Impact of Helicobacter pylori infection on fluid duodenal microbial community structure and microbial metabolic pathways.

BACKGROUND: The bioactivities of commensal duodenal microbiota greatly influence the biofunction of hosts. We investigated the role of Helicobacter pylori infection in extra-gastroduodenal diseases by determining the impact of H. pylori infection on the duodenal microbiota. We sequenced 16 S rRNA genes in samples aspirated from the descending duodenum of 47 (male, 20; female, 27) individuals who were screened for gastric cancer. Samples were analysed using 16 S rRNA gene amplicon sequencing, and the LEFSe and Kyoto Encyclopaedia of Genes and Genomes methods were used to determine whether the duodenal microflora and microbial biofunctions were affected using H. pylori infection. RESULTS: Thirteen and 34 participants tested positive and negative for H. pylori, respectively. We identified 1,404 bacterial operational taxonomic units from 23 phyla and 253 genera. H. pylori infection changed the relative mean abundance of three phyla (Proteobacteria, Actinobacteria, and TM7) and ten genera (Neisseria, Rothia, TM7-3, Leptotrichia, Lachnospiraceae, Megasphaera, F16, Moryella, Filifactor, and Paludibacter). Microbiota features were significantly influenced in H. pylori-positive participants by 12 taxa mostly classified as Gammaproteobacteria. Microbial functional annotation revealed that H. pylori significantly affected 12 microbial metabolic pathways. CONCLUSIONS: H. pylori disrupted normal bacterial communities in the duodenum and changed the biofunctions of commensal microbiota primarily by upregulating specific metabolic pathways. Such upregulation may be involved in the onset of diseases associated with H. pylori infection.

Effect of antibiotics for infectious diarrhea on the duration of hospitalization: A retrospective cohort study at a single center in Japan from 2012 to 2015.

OBJECTIVE: Routine empirical antimicrobial therapy for patients with infectious diarrhea is not recommended in general practice. Conversely, prescription of empirical antibiotics for hospitalized patients remains controversial due to a lack of studies providing evidence for its benefits. Thus, this study aimed to examine whether empirical antimicrobial therapy would shorten the hospitalization duration for infectious diarrhea patients. METHODS: This single-center, retrospective cohort study was performed at the Department of General Medicine and Emergency Care, Toho University Medical Center Omori Hospital, using medical records. Adult patients (aged ≥16 years) hospitalized for infectious diarrhea from 2012 to 2015 were enrolled. The primary outcome was the duration of hospitalization. Risk factors examined in parallel to antibiotic therapy included age, sex, relevant medical history, probiotics use, vital signs, leukocyte count, liver and renal functions, and microbiological data. RESULTS: We enrolled 138 and 50 patients treated with and without antimicrobial therapy, respectively. The median hospitalization periods were 6.0 days (interquartile range, 4.0-7.0 days) and 5.0 days (interquartile range, 3.25-6.0 days) for patients treated with and without antibiotics, respectively (p = 0.007). Multiple regression showed that empiric antimicrobial therapy (p = 0.017), advanced age (p = 0.003), hematochezia (p = 0.008), elevated serum creatinine (p < 0.001), and elevated serum C-reactive protein (p = 0.002) were significant risk factors of longer hospitalization duration. CONCLUSION: Empirical antimicrobial therapy was found to relate to a longer hospitalization duration for infectious diarrhea patients. Although its effects on the patients' symptoms were not evaluated, our results suggest that empirical antimicrobial therapy should be administered cautiously to not only outpatients, but also hospitalized patients.

Alteration of Breath Hydrogen and Methane in Ethanol-Fed Rats.

