Interactions of the invasive pathogens Salmonella typhimurium, Listeria monocytogenes, and Shigella flexneri with M cells and murine Peyer's patches

Invasive enteric bacteria must pass through the intestinal epithelium in order to establish infection. It is becoming clear that a common target for intestinal mucosa penetration is the specialized epithelial cell of Peyer's patches, the M cell. In order to gain a better understanding of how bacteria interact with M cells, we have compared the interactions of Salmonella typhimurium, Listeria monocytogenes, and Shigella flexneri with M cells by using a murine ligated-loop model. Our results indicate that S. typhimurium possesses a highly efficient mechanism for M cell entry that targets and destroys these cells, while L. monocytogenes and S. flexneri appear to be internalized into M cells in a less disruptive fashion. Early uptake of Listeria or Shigella into M cells appeared to lead to the death of some cells, as evidenced by the appearance of holes in the intestinal epithelium. At later time points, the follicle-associated epithelium of animals infected with these bacteria displayed extensive destruction. These data indicate that enteric pathogens use different strategies to interact with M cells and initiate infection of a host.     

Enteric pathogens in severe forms of acute gastroenteritis in Ghanaian children

Diarrheal disease is the major cause of childhood morbidity in developing countries. Although malnutrition is known as a risk factor for severe gastroenteritis, the role of enteric pathogens in the clinical severity is unclear. The present study was conducted in well nourished Ghanaian preschool children during a 3 month period of the rainy season to assess the relationship between enteric pathogens and severe gastroenteritis. Two hundred and twenty-five children with acute gastroenteritis and 64 age-matched control children were prospectively examined for the severity of dehydration and enteric pathogens in their stools. Of the 225 children with gastroenteritis, 69.8% (157/225) had mild dehydration and 30.2% (68/225) had severe dehydration. Bacteria were similarly isolated in stool samples from children with mild and severe dehydration and controls. Rotavirus accounted for 20.6% of children with severe dehydration and was more often isolated in stools from patients with severe dehydration than those from controls. Furthermore, the mixed infections associated with rotavirus and bacteria were more often found in patients with severe dehydration than those with mild dehydration or controls. Parasites were similarly found at low incidences among the three groups. The present study implied that rotavirus was more responsible for severe gastroenteritis than bacteria or parasites. However, factors other than enteric pathogens must be sought in a considerable number of severe cases. A large scale study throughout a year is recommended to obtain more precise information that would reflect the seasonal variation of rotavirus infections.     

Use of the swarming phenomenon for the purpose of isolating pure cultures of salmonellae from feces. I

The authors elaborated and tested a number of elective-differential media for swarming of salmonellae. When pure cultures of Proteus, E. coli and salmonellae were seded on these media the latter exeeded the rest of enteric bacteria by the intensity of swarming. In the capacity of saprophyte inhibitors the most effective were media with the addition of penicillin and sodium selenite. Satisfactory results were obtained on the mentioned media in isolation of salmonellae from the artificially contaminated feces by the method of swarming     

Etiopathogenesis of ankylosing spondylitis and reactive arthritis

In ankylosing spondylitis and reactive arthritis, an interplay of microbe and major histocompatibility complex initiates a sequence of events resulting in chronic inflammation. With the use of molecular probes as direct evidence and immune response patterns as indirect evidence, a strong case has been made for a central role of local microbial antigen in reactive arthritis. Cofactors such as gender, persistent gut inflammation, and antibiotic treatment may contribute to this process. Studies of transgenic rats and of familial spondylitis implicate B27 itself as the critical host variable. The results of recent studies point to intimate B27-bacteria interrelationships. HLA-B27 and proteins from enteric bacteria are structurally related, in a manner that may affect T cell response to enteric pathogens. B27 also may directly affect host-microbe interactions by modulating the invasive potential of these bacteria into target cells. Studies are in progress to apply the predictions of these in vitro systems to the in vivo situations of these diseases. The insights of research in the spondyloarthropathies may find broad applications in the rheumatic diseases.     

