Jejunal microflora in malnourished Gambian children

The eukaryome of African children is influenced by geographic location, gut biogeography, and nutritional status

Eukaryotes have historically been studied as parasites, but recent evidence suggests they may be indicators of a healthy gut ecosystem. Here, we describe the eukaryome along the gastrointestinal tract of children aged 2-5 years and test for associations with clinical factors such as anaemia, intestinal inflammation, chronic undernutrition, and age. Children were enrolled from December 2016 to May 2018 in Bangui, Central African Republic and Antananarivo, Madagascar. We analyzed a total of 1104 samples representing 212 gastric, 187 duodenal, and 705 fecal samples using a metabarcoding approach targeting the full ITS2 region for fungi, and the V4 hypervariable region of the 18S rRNA gene for the overall eukaryome. Roughly, half of all fecal samples showed microeukaryotic reads. We find high intersubject variability, only a handful of taxa that are likely residents of the gastrointestinal tract, and frequent co-occurrence of eukaryotes within an individual. We also find that the eukaryome differs between the stomach, duodenum, and feces and is strongly influenced by country of origin. Our data show trends towards higher levels of Fusarium equiseti, a mycotoxin producing fungus, and lower levels of the protist Blastocystis in stunted children compared to nonstunted controls. Overall, the eukaryome is poorly correlated with clinical variables. Our study is of one of the largest cohorts analyzing the human intestinal eukaryome to date and the first to compare the eukaryome across different compartments of the gastrointestinal tract. Our results highlight the importance of studying populations across the world to uncover common features of the eukaryome in health.

Parasites and childhood stunting - a mechanistic interplay with nutrition, anaemia, gut health, microbiota, and epigenetics

Globally, stunting affects approximately 149.2 million children under 5 years of age. The underlying aetiology and pathophysiological mechanisms leading to stunting remain elusive, and therefore few effective treatment and prevention strategies exist. Crucial evidence directly linking parasites to stunting is often lacking - in part due to the complex nature of stunting, as well as a lack of critical multidisciplinary research amongst key age groups. Here, based on available studies, we present potential mechanistic pathways by which parasitic infection of mother and/or infant may lead to childhood stunting. We highlight the need for future multidisciplinary longitudinal studies and clinical trials aimed at elucidating the most influential factors, and synergies therein, that can lead to stunting, and ultimately towards finding solutions to successfully mitigate against it.

Stunted childhood growth is associated with decompartmentalization of the gastrointestinal tract and overgrowth of oropharyngeal taxa

Linear growth delay (stunting) affects roughly 155 million children under the age of 5 years worldwide. Treatment has been limited by a lack of understanding of the underlying pathophysiological mechanisms. Stunting is most likely associated with changes in the microbial community of the small intestine, a compartment vital for digestion and nutrient absorption. Efforts to better understand the pathophysiology have been hampered by difficulty of access to small intestinal fluids. Here, we describe the microbial community found in the upper gastrointestinal tract of stunted children aged 2-5 y living in sub-Saharan Africa. We studied 46 duodenal and 57 gastric samples from stunted children, as well as 404 fecal samples from stunted and nonstunted children living in Bangui, Central African Republic, and in Antananarivo, Madagascar, using 16S Illumina Amplicon sequencing and semiquantitative culture methods. The vast majority of the stunted children showed small intestinal bacterial overgrowth dominated by bacteria that normally reside in the oropharyngeal cavity. There was an overrepresentation of oral bacteria in fecal samples of stunted children, opening the way for developing noninvasive diagnostic markers. In addition, Escherichia coli/Shigella sp. and Campylobacter sp. were found to be more prevalent in stunted children, while Clostridia, well-known butyrate producers, were reduced. Our data suggest that stunting is associated with a microbiome "decompartmentalization" of the gastrointestinal tract characterized by an increased presence of oropharyngeal bacteria from the stomach to the colon, hence challenging the current view of stunting arising solely as a consequence of small intestine overstimulation through recurrent infections by enteric pathogens.