Chronic alcohol consumption can cause dysbiosis, but it is difficult to determine the effect of alcohol on the structure and activity of gastrointestinal tract microbiota. We therefore designed a noninvasive hydrogen breath test (HBT) to investigate the alteration in the chemical profile of gut microbiota in ethanol-fed rats. Thirteen F344/DuCri rats were fed on a commercial mash food with 16% ethanol solution drinking fluid from 4 weeks of age. HBTs were carried out on six 8-week-old and seven 24-week-old ethanol-fed rats. As controls, HBTs were carried out on sixteen 8-week-old, six 24-week-old, and five 48-week-old male rats. Six 24-week- old male rats were examined twice at 1-week intervals. HBTs were performed after fasting for 24 hr. Rats were orally administrated 4 mL/kg of 65% lactulose solution and housed in an animal chamber. The expired air was collected in a breath-sampling bag at 10-min intervals for 180 min. The hydrogen (H2) and methane (CH4) levels in the breath sample were measured using a breath analyzer and were expressed.as parts- per million (ppm). Elevated H2 and CH4 levels were more frequent in male rats. Maximal values of H2 and CH4 were highest in 8-week- old rats, followed by 48-week-old and 24-week-old rats. No ethanol-fed rat exhaled more than 2 ppm of H2 or CH4 until 180 min after the oral administration of lactulose, unlike the controls. This alteration was more obvious than that of aging or gender differentiation. We conclude that there is a close association between chronic ethanol consumption and H2 and CH4 production. An asymptomatic heavy drinker might have dysbiosis that involves gut microbiota with lower fermentation performance.

Role of infected grandmothers in transmission of Helicobacter pylori to children in a Japanese rural town.

AIM: Although the prevalence of Helicobacter pylori (H. pylori) increases with age and the main period of acquisition is childhood, the route of transmission of H. pylori infection remains unclear. This study aims to evaluate the relationship between prevalence of children and grandparents. METHODS: A total of 838 consecutive children who attended the Urita clinic and whose blood was taken for work up were enrolled in the present study. They were 449 boys and 389 girls, with a mean age of 12.4 years. H. pylori serology of their family members who were living together in one house was picked up to analyse intra-familial clustering of H. pylori infection. The family members of these children consisted of 448 fathers, 597 mothers, 205 grandfathers, 361 grandmothers and 589 siblings. RESULTS: The seropositive rates of mothers, grandmother and siblings in seropositive children were significantly higher than those in seronegative children. H. pylori infection in mothers and grandmothers was a marked risk factor for infection in the index children. Larger family size was not a risk factor for H. pylori infection. In contrast, having an infected father or grandfather was not an independent predictor for children infection. CONCLUSIONS: Our data demonstrate that not only mother-to-child transmission but also grandmother-to-child transmission is an important mechanism for the spread of H. pylori in a three-generation household.

Form of gastric air bubble is associated with gastroesophageal reflux symptoms.

BACKGROUND/AIMS: Gastric bubble is present in approximately 70% of normal chest and abdominal radiograph. Most swallowed air is regurgitated and belching is a physiological phenomenon to expel ingested gas from the stomach and is a common symptom in normal adults. In the present study it was investigated whether gastric bubble detected on abdominal radiograph is associated with GERD symptoms. METHODOLOGY: All of the patients who first attend our hospital were asked to respond the F-scale questionnaire regardless of their chief complaints to diagnose GERD. Plain abdominal films in the erect position were used to measure the size of gastric bubble and to classify the form of gastric bubble into four groups: dome-type; irregular-type; stomach-type; and undetected-type. The quantity of gastric bubble (gastric bubble score) was determined as the pixel value on image collected from hospital's digital database. RESULTS: The gastric bubble score of irregular-type was significant lower than that of dome-type and stomach-type. GERD was most frequently detected in stomach-type group, followed by undetected-type, irregular-type, and dome-type. The mean score of F-scale was significantly higher in stomach-type than in dome-type. CONCLUSIONS: It is concluded that gastric bubble detected on plain abdominal films is an informative marker for evaluating the functional disorder of upper digestive tracts. Physicians have to recognize the importance of plain films of the abdomen in the diagnostic process of GERD.