Resident enteric bacteria are necessary for development of spontaneous colitis and immune system activation in interleukin-10-deficient mice

Mice with targeted deletion of the gene for interleukin-10 (IL-10) spontaneously develop enterocolitis when maintained in conventional conditions but develop only colitis when kept in specific-pathogen-free (SPF) environments. This study tested the hypothesis that enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice. IL-10-deficient mice were maintained in either SPF conditions or germfree conditions or were populated with bacteria known to cause colitis in other rodent models. IL-10-deficient mice kept in SPF conditions developed colitis in all segments of the colon (cecum and proximal and distal colon). These mice exhibited immune system activation as evidenced by increased expression of CD44 on CD4(+) T cells; increased mesenteric lymph node cell numbers; and increased production of immunoglobulin A (IgA), IgG1, and IL-12 p40 from colon fragment cultures. Mice populated with bacterial strains, including Bacteroides vulgatus, known to induce colitis in other rodent models had minimal colitis. Germfree IL-10-deficient mice had no evidence of colitis or immune system activation. We conclude therefore that resident enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice.     

Fimbrial expression in enteric bacteria: a critical step in intestinal pathogenesis

The ability of species of enteric bacteria to recognize and colonize unique niches along the intestine is mainly based on receptor distribution and interpretation of a combination of environmental signals leading to the expression of specific adherence factors. Such elaborate orchestration of events is critical during the initial steps of pathogenesis.     

Partially purified soy hydrolysates retard proliferation and inhibit bacterial translocation in cultured C2BBe cells

Hydrolyzed soybean isolates SP-A and SP-B (Abbott Laboratories, OH), developed for use in enteral nutritional products, were tested in cultures of C2BBe cells, a colonic adenocarcinoma cell line with enterocytic differentiation, to evaluate effects on cell growth, maturation and ability to resist infection by enteric bacteria. SP-A delayed formation of confluent monolayers by 10 d compared with cells cultured without SP-A. SP-A also caused a retardation in the development of intercellular tight junctions as measured by transmonolayer electrical resistance (TER). SP-B had no effect on cell proliferation or TER of intestinal cell cultures. SP-A and SP-B enhanced the development of the brush border enzymes alkaline phosphatase and isomaltase over a 28 d period. By these criteria, SP-A and SP-B appear to affect intestinal epithelial cell development in culture. When C2BBe monolayers were exposed to the enteric bacteria, Salmonella typhimurium or Salmonella typhi, an inhibition of the passage of S. typhi was seen in cultures with SP-A and SP-B. No effect on the passage of S. typhimurium was seen with either soy isolate. Partially purified soy isolates therefore impart resistance to selected enteroinvasive bacteria. Addition of soy hydrolysates to the media of cultured intestinal cells may serve as a rapid and economical screening mechanism for preclinical trials that would test the therapeutic benefits of soybean isolates.     

Analysis of amino acid sequences of Rhodobacter sphaeroides glutamine synthetase

A comparative analysis of the amino acid sequence of glutamine synthetase (GS) of the photosynthetic purple bacterium Rhodobacter sphaeroides revealed that the enzyme is typical for first type procaryotic GSs and structurally resembles GSs of enteric bacteria. The data obtained indicate that the complex phenotype of purple bacterial mutants at the glnA gene coding for GS may be conditioned by specific regulation of nitrogen metabolism in bacterial cells rather than by structural-and-functional peculiarities of GS.     

A new substrate for the rapid evaluation of enteric microbial overgrowth

The possibility of a new approach to diagnosis of intestinal bacterial overgrowth has been evaluated in laboratory animals. The diagnostic test involves oral administration of an enzyme-labile substrate consisting of para-aminobenzoic acid (PABA) conjugated to a bile acid. In the presence of enteric bacteria, PABA is split from the bile acid and is rapidly absorbed and excreted in the urine. The amount of PABA recovered during the 6 hr following the administered dose of the conjugate may be used as an index of bacterial overgrowth in the upper-gastrointestinal tract. The procedure has been shown to be a reliable index of this condition in laboratory animal models.     