Starved Guts: Morphologic and Functional Intestinal Changes in Malnutrition

Malnutrition contributes significantly to death and illness worldwide and especially to the deaths of children younger than 5 years. The relation between intestinal changes in malnutrition and morbidity and mortality has not been well characterized; however, recent research indicates that the functional and morphologic changes of the intestine secondary to malnutrition itself contribute significantly to these negative clinical outcomes and may be potent targets of intervention. The aim of this review was to summarize current knowledge of experimental and clinically observed changes in the intestine from malnutrition preclinical models and human studies. Limited clinical studies have shown villous blunting, intestinal inflammation, and changes in the intestinal microbiome of malnourished children. In addition to these findings, experimental data using various animal models of malnutrition have found evidence of increased intestinal permeability, upregulated intestinal inflammation, and loss of goblet cells. More mechanistic studies are urgently needed to improve our understanding of malnutrition-related intestinal dysfunction and to identify potential novel targets for intervention.

Hunger and microbiology: is a low gastric acid-induced bacterial overgrowth in the small intestine a contributor to malnutrition in developing countries?

Underproduction of hydrochloric acid into the stomach is frequently encountered in subjects from developing countries. We explore the hypothesis that hypochlorhydria compromises the gastric barrier and favours bacterial overgrowth in the proximal parts of the small intestine where nutrient absorption takes place. Food calories are thus deviated into bacterial metabolism. In addition to an adequate caloric supply, correcting hypochlorhydria might be needed to decrease childhood malnutrition.

Nutrient-sensing nuclear receptors PPARα and FXR control liver energy balance

The nuclear receptors PPARα (encoded by NR1C1) and farnesoid X receptor (FXR, encoded by NR1H4) are activated in the liver in the fasted and fed state, respectively. PPARα activation induces fatty acid oxidation, while FXR controls bile acid homeostasis, but both nuclear receptors also regulate numerous other metabolic pathways relevant to liver energy balance. Here we review evidence that they function coordinately to control key nutrient pathways, including fatty acid oxidation and gluconeogenesis in the fasted state and lipogenesis and glycolysis in the fed state. We have also recently reported that these receptors have mutually antagonistic impacts on autophagy, which is induced by PPARα but suppressed by FXR. Secretion of multiple blood proteins is a major drain on liver energy and nutrient resources, and we present preliminary evidence that the liver secretome may be directly suppressed by PPARα, but induced by FXR. Finally, previous studies demonstrated a striking deficiency in bile acid levels in malnourished mice that is consistent with results in malnourished children. We present evidence that hepatic targets of PPARα and FXR are dysregulated in chronic undernutrition. We conclude that PPARα and FXR function coordinately to integrate liver energy balance.

Candida parapsilosis Protects Premature Intestinal Epithelial Cells from Invasion and Damage by Candida albicans

Candida is a leading cause of late-onset sepsis in premature infants and is thought to invade the host via immature or damaged epithelial barriers. We previously showed that the hyphal form of Candida albicans invades and causes damage to premature intestinal epithelial cells (pIECs), whereas the non-hyphal Candida parapsilosis, also a fungal pathogen of neonates, has less invasion and damage abilities. In this study, we investigated the potential for C. parapsilosis to modulate pathogenic interactions of C. albicans with the premature intestine. While a mixed infection with two fungal pathogens may be expected to result in additive or synergistic damage to pIECs, we instead found that C. parapsilosis was able to protect pIECs from invasion and damage by C. albicans. C. albicans-induced pIEC damage was reduced to a similar extent by multiple different C. parapsilosis strains, but strains differed in their ability to inhibit C. albicans invasion of pIECs, with the inhibitory activity correlating with their adhesiveness for C. albicans and epithelial cells. C. parapsilosis cell-free culture fractions were also able to significantly reduce C. albicans adhesion and damage to pIECs. Furthermore, coadministration of C. parapsilosis cell-free fractions with C. albicans was associated with decreased infection and mortality in zebrafish. These results indicate that C. parapsilosis is able to reduce invasion, damage, and virulence functions of C. albicans. Additionally, the results with cellular and cell-free fractions of yeast cultures suggest that inhibition of pathogenic interactions between C. albicans and host cells by C. parapsilosis occurs via secreted molecules as well as by physical contact with the C. parapsilosis cell surface. We propose that non-invasive commensals can be used to inhibit virulence features of pathogens and deserve further study as a non-pharmacological strategy to protect the fragile epithelial barriers of premature infants.

