Gastric Microflora Research Articles

Vaccination preventsHelicobacter pylori-induced alterations of the gastric flora in mice

Molecular analysis of the gastric microflora in mice revealed that Helicobacter pylori infection causes an increase in microbial diversity. The stomachs of H. pylori-infected animals were colonized by bacteria which are naturally restricted to the lower intestinal tract. Clostridia, Bacteroides/Prevotella spp., Eubacterium spp., Ruminococcus spp., streptococci and Escherichia coli were detected exclusively in the stomachs of infected animals, whereas lactobacilli dominated the gastric flora in noninfected mice. The H. pylori-induced shifts in the gastric microbiota were independent from histological pathology and from changes in the gastric pH but were prevented by immunization of mice with live Salmonella expressing H. pylori urease. Immunized mice displayed reduced H. pylori levels in the gastric epithelium and developed a normal gastric microflora, indicating that vaccination may be protective against H. pylori-induced changes in the gastric flora.

Cimetidine and the potential risk of postoperative sepsis.

The gastric microflora of patients receiving cimetidine for duodenal ulceration has been investigated and the results compared with those from a group of untreated patients. Cimetidine-induced hypochlorhydria allows bacterial proliferation in the stomach; 75 per cent of aspirates from 44 fasting patients taking cimetidine 1 g daily were found to contain bacteria 2--4 h after the last dose. Of 41 patients taking cimetidine 400 mg at night, 34 per cent still had bacteria in their aspirates 12--13 h later. Patients treated with cimetidine are likely to be at an increased risk of postoperative sepsis. The drug should either be withdrawn before gastric surgery is undertaken or patients with gastric contents of pH 4 or above should receive antibiotic cover.

Effect of combinations of organic acids in weaned pig diets on microbial species of digestive tract contents and their response on digestibility

The effect of combinations of organic acids on digestive microbial population and total tract digestibility of piglets was studied. Thirty 19-21 days weaned pigs (5.4 +/- 0.23 kg, six pigs per treatment) were given a mixed feed with 10 ml water/kg (CTL) or 200 mEq/kg of formic acid (FOR), 1:1 formic:fumaric (FOFU), 1:1 formic:lactic (FOLA) or 2:1 formic:lactic (2FOLA). After 6-8 days, animals were slaughtered. In gastric contents, pH was higher (p = 0.01) with FOFU and lactobacilli tended (p = 0.08) to be lower with FOFU than CTL and FOLA, but coliform counts did not differ (p = 0.14). Acetate proportion was lower (p = 0.03), and propionate (p = 0.05) and butyrate (p = 0.01) higher, with FOFU than CTL, FOLA and 2FOLA. Intestinal coliform counts were higher (p = 0.03) with CTL than FOLA and 2FOLA, but there were no differences on lactobacilli. In intestinal contents, acetate tended (p = 0.06) to be lower with FOR than FOLA and 2FOLA, and butyrate was higher (p = 0.001) with FOR. Although not significantly, dry matter digestibility was 0.03-0.05 lower with CTL than with the other treatments. Combinations of organic acids in piglet diets modify gastric and intestinal microflora, the mixtures of formic:lactic appearing as the most interesting.

Adrenomedullin and mucosal defence: interaction between host and microorganism

Many surface epithelial cells express adrenomedullin (AM) and it is postulated that it may have an important protective role. This peptide has many properties in common with other cationic antimicrobial peptides including the human β-defensins. Antimicrobial activity against members of the human skin, oral, respiratory tract and gastric microflora has been demonstrated. Both pathogenic and commensal strains of bacteria are sensitive; Gram-positive and Gram-negative bacteria being equally susceptible. No activity against the yeast Candida albicans was observed. Minimum inhibitory and minimum bacteriocidal concentrations range from 7.75×10 −4 to 12.5 and 0.003 to >25.0 μg ml −1, respectively. On exposure of oral, skin and gastric epithelial cells to whole cells and culture supernatants from bacteria isolated from these sites an increase in AM peptide and gene expression has been observed. No upregulation was detected with C. albicans. In cultured cells and an animal infection model increased AM peptide and gene expression has been demonstrated using immunohistochemical and in situ hybridization techniques. These collective findings suggest that AM represents a new category of antimicrobial peptide, which contributes to the mucosal host defence system.

