Intimin from enteropathogenic Escherichia coli restores murine virulence to a Citrobacter rodentium eaeA mutant: induction of an immunoglobulin A response to intimin and EspB

The formation of attaching and effacing (A/E) lesions is central to the pathogenesis of enteropathogenic Escherichia coli (EPEC)-mediated disease in humans and Citrobacter rodentium (formerly C. freundii biotype 4280)-mediated transmissible colonic hyperplasia in mice. Closely related outer membrane proteins, known as intimins, are required for formation of the A/E lesion by both EPEC (Int(EPEC)) and C. rodentium (Int(CR)). A secreted protein, EspB (formally EaeB), is also necessary for A/E-lesion formation. Here we report that expression of a cloned Int(EPEC), encoded by plasmid pCVD438, restores murine virulence to an intimin-deficient mutant of C. rodentium DBS255. Replacement of Cys937 with Ala abolished the ability of the cloned EPEC intimin to complement the deletion mutation in DBS255. Ultrastructural examination of tissues from wild-type C. rodentium and DBS255(pCVD438)-infected mice revealed multiple A/E lesion on infected cells and loss of contact between enterocytes and basement membrane. Histological investigation showed that although both wild-type C. rodentium and DBS255(pCVD438) colonized the descending colon and induced colonic hyperplasia in orally infected 21-day-old mice, the latter strain adhered to epithelial cells located deeper within crypts. Nonetheless, infection with the wild-type strain was consistently more virulent, as indicated by a higher mortality rate. All the surviving mice, challenged with either wild-type C. rodentium or DBS255(pCVD438), developed a mucosal immunoglobulin A response to intimin and EspB. These results show that C. rodentium infection provides a relevant, simple, and economic model to investigate the role of EPEC proteins in the formation of A/E lesions in vivo and in intestinal disease.

Adhesion of enteroaggregative Escherichia coli to pediatric intestinal mucosa in vitro

Organ cultures of small- and large-intestinal mucosa from children were used to examine the interactions of enteroaggregative Escherichia coli (EAEC) with human intestine. Mucosae from patients aged between 3 and 190 months were cultured with five EAEC strains isolated from infants with diarrhea in the United Kingdom and with two well-described prototype EAEC strains, 17-2 and 221. The prototype strains adhered to jejunal, ileal, and colonic mucosae. The wild-type strains also adhered to this tissue but showed a variable pattern of adhesion: two adhered to all intestinal levels, one adhered to jejunum and ileum, one adhered to ileum only, and one adhered to ileum and colon. Adherence was in an aggregative or stacked-brick pattern, resembling that seen on HEp-2 cells. Electron microscopy of infected small intestinal mucosa revealed bacteria in association with a thick mucus layer above an intact enterocyte brush border, which contained extruded cell fragments. This mucus layer was not present on controls. EAEC adherence to colonic mucosa was associated with cytotoxic effects including microvillous vesiculation (but without evidence of an attaching/effacing lesion), enlarged crypt openings, the presence of intercrypt crevices, and increased epithelial cell extrusion. These results demonstrate that in vitro organ culture of intestinal mucosa from children can be used to investigate EAEC pathogenesis in childhood directly. EAEC strains appear able to colonize many regions of the gastrointestinal tract, without overt changes to small intestinal mucosa but with cytotoxic effects on colonic mucosa.

The cell-binding domain of intimin from enteropathogenic Escherichia coli binds to beta1 integrins

Bacteria interact with mammalian cells surface molecules, such as integrins, to colonize tissues and evade immunological detection. Herein, the ability of intimin, an outer membrane protein from enteropathogenic Escherichia coli, to bind beta1 integrins was investigated. Solid-phase binding assays revealed binding of the carboxyl-terminal 280 amino acids of intimin (Int280) to alpha4beta1 and alpha5beta1 integrins. The binding required divalent ions (in particular, it was enhanced by Mn2+) and was inhibited by an RGD-containing peptide. Nonderivatized Int280, but not Int280CS (like Int280 but with Cys-937 replaced by Ser) blocked the binding of biotinylated Int280 to integrins. Int280 did not efficiently inhibit beta1 integrin binding of invasin from Yersinia pseudotuberculosis. Both intimin and invasin, immobilized on plastic surfaces, mediated adherence of resting or phorbol 12-myristate 13-acetate-activated human CD4(+) T cells, whereas fibronectin mediated the adherence of only activated T cells. T cell binding to intimin and invasin was integrin mediated because it was specifically blocked by an RGD-containing peptide and by antibodies directed against the integrin subunits beta1, alpha4, and alpha5. These results demonstrate a specific integrin binding activity for intimin that is related to, but distinct from, that of invasin.

Adhesion of enteroaggregative Escherichia coli to formalin-fixed intestinal and ureteric epithelia from children

The adhesion characteristics of enteroaggregative Escherichia coli (EAggEC) to the mucosal surfaces of formalin-fixed paediatric intestinal and ureteral tissue were studied. The technique offers a means of overcoming the problem of limited tissue access in childhood and a way of examining the initial steps of bacterial adhesion. Five EAggEC strains isolated from children with diarrhoea in the UK and a well characterised, prototype EAggEC strain (221) were examined. Five of the six EAggEC strains showed preferential adhesion to jejunal mucosa with limited adhesion to ileum and colon. Five of the six also adhered to ureteric tissue. EAggEC can adhere to proximal, as well as distal, regions of the gastrointestinal tract in children, a previously unrecognised characteristic.

