This reference study aims to survey the bacterial flora of the healthy lower human esophagus and to compare it with that of the upper esophagus and oral mucosa. The use of biopsies, in addition to brush samples, allows inclusion of not only transient bacteria present on the surface but also bacteria residing in the epithelia, and the yield of the two methods can be compared. Forty patients scheduled for surgery for reasons with no known influence on esophageal flora and with no symptoms or endoscopic signs of esophageal disease were included. Samples were collected from the oral, upper esophageal, and lower esophageal mucosa using sealed brushes and biopsy forceps. Colonies cultivated on agar plates were classified and semiquantified. Twenty-three different bacterial species were identified, with similar strains present at the three sites. The most common group of bacteria was viridans streptococci, with an occurrence rate in brush samples and biopsies of 98% and 95%, respectively. The median number of species occurring in the oral cavity, upper esophagus, and lower esophagus was between 3 and 4 (range 0-7). The total number of species in the oral cavity was significantly higher when compared with either level in the esophagus, while the yields obtained by brush and biopsy sampling were highly correlated. Hence, the normal human esophagus is colonized with a resident bacterial flora of its own, which has similarities to that of the oral mucosa. There are diverse species that make up this flora, although in relatively low amounts. The most frequent inhabitants of the esophagus are streptococci, with an occurrence rate in brush samples and biopsies of 95-98%. Comparative studies of patients with eosinophilic esophagitis and gastroesophageal reflux disease are warranted.

Subjects with GERD had significantly less bacterial diversity in both oral and esophageal samples than EoE-subjects. Whether this discrepancy might be explained by an effect on the protective mucosal biofilm by the acidic content of the reflux in subjects with GERD remains unclear.

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The aim of this study was to assess whether the symptom severity and health-related quality of life (HRQL) of patients with dysphagia and esophageal eosinophilia correlate with disease activity as expressed by the number of eosinophils in the esophageal mucosa. This study included newly diagnosed (n = 58) or relapsed patients (n = 7), where 40% were diagnosed in connection with esophageal bolus impaction. The mean age was 45 years (19-88), and 74% were men. Symptoms and HRQL were recorded using the Watson Dysphagia Scale (WDS), the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire - Oesophageal Module 18 and the Short Form-36 Questionnaire. Histological samples gathered from the proximal and distal esophageal mucosa were stained using both hematoxylin and eosin (HE) and an immunohistochemical (IHC) technique against 'Eosinophil Major Basic Protein,' and the peak number of eosinophils per high-power field was assessed. More eosinophils were detected after IHC staining than HE staining (P < 0.001). No correlation was found between symptoms or the HRQL and the number of eosinophils. However, higher numbers of eosinophils at the proximal esophagus were found in patients with concomitant bolus impaction (IHC P < 0.05 and HE P < 0.05) and could serve as a risk marker.