Effect of type and level of fibre on gastric microbial activity and short-chain fatty acid concentrations in gestating sows

The present study was undertaken to study the effect of dietary fibre on gastric microflora, and short-chain fatty acids (SCFA) concentrations at different time after feeding in gestating sows. Three experimental diets consisting of two dietary fibre-rich diets and one concentrated, low dietary fibre diet (C) were used. One fibre-rich diet contained soluble dietary fibre from sugar beet pulp (S) and the other contained insoluble dietary fibre from wheat bran (W). The experiment was carried out as repeated 3×3 Latin squares with six gastric-cannulated gestating sows fed one of the three experimental diets, with experimental periods of 7 days, comprising 3 days of adaptation to each diet, followed by 4 days of collection of gastric digesta. The gastric digesta were evacuated once daily through the gastric cannula in a randomized order 0.5, 1, 2, 3, 5 and 15.5 h after feeding the morning meal. The evacuated gastric digesta were quantified and a representative sample collected for measuring pH, dry matter (DM) content, SCFA, density of various bacterial populations (including coliform bacteria, lactic acid bacteria, lactobacilli, enterococci and yeasts), adenosine 5′-triphosphate (ATP), and adenylate energy charge (AEC). With all three diets, gastric pH was highest at 0.5 h after feeding, and then fell gradually with increasing time (especially between 0.5 and 2 h) after feeding. The changing trend of pH with the three diets was not significantly different. The total counts of coliform bacteria, lactic acid bacteria, lactobacilli, enterococci and yeasts were also highest at 0.5 h after feeding, in agreement with gastric pH values. The population of coliform bacteria with diet S decreased significantly compared with diet C or diet W ( P<0.05). The concentration of gastric ATP was highest at 15.5 h after feeding. The level of acetate had the lowest value at 0.5–1 h with diets S and C, but at 2 h with diet W. In conclusion, gastric pH was unstable at different time after feeding, and was highest at 0.5 h after feeding. The highest populations of various gastric bacteria were found at 0.5 h after feeding, irrespective of type of diet. As gastric pH increased, gastric microbial activity was inhibited. The populations of lactic acid bacteria and lactobacilli with the insoluble dietary fibre were always higher than with the soluble dietary fibre at all times after feeding. Soluble dietary fibre increased the level of acetate.

Gut origin of sepsis: a prospective study investigating associations between bacterial translocation, gastric microflora, and septic morbidity

AIMSTo investigate the “gut origin of sepsis” hypothesis.METHODSProspective controlled study of 279 surgical patients in which cultures of nasogastric aspirates were compared with those obtained from mesenteric lymph nodes taken...

The normal gastric microflora and Helicobacter pylori; before, during and after treatment with omeprazole and amoxycillin

Objective To study the microflora in patients with Helicobacter pylori infection during treatment with omeprazole alone and in combination with amoxycillin, to study transmission of relapsing H. pylori strains by fingerprinting and to investigate if H. pylori is detectable in saliva and dental plaque by polymerase chain reaction (PCR). Methods Twenty-eight dyspeptic patients with H. pylori infection were divided into two treatment groups omeprazole 20 mg plus amoxycillin 1000 mg, or omeprazole 20 mg plus placebo twice a day for 14 days. Biopsies were taken before, during and after treatment. The biopsies were cultivated in order to study the commensal microflora and H. pylori PCR was used to detect H. pylori in the biopsies, saliva and dental plaque. The H. pylori strains were fingerprinted with arbitrary primed PCR. Results Twenty-five patients harbored H. pylori , of whom 22 also harbored a normal mucosal microflora. H. pylori was present in all patients in the omeprazole-placebo group and in 39% of the patients in the omeprazole-amoxycillin group 4 weeks after treatment. There were no significant differences in the number of bacteria in antrum and corpus. Conclusions There was an inverse relationship between the growth of commensal microflora and H. pylori during treatment in both groups. H. pylori was detectable in saliva and dental plaque by PCR. The original H. pylori strain was present in all but one relapsing patient.