Osmotic diarrhoea and skeletal muscle protein synthesis in vivo

The pathogenic nature of the wasting seen in diarrhoea is unknown. This study measured protein synthesis in an established model of diarrhoea using lactose for seven days. Comparisons were also made with data obtained from rats fed an identical diet in which lactose was replaced by isocaloric glucose ad libitum (that is, the control diet). To account for diarrhoea induced anorexia, a third group of rats were included, which were fed identical amounts of the control diet as the rats with diarrhoea inducing diet. Comparisons of the diarrhoea induced group with rats fed the control diet ad libitum showed that diarrhoea caused a significant reduction in body weights. Type I and type II muscles showed significant reductions in protein, RNA, and DNA contents, as well as a fall in the derived parameters, RNA/DNA, protein/DNA, and RNA/protein. Fractional rates of protein synthesis (ks) were also reduced. However, synthesis rates of type I and II muscles relative to RNA (kRNA) were unchanged in these muscles in diarrhoea induced rats compared with ad libitum fed controls. In the jejunum there was an increase in the RNA/DNA ratio, and reductions in ks and kRNA. Comparisons were also made between rats with diarrhoea and rats pair fed the control diet. There were no changes in total muscle protein, RNA or DNA contents. This suggests that an important feature of body wasting in diarrhoea is the element of anorexia, which induces severe metabolic changes. The comparison between rats with diarrhoea and the pair fed group showed that histological features of the plantaris were not overtly changed, though diarrhoea caused significant reductions in RNA/DNA, protein/DNA, ks, and kRNA. Similar changes were seen for the soleus; though the reduction in ks failed to attain statistical significance. In the jejunum a comparison of diarrhoea induced rats with pair fed controls, showed increases in the ratios of RNA/DNA and protein/DNA.

Molecular characterization of a carboxy-terminal eukaryotic-cell-binding domain of intimin from enteropathogenic Escherichia coli

A eukaryotic cell-binding domain from the intimin (Int) polypeptide of enteropathogenic Escherichia coli O127 (EPEC) was investigated. Derivatives of the carboxy-terminal 280-amino-acid domains of Int (Int-EPEC280) and the Int homolog invasin (Inv) from Yersinia pseudotuberculosis (InvYP280) were fused to the E. coli maltose-binding protein (MBP), expressed, and purified. The smallest MBP-IntEPEC fusion protein that efficiently mediated binding to HEp-2 cells, monitored by using purified fusion proteins in fluorescence activated cell sorter analysis or by using fluorescent Covaspheres coated with purified fusions, contained the carboxy-terminal 150 amino acids of Int. Replacement of Cys-937 with Ser (IntEPEC280CS) destroyed the cell-binding activity of IntEPEC280. Covaspheres coated with MBP-IntEPEC280 were associated with HEp-2 cell microvilli but failed to induce actin accumulation underneath bound particles or cell spreading on coated plastic surfaces. MBP-IntEPEC280, but not MBP, MBP-IntEPEC280CS, or MBP-InvYP280, inhibited EPEC entry into HEp-2 cells.

Characterization of the C-terminal domains of intimin-like proteins of enteropathogenic and enterohemorrhagic Escherichia coli, Citrobacter freundii, and Hafnia alvei

Surface proteins called intimins (Int), which are homologous to the invasin protein (Inv) of Yersinia spp., play a role in inducing brush border damage, termed attachment and effacement, which follows infection by enteropathogenic and enterohemorrhagic Escherichia coli, Citrobacter freundii biotype 4280, and Hafnia alvei. Maltose-binding protein (MBP) fusions containing the C-terminal 280 amino acids of Int-like proteins of strains of enteropathogenic E. coli, enterohemorrhagic E. coli, H. alvei, and C. freundii biotype 4280 and of Yersinia pseudotuberculosis Inv were constructed and purified. The 3' end of the gene for the H. alvei Int-like protein was sequenced and showed homology to corresponding regions of other Int-encoding genes. Binding of MBP-Int-like and MBP-Inv fusion proteins to HEp-2 cells was demonstrated by immunofluorescence microscopy and by fluorescence-activated cell sorting. MBP-Inv induced attachment and spreading of HEp-2 cells to plastic-coated wells, but MBP-Int-like fusion proteins did not. Preincubation of HEp-2 cells with MBP-Inv, but not with MBP-Int-like fusion proteins, inhibited MBP-Inv-induced cell attachment. Fixed staphylococci and fluorescent polymer microspheres coated with both MBP-Int-like and MBP-Inv fusion proteins showed enhanced adhesion to HEp-2 cells. These fusion proteins will facilitate studies of the role of intimin in the pathogenesis of diarrhea associated with members of the family Enterobacteriaeceae that induce attachment and effacement.