Mechanisms of cross-talk between the diet, the intestinal microbiome, and the undernourished host

Undernutrition remains one of the most pressing global health challenges today, contributing to nearly half of all deaths in children under five years of age. Although insufficient dietary intake and environmental enteric dysfunction are often inciting factors, evidence now suggests that unhealthy gut microbial populations perpetuate the vicious cycle of pathophysiology that results in persistent growth impairment in children. The metagenomics era has facilitated new research identifying an altered microbiome in undernourished hosts and has provided insight into a number of mechanisms by which these alterations may affect growth. This article summarizes a range of observational studies that highlight differences in the composition and function of gut microbiota between undernourished and healthy children; discusses dietary, environmental and host factors that shape this altered microbiome; examines the consequences of these changes on host physiology; and considers opportunities for microbiome-targeting therapies to combat the global challenge of child undernutrition.

Environmental enteric dysfunction: an overview

BACKGROUND

Environmental enteric dysfunction (EED) refers to an incompletely defined syndrome of inflammation, reduced absorptive capacity, and reduced barrier function in the small intestine. It is widespread among children and adults in low- and middle-income countries. Understanding of EED and its possible consequences for health is currently limited.

OBJECTIVE

A narrative review of the current understanding of EED: epidemiology, pathogenesis, therapies, and relevance to child health.

METHODS

Searches for key papers and ongoing trials were conducted using PUBMED 1966-June 2014; ClinicalTrials.gov; the WHO Clinical Trials Registry; the Cochrane Library; hand searches of the references of retrieved literature; discussions with experts; and personal experience from the field.

RESULTS

EED is established during infancy and is associated with poor sanitation, certain gut infections, and micronutrient deficiencies. Helicobacter pylori infection, small intestinal bacterial overgrowth (SIBO), abnormal gut microbiota, undernutrition, and toxins may all play a role. EED is usually asymptomatic, but it is important due to its association with stunting. Diagnosis is frequently by the dual sugar absorption test, although other biomarkers are emerging. EED may partly explain the reduced efficacy of oral vaccines in low- and middle-income countries and the increased risk of serious infection seen in children with undernutrition.

CONCLUSIONS

Despite its potentially significant impacts, it is currently unclear exactly what causes EED and how it can be treated or prevented. Ongoing trials involve nutritional supplements, water and sanitation interventions, and immunomodulators. Further research is needed to better understand this condition, which is of likely crucial importance for child health and development in low- and middle-income settings.

An integrative view of microbiome-host interactions in inflammatory bowel diseases

The intestinal microbiota, which is composed of bacteria, viruses, and micro-eukaryotes, acts as an accessory organ system with distinct functions along the intestinal tract that are critical for health. This review focuses on how the microbiota drives intestinal disease through alterations in microbial community architecture, disruption of the mucosal barrier, modulation of innate and adaptive immunity, and dysfunction of the enteric nervous system. Inflammatory bowel disease is used as a model system to understand these microbial-driven pathologies, but the knowledge gained in this space is extended to less-well-studied intestinal diseases that may also have an important microbial component, including environmental enteropathy and chronic colitis-associated colorectal cancer.

Severe acute malnutrition and infection

Severe acute malnutrition (SAM) is associated with increased severity of common infectious diseases, and death amongst children with SAM is almost always as a result of infection. The diagnosis and management of infection are often different in malnourished versus well-nourished children. The objectives of this brief are to outline the evidence underpinning important practical questions relating to the management of infectious diseases in children with SAM and to highlight research gaps. Overall, the evidence base for many aspects covered in this brief is very poor. The brief addresses antimicrobials; antipyretics; tuberculosis; HIV; malaria; pneumonia; diarrhoea; sepsis; measles; urinary tract infection; nosocomial Infections; soil transmitted helminths; skin infections and pharmacology in the context of SAM. The brief is structured into sets of clinical questions, which we hope will maximise the relevance to contemporary practice.