The Importance of Urease in Acid Protection for the Gastric-colonising BacteriaHelicobacter pyloriandHelicobacter felissp. nov

The urease of the gastric pathogen Helicobacter pylori shares numerous characteristics with the urease of a bacterium isolated from cat gastric mucosa, Helicobacter felis sp. nov. The native enzymes have similar apparent molecular weights and, when subjected to SDS-PAGE, disassociate into active subunits of comparable relative mobilities. In contrast, a bacterium (St1) that colonises rodent ileal mucosa, and is related to Helicobacter spp., expresses a distinct urease from those of the gastric bacteria. Cell-free preparations of H. felis and of four strains of H. pylori had mean apparent K m values of 0.5 ± 0.2 mM and 0.4 ± 0.1 mM urea, respectively. The K m value estimated for cell-free extracts of St 1 was 1.7 ± 0.3 mM urea. Under physiological conditions ([urea] = 3 mM), this difference was unlikely to be important. Of several ureolytic bacteria tested, only H. pylori and H. felis tolerated acid when a physiological level of urea was present. It was concluded that urease is important for the protection of H. felis and H.pylori from lethal gastric acidity. This acid protection may be dependent upon the intrinsic acid stability of the ureases, both enzymes retaining substantial activity between pH 4 and 6. Inhibition of urease activity in vivo , by treatment of mice with acetohydroxamic acid, significantly reduced gastric colonisation by H. felis , whilst treatment of already colonised animals had no effect. This finding confirms the importance of urease in the initial steps of colonisation, prior to entry of bacteria into the neutral mucous layer. Keywords: Helicobacter ( Campylobacter ) pylori ; Helicobacter spp.; Urease; Mucosa-associated bacteria; Spiral/ helical bacteria; Gastric microflora.

Gastric nitrate reduction and nitrosation of trimethylurea in swine treated with pentagastrin or cimetidine

Swine were treated with cimetidine in order to quantify the reduction of nitrate to nitrite and the gastric formation of N-nitrosotrimethylurea (NTMU) under conditions similar to those in the achlorhydric human stomach. Gastric-fistulated swine were instilled with 6.0 mmol of nitrate in 50 ml water, after which gastric nitrate, nitrite and pH were monitored. Trimethylurea, 250 mumol in 50 ml water, was instilled via the fistula 10 min following the peak gastric nitrite concentration. Similar experiments were conducted with pentagastrin-stimulated animals, in order to quantitate the effect of gastric pH and microflora on the presence of nitrate, nitrite and NTMU formation. The stomachs of cimetidine-treated pigs (elevated pH) were colonized by nitrate reductase organisms to levels of 10(4)-10(7)/ml gastric fluid. Gastric nitrite concentration in cimetidine-treated animals reached a maximum of 370-2085 microM, 60 min following the nitrate dose. Trimethylurea was only marginally nitrosated (less than 0.1 mumol/l gastric fluid) in cimetidine- or pentagastrin-stimulated animals. The low yield of NTMU at elevated pH, in the presence of substantial nitrite, suggests that the nitrate-reducing bacteria present in the porcine stomach did not catalyze trimethylurea nitrosation in vivo.

Septic complications in relation to factors influencing the gastric microflora in patients undergoing gastric surgery

Postoperative septic complications and micro-organisms found in primary infections were studied in 750 gastric operations performed between 1972 and 1986. The overall rate of primary infections was 23%. The infection rates were related to the diagnosis and to factors that could influence the colonization of the stomach. No significant differences in the rates of postoperative infections were found between patients who had received preoperative antibiotic prophylaxis and those who had not. In all groups of patients, aerobic and anaerobic gram-positive and gram-negative bacteria and yeasts were isolated in primary infections. Enterobacteriaceae, enterococci and Bacteroides fragiis were more frequent in patients with gastric bleeding or carcinoma.