Temporal changes in gastric volume in the human fetus in late pregnancy

Disturbed fetal gastrointestinal tract function is associated with hydramnios and may be a marker of later gastrointestinal disease. We investigated gastric motor function in the human fetus to establish the range and rate of fluctuation of gastric volume. Two pairs of orthogonal gastric diameters were measured at 5-min intervals for 1-h periods using a linear-array ultrasound scanner in 12 fetuses in late pregnancy (26-40, median 35.5 weeks gestation). A gastric volume index (GVI) was calculated. Maximum absolute gastric volume index correlated significantly with gestational age. The minimum gastric volume index as a percentage of the maximum (0-60.4%, median 28.1%) showed that marked changes in gastric dimensions occur. Filling (41.5-74.1, median 62.6 degrees) and emptying (46.6-80.9, median 61.7 degrees angles were calculated for the longest continuous filling and emptying periods using a linear model, and showed no difference in the rates of filling and emptying. Peak-to-peak and trough-to-trough durations suggested a periodicity of 35-55 min. Investigation of the development of normal fetal gastric motor activity may lead to a better understanding of postnatal adjustment to enteral feeding, and may provide a diagnostic method for antenatal diagnosis of gastrointestinal functional disturbances.

Concentrations of interleukin 6 and tumour necrosis factor in serum and stools of children with Shigella dysenteriae 1 infection

Serum interleukin 6 (IL-6) and tumour necrosis factor (TNF) were measured in children with dysentery during an epidemic caused by Shigella dysenteriae 1. IL-6 and TNF were also measured in fresh stool filtrates from children with acute gastroenteritis. The median serum IL-6 concentration was raised significantly in the children with complications (haemolytic uraemic syndrome, leukemoid reaction, thrombocytopenia, thrombocytosis, and severe colitis lasting more than one week) during the first week (n = 18, 9-7728 pg/ml; median 107) and in the second week (n = 13, 5-312 pg/ml; median 77), compared with convalescent sera (n = 10, < 3-85 pg/ml; median 39; p < 0.02 and < 0.05 respectively). The median IL-6 concentration during the first week was significantly higher in the group with complicated disease than in those with no complications (n = 8, < 3-37 pg/ml; median 5; p < 0.001). Although serum TNF concentrations were significantly raised in the complicated group during the first and second weeks of the illness and in the uncomplicated group compared with convalescence, there was no significant difference in the TNF concentrations between the complicated and uncomplicated groups. IL-6 was detectable in stool filtrates from eight of 13 children with S dysenteriae 1 infection and four of eight children with S flexneri infection. It was not detectable in Cryptosporidia, rotavirus, or adenovirus infections, those with pathogen-negative acute diarrhoea or controls. Seven of 13 children with S dysenteriae 1 and three of nine children with S flexneri infections had TNF detectable in stools. None of the children with Salmonella, Cryptosporidia, rotavirus of children with pathogen-negative diarrhoea and controls had detectable TNF in stool filtrates. It is postulated that the local and generalised vasculitis observed in shigellosis may be related to a direct effect of Shiga toxin on endothelial cells or caused by cytokine production stimulated by endotoxin, or both.

Serological diagnosis of infection by Shigella dysenteriae-1 in patients with bacillary dysentery

A total of 192 samples of serum from 113 Sri Lankan patients with clinical dysentery was examined for antibodies of the IgM class to the lipopolysaccharides (LPSs) of Shigella dysenteriae-1 and Escherichia coli O157:H7. By means of ELISA and immunoblotting, 59 patients were found to have serum antibodies to the LPS of S. dysenteriae-1 only. Four samples from one patient were found to contain serum antibodies to the LPSs of both S. dysenteriae-1 and E. coli O157:H7. Antibodies to the LPS of S. dysenteriae-1 were also detected in 16 samples from 25 children, from Sri Lanka, with no previous history of dysentery; one of these children also had antibodies to the LPS of E. coli O157:H7. Analysis of 16 samples from apparently healthy children in the U.K. showed that only one serum contained antibodies to the LPS of S. dysenteriae-1. This patient had a history of recent travel to Pakistan. The isolation of S. dysenteriae-1 remains the preferred test for the diagnosis of bacillary dysentery. The use of serology as a means of providing evidence of infection with S. dysenteriae-1, however may prove to be a useful adjunct to cultural techniques but needs to be validated in an area where this organism is endemic.

Relationship between fetal acidemia at cordocentesis and subsequent neurodevelopment

To determine whether there is a relationship between chronic fetal acidemia and subsequent neurodevelopment, a follow-up study was undertaken of 36 children with normal karyotype and morphology, who had prenatal cordocentesis for severe growth retardation. The main outcome measure was the Griffiths neurodevelopmental quotient. The children who had acidemia as fetuses (n = 13) had a significantly lower developmental quotient (mean = 91.8, SD = 6.3) than those with normal (n = 23) fetal blood pH (mean = 100.3, SD = 10.3; t = -2.68, p = 0.011). There was also a significant correlation between developmental quotient and the degree of fetal acidemia (r = 0.41, n = 36, p = 0.012). The pregnancies with acidemic fetuses had similar epidemiological characteristics to those with fetuses with a normal pH, except for a higher incidence of smoking. There was no significant correlation between the degree of growth retardation (birth weight expressed as multiples of SD from the mean for gestational age and sex) and fetal acidemia (r = -0.23, n = 36, NS) or subsequent Griffiths developmental quotient (r = -0.005, n = 36, NS). The results show an association between chronic fetal acidemia and subsequent impaired neurodevelopment. This observation suggests that future preventative interventions may be possible.

