Commensal Gut Flora Research Articles

Anti-tumor necrosis factor treatment restores the gut barrier in Crohn's disease.

A primary defect of the tight junctions and, hence, increased intestinal epithelial permeability has been proposed as a basic pathogenic event in Crohn's disease. Challenge of the mucosal immune system by the commensal gut flora would then result in chronic inflammation. Alternatively, increased permeability could be the result of inflammation. Our aim was to study intestinal permeability in refractory Crohn's disease before and after treatment with monoclonal chimeric antibodies directed against tumor necrosis factor (TNF) to investigate whether the abnormal permeability persists after control of inflammation. Twenty-three patients with active Crohn's disease were evaluated before and 4 wk after a single infusion of 5 mg/kg infliximab. Intestinal permeability was studied by measurement of urinary excretion of 51Cr-EDTA after oral intake. The increased permeation of 51Cr-EDTA through the small intestine (1.63% interquartile range [IQR] 1.06-2.07) and the overall permeation (3.27% IQR 2.40-4.38) before therapy decreased significantly after infliximab infusion to values (1.04% IQR 0.74-1.54 and 2.42% IQR 2.03-2.80, respectively) in the range of those found in normal volunteers (1.12% IQR 0.85-1.58 and 2.28% IQR 1.88-2.86, respectively). Inhibiting the proinflammatory cytokine tumor necrosis factor dramatically reduces gut inflammation and largely restores the gut barrier in Crohn's disease. Our data confirm the central role of TNF in gut barrier modulation in inflammatory conditions in vivo.

Anti-tumor necrosis factor treatment restores the gut barrier in Crohn’s disease

OBJECTIVES: A primary defect of the tight junctions and, hence, increased intestinal epithelial permeability has been proposed as a basic pathogenic event in Crohn’s disease. Challenge of the mucosal immune system by the commensal gut flora would then result in chronic inflammation. Alternatively, increased permeability could be the result of inflammation. Our aim was to study intestinal permeability in refractory Crohn’s disease before and after treatment with monoclonal chimeric antibodies directed against tumor necrosis factor (TNF) to investigate whether the abnormal permeability persists after control of inflammation. METHODS: Twenty-three patients with active Crohn’s disease were evaluated before and 4 wk after a single infusion of 5 mg/kg infliximab. Intestinal permeability was studied by measurement of urinary excretion of 51Cr-EDTA after oral intake. RESULTS: The increased permeation of 51Cr-EDTA through the small intestine (1.63% interquartile range [IQR] 1.06–2.07) and the overall permeation (3.27% IQR 2.40–4.38) before therapy decreased significantly after infliximab infusion to values (1.04% IQR 0.74–1.54 and 2.42% IQR 2.03–2.80, respectively) in the range of those found in normal volunteers (1.12% IQR 0.85–1.58 and 2.28% IQR 1.88–2.86, respectively). CONCLUSION: Inhibiting the proinflammatory cytokine tumor necrosis factor dramatically reduces gut inflammation and largely restores the gut barrier in Crohn’s disease. Our data confirm the central role of TNF in gut barrier modulation in inflammatory conditions in vivo.

An Analysis of Human Pathogens Found in Horse/Mule Manure Along the John Muir Trail in Kings Canyon and Sequoia and Yosemite National Parks

To determine the prevalence of microorganisms that are potentially pathogenic for humans in horse/mule manure along the John Muir Trail (JMT). Random samples of horse/mule manure were collected along sections of the JMT in Yosemite, Kings Canyon, and Sequoia national parks (NP), as well as in portions of the Pacific Crest Trail (PCT) and selected JMT/PCT access trails. Convenience samples of wild animal scat found within I mile of trails were also collected. The fresh specimens were individually preserved both in 0.9% saline and polyvinyl alcohol (PVA)-containing tubes and stored at 4 degrees C until time of analysis. Bacteriological analysis was performed using standard microbiology laboratory procedures. PVA samples were stained with trichrome and were then examined by a parasitologist. Collection: A total of 186 trail miles were sampled, including 113 on the JMT (Yosemite 37, Kings 53, and Sequoia 23). The PCT samplings included 24 miles, and NP and wilderness area access trails added an additional 49 miles. A total of 102 samples were collected, which included 81 samples from pack animals and 21 identified as having come from wild animals. Pack Animal Bacteria: All plated specimens grew large numbers of commensal gut flora. Potential pathogenic bacteria were found in only 12 samples and included Hafnia alvei (4), Serratia odorifera (1), Citrobacter freundii (1), Escherichia vulneris (1), Clostridium clostridioforme (1), Yersinia enterocolitica (1), Sherwinella putraformus (1), and Enterobacter spp (4). No Escherichia coli O157, Salmonella, or Aeromonas were found. Microscopic examination for protozoal organisms revealed occasional commensal ciliates and I Giardia. Wild Animal Pathogens: One specimen grew Y enterocolitica, and another grew Enterobacter amnigenus. We found a low prevalence of human pathogens in pack animal manure on the JMT.