Gastric microflora in patients receiving H2-blocker

The gastric microflora of 21 cases receiving histamine H2-receptor antagonists (H2-blocker) were studied. Patients not given H2-blocker were also examined for gastric microflora. The gastric pH of patients who were receiving H2-blocker ranged from 1.91 to 6.51 (mean, 4.32). The gastric pH of over 5.00 was seen in 10 cases. Aerobic bacteria were isolated from 20 cases (95%). Aerobic bacterial counts per ml of gastric aspirates correlated positively with the pH of those aspirates but was little correlation between the pH of the gastric aspirates and the number of anaerobic bacteria of the samples, which were positive in 7 cases (33%). Candida and Staphylococcus were predominant isolates with positive rates of 82% and 41%, respectively. While Fusobacterium was isolated from 33% of the samples, none of the Bacteroides fragilis group organisms were isolated. It was also observed in the control group that aerobic and anaerobic bacteria were isolated from the gastric aspirates with high pH. These results suggest that in patients receiving H2-blocker anaerobes as well as aerobes may have the possibility to become pathogen for aspirate pneumonia and so on because of the overgrowth of anaerobic bacteria in the gastric fluid.

Relative volume of membrane microflora and epitheliocyte morphology after combined helium-neon laser irradiation of chronic gastric ulcers and vagotomy

The relative volume of the microflora located directly on the surface of epitheliocytes in different parts of the stomach, especially the pyloroantral part, to which the name membrane microflora (MM) has been given, is increased in chronic ulcers and after vagotomy [4]. The gastric microflora and, in particular, Cc~rpylobacter pyloridis, are ascribed an important role in the development of gastritis and peptic ulcer [8, 12, 13].

Use of continuous culture to study the gastric microflora of a hypochlorhydric patient

A method of maintaining the microflora obtained from the hypochlorhydric stomach of a patient suffering from hypogammaglobulinaemia has been developed using continuous culture (chemostat) techniques. The culture was maintained at pH 8.0 (the pH of the original gastric juice) and subsequently at pH 7.0 and pH 6.0. Throughout the experiment the total population of the culture remained constant, although the populations of individual bacterial strains varied. Two enzyme parameters, nitrate reductase and β-glycosidase, were also measured. Optimal enzyme activity was observed at pH 7.0. The results suggest that at the physiological pH values found in hypochlorhydric patients, the gastric flora may play a role in the generation of genotoxins and/or their precursors.

Gastrin, gastric acid secretion, and gastric microflora in patients with rheumatoid arthritis.

The relation between the basal and stimulated gastric acid secretion, plasma gastrin, and the gastric microflora was examined in 45 patients with rheumatoid arthritis. Sixteen patients (36%) had basal achlorhydria, and of these, 10 (22%) had achlorhydria or hypochlorhydria after stimulation with pentagastrin. The peak acid output and acidity showed inverse correlation with the disease duration but were not associated with age or with the degree of physical disability. Hypergastrinaemia was found in nine patients (20%), of whom 6 (13%) had significant titres of parietal cell antibody. The acidity of the peak acid output showed negative correlation with plasma gastrin. It was confirmed that the gastric secretory state is a determinant of plasma gastrin levels and in addition influences the growth of micro-organisms in the gastric lumen. The type of microflora in the non-acid stomach was similar to that found in the saliva. A subgroup of eight females was identified who showed low gastric acid secretion rates, positive bacterial cultures, and atlantoaxial subluxation. Gastrin- and insulin-like immunoreactivities were found in joint fluid. The concentrations reflected their plasma levels, suggesting that the peptides are not released at the inflammatory site, but rather that they reach synovial fluid from circulating blood.

Clostridial Myonecrosis of the Chest Wall Complicating Spontaneous Esophageal Rupture

Spontaneous rupture of the esophagus (Boerhaave's syndrome) has a dismal survival rate without prompt surgical management. A variety of surgical regimens have achieved survival of 70% or greater; however, the postoperative course is frequently complicated by fistula, would infection, empyema, and sepsis. We report an unusual postoperative chest wound infection of clostridial myonecrosis, which presumably originated from the patient's gastric microflora. He was treated with immediate surgical debridement of all involved tissue, prolonged ventilation, total parenteral nutrition, and frequent dressing changes. The remaining defect was closed with a skin graft. Anaerobic wound infections of the chest wall and their management are discussed.