Disaccharidase activities in small intestine of rotavirus-infected suckling mice: a histochemical study

A histochemical study of the time course of the appearance and location of lactase and alpha-glucosidase (used to detect sucrase and maltase) activities was carried out on control and rotavirus-infected mice from 7 to 14 days old. The overall pattern of enzyme activity was in agreement with previous quantitative studies on the activities of these enzymes. No evidence was obtained to support the idea that lactase deficiency was the result of repopulation of villi (denuded of lactase-producing villus cells) with immature lactase-negative cells. Low lactase activity was more likely to reflect profound changes in metabolically crippled cells, and recovery of lactase activity with recovery of normal metabolic functions. The location of enzyme activity to brush border regions rather than the cytoplasm of villus enterocytes enhances the significance of previous quantitative studies on these enzymes. The timing and duration of diminished lactase activities were such that they were unlikely to cause the induction or perpetuation of diarrhea in murine rotavirus diarrhea. The appearance in infected animals of alpha-glucosidase 3 days earlier than normal indicates that, in addition to reversible changes seen with lactase, developmental changes were accelerated that affected both crypt and villus cells.

X-ray microanalysis of rotavirus-infected mouse intestine: a new concept of diarrhoeal secretion

Neonatal mice were infected at 7 days of age with rotavirus [epizootic diarrhea of infant mice (EDIM) virus] and killed at 24-h intervals postinfection (PI). Cytoplasmic concentrations of Na, Mg, P, S, Cl, K, and Ca intestinal epithelial cells from infected and age-matched control animals were measured by x-ray microanalysis. In villus tip cells, Ca concentration increased at 24-96 h PI; Na concentration increased at 24-72 h PI; Ca and Na concentrations were near normal by 168 h PI. K concentration decreased 24-72 h PI, and Cl concentration decreased 48-96 h PI. In crypt cells, changes were observed without a discernible pattern: at 96 h PI, Na, Mg, S, and Cl concentrations increased and K concentration decreased; at 120 h PI, the concentrations of all elements except Na and Ca increased. In villus base cells, the mean concentrations of all elements except Ca peaked at 48-72 h PI and at 120 h PI. Na and Cl concentrations increased dramatically in some cells from 48 h PI onward. All the above concentration values were obtained from freeze-dried specimens and expressed in millimoles per kilogram of dry weight. Conversion of a limited number of data, pertaining to villus base cells, from dry weight to wet weight was possible. This conversion revealed that villus base cells in infected animals were more hydrated than corresponding cells from control animals. Also, the Na and Cl concentrations in mmol/kg H2O were significantly higher in villus base cells from infected animals than in those from corresponding controls: 137 +/- 7 versus 38 +/- 4 (Na) and 121 +/- 5 versus 89 +/- 6 (Cl). Wet weight concentrations of other elements were either the same (Mg) or lower (P, S, and K) after infection with virus. From these studies, a new concept of the pathophysiology of rotavirus-induced diarrhoeal secretion is proposed: stimulation of villus base cells to rapid cell division is accompanied by transient accumulation of Na and Cl; excess NaCl is secreted into the lumen, which is the driving force for fluid loss.

An in vitro model to study aspects of the pathophysiology of murine rotavirus-induced diarrhoea

An in vitro system is described and validated for studying transport of solutes and water in both uninfected and rotavirus-infected neonatal mouse intestine. Control intestine exhibited stable water absorption for periods of up to 40 min. Water absorption was temperature-dependent. Na-dependent, and enhanced by glucose-containing perfusion solutions. Theophylline induced net secretion of water by control intestinal tissue. Water transport by rotavirus-infected lower small intestine was significantly depressed as compared to control levels, and rotavirus-infected middle small intestine exhibited net secretion of water. Upper small intestine and colon from infected animals did not differ significantly from control tissues in their ability to transport water. Water secretion by infected middle small intestine was reversed to absorption by glucose-containing solutions.

The role of leucocytes in the induction of fluid secretion by Salmonella typhimurium

Nitrogen mustard (N2M) treatment of rabbits induced neutropenia, and, in ligated ileal loops, it inhibited fluid secretion induced by salmonella or by cholera toxin (CT). Pretreatment of rabbits with indomethacin almost abolished salmonella-induced fluid secretion and significantly reduced that induced by CT. Similar effects of N2M and indomethacin on fluid secretion induced by salmonella, but not by CT, have been reported by other workers and used to implicate prostaglandins, from the salmonella-induced inflammation, as mediators of fluid secretion. In contrast, we show that N2M treatment, in addition to reducing CT-induced secretion, caused severe morphological alterations to ileal mucosa. Irradiation techniques were developed for inducing neutropenia, but they did not totally inhibit salmonella-induced leucocyte influx into ileal mucosa. We propose an alternative mechanism for the inhibitory effect of N2M on salmonella- and CT-induced secretion, based on the known anti-mitotic activity of N2M. Also, the anti-secretory effect of indomethacin cannot be attributed uniquely to its anti-inflammatory activity because it depressed CT-induced secretion as well as salmonella-induced secretion. These results support the concept of pathophysiological secretion in infectious diarrhoea, developed previously for rotavirus and extended to bacterial infections.