2,4,6-Trinitrotoluene (TNT) transformation by clostridia isolated from a munition-fed bioreactor: comparison with non-adapted bacteria

Several bacterial strains were examined for their ability to degrade the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). The strains examined included various clostridial strains isolated from a 4-year-old munition enrichment, related clostridial strains obtained from a culture collection, two enteric bacteria, and three lactobacilli. All Clostridium species tested were able to reduce TNT rapidly in a complex medium. In cell suspension experiments, these strains were also able to reduce 2,4-diamino-6-nitrotoluene (DANT) to 2,4,6-triaminotoluene (TAT) and to produce a compound that is not yet identified; thus, they could not be distinguished from one another with regard to the pathway of transformation. The enteric strains and the lactobacilli were able to perform the initial reduction of TNT, but none was capable of reducing DANT in cell suspensions.     

A case of split notochord syndrome: presence of dorsal enteric diverticulum adjacent to the dorsal enteric fistula

Like umblical enteric remnants (eg, umblical sinus and omphalomesenteric fistula), enteric remnants can be seen on the dorsal aspect of the body (dorsal enteric sinus, dorsal enteric fistula IDEF], dorsal enteric diverticulum) in conjunction with complete cleft of the vertebral column. Complete cleft of the vertebral column associated with gastrointestinal tract and central nervous system anomalies is known as "split notochord syndrome" (SNS). The authors present an unreported variant of SNS having dorsal enteric diverticulum adjacent to the DEF. The patient died 17 days after surgical repair.     

An evaluation of lectin-mediated magnetic bead cell sorting for the targeted separation of enteric bacteria

Lectin-labelled magnetic beads were assessed and compared with antisera as an alternative approach for the targeted separation and isolation of enteric bacteria. Of the 16 lectins tested against a range of bacterial species, concanavalin A (conA) showed the greatest potential. Agglutination of bacterial cells in suspension using conA and methods for effective labelling of the magnetic beads with the lectin were optimized. ConA-labelled magnetic beads were compared with antibody-labelled beads for recovery of bacterial cells from pure or mixed laboratory cultures and from natural populations in river water. Recovered cell populations were free from environmental impurities and a high percentage of the culturable cells was extracted. Specific cell recovery was found to be variable, but the use of lectins offers some promise as an alternative cell discriminator.     

Value of clinical features in the diagnosis of enteric fever

There is no objective data on the value of individual clinical symptoms or signs in the diagnosis of enteric fever in a febrile patient. The purpose of the study was to assess the value of some clinical and simple laboratory features in the diagnosis of enteric fever. One hundred & six patients with microbiologically confirmed enteric fever and 170 patients with other established febrile illnesses were included in the evaluation. History of stepladder pattern of rise of temperature, loose motions, relative bradycardia and coated tongue proved to be powerful markers of enteric fever with high specificity (100%, 94.71%, 94.71%, 94.12% respectively), positive and negative predictive values. Headache, hepatomegaly and splenomegaly were moderately powerful. ESR and WBC count appeared to have little value in the diagnosis of enteric fever. Pattern of onset and loose motions did not discriminate between typhoid and paratyphoid fever. Most of these patients had illness persisting beyond one week by which viral infections and infectious enterocolitides were largely excluded. Elucidation of power of these markers in distinguishing enteric fever from other febrile illnesses with the help of better designed prospective studies would lessen our dependence on expensive and time consuming laboratory investigations.     

Pathogenic intestinal bacteria: adhesion and invasion

Enteric bacterial pathogens cause considerable morbidity and mortality in developing countries. However, also industrialised countries are burdened with these microorganisms, and there is an increasing public awareness of the problems associated with foodborne diarrhoeal diseases. The ability to interact with the gut epithelium is essential for these bacteria. During the last 10-15 years our insight into the mechanisms for bacterial adhesion and invasion has increased dramatically, and, based upon this, new strategies for prevention and treatment of diarrhoeal diseases have been suggested. This review summarises the present general knowledge about bacterial adhesion and invasion in the gut and gives details for bacteria, that are recognised enteric pathogens. Examples are given about possible future use of this knowledge in the prevention or treatment of diarrhoeal disease.     