Gastrointestinal microecology in the critically ill neonate

The fecal and gastric microflora of 178 critically ill neonates was compared with that of 30 normal full-term infants. Significant findings included increased frequency of single species retrieval and decreased frequency of mixed aerobic-anaerobic fecal cultures in the ill infants. Also noted were increased retrieval of pathogenic organisms, ie, staphylococcus aureus from gastric and fecal cultures of the ill infants, and decreased retrieval rates of Escherichia coli enterococcus, B fragilis, and other anaerobes in the feces of this group. Yeast retrieval was increased in the feces of the ill neonates. Statistical analysis showed that delivery route, birth weight, and antibiotic therapy were significantly related to the retrieval rates of certain organisms in the gastric and fecal flora of the ill neonate. Given the breast-fed and formula-fed infants have different normal floral patterns, this study suggests that the flora of the ill neonate conforms to a different pattern. Implications in the prevention and treatment of various neonatal septic processes may be drawn from this data.

Rate of wound sepsis with "selective" short-term antibiotic prophylaxis in gastric surgery.

AbstractA policy of selective antibiotic prophylaxis was used in 75 consecutive patients undergoing elective gastric operation. Only patients with preoperative bacterial counts in the gastric aspirate exceeding 106 organisms/ml were given antibiotics, and the choice of agent was determined by preoperative gastric culture. Using this policy, only 8% of patients developed wound sepsis and only 19 patients received an antibiotic. There was a close correlation between the pH of the gastric aspirate and bacterial contamination, which indicates that the measurement of the pH may serve as a basis for prophylactic antibiotic administration and obviate the need for elaborate preoperative bacteriological studies. The results were significantly better than in a previous group of 73 patients who were given no antibiotic cover irrespective of the preoperative gastric microflora.

GASTROINTESTINAL MICROFLORA IN INFANTS WITH NECROTIZING ENTEROCOLITIS (NEC)

Gastric and fecal microflora were studied in 3 groups of infants: 1-27 infants with NEC; II-41 Infants in the same neonatal intensive care unit; III-30 full-term neonates. There were no significant differences among the groups except for the geatational ages and birth weights in group III. Significantly greater (p<0.05) numbers of gram negative aerobic species were isolated from gastric aspirates of NEC patients than from infants and controls; for K. pneumoniae the difference between NEC infants and controls was significant at p<0.001. Fecal gram negative aerobic organisms were recovered from infants with NEC in a frequency similar to full-term infants but greater (p<0.01) than other sick neonates. Fecal anaerobes were recovered from infants with NEC and other sick neonates significantly less frequently (p<0.005) than from healthy infants. Analysis of the gastric and fecal microflora of infants with NEC shows a characteristic pattern. This may, in part, account for the development of NEC in certain infants. It may also explain the benefits accrued from aminoglycoside therapy in NEC.

Septic Complications Following Gastric Surgery: Relationship to the Endogenous Gastric Microflora

The microflora of the stomach is derived from both the ingestion of food and saliva and the reflux of proximal intestinal contents through the pylorus. Normally, this microflora is inhibited by gastric acid and normal gastric motility. In disease states, however, such as bleeding or obstructing duodenal ulcer, gastric ulcer or carcinoma, the level of gastric acid is reduced or the gastric motility is altered. Thus, endogenous microflora persists and often becomes the source of postoperative wound infections following gastric resection.

Intragastric microbial colonization in common disease states of the stomach and duodenum.

Forty-nine patients undergoing elective or emergent gastric surgery have been included in this study. Gastric needle aspiration was performed at the time of surgery in each case, followed by qualitative aerobic and anaerobic bacteriologic analysis. In 18 patients undergoing elective operation for chronic nonobstructing duodenal ulcer a gastric microflora was present in only three patients and no postoperative wound infections were observed. In 29 of 31 patients, in the other groups of patients with bleeding or obstructing duodenal ulcer or in those with gastric ulcer or malignancy, intragastric micro-organisms were present. Six of the 7 postoperative wound infections which developed in these groups of patients were due to one of the same bacteria isolated at the time of original needle aspiration. It appears that the endogenous intragastric microflora is a significant factor in the development of postoperative wound sepsis following gastric resection, in those groups of patients with a compromise of their normal gastric antibacterial inhibitory mechanisms.