Quantification of the leucocyte influx into rabbit ileal loops induced by strains of Salmonella typhimurium of different virulence

Leucocyte influx into rabbit ileal loops, induced by strains of Salmonella typhimurium of different virulence, was assessed with 111Indium-labelled leucocytes. Strains fell into two groups on the basis of their leucotactic potential: "virulent" strains (which induced fluid secretion) caused a dose-dependent leucocyte influx; strains which did not induce fluid secretion failed to induce a significant leucocyte influx. Fluid secretion was never observed in the absence of leucocyte influx, but leucocyte influx per se did not induce fluid secretion. The phenotype of the challenge inoculum influenced fluid secretion; young log-phase organisms induced fluid secretion with a higher frequency than overnight cultures. These findings support earlier evidence implicating leucocytes in an interactive but not exclusive role in the genesis of salmonella-induced fluid secretion. They suggest, though do not prove, that interaction of leucocytes with the appropriate phenotype of organisms results in the release of a host-derived or bacterial secretagogue, or both. The bacterial factor may or may not be the antigen related to cholera toxin, described previously.

Studies on early association of Salmonella typhimurium with intestinal mucosa in vivo and in vitro: relationship to virulence

The abilities of six strains of Salmonella typhimurium to associate with rabbit ileal mucosa have been measured in vitro. Two were "virulent" strains (TML and W118 which are invasive and inducers of fluid secretion in rabbit ileal loops); four were "avirulent" (LT7, M206 and SL1027 which are invasive but induce negligible fluid secretion, and Thax-1 which is neither invasive nor an inducer of fluid secretion). A special organ-culture apparatus was designed to expose only the luminal surface of the mucosa to organisms. Viable counts of washed homogenised tissue taken 30 min after challenge showed that virulent strains TML and W118 and avirulent strains LT7 and M206 could not be distinguished from each other. Avirulent strain SL1027 associated less well than the other four strains, and Thax-1 associated less well than SL1027; both these strains were non-motile whereas the other four were motile. Thus, early association with gut mucosa did not discriminate all avirulent strains from the virulent strains. Qualitative examination of tissues by scanning electronmicroscopy did not detect strains LT7 and M206 on the mucosal surface whereas strains TML and W118 were readily seen, suggesting that the nature of association of virulent and avirulent strains was different. Qualitative examination by transmission electronmicroscopy of tissues challenged in vivo for 120 min showed virulent strains TML and W118 invading epithelial cells; similar events were reproduced after 120-min challenge in vitro. In contrast, invasion by avirulent strains was observed only very rarely.

Intestinal enzyme profiles in normal and rotavirus-infected mice

To investigate further the pathophysiology of rotavirus-induced diarrhea, changes in specific activities of eight relevant intestinal enzymes [alkaline phosphatase, thymidine kinase, lactase, maltase, sucrase, Na+,K+-adenosine triphosphatase (ATPase), adenylate and guanylate cyclases] were measured following infection of suckling mice with murine rotavirus (epizootic diarrhea of infant mouse strain) and compared with age-matched control mice. The concentration of lactose within the lumen of the gastrointestinal tract during infection was also measured. During the course of infection, activities of alkaline phosphatase and lactase decreased, whilst the activity of thymidine kinase increased. Precocious maturation profiles of sucrase and maltase enzymes were observed. No significant changes were detected in the activities of Na+,K+-ATPase or the adenylate and guanylate cyclases. These results are discussed in relation to existing and novel hypotheses on the pathogenesis of rotavirus-induced diarrhea.

An electron microscopic investigation of time-related changes in the intestine of neonatal mice infected with murine rotavirus

Seven-day-old mice were infected orally with murine rotavirus (EDIM) and regions of the gut examined at 24 h intervals up to 7 days by electron microscopy. Structural changes were correlated with data on viral antigen production, thymidine kinase activity, and clinical signs of diarrhea. No pathological changes were detected in the colon. Infection and structural damage were confined to the small intestine, with middle regions showing the most pronounced changes. Constriction of villus bases, edema of the lamina propria, and vacuolation of enterocytes occurred at 24 h postinfection (PI), i.e., before evidence of major virus replication. Transient villus atrophy occurred at 48 h PI. Recovery of villus length was evident by 72 h PI accompanied by evidence of marked enterocyte replication at villus bases. Many enterocytes were damaged with little evidence for the presence of virus particles. By 96 h PI, villi had almost recovered from infection although some enterocytes were still damaged; no virus particles were detected in these cells. A second phase of villus damage and edema of the lamina propria occurred at 120 h PI; the pathology resembled that at 24-48 h PI. By 144 to 168 h PI, recovery of the mucosa from infection was virtually complete. We suggest that many of the pathological features following rotavirus infection result from rotavirus-induced ischemia of villi and that diarrhea results from malabsorption of fluid by damaged villi and hypersecretion of ions released from increased numbers of dividing cells at villus-crypt borders.