Resistance of eels (Gymnothorax) to the venom of sea kraits (Laticauda colubrina): a test of coevolution

This study calculated yearly estimated national hospital discharge (1985 to 1994) and age-adjusted death rates (1980 to 1992) due to bacterial, viral, protozoal, and ill-defined enteric pathogens. Infant and young child hospitalization (but not death) rates in each category increased more than 50% during 1990 to 1994. Age-adjusted death and hospitalization rates due to enteric bacterial infections and hospitalizations due to enteric viral infections have increased since 1988. The increases in hospitalization and death rates from enteric bacterial infections were due to a more than eightfold increase in rates for specified enteric bacterial infections that were uncoded during this period (ICD9 00849). To identify bacterial agents responsible for most of these infections, hospital discharges and outpatient claims (coded with more detail after 1992) were examined for New Mexico's Lovelace Health Systems for 1993 to 1996. Of diseases due to uncoded enteric pathogens, 73% were due to Clostridium difficile infection. Also, 88% of Washington State death certificates (1985 to 1996) coded to unspecified enteric pathogen infections (ICD0084) listed C. difficile infection.     

Assessment of a new four-hour diagnostic kit--RapID onE system for the identification of enteric bacteria

RapID onE System is a newly developed four-hour rapid diagnostic kit for the identification of enteric bacteria. To know the effectiveness of this system, we used 125 strains of oxidase-negative, gram-negative bacilli for this evaluation. Except for Acinetobacter calcoaceticus, all the bacilli belong to family Enterobacteriaceae. The bacterial strains of this assessment belong to 12 genera and 20 species. Among them, 84 strains were freshly isolated from clinical specimens and 41 strains were frozen (-70 degrees C) stock clinical isolates. The results show that 115 (92.0%) strains were correctly identifed to the species level. It yielded 92.9% and 90.2% of correct identification of fresh isolates and frozen stocks, respectively. In this paper, the reading criteria of RapID onE System would also be discussed.     

New protein kinase and protein phosphatase families mediate signal transduction in bacterial catabolite repression

Carbon catabolite repression (CCR) is the prototype of a signal transduction mechanism. In enteric bacteria, cAMP was considered to be the second messenger in CCR by playing a role reminiscent of its actions in eukaryotic cells. However, recent results suggest that CCR in Escherichia coli is mediated mainly by an inducer exclusion mechanism. In many Gram-positive bacteria, CCR is triggered by fructose-1,6-bisphosphate, which activates HPr kinase, presumed to be one of the most ancient serine protein kinases. We here report cloning of the Bacillus subtilis hprK and hprP genes and characterization of the encoded HPr kinase and P-Ser-HPr phosphatase. P-Ser-HPr phosphatase forms a new family of phosphatases together with bacterial phosphoglycolate phosphatase, yeast glycerol-3-phosphatase, and 2-deoxyglucose-6-phosphate phosphatase whereas HPr kinase represents a new family of protein kinases on its own. It does not contain the domain structure typical for eukaryotic protein kinases. Although up to now the HPr modifying/demodifying enzymes were thought to exist only in Gram-positive bacteria, a sequence comparison revealed that they also are present in several Gram-negative pathogenic bacteria.     

Metabolism and cardiovascular effects of leukotrienes in the marine toad Bufo marinus

Interspersed repeated DNA sequences are characteristic features of both prokaryotic and eukaryotic genomes. REP sequences are defined as conserved repetitive extragenic palindromic sequences and are found in Escherichia coli, Salmonella typhimurium and other closely related enteric bacteria. These REP sequences may participate in the folding of the bacterial chromosome. In this work we describe a unique class of 28 conserved complex REP clusters, about 100bp long, in which two inverted REPs are separated by a singular integration host factor (IHF) recognition sequence. We term these sequences RIP (for repetitive IHF-binding palindromic) elements and demonstrate that IHF binds to them specifically. It is estimated that there are about 70 RIP elements in E. coli. Our analysis shows that the RIP elements are evenly distributed around the bacterial chromosome. The possible function of the RIP element is discussed.