Is the metabolism of toast alcohol beverages influenced by a meal taken five minutes later?

Alcohol is commonly consumed with, or soon after, a meal that affects gastric emptying and thus, absorption and metabolism of alcohol. The aim of this study is to evaluate the effect of liquid test meal ingested soon after, alcohol ingestion on alcohol metabolism, as is common in the social setting. First, a 100 mL of water containing of 80 mg of 13C-ethanol was administrated orally in 7 healthy subjects, and 200 mL of liquid meal (200 kcal) was administrated 5 min after alcohol ingestion. Breath samples were taken at baseline and at 10-min interval for 150 min. Next, 13C-ethanol breath test was performed without ingestion of liquid meal. Cmax was decreased after ingestion of liquid meal, whereas Tmax was unchanged. The descending gradient of 13CO2 excretion curves after ingestion of liquid meal is parallel to that without liquid meal, while the ascending gradient of 13CO2 excretion curves in the first 10 min had a tendency to be greater after ingestion of liquid meal than without ingestion of liquid meal. A significant delay in breath 13CO2 excretion after ingestion of liquid meal was found and the AUC values were lower after ingestion of liquid meal in each time point, indicating that liquid meal ingested soon after alcohol ingestion may not affect elimination but absorption and/or metabolism of a small amount of alcohol.

Extensive atrophic gastritis linked to increased levels of intraluminal hydrogen gas.

BACKGROUND/AIMS: Gastric acid plays an important part in the prevention of bacterial colonization of the gastrointestinal tract. If these bacteria have an ability of hydrogen (H2) fermentation, intraluminal H2 gas might be detected. We attempted to measure the intraluminal H2 concentrations to determine the bacterial overgrowth in the gastrointestinal tract. METHODOLOGY: Studies were performed in 647 consecutive patients undergoing upper endoscopy. At the time of endoscopic examination, we intubated the stomach and the descending part of the duodenum without inflation by air, and 20 ml of intraluminal gas samples of both sites was collected through the biopsy channel. Intraluminal H2 concentrations were measured by gas chromatography. RESULTS: Over all, intragastric and intraduodenal H2 gas was detected in 566 (87.5%) and 524 (81.0%), respectively. The mean values of intragastric and intraduodenal H2 gas were 8.5 +/- 15.9 and 13.2 +/- 58.0 ppm, respectively. The intraduodenal H2 level was increased with the progression of atrophic gastritis, whereas the intragastric H2 level was the highest in patients without atrophic gastritis. CONCLUSIONS: The intraduodenal hydrogen levels were increased with the progression of atrophic gastritis. It is likely that the influence of hypochlorhydria on bacterial overgrowth in the proximal small intestine is more pronounced, compared to that in the stomach.

The incidence of pancreatic and extrapancreatic cancers in Japanese patients with chronic pancreatitis.

BACKGROUND/AIMS: Although an association between chronic pancreatitis and malignancies has been reported in the Western literature, in Japan there have been few reports that have dealt with this issue. We investigated the incidence of pancreatic and extrapancreatic cancers in Japanese patients with chronic pancreatitis. METHODOLOGY: We studied 170 Japanese patients with definite chronic pancreatitis with respect to the occurrence of pancreatic and extrapancreatic cancers during follow-up and compared the incidence with that reported in the Western literature. RESULTS: The patients developed 29 cancers including 5 pancreatic cancers. Four patients had two different types of cancer. The extrapancreatic cancer incidence (24/170: 14.1%) was significantly higher than in the West (8.3%, p < 0.01). The major organs in which cancer developed were stomach (n=9), pancreas (n=5), esophagus (n=4), colon (n=3), lung (n=2) and hemopoietic tissue (n=2). The overall incidence (8.2%) of associated cancers of the digestive system including, stomach, intestine, liver, biliary duct, and gallbladder, was significantly higher than in the West (1.3%, p < 0.01). CONCLUSIONS: The risk of extrapancreatic cancers during the course of chronic pancreatitis is significantly increased in Japan than in Western countries. In particular, cancers of the digestive system are frequently associated with chronic pancreatitis in Japan.