The problem of bacterial diarrhoea

The reported incidence of "pathogenic" bacteria, as judged by serotype, in the stools of children with acute diarrhoea has varied from 4 to 33% over the last twenty years. Techniques such as tissue culture provide a means for detecting enterotoxin-producing strains of bacteria, strains which often do not possess "pathogenic" serotypes. "Pathogenicity" requires redefinition, and the aetiological importance of bacteria in diarrhoea is probably considerably greater than previous reports have indicated. Colonization of the bowel by a pathogen will result in structural and/or mucosal abnormalities, and will depend on a series of complex interactions between the external environment, the pathogen, and the host and its resident bacterial flora. Enteropathogenic bacteria may be broadly classified as (i) invasive (e.g. Shigella, Salmonella and some Escherichia coli) which predominantly affect the distal bowel, or (ii) non-invasive (e.g. Vibrio cholerae and E. coli) which affect the proximal bowel. V. cholerae and E. coli elaborate heat-labile enterotoxins which activate adenylate cyclase and induce small intestinal secretion; the secretory effects of heat-stable E. coli and heat-labile Shigella dysenteriae enterotoxins are not accompanied by cyclase activation. The two major complications of acute diarrhoea are (i) hypernatraemic dehydration with its attendant neurological, renal and vascular lesions, and (ii) protracted diarrhoea which may lead to severe malnutrition. Deconjugation of bile salts and colonization of the small bowel with toxigenic strains of E. coli may be important in the pathophysiology of the protracted diarrhoea syndrome. The control of bacterial diarrhoea requires a corrdinated political, educational, social, public health and scientific attack. Bacterial diarrhoea is a major health problem throughout the world, and carries an appreciable morbidity and mortality. This is particularly the case during infancy, and in those developing parts of the world where malnutrition is common. This paper is concerned mainly with acute bacterial diarrhoea, and reviews the problem as a whole.

Faecal candida and diarrhoea

BACKGROUND

Candida species are frequently isolated from stools of children with diarrhoea but are not proven enteropathogens. It is hypothesised that faecal candida causes diarrhoea.

AIMS

To determine the prevalence of faecal candida in childhood diarrhoea and the relation between faecal yeasts and diarrhoea.

METHODS

Comparison of clinical and laboratory data, including quantitative stool culture for yeasts from 107 children hospitalised with diarrhoea and 67 age matched controls without diarrhoea.

RESULTS

Yeast species, predominantly candida, were identified in the stools of 43 children (39%) with diarrhoea and 26 (36%) without diarrhoea. The concentration of candida was positively associated with recent antibiotic use (p = 0.03) and with the presence of another enteric pathogen (p < 0.005), but not with patient age, nutritional status, or duration of diarrhoea.

CONCLUSION

Candida species do not cause childhood diarrhoea in well nourished children.

Nutritional management of acute diarrhea

Despite recommendations from several bodies such as the World Health Organization and others that feeding should be continued during diarrhea, the practice of withholding food during the early stages of diarrhea is still widespread. This contributes to a deterioration in patients' nutritional state. The principal controversy in the nutritional therapy of acute gastroenteritis centers on the relative risks of cows'-milk feeds. The two things that need to be considered in determining the optimum approach to feeding the child with acute diarrhea are the optimum timing for feeding children in relation to the onset of and recovery from symptoms and, secondly, the effects of specific food ingredients in the diet. Recent studies have demonstrated that the vast majority of young children with acute diarrhea can be successfully managed with continued feeding of undiluted non-human milk. Routine dilution of milk and routine use of lactose-free formula are not necessary, especially when oral rehydration therapy and early feeding (in addition to milk) form the basic approach to the clinical management of diarrhea in children. Confounding factors are the severity of the diarrhea, coexistent malnutrition, and young age (< 1 y); such infants are much more likely to have complications from early feeding with undiluted milk and some would advocate use of specifically designed lactose-free formula in such children. Children who are fed exclusively with human milk and those who receive solid foods with or without human milk may safely continue to receive their usual diets during diarrhea. Those who are fed exclusively with non-human milk--especially when very young and with severe diarrhea or malnutrition--should be closely observed if they continue to consume milk or they should receive a special formulation (e.g., a cereal-milk mixture or fermented milk product). The use of nutrient-dense mixtures of common foods may be advisable to promote compensatory growth in those who lose weight during illness or because of anorexia or malabsorption.

A Klebsiella pneumoniae strain that shares a type-specific antigen with Shigella flexneri serotype 6. Characterization of the strain and strain and structural studies of the O-antigenic polysaccharide