Lymphoid Hyperplasia, Autoimmunity, and Compromised Intestinal Intraepithelial Lymphocyte Development in Colitis-Free Gnotobiotic IL-2-Deficient Mice

IL-2-deficient (IL-2(-/-)) mice develop disorders of the hemopoietic and immune systems characterized by anemia, lymphocytic hyperplasia, and colitis. The mechanisms responsible for these abnormalities remain unclear. To investigate the underlying basis of autoimmunity, the particular role of commensal gut flora in the initiation of colitis, and the role of IL-2 in the development of intestinal intraepithelial lymphocytes (iIEL), we evaluated IL-2(-/-) mice reared and maintained under gnotobiotic (germfree) conditions. By 8 wk of age, 80% (20 of 25) of germfree IL-2(-/-) mice show signs of disease, including anemia, disturbances in bone marrow hemopoietic cells, lymphocytic hyperplasia, and generalized autoimmunity, similar to those seen in specific pathogen-free (SPF) IL-2(-/-) mice. In striking contrast to SPF IL-2(-/-) mice, germfree IL-2(-/-) mice do not develop colitis. However, the numbers of gammadelta+ and TCR alphabeta+ CD8 alphaalpha+ iIELs are reduced, and in lethally irradiated SPF IL-2(+/+) mice, reconstituted with IL-2(-/-) bone marrow TCR gammadelta+ iIELs fail to develop, consistent with an important role of IL-2/IL-2R signaling in the development of gammadelta iIELs. Consequently, our findings demonstrate that the colitis seen in SPF IL-2(-/-) mice depends upon the presence of intestinal bacterial flora and that environmental Ags are not responsible for the anemia and extraintestinal lymphoid hyperplasia that occur in IL-2(-/-) mice. Thus, germfree IL-2(-/-) mice represent a unique system in which the role of IL-2 deficiency in hemopoietic and immune system disorders can be investigated in dissociation from complications that may arise due to colitis.

Serum antibodies to commensal oral and gut bacteria vary with age

This study examined the relationship between serum antibody levels to selected bacteria from the commensal oral and gut flora with increased age in a healthy adult population. A total of 116 healthy subjects were studied consisting of the following age groups: 20–39 years (group A), 40–59 years (group B), 60–79 years (group C) and 80 + years (group D). Only significantly lower mean IgM antibody levels to Streptococcus mutans strain Guy's serotype c were observed in older age groups ( P < 0.001). With Actinomyces viscosus NCTC 10951 significantly reduced IgM levels ( P < 0.02) and significantly elevated IgA levels were observed with increased age ( P < 0.05). IgA and IgG antibodies to Escherichia coli NCTC 10418 were increased significantly in the older age groups ( P < 0.001), whilst a trend toward lower levels of IgM antibodies was recorded with age. No changes in IgA antibodies to Streptococcus faecalis NCTC 775 were observed but the lowest level of IgM antibodies were detected in the oldest age group ( P < 0.05). Mean specific activity was decreased with age with IgM antibodies to the oral bacteria and increased with age with IgG and IgA antibodies to E. coli. Overall, our results suggest a general reduction in serum IgM antibody responses. This impairment in the circulatory IgM immune response may contribute to the increased occurrence of infections in the elderly.

Serum antibodies to commensal oral and gut bacteria vary with age.

This study examined the relationship between serum antibody levels to selected bacteria from the commensal oral and gut flora with increased age in a healthy adult population. A total of 116 healthy subjects were studied consisting of the following age groups: 20-39 years (group A), 40-59 years (group B), 60-79 years (group C) and 80+ years (group D). Only significantly lower mean IgM antibody levels to Streptococcus mutans strain Guy's serotype c were observed in older age groups (P < 0.001). With Actinomyces viscosus NCTC 10951 significantly reduced IgM levels (P < 0.02) and significantly elevated IgA levels were observed with increased age (P < 0.05). IgA and IgG antibodies to Escherichia coli NCTC 10418 were increased significantly in the older age groups (P < 0.001), whilst a trend toward lower levels of IgM antibodies was recorded with age. No changes in IgA antibodies to Streptococcus faecalis NCTC 775 were observed but the lowest level of IgM antibodies were detected in the oldest age group (P < 0.05). Mean specific activity was decreased with age with IgM antibodies to the oral bacteria and increased with age with IgG and IgA antibodies to E. coli. Overall, our results suggest a general reduction in serum IgM antibody responses. This impairment in the circulatory IgM immune response may contribute to the increased occurrence of infections in the elderly.