Expression of an antigen in strains of Salmonella typhimurium which reacts with antibodies to cholera toxin

Six strains of Salmonella typhimurium (W118, TML, SL1027, LT7, M206 and Thax 1) of different virulence were examined for the presence of antigens which react with antibodies to cholera toxin (anti-CT). A fluorescent-antibody-labelling technique employing anti-CT was used to analyse antigen expression. A rapid increase in the proportion of cells producing a CT-related antigen was demonstrated in cells in early log phase (1-4 h growth) followed by a rapid decline during mid-late log phase in each of the six strains. The nature of the CT-related antigen was analysed by immunoblotting using anti-CT. An antigen of mol. wt equivalent to a high-mol. wt species of CT B subunit was detected in polymyxin-B extracts of all strains but greater amounts were observed in the strains that we consider avirulent. Nothing equivalent to a CT A-related subunit was observed in any of the strains. The relatedness of the salmonella antigen to CT was limited. The high-mol. wt antigen was not disrupted in the denaturing conditions of SDS-PAGE; nothing was detected by enzyme-linked immunosorbent assays with either ganglioside or anti-CT as anchor.

The effects of Clostridium difficile crude toxins and toxin A on ileal and colonic loops in immune and non-immune rabbits

Rabbits were solidly immunised by parenteral injection of purified Clostridium difficile toxin A such that they resisted an intravenous challenge with a normally lethal dose of toxin A. Ileal and colonic loops constructed in non-immune and immune animals received challenge injections of crude culture filtrate or purified toxin A of C. difficile. Protection of ileum was manifest after sufficient initial mucosal damage resulted in release of high levels of antitoxin A into the loop lumen of immune animals. There was less fluid accumulation in ligated ileal loops of immune than of non-immune rabbits. Less protection was observed when loops were challenged with crude culture filtrate containing toxins A and B than when challenged with purified toxin A. In-vitro studies with Ussing chambers yielded no evidence for tissue-localised immunity as judged by electrical responses and histology of toxin-treated tissue from non-immune and immune animals. No differences were found in the degree of epithelial damage, or volume or composition of fluid accumulating in colonic loops of non-immune and immune rabbits challenged with toxin A or crude culture filtrate. However, in colonic loops of immune rabbits there was no overt tissue-localised haemorrhage, whereas in those of non-immune rabbits tissue-localised haemorrhage was marked. In contrast to our findings with ileal loops, fluid accumulating in colonic loops was watery and contained substantially less total protein and (in immune animals) antitoxin A.

Biological mode of action of Clostridium difficile toxin A: a novel enterotoxin

Antibody neutralisation and toxin A elution experiments showed that toxin A uptake from rabbit intestinal lumen was a continuous process. The kinetics of the ileal and colonic responses were significantly different; a much longer incubation (4 h) with toxin was required for colon, compared with 45 min for the ileum, to induce fluid accumulation at 12 h. Fluid secretion was induced only when toxin had gained access to deeper tissues, probably achieved by several toxin uptake-tissue damage cycles. Toxin A induced haemorrhage in both ileal and colonic tissues. In ileum, the villus architecture was severely damaged and this gave rise to protein-rich bloody luminal fluid. In the colon, although colonocytes were removed, the basement membrane remained intact; this resulted in a tissue-localised haemorrhage and a protein-low watery ultrafiltered luminal fluid. Toxin A is thus a novel type of histotoxic enterotoxin.

The effects of Clostridium difficile crude toxins and purified toxin A on stripped rabbit ileal mucosa in Ussing chambers

Clostridium difficile crude toxins and purified toxin A had similar effects on stripped rabbit ileal mucosa in Ussing chambers. Both toxin preparations caused secretion of sodium and chloride ions by increasing serosa to mucosa (s----m) fluxes. Transmural potential difference and resistance decreased after toxin treatment. Onset of changes in electrical measurements and ion fluxes coincided with onset of histological changes. The response to theophylline was greatly reduced in toxin-treated tissue compared with control tissue.

The effects of Clostridium difficile toxins A and B on membrane integrity and protein synthesis in intestinal cells in vivo and in vitro and in McCoy cells in vitro

Clostridium difficile toxins A and B inhibited protein synthesis in McCoy tissue-culture cells but not in intestinal cells in vitro or in vivo. Toxins A and B had no effect on membrane permeability of either intestinal cells or McCoy cells.