A strain of Klebsiella pneumoniae was found as the only isolate with pathogenic potential from the stool of a two-year old patient with diarrhoea. A strong serological cross-reactivity with Shigella flexneri serotype 6 was demonstrated. The cross-reacting antigens were shown to reside in the cell wall lipopoly-saccharide. Studies of the pathogenic potential of the Klebsiella strain showed low level of invasion of HEp-2 cells. However, tests for adherence to HEp-2 cells as well as tests for toxin production were negative. The strain had several small plasmids and was multidrug resistant. These data do not form a sufficient basis for estimating the pathogenic potential of the organism. No K antigen was detected. The structure of the O-antigenic polysaccharide from the K. pneumoniae strain was investigated using methylation analysis, NMR spectroscopy, and Smith degradation as the principal methods. The O-antigenic polysaccharide has the following pentasaccharide repeating unit: -->3)- alpha -L-Rhap-(1-->3)- alpha -L-Rhap-(1-->2)- alpha-L-Rhap- (1-->2)- alpha-L-Rhap-(1-->2)- alpha-L-Rhap-(1-->. This structure is not identical to any of the previously described O-antigens of K. pneumoniae. The strong serological cross-reactivity with the Shigella flexneri serotype 6 O-antigen can most likely be attributed to the structural element alpha-L-Rhap-(1-->2)- alpha -L-Rhap present in the O-polysaccharide repeating unit of this serotype. Antiserum raised against the K. pneumoniae strain also agglutinated S. dysenteriae serotype 1 and strains of all different serotypes of S. flexneri. The Shigella strains contain the structural element alpha-L-Rhap-(1-->3)- alpha-L-Rhap in their O-antigen polysaccharides which may be responsible for the observed cross-reactivity.

Effects on growth of single short courses of fluoroquinolones

The aim of the study was to document the effects of short courses of fluoroquinolones given during an outbreak of multidrug resistant typhoid fever in southern Viet Nam on the growth of children over a period of two years. In a prospective cohort study, 326 Vietnamese children aged between 1 and 14 years were followed up for two years after receiving either ciprofloxacin (70 mg/kg given over 7 d) (n = 173) or ofloxacin (45-50 mg/kg given over 3-5 d) (n = 153) for suspected typhoid fever. Growth velocity and weight for height were compared with an age matched control group of children from the same locality (n = 223) who had not contracted typhoid or received any fluoroquinolones. In the ofloxacin and ciprofloxacin treated patients there was no evidence of acute joint toxicity, nor of any joint symptoms attributable to either of the fluoroquinolones. There was no difference in expected weight for height measurements between the three groups of children over the two year period. During the first year, height velocity in ciprofloxacin treated children was greater than in either ofloxacin treated children or untreated controls. Height velocity in the latter two groups was not significantly different. After two years height velocity was similar in the three groups. The results support the use of short course fluoroquinolone treatment in childhood typhoid, especially when caused by strains resistant to other antibiotics.

The role of the duodenal microflora as a determinant of persistent diarrhoea

It has been suggested that proliferation of enterobacteriaceae and/or anaerobes in the duodenum of some children with acute diarrhoea determines whether the episode becomes persistent. A review of published studies and the comparison of cultures of duodenal aspirates from Peruvian children with acute and persistent diarrhoea and diarrhoea-free children did not support this hypothesis. Although many children had enterobacteriaceae and/or anaerobes cultured there was no correlation with clinical and nutritional outcome. Age, nutritional status, the environment and the aetiology of the episode were determinants of the duodenal microflora independent of diarrhoea. Culture of the duodenal aspirates did not increase the yield of enteropathogens which were isolated more frequently from stools than from the duodenum. Despite the presence of a single strain or serotype of enterobacteriaceae suggesting that these bacteria were colonizing the duodenum, we were unable to demonstrate any adherence mechanisms in the majority of them. Two of ten bacteria with no other evidence of virulence caused diarrhoea in the RITARD rabbit model.

Oral gentamicin is not effective treatment for persistent diarrhea

We conducted a randomized, double-blind, placebo controlled clinical trial of oral gentamicin (10 milligrams/kilogram body weight/day for five days) in treatment of unselected cases of persistent diarrhea (duration 14-18 days at initiation of treatment) among 3-36-month-old children in a rural Guatemalan community. Following random assignment of each child to a treatment group, the appropriate dose of gentamicin or placebo was administered to the child three times daily by a study nurse; this nurse also identified the presence or absence of diarrhea on each day of treatment and for the next two days. Cure was defined as cessation of diarrhea during the five-day treatment period, sustained through at least the two days after completion of treatment. Among 92 evaluable cases who entered the clinical trial, there was essentially no difference in cure rate between gentamicin and placebo treatment groups (42% versus 43%). Enteroadherent strains of Escherichia coli were identified in 46% of children tested in this trial; no significant difference existed between treatment groups in frequency of isolation of this or any other enteropathogen. Among 40 children having successful duodenal cultures immediately prior to beginning treatment, > or = 10(4) aerobic organisms per milliliter of fluid were identified in 12 (30%); treatment groups did not differ substantially with respect to proportion of children identified with this level of duodenal microbial colonization. Failure of gentamicin treatment did not appear to be explained by emergence of resistance, although a small number of resistant enteropathogens were identified near the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Net fluid secretion and impaired villous function induced by colonization of the small intestine by nontoxigenic colonizing Escherichia coli