The germfree state prevents development of gut and joint inflammatory disease in HLA-B27 transgenic rats.

A number of inflammatory disease states occur with greatly increased frequency in individuals inheriting the human major histocompatibility complex class I allele HLA-B27. In a minority of cases, namely those with B27-associated reactive arthritis, there is good evidence that the disease state is triggered by infection with an enteric or genitourinary bacterial pathogen. For the majority of B27-associated disease, no definite pathogenetic role for bacteria has been established. However, in these latter cases intestinal inflammation can often be demonstrated, and it sometimes occupies a major part of the clinical picture. Rats transgenic for B27 are known to develop a disorder resembling B27-associated human disease, with prominent intestinal, joint, skin, and male genital inflammatory lesions. We report here that B27 transgenic rats raised in a germfree environment do not develop inflammatory intestinal or peripheral joint disease, whereas the skin and genital inflammatory lesions are unaffected by the germfree state. These findings support the concept that gut and joint inflammation are pathogenetically closely related, and they provide direct evidence that the commensal gut flora play an important role in the pathogenesis of B27-associated gut and joint inflammation.

Barophilic Bacteria Associated with Digestive Tracts of Abyssal Holothurians

Abyssal holothurians and sediment samples were collected at depths of 4,430 to 4,850 m in the Demerara abyssal plain. Bacterial concentrations in progressive sections of the holothurian digestive tract, as well as in surrounding surface sediments, were determined by epifluorescence microscopy. Total bacterial counts in sediments recently ingested by the animals were 1.5- to 3-fold higher than in surrounding sediments at the deepest station. Lowest counts were observed consistently in the foregut, where the digestive processes of the holothurian are believed to occur. In most animals, counts increased 3- to 10-fold in the hindgut. Microbial activity at 3 degrees C and in situ and atmospheric pressure were determined for gut and sediment samples by measuring the utilization of [C]glutamic acid, the doubling time of the mixed-population of culturable bacteria, and the percentage of the total bacterial count responsive to yeast extract in the presence of nalidixic acid, using epifluorescence microscopy. A barophilic microbial population, showing elevated activity under deep-sea pressure, was detected by all three methods in sediments removed from the hindgut. Transmission electron micrographs revealed intact bacteria directly associated with the intestinal lining only in the hindgut. The bacteria are believed to be carried as an actively metabolizing, commensal gut flora that transforms organic matter present in abyssal sediments ingested by the holothurian. Using data obtained in this study, it was calculated that sediment containing organic matter altered by microbial activity cleared the holothurian gut every 16 h, suggesting that abyssal holothurians and their associated gut flora are important participants in nutrient cycles of the abyssal benthic ocean.

Barophilic growth of bacteria from intestinal tracts of deep-sea invertebrates

Digestive tracts of abyssal scavenging amphipods and a deep-sea holothurian were examined for the presence of intestinal microflora capable of rapid proliferation under in situ pressures of 430 to 520 atmospheres (atm) and temperatures of 3-5°C. For two amphipod specimens, population doubling times of 5 and 6 hours were observed under in situ conditions, compared to 8 and 6 hours, respectively, at 1 atm. Growth enhancement under pressure was related inversely to initial population size and directly to concentration of available nutrient. In the case of the deposit-feeding holothurian, attached bacteria scraped from the intestinal lining showed a doubling time, under pressure, of 11 hours, compared to 36 hours for transient sediment bacteria that comprised the gut contents. These data suggest that deep-sea animals possess a commensal gut flora capable of responding to increased nutrient levels, via feeding of the host, without inhibition by the elevated hydrostatic pressures encountered in the deep ocean environment.

Bacteriostasis ofEscherichia coliby milk: IV. The bacteriostatic antibody of human milk

Bacteriostatic activity for milk-sensitive and milk-resistant strains of Escherichia coli is reduced when IgA is removed from milk by precipitation. Lysozyme is not involved in bacteriostasis and can be removed without loss of activity; heavy bentonite absorption however removes some lactoferrin causing partial loss of activity. The heat-labile antigen eliciting bacteriostatic antibody for E. coli is present in milk-sensitive and milk-resistant strains and in some other Enterobacteriaceae, e.g. salmonella; it cross reacts with the antigen in others, e.g. proteus and enterobacter. The antibody is therefore likely to be present in all human milk as a result of the normal commensal gut flora and with widespread activity.