Autoimmune pancreatitis metachronously associated with retroperitoneal fibrosis with IgG4-positive plasma cell infiltration.

Retroperitoneal fibrosis is an uncommon disorder characterized by the formation of a dense plaque of fibrous tissue in the retroperitoneum, and its etiology remains unknown. Autoimmune pancreatitis is a rare type of chronic pancreatitis characterized by fibrosis with abundant infiltration of IgG4-positive plasma cells and lymphocytes and obliterative phlebitis in the pancreas. We present a case of autoimmune pancreatitis that developed 10 mo after the occurrence of retroperitoneal fibrosis. Histological findings of the resected retroperitoneal mass were marked periureteral fibrosis with abundant infiltration of IgG4-positive plasma cells and lymphocytes and obliterative phlebitis. These findings suggest a common pathophysiological mechanism for retroperitoneal fibrosis and autoimmune pancreatitis in this case. Some cases of retroperitoneal fibrosis might be a retroperitoneal lesion of IgG4-related sclerosing disease.

Involvement of pancreatic and bile ducts in autoimmune pancreatitis.

AIM: To examine the involvement of the pancreatic and bile ducts in patients with autoimmune pancreatitis. METHODS: Clinical and cholangiopancreatographic findings of 28 patients with autoimmune pancreatitis were evaluated. For the purposes of this study, the pancreatic duct system was divided into three portions: the ventral pancreatic duct; the head portion of the dorsal pancreatic duct; and the body and tail of the dorsal pancreatic duct. RESULTS: Both the ventral and dorsal pancreatic ducts were involved in 24 patients, while in 4 patients only the dorsal pancreatic duct was involved. Marked stricture of the bile duct was detected in 20 patients and their initial symptom was obstructive jaundice. Six patients showed moderate stenosis to 30%-40% of the normal diameter, and the other two patients showed no stenosis of the bile duct. Although marked stricture of the bile duct was detected in 83% (20/24) of patients who showed narrowing of both the ventral and dorsal pancreatic ducts, it was not observed in the 4 patients who showed involvement of the dorsal pancreatic duct alone (P=0.0034). CONCLUSION: Both the ventral and dorsal pancreatic and bile ducts are involved in patients with autoimmune pancreatitis.

Usefulness of biopsying the major duodenal papilla to diagnose autoimmune pancreatitis: a prospective study using IgG4-immunostaining.

AIM: To examine the histological and immunohistochemical findings of biopsy specimens taken from the major duodenal papilla of autoimmune pancreatitis (AIP) patients. METHODS: The major duodenal papilla in the resected pancreas of 3 patients with AIP and of 5 control patients [pancreatic carcinoma (n = 3) and chronic alcoholic pancreatitis (n = 2)] was immunostained using anti-CD4-T cell, CD8-T cell and IgG4 antibodies. Forceps biopsy specimens taken from the major duodenal papilla of 2 patients with AIP and 5 control patients with suspected papillitis were prospectively taken during duodenoscopy and immunohistochemically examined. RESULTS: Moderate or severe lymphoplasmacytic infiltration including many CD4-positive or CD8-positive T lymphocytes and IgG4-positive plasma cells (>or=10/HPF), was observed in the major duodenal papilla of all 3 patients with AIP. The same findings were also detected in the biopsy specimens taken from the major duodenal papilla of 2 patients with AIP, but in controls, there were only a few (

Sclerosing cholecystitis associated with autoimmune pancreatitis.

