Table 2.

Characteristics of bacteria found in the esophagus

Phylum	Genus	Characteristics	Results	Pathogenicity status	Previously associated with
Proteobacteria	Neisseria	Gram‐negative, aerobic. They extract and import iron from the human host through iron‐binding proteins hemoglobin, lactoferrin, and transferrin 28	Contradicting results showed this genus to be enriched in EoE samples 18 and enriched in non‐EoE controls. 19 However, the non‐EoE controls in Hiremath et al's 19 study presented symptoms of esophageal dysfunction.	Pathogen or opportunistic commensal 29	Abundant in the oral cavity. Lower respiratory tract infection 30 N. mucosa found to be present in six fold higher amounts among obese participants compared with normal weight individuals 31 Higher in tongue/pharyngeal cancer patients compared with controls 32
Proteobacteria	Aggregatibacter	Formerly Haemophilus. Gram‐negative, fastidious, non‐hemolytic, capnophilic 33	Enriched in EoE samples 20	Pathogen or opportunistic commensal.	Higher in fecal samples of patients with Grave's disease 34 Oral Aggregatibacter actinomycetemcomitans associated with higher risk of pancreatic cancer 35
Proteobacteria	Pasteurella	Gram‐negative, anaerobic	Enriched in EoE samples 20	Pathogen or opportunistic commensal capable of causing infections in humans, domestic and wild animals	Infections resulting from animals bite or scratch wounds 36 Meningitis 37
Proteobacteria	Actinobacillus	Gram‐negative, aerobic, microaerophilic or facultatively anaerobic, fermenting carbohydrates with the production of acid 38	Enriched in EoE 39	Pathogen or opportunistic commensal	Periodontitis 33
Proteobacteria	Campylobacter	Gram‐negative, microaerophilic, presents flagella (adhesion and invasion) and produces toxins. 40	Enriched in addition to food trigger to diet 18	Pathogen or opportunistic commensal	Gastroenteritis Diarrhea Periodontitis Associated with Barret's esophagus, Crohn's disease and ulcerative colitis 41
Proteobacteria	Haemophilus	Gram‐negative, often encapsulated 42	Enriched in active EoE, 19 Enriched in EoE samples 20	Pathogen or opportunistic commensal	Sinusitis Acute tracheobronchitis Pneumonia Epiglottitis 43 Exacerbation of chronic obstructive pulmonary disease 44 Increased in middle and inferior meatus of chronic rhinosinusitis patients 45
Firmicutes	Streptococcus	Gram‐positive, non‐motile, catalase‐negative, facultative anaerobic. They are classified based on their hemolytic capacity (α‐, β‐, γ‐hemolysis). 42	Enriched in non‐EoE control samples, 18 Enriched with PPI use, 19 Decreased in active EoE 19	Commensal, beneficial and pathogenic species 46	Used as a probiotic, reduces uremia 47 High in antral gastritis patients 48 S. pyogenes causes upper respiratory tract and skin infections. S. pneumoniae cause infections of the respiratory tract 42
Firmicutes	Granulicatella	Gram‐positive, facultative anaerobic 49	Enriched in addition to food trigger to diet 18	Normal flora or opportunistic commensal	Endocarditis Infections related to prosthetic material infections of breast implants 49
Firmicutes	Lactobacillus	Gram‐positive, aero tolerant anaerobes or microaerophilic, non‐spore‐forming	Decreased in active EoE 19	Commensal, beneficial, commonly used as probiotics 50	Probiotic to reduce uremia, 47 asthma, atopic dermatitis Improve diarrhea symptoms Aid in weight loss 50
Firmicutes	Veillonella	Gram‐negative, lactate fermenting, anaerobic. 51	Decreased in EoE samples 20	Normal flora but have also been associated with oral diseases.	Aids in the removal of toxic waste products from biofilm communities, due to their unusual preference for organic acid carbon sources. Produces heme, an essential nutrient required by oral pathogens 51