The role of colonizing bacteria in the small bowel in causing diarrhea remains unclear. We examined whether colonizing, nontoxigenic Escherichia coli could alter small bowel function by determining net water and electrolyte fluxes and sucrase activity in colonized and noncolonized ileal segments by using the reversible-ileal-tie adult rabbit model. Colonization of the ileum with nontoxigenic E. coli for greater than or equal to 72 h at greater than or equal to 10(4)/cm2 was associated with significant functional derangements, as follows: (i) overt liquid diarrhea in 50% of animals colonized at greater than 10(4)/cm2; (ii) reversal of normal net ileal absorption to net secretion of water, sodium, and chloride; and (iii) significant decrease in mucosal sucrase activity. We conclude that small bowel colonization by colonizing, nontoxigenic E. coli impairs water and electrolyte absorption and sucrase activity in the absence of recognized enterotoxin, cytotoxin, invasion, or effacement traits.

Prothrombin time as an index of mortality in kwashiorkor

Prothrombin time, serum albumin, aminotransferases and liver size were evaluated in 40 consecutive cases of kwashiorkor. Eleven (27.5%) of the 40 patients died. Eight out of the 11 patients who died had a prolonged prothrombin time of more than 3 s above the control compared to only 4 out of the 29 who survived (p = 0.005). Mean serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) albumin, globulin and liver size were abnormal but similar in both groups. These results may indicate a predictive mortality value of prothrombin time in kwashiorkor.

Small-bowel colonization alone is a cause of diarrhea

Bacterial overgrowth in the small bowel is known to occur in patients with persistent diarrhea, but it has been unclear if colonization alone causes fluid secretion. We studied isogenic, nontoxigenic Escherichia coli strains with colonizing factor antigen II (CFA/II) (1392+) and without CFA/II (1392-) in 18-h rabbit ileal loops. Neither strain produced fluid, but quantitative cultures of rabbit ileal loops with the CFA/II-positive strain had a mean of 10(3) more CFU of bacteria per cm2 than did cultures of rabbit ileal loops with the CFA/II-negative strain or a negative control (P less than 0.05). Of 11 rabbits given strain 1392+ via the small bowel in the reversible ileal tie model, 7 became colonized (mean, 10(10.4) +/- 1.6 CFU/cm2) over 72 h, and all 7 developed diarrhea and had gross gut fluid accumulation, versus none of 10 rabbits given strain 1392- (mean, 10(3.6) +/- 1.9 CFU/cm2) (P less than 0.05). Both strains grew equivalently in vitro. The mechanism by which this E. coli strain which colonizes small-bowel mucosa but produces no recognized toxins causes fluid accumulation and diarrhea in a rabbit model at 72 h remains to be elucidated.

Bacterial contamination of the small intestine of infants with enteropathogenic Escherichia coli and other enteric infections: a factor in the aetiology of persistent diarrhoea?

The duodenal microflora was studied during the first week of diarrhoea in 40 infants with acute infectious diarrhoea of different aetiologies and compared with that in a convalescent group and a group in whom diarrhoea of known aetiology had persisted for more than 14 days after an acute onset. In the acute phase 16 of the 40 infants had more than 10(4) colony forming bacteria/ml, predominantly upper respiratory commensals. In over half of the infants infected with enteropathogenic Escherichia coli a faecal type flora was found in the duodenum. This flora included the enteropathogenic E coli serotype isolated from the stool in three quarters of cases. Infants with persisting diarrhoea had significantly more faecal type bacteria in the duodenum than either those with acute diarrhoea or the convalescent group. In addition, there was a significant further increase in Enterobacteriaceae in infants whose persistent diarrhoea occurred after infection with enteropathogenic E coli. Infections with enteropathogenic E coli may have a predilection for disturbing the duodenal microflora, which may contribute to the development of persistent diarrhoea.