Kinetics, tissue specificity and pathological changes in murine rotavirus infection of mice

Mice that did not contain antibodies to rotavirus were orally infected with murine rotavirus (EDIM strain) and observed over 7 days. As judged by ELISA, only the small intestine was infected, not the colon. The infection was biphasic, viral antigen peaks being observed at 48 h and approximately 120 h post-infection. Clinically evident diarrhoea was maximal at 72 h. Virus in the upper, middle and lower regions of the small intestine was mainly tissue-associated; most virus was found in the middle small intestine. Two peaks (48 h and 120 h post-infection) of virus antigen were observed in the colon, but these corresponded to luminal, not tissue-associated viral antigen. Only enterocytes in the upper two-thirds of villus epithelia were infected as judged by fluorescent-antibody analysis and transmission electron microscopy. Scanning electron microscopy revealed morphological appearances not hitherto correlated with the progress of the infection: villus tips were convoluted, corresponding to the shedding of virus-infected cells but the lower regions of infected villi were shrunken and considerably narrowed compared to tips.

The nature and role of mucosal damage in relation to Salmonella typhimurium-induced fluid secretion in the rabbit ileum

The time course and nature of mucosal damage induced in rabbit ileal loops by two strains of Salmonella typhimurium (TML and W118) isolated from human infections was assessed by immunofluorescence microscopy and by scanning and transmission electronmicroscopy. Salmonella-induced fluid secretion occurred in the presence or absence of gross mucosal architectural damage. Neither strain caused mucosal ulceration. When damage did occur, the villi were shortened by loss of their tip regions with concomitant reforming of an intact mucosal surface. Immediately preceding the onset of fluid secretion, marked infiltration of the mucosa with polymorphonuclear leukocytes and occasional macrophages was seen. This revives an earlier suggestion that interaction between invading salmonellae and acute inflammatory cells may be an important factor in initiation of fluid secretion. Brush-border invasion by salmonellae cannot per se be the immediate cause of fluid secretion, because the latter occurred several hours after initial invasion.

Sporogenesis and toxin A production by Clostridium difficile

The kinetics of spore production by Clostridium difficile were not paralleled by release of C. difficile toxin A in vitro. Toxin A was not found to be associated with either purified whole spores or spore coats. Residual traces of toxin A detected in spore contents were almost certainly derived from contaminating vegetative cell debris. Thus, toxin A is unlikely to be a spore constituent or associated with sporogenesis.

Growth of Clostridium difficile and production of toxins A and B in complex and defined media

The ability of several strains of Clostridium difficile to grow and to produce toxins A and B in complex and defined culture media has been studied with special reference to the amino-acid composition of the medium. The production of these toxins varied with the strain used and with the composition of the growth medium. Toxin A production was not inextricably linked to production of toxin B since conditions were found in which only one or other toxin was produced.

Enterotoxin production by Salmonella typhimurium strains of different virulence

Six strains of Salmonella typhimurium (TML, W118, LT7, SL1027, M206 and Thax-1) of known virulence and ability to induce fluid secretion when inoculated into the rabbit ileum were examined for enterotoxin production. Enterotoxic activity, assayed in the rabbit ileal-loop test, was detected in polymyxin-B extracts from all strains (with the possible exception of Thax-1) cultured for 6 h in casamino acid-yeast extract medium. The extracts were inactive in tissue-culture assays with CHO, Y-1 adrenal and Vero cells, and in the infant mouse assay for enterotoxin. There was no correlation between enterotoxigenicity in vitro and the ability of whole organisms to induce fluid secretion in vivo. The significance of these results in relation to salmonellosis is discussed.

Effect of toxin A and B of Clostridium difficile on rabbit ileum and colon

The effect of purified toxin A and partially purified toxin B on rabbit ileum and colon was investigated. Toxin A caused tissue damage which was followed by permeability changes and fluid accumulation in both tissues. Toxin A did not increase the permeability of the colon to the extent observed for ileum; secreted fluid contained less protein of plasma origin. Toxin B had no effect on either tissue. Secretory and tissue damaging properties of crude C difficile toxins were found to be due to toxin A.

The microcomputer: an aid to paediatric parenteral nutrition

Approximately 50% of the pharmacy man-hours committed to providing a parenteral nutrition service at the Children's Hospital, Birmingham were spent in calculations, form filling and record keeping. An increasing demand for the service, with no extra staff available, meant that the service had to be made more efficient. A 90% time saving was achieved by using a microcomputer to free the pharmacy staff from many of the laborious mathematical and clerical chores. The program was developed by a member of the nutritional care team; this meant that it was designed with the specific needs of the service in mind. In addition the detail and accuracy of patient data recording have been greatly improved.

Widespread cutaneous Crohn's disease presenting in childhood

Cutaneous lesions containing Crohn's granulomata are rare and tend to occur in submammary or abdominal wall skin folds when they are to be found (1). Crohn's disease of the skin in nonflexural locations has been reported (2,3) although not in children. We report a 5-year-old girl with extensive colonic Crohn's disease, who at presentation was noted to have a generalised erythematous papular rash which histologically showed typical noncaseating granulomata.