Firmicutes	Filifactor	Gram‐positive, anaerobic 52	Decreased in active EoE 22	Pathogen or opportunistic commensal	Periodontitis Gingivitis Diabetes during pregnancy Oral squamous cell carcinoma 52
Firmicutes	Parvinomas	Anaerobic, Gram‐positive 53	Decreased in active EoE 22	Commensal, found in the oral cavity, respiratory system, gastrointestinal tract and vagina	Periodontitis Meningitis Bacteremia 53
Bacteroidetes	Porphyronomas	Anaerobic, Gram‐negative 54	Decreased in active EoE 22	Keystone pathogen	Porphyromonas gingivali can manipulate complement‐TLR crosstalk and increase inflammation, even at low concentrations Periodontitis 54
Actinobacteria	Atopobium	Anaerobic, catalase‐negative, Gram‐positive	Enriched in non‐EoE control samples 18	Normal oral flora, vaginal commensal	Increased in the saliva of patients with esophageal squamous cell carcinoma compared with healthy controls 55 , 56
Actinobacteria	Actinomyces	Facultative anaerobic, Gram‐positive	Decreased in active EoE, 19 Decreased in EoE samples 20	Commensal inhabitants of the oral cavity, pharynx, gut, genitourinary tract, and skin. Facultative pathogenic	A. odontolyticus in the oral cavity has the ability to degrade gluten. 57 Increased in fecal samples of pediatric Crohn's disease patients. 58
Actinobacteria	Corynebacterium	Catalase‐positive, aerobic, Gram‐positive bacilli	Enriched in EoE samples, 18 Enriched with PPI use 19	Commensal, opportunistic.	Respiratory infections Wound infections Urinary tract infections 59
Actinobacteria	Rothia	Aerobic or facultative anaerobic, non‐motile non‐spore‐forming Gram‐positive cocco‐bacilli	Decreased with PPI use, 19 Decreased in EoE samples 20 , 39	Normal flora of the human oropharynx and upper respiratory tract, opportunistic.	Dental caries and periodontal disease Bacteraemia Endocarditis Meningitis 60
Fusobacteria	Leptotrichiaceae	Obligate anaerobic or capnophilic. 61	Decreased in active EoE 19	Present in the oral cavities, gastrointestinal or urogenital tracts of humans and animals, containing both members of the resident microbiota and pathogens.	The Leptotrichiaceae family is rarely isolated and are found in mucous membranes, but when introduced into new tissue, they gain pathogenic potential. 61
Fusobacteria	Fusobacterium	Obligate anaerobic Gram‐negative	Enriched in EoE samples 20	Symbiont, opportunist, commensal of the oral cavity.	Periodontitis, endodontic infections, head and neck cancers Inflammatory bowel disease, colorectal cancer Produces significant LPS which may account for virulence 62
Spirochaete	Not specified	Unique architecture embracing both Gram‐positive and Gram‐negative features. Treponemes and Borrelia lack lipopolysaccharide. 63	Enriched in active EoE 27	Parasitic and commensal species	Treponema pallidum causes syphilis Treponemes are present in the gum of periodontitis patients 63
Proteobacteria	Burkholderia	Gram‐negative, previous part of Pseudomonas genus 64	Enriched with PPI use 24	Oportunistic pathogen, obligate pathogen and commensal species. Some possess anti‐fungal properties	Nosocomial infections, especially in cystic fibrosis Glanders 64
Proteobacteria	Eikenella	Facultative anaerobic, Gram‐negative. 65	Enriched with PPI use 24	Commensal of the mouth, intestine and genital tract	Respiratory infecions Bite wounds 65
Proteobacteria	Kingella	Gram‐negative, facultative anaerobic 66	Enriched with PPI use 24	Commensal organism in the oropharynx	Epiglottitis Oropharyngeal infections Pneumonia 66