Enteropathogenicity of Klebsiella pneumoniae strains isolated from stools of diarrhoeal patients and other clinical specimens: an experimental study

In recent years strains of Klebsiella pneumoniae have been implicated as intestinal pathogen. Sixty three strains isolated from faeces of children with or without diarrhoea and other specimens of extraintestinal infections were tested for their enteropathogenicity in biological models. Thirty nine of them isolated from different sources caused accumulation of fluid in rabbit ileal loops comparable to that caused by toxigenic V. cholerae 569B. Ten strains, however, required 1-3 serial passages in rabbit gut before giving a positive loop reaction. Culture filtrates of these 39 strains also caused fluid accumulation comparable to that caused by live cells indicating elaboration of enterotoxic substance(s) in the medium. The enterotoxic factor was found to be heat-stable. However, the pattern of time course of fluid accumulation in ileal loops indicated elaboration of an additional heat labile factor. Most of the strains produced cytoxic factor as well. The mode of action of the toxin/s in secretion of fluid in experimental model possibly involve cAMP and prostaglandin. However, further studies are necessary to elucidate the exact mode of action of the enterotoxins. None of the strains tested was found to be enteroinvasive.

Mechanisms of malabsorption in the "Contaminated Small-Bowel syndrome"

The mucosa of the upper small intestine in humans is repeatedly exposed to potentially harmful environmental influences: infective, toxic and antigenic. One of the most significant manifestations of the control over environmental risks is how the upper intestinal milieu is kept relatively sterile and pathogen-free despite constant exposure to a potentially hostile and pathogen-ridden environment. This control is lost in the so-called "Contaminated Small-Bowel Syndrome" when profuse numbers of bacteria contaminate the contents of the upper bowel. This can occur in a vast array of clinical situations ranging from infancy to old age. The consequences of upper intestinal bacterial overgrowth are very diverse. The mechanisms causing diarrhoea and malabsorption in this syndrome illustrate facets of pathophysiology of many inter-relating processes of intestinal digestion and absorption.

Increased adhesion of Escherichia coli to mucosal cells from infants with protracted diarrhoea: a possible factor in the pathogenesis of bacterial overgrowth and diarrhoea

Mucosal adhesion of bacteria has been studied in eight infants with protracted diarrhoea and malnutrition, using a buccal epithelial cell technique. A known non-adhesive strain of Escherichia coli (O1:K1:H7) adhered to a significantly greater (p less than 0.001) proportion of buccal epithelial cells from patients with protracted diarrhoea, compared with children with acute diarrhoea, healthy infants, and healthy adults. Also, Enterobacteria isolated from the jejunum or stools of patients with protracted diarrhoea adhered to far greater numbers of their own buccal epithelial cells compared with healthy adults. These results suggest that bacterial adhesion may play an important role in the pathogenesis of protracted diarrhoea.

Duodenal microflora in infants with acute and persistent diarrhoea

The duodenal bacterial population was determined qualitatively and quantitatively in 3 groups of infants with diarrhoeal disease of varying duration. Infants with acute self limiting diarrhoea (group 1) had an abnormal overgrowth of organisms in the upper small bowel which was similar to that found in infants whose diarrhoea persisted after 4 days in hospital (group 2). The total duodenal organism count in infants with diarrhoea persisting after 7 days in hospital (group 3) was almost 100 times greater than either of the other groups. The findings may have important implications in preventing persistent diarrhoea from becoming protracted.

Colonization of the upper jejunum by enteropathogenic and enterotoxigenic Escherichia coli in paediatric diarrhoea

Aspirated fluid from the upper jejunum was obtained by intubation of 27 children with diarrhoea and 7 control children without diarrhoea. The aspirated jejunal fluid was analysed for total counts of viable aerobic and anaerobic microorganisms. Gram-negative aerobic bacteria were typed biochemically and analysed for the production of heat-labile and heat-stable enterotoxin. Enteropathogenic Escherichia coli (EPEC) strains of serogroups 0111, 055 and 0127 were detected in the stools of nine patients and the respective strains concomitantly in the upper jejunum (10(3)-10(8) bact/ml) in 7 patients with diarrhoea. In 6 patients from whom isolates of enterotoxigenic E. coli (ETEC) were obtained, there were high total viable counts of non-enterotoxigenic bacteria in the upper jejunum and ETEC were recovered from this location in 3 cases. Enterotoxigenic Klebsiella was recovered from faeces but not from upper jejunum in one case. Compared to the controls