Adhesion of enterotoxigenic Escherichia coli to human small intestinal enterocytes

An improved enterocyte adhesion assay has been used to examine a collection of 44 strains of enterotoxigenic Escherichia coli (ETEC) for their ability to adhere to the brush border of isolated human duodenal enterocytes. Fourteen strains showed good adhesion; in each case the ability to adhere correlated with the production of colonization factor antigen I or II (CFA/I or CFA/II) fimbriae. CFA/II-positive producing coli surface antigens 1 and 3 (CS1 and CS3), coli surface antigens 2 and 3 (CS2 and CS3), and only coli surface antigen 3 (CS3) each showed good adhesion. CS3-mediated brush border attachment of CFA/II-positive ETEC was demonstrated by electron microscopy with monospecific antibody and an immunogold labeling technique. One CFA/I-positive ETEC strain was nonadherent in the assay, as were ETEC producing type 1 somatic fimbriae. Five animal ETEC strains producing K88, K99, F41, and 987P fimbriae were slightly more adhesive than control strains, but adhesion was significantly less than that of CFA-positive ETEC. Twenty five human ETEC strains that lacked CFA/I and CFA/II were nonadherent, suggesting either that the surface antigens responsible for adhesion to human intestinal mucosa in these strains were not being produced or that mucosal receptors for these strains are present in regions of the small intestine other than the duodenum.

Portable bedside microcomputer system for management of parenteral nutrition in all age groups

A microcomputer program has been designed to provide comprehensive assistance to the clinician in prescribing parenteral nutrition in children of all ages. It is implemented on a fully portable, independent machine that can be taken to the bedside anywhere in the hospital. The user is guided through a standardised prescribing process based on a well tried protocol and taking into account the patient's age, clinical condition, concurrent parenteral infusions, laboratory findings, and enteral intake. A printout is produced for insertion into the patient's clinical record, giving all concerned in the care of the child a clear, legible record of when, how, and by whom the prescription was calculated. The user can review and amend the proposed prescription before printing, giving ultimate control to the prescriber, not the computer. The system saves time by performing accurately the necessary calculations, and provides financial savings by reducing wastage of parenteral nutrition during the re-introduction of enteral feeding.

New enteric vaccines: application of new knowledge of receptors and recognition in enteric infections

Advances in understanding of the "receptors and recognition" mechanisms of virulence factors of enteric pathogens have been important in the development of enteric vaccines. Sophisticated techniques of molecular biology have proved essential to this endeavour. This review summarizes progress in development of vaccines against disease due to Vibrio cholerae, Escherichia coli, Salmonella typhi, Shigella and rotavirus enteric infections. All of these vaccines are undergoing, or are about to undergo, field trials.

Production and release of toxins A and B by Clostridium difficile

The production and release of toxins A and B by Clostridium difficile during in-vitro culture was investigated. Cell-associated toxin A was detected by immunoelectrophoresis of bacterial extracts released by ultrasonication and by fluorescent antibody labelling of whole cells. Extracellular toxin A was detected by immunoelectrophoresis and by enzyme-linked immunosorbent assay; extracellular toxin B was detected by cytotoxin assay. Both toxins A and B were produced and released during the decline phase of the bacterial growth cycle. The possible significance of these results in relation to the pathogenesis of pseudomembranous colitis is discussed.

Familial defect of polymorph neutrophil phagocytosis associated with absence of a surface glycoprotein antigen (OKMI)

Two siblings with delayed separation of the umbilical cord, recurrent skin ulceration and dental sepsis were shown to have defective neutrophil phagocytosis of opsonized yeast (S. cerevisiae) and respiratory burst to opsonized and unopsonized zymosan. Increased activity in the NBT reduction test, normal ingestion and killing of S. aureus, and normal spontaneous and directional motility were also demonstrated. These abnormalities of neutrophil phagocytosis were confined to the affected siblings; their healthy parents and brother showed normal neutrophil function. Both children had a polymorph neutrophil leucocytosis, and had normal humoral and cell-mediated immunity. SDS electrophoresis of neutrophil cell membrane preparations showed absence of a glycoprotein band of 175,000 daltons, which was present in the parents' neutrophils in reduced amounts. OKMI monoclonal antibody, which recognized the C3bi receptor (CR3) failed to bind to the affected siblings neutrophils. The findings in these children emphasize the importance of this receptor in phagocytosis, and possibly other neutrophil functions.

Characterization of nonfimbrial mannose-resistant protein hemagglutinins of two Escherichia coli strains isolated from infants with enteritis

Escherichia coli strains 444-3 and 469-3, isolated from patients with severe infantile enteritis, are able to adhere to and penetrate human epithelial cells in culture. In addition to type 1 fimbriae and glycocalyces , both strains elaborate mannose-resistant nonfimbrial protein hemagglutinins specific for human erythrocytes. Purified agglutinins are aggregates (greater than 4 X 10(6) daltons) of a single protein subunit of apparent Mr 14,000 (469-3) to 14,500 (444-3). The optimal temperature for expression of the agglutinins is 37 degrees C. Bacteria grown at 22 degrees C, which show 1% or less of maximal activity, and mutants deficient in the ability to agglutinate human erythrocytes do not synthesize detectable levels of these surface proteins and, moreover, do not adhere to cultured epithelial cells. Coupled with the observation that purified agglutinins competitively inhibit bacterial adherence to cultured cells, these data indicate that the nonfimbrial surface proteins expressed by strains 444-3 and 469-3 are essential for adherence both to erythrocytes and to cultured epithelial cells.