AIM: To evaluate the histopathological and radiological findings of the gallbladder in patients with autoimmune pancreatitis (AIP). METHODS: The radiological findings of the gallbladder of 19 AIP patients were retrospectively reviewed. Resected gallbladders of 8 AIP patients were examined histologically and were immunostained with anti-IgG4 antibody. Controls consisted of gallbladders resected for symptomatic gallstones (n = 10) and those removed during pancreatoduodenectomy for pancreatic carcinoma (n = 10), as well as extrahepatic bile ducts and pancreases removed by pancreatoduodenectomy for pancreatic carcinoma (n = 10). RESULTS: Thickening of the gallbladder wall was detected by ultrasound and/or computed tomography in 10 patients with AIP (3 severe and 7 moderate); in these patients severe stenosis of the extrahepatic bile duct was also noted. Histologically, thickening of the gallbladder was detected in 6 of 8 (75%) patients with AIP; 4 cases had transmural lymphoplasmacytic infiltration with fibrosis, and 2 cases had mucosal-based lymphoplasmacytic infiltration. Considerable transmural thickening of the extrahepatic bile duct wall with dense fibrosis and diffuse lymphoplasmacytic infiltration was detected in 7 patients. Immunohistochemically, severe or moderate infiltration of IgG4-positive plasma cells was detected in the gallbladder, bile duct, and pancreas of all 8 patients, but was not detected in controls. CONCLUSION: Gallbladder wall thickening with fibrosis and abundant infiltration of IgG4-positive plasma cells is frequently detected in patients with AIP. We propose the use of a new term, sclerosing cholecystitis, for these cases that are induced by the same mechanism as sclerosing pancreatitis or sclerosing cholangitis in AIP.

Pancreatic cancer with a high serum IgG4 concentration.

Differentiation between autoimmune pancreatitis and pancreatic cancer is sometimes difficult. It has been reported that serum IgG4 concentrations are significantly elevated and particularly high (>135 mg/dL) in autoimmune pancreatitis. Measurement of serum IgG4 has become a useful tool for differentiating between autoimmune pancreatitis and pancreatic cancer. However, we present a 74-year-old female with a markedly elevated serum IgG4 (433 mg/dL) who underwent pancreaticoduodenectomy for pancreatic cancer. Elevated serum IgG4 levels continued after the resection. On histology, adenocarcinoma of the pancreas accompanied with moderate lymphoplasmacytic infiltration infiltrated the lower bile duct and duodenum, but there were no findings of autoimmune pancreatitis. Although a small metastasis was detected in one parapancreatic lymph node, regional lymph nodes were swollen. Abundant IgG4-positive plasma cells infiltrated the cancerous areas of the pancreas, but only a few IgG4-positive plasma cells were detected in the noncancerous areas. Pancreatic cancer cells were not immunoreactive for IgG4. An abundant infiltration of IgG4-positive plasma cells was detected in the swollen regional lymph nodes and in the duodenal mucosa. We believe that the serum IgG4 level was elevated in this patient with pancreatic cancer as the result of an IgG4-related systemic disease that had no clinical manifestations other than lymphadenopathy.

MRCP and MRI findings in 9 patients with autoimmune pancreatitis.

AIM: To evaluate magnetic resonance cholangiopancreatography (MRCP) findings in conjunction with magnetic resonance (MR) images in autoimmune pancreatitis (AIP) patients. METHODS: Nine patients with AIP underwent MRI, MRCP, endoscopic retrograde cholangiopancreatography (ERCP), computed tomography, and ultrasonography. The MRCP and MR images taken before and after steroid therapy were reviewed and compared with other imaging modalities. The MRCP findings of the AIP cases were compared to those of 10 cases with carcinoma of the head of the pancreas. RESULTS: On MRCP, the narrowed portion of the main pancreatic duct noted on ERCP was not visualized, while the non-involved segments of the main pancreatic duct were visualized. The degree of upstream dilatation of the proximal main pancreatic duct was milder than that seen in cases of pancreatic carcinoma. Stenosis or obstruction of the lower bile duct was detected in 8 patients. MR images showed enlargement of the pancreas with decreased signal intensity on T1-weighted MR images, increased signal intensity on T2-weighted MR images, and, in 3 patients, a hypointense capsule-like rim. After steroid therapy, the previously not visualized portion of the main pancreatic duct was seen, along with improvement of the bile duct stenosis. Pancreatic enlargement decreased, and the abnormal signal intensity on both T1- and T2-weighted MR images became isointense. CONCLUSION: MRCP cannot differentiate irregular narrowing of the main pancreatic duct seen with AIP from stenosis of the main pancreatic duct seen with pancreatic carcinoma. However, MRCP findings in conjunction with MR imaging of pancreatic enlargement that shows abnormal signal intensity on T1- and T2-weighted MR images are useful in supporting a diagnosis of AIP.

