Netherlands	467 (6.1)	Nutrients	148 (1.9)	Wang X (68)
	4	Switzerland	446 (5.8)	Gut Microbes	138 (1.8)	de Vos WM (60)
	5	Germany	312 (4.0)	World Journal of Gastroenterology	132 (1.7)	Wang Y (59)
	6	China	119 (1.5)	Microbiome	100 (1.3)	Li Y (58)
	7	Japan	105 (1.3)	Food and Function	93 (1.2)	Zhang X (50)
	8	France	97 (1.2)	Gut	80 (1.0)	Gasbarrini A (49)
	9	United Arab Emirates	76 (0.9)	International Journal of Molecular Sciences	67 (0.8)	Li L (49)
	10	Australia	62 (0.8)	Journal of Agricultural and Food Chemistry	67 (0.8)	Cryan JF (48)
	Total		7091 (92.8)		1221 (15.9)

Table 2 Results of biclustering analysis on high-frequency major Medical Subject Heading terms/Medical Subject Heading subheadings in the research field of gut microbiota in three periods

Period	Cluster	Number of MeSH terms1	Cluster analysis
2004-2008	0	1, 8, 12, 15, 19, 23, 31, 46	(1) Intestinal mucosa and intestines metabolism; and (2) Probiotics pharmacology.
	1	6, 7, 13, 17, 22, 28, 34, 36, 44	(1) Inflammatory bowel diseases microbiology and immunology; (2) Gut microbiota immunology; and (3) Intestinal mucosa immunology and microbiology.
	2	5, 9, 20, 25, 26, 29, 35, 39, 40, 41, 48	(1) Bifidobacterium metabolism, physiology and drug effects; and (2) Bifidobacterium growth and development.
	3	2, 10, 16, 21, 27, 32, 33, 38, 42, 49	(1) Inflammatory bowel disease drug therapy; and (2) Probiotics therapeutic use.
	4	3, 4, 11, 14, 18, 24, 30, 37, 43, 45, 47, 50	(1) Feces microbiology and gastrointestinal tract microbiology; (2) Gut microbiota isolation, purification classification, growth and development; and (3) Irritable bowel syndrome microbiology.
2009-2013	0	8, 17, 21, 25, 26, 29, 31, 34, 35	(1) Gastrointestinal tract immunology; (2) Inflammatory bowel diseases microbiology and immunology; and (3) Intestinal mucosa microbiology and immunology.
	1	10, 20, 23, 30, 33, 39, 42, 44	(1) Anti-bacterial agents pharmacology, therapeutic use and adverse effects; and (2) Gut microbiota growth and development.
	2	3, 4, 14, 15, 18, 19, 22, 28, 32, 38, 40, 43	(1) Irritable bowel syndrome microbiology; (2) Gut microbiota classification, isolation and purification; and (3) Feces microbiology.
	3	1, 2, 5, 6, 7, 9, 11, 12, 13, 16, 24, 27, 36, 37, 41	(1) Intestines and intestinal mucosa metabolism; (2) Gastrointestinal tract microbiology; (3) Obesity microbiology; and (4) Probiotics pharmacology and therapeutic use.
2014-2018	0	7, 9, 15, 17, 27, 28, 31, 46, 55, 65	(1) Gut microbiota genetics; (2) Metagenomics methods; and (3) Feces microbiology.
	1	8, 23, 30, 32, 38, 40, 57, 58, 59, 60, 66	(1) Inflammatory bowel diseases immunology; (2) Fecal microbiota transplantation methods; (3) Gastrointestinal tract and intestinal mucosa immunology; and (4) Intestinal mucosa immunology.
	2	18, 20, 21, 29, 34, 42, 44, 53, 54, 56	(1) Irritable bowel syndrome microbiology; (2) Dysbiosis microbiology; (3) Gut microbiota growth and development; and (4) Intestinal mucosa microbiology.
	3	1, 4, 5, 10, 11, 14, 19, 25, 45, 51, 61	(1) Probiotics therapeutic use; and (2) Intestines and intestinal mucosa metabolism.
	4	6, 13, 22, 24, 26, 35, 37, 41, 47, 48, 62, 63	(1) Anti-bacterial agents pharmacology, therapeutic use and adverse effects; and (2) Prebiotics therapeutic use and pharmacology.
	5	2, 3, 12, 16, 33, 36, 39, 43, 49, 50, 52, 64	(1) Gastrointestinal tract microbiology; and (2) Non-alcoholic fatty liver disease, obesity and diabetes mellitus (type2) microbiology.

¹Represents the serial number of high-frequency major Medical Subject Heading (MeSH) terms/MeSH subheadings in each period which shown in Supplementary Tables 5-7.