Pancreaticopleural fistula visualized by computed tomography scan combined with pancreatography.

CONTEXT: We report a case of a pancreaticopleural fistula which was clearly demonstrated by computed tomography (CT) scan following pancreatography and which was successfully treated with endoscopic nasopancreatic drainage combined with octreotide. CASE REPORT: A 52-year-old male was admitted to our hospital for additionally evaluation of bilateral pleural effusion. The pleural fluid amylase level was markedly elevated. Endoscopic retrograde pancreatography showed a cyst in the body of the pancreas and extravasation of contrast medium extending cranially from the cyst. The disease was treated successfully with endoscopic nasopancreatic drainage combined with the administration of octreotide. A pancreaticopleural fistulous route was clearly demonstrated by CT scan following pancreatography through the nasopancreatic drainage tube. CONCLUSIONS: A CT scan following pancreatography was useful in demonstrating a pancreaticopleural fistulous route.

Digestion and absorption of patients with autoimmune pancreatitis.

BACKGROUND/AIMS: In patients with autoimmune pancreatitis, radiological, serological and pancreatic functional abnormalities usually improve with steroid therapy. However, no studies have specifically focused on digestion and absorption in such patients. This study aims to investigate digestion and absorption, in addition to pancreatic endocrine and exocrine function, and their responses to steroid therapy in patients with autoimmune pancreatitis. METHODOLOGY: Ideal body weight index, levels of serum albumin, total cholesterol and glucose, or glycosylated hemoglobin values were investigated in 22 patients with autoimmune pancreatitis. N-benzoyl-L-tyrosyl-paraminobenzoic acid excretion test was performed in 9 patients. In 10 patients treated with steroids, these factors were examined again about 2 months after medication. RESULTS: Levels of serum albumin decreased, while ideal body weight index and levels of serum albumin and cholesterol significantly increased after steroid therapy. Eleven (50%) patients showed evidence of diabetes mellitus, but this improved in 6 of 8 patients treated with steroids. Pancreatic exocrine function was reduced in 88% of patients. Impaired pancreatic exocrine function improved after steroid therapy in 3 of 7 patients treated. CONCLUSIONS: Mild malnutrition as well as impaired pancreatic endocrine and exocrine function were frequently detected in patients with autoimmune pancreatitis. Steroid therapy was occasionally effective for these conditions.

Biliary carcinoma risk in patients with pancreaticobiliary maljunction and the degree of extrahepatic bile duct dilatation.

BACKGROUND/AIMS: Pancreaticobiliary maljunction (PBM) carries a high risk of biliary carcinoma. This study aimed to examine the biliary complications of patients with PBM in relation to the degree of extra-hepatic bile duct dilatation. METHODOLOGY: Ninety-eight cases of PBM could be divided into 5 groups according to the maximum diameter of the extrahepatic bile duct: < or = 10mm, 11-15mm, 16-20mm, 21-30mm, > or = 31mm. The clinicopathological findings of biliary carcinomas associated with PBM were compared with 232 cases of gallbladder carcinoma and 159 cases of bile duct carcinoma that were not associated with PBM. RESULTS: Gallbladder carcinoma occurred in 36 of 65 patients (55%) with PBM whose maximum diameter of the extrahepatic bile duct was < or = 30mm, but no gallbladder carcinoma occurred in patients with PBM whose diameter was > or = 31mm. Bile duct carcinoma occurred in 6 of 52 patients (12%) with PBM whose diameter was > or = 21mm, but no bile duct carcinoma occurred in patients with PBM whose diameter was < or = 20mm. The age at diagnosis of the patients with gallbladder or bile duct carcinoma associated with PBM was significantly younger than those without PBM (p<0.01). CONCLUSIONS: PBM with an extrahepatic bile duct diameter < or = 30mm is associated with a high risk of gallbladder carcinoma. PBM with an extrahepatic bile duct diameter > or = 21mm is associated with a high risk of bile duct carcinoma. Prophylactic cholecystectomy is recommended for patients with PBM without biliary dilatation.

Comparison of radiological and histological findings in autoimmune pancreatitis.

BACKGROUND/AIMS: Autoimmune pancreatitis displays radiological findings that are sometimes difficult to differentiate from pancreatic carcinoma. To understand the essential radiological features of autoimmune pancreatitis (AIP), we compared imaging and histological findings in resected AIP specimens. METHODOLOGY: Findings of ultrasonography, computed tomography, endoscopic retrograde cholangiopancreatography and angiography were examined retrospectively for 6 patients who underwent pancreatoduodenectomy on suspicion of pancreatic carcinoma, and compared with histological findings of the resected specimens. RESULTS: Ultrasonography showed an enlarged hypoechoic pancreas with sausage-like appearance and no lobulation in the contour of the pancreas. On computed tomography imaging, delayed enhancement of the swollen pancreatic parenchyma became evident. Dense lymphoplasmacytic infiltration with fibrosis involving peripancreatic tissue was observed throughout almost the entire pancreas. Periductal non-occlusive fibrosis with lymphoplasmacytic infiltration induced narrowing of the pancreatic duct. Stenosis of the common bile duct is frequently associated with autoimmune pancreatitis and is induced by diffuse thickening of the duct wall by the same inflammatory process as that of the pancreas. The fibroinflammatory process also involves blood vessels. CONCLUSIONS: Characteristic radiological findings of autoimmune pancreatitis are induced with systemic histological changes of lymphoplasmacytic infiltration with fibrosis, and differ from schirrous invasion of pancreatic carcinoma.

An examination of co-infection in acute gastroenteritis and histo-blood group antigens leading to viral infection susceptibility.

The aim of the present study was to evaluate co-infection in the gastrointestinal tract in terms of viruses, bacteria and the ABO blood group. We hypothesized that a combination of norovirus (NV) and bacteria in the gastrointestinal tract could affect the likelihood of an individual to contracting NV. Histo-blood group antigens (HBGAs) are considered to act as receptors that can lead to NV susceptibility. In addition to genetics, co-infection in the gastrointestinal tract may be associated with this mechanism. A total of 370 patients with acute gastroenteritis presenting with diarrhea (14-89 years) were recruited. The male/female ratio was 20/17. Single infection (bacteria or virus), co-infection with two viruses, and co-infection with one virus and one bacterium were statistically analyzed. In total, 88 of the 376 subjects (23.4%) were positive for one virus, and 50 (13.3%) were positive for one bacterium. Co-transfection with bacteria and a virus were detected in 46 (47.9%) of the 96 bacterial gastroenteritis cases. Statistical analysis revealed that co-infection of bacteria and NV was not significant in all viral infections (P=0.768). In terms of the ABO histo-blood group type and NV infection, the frequency in the O type was not significantly increased (P=0.052). Co-infection of bacteria and a virus occurred frequently in the gastrointestinal tract. The ABO blood phenotype expression was not a significant factor in NV infection in the present case series and the results did not suggest an affinity of NV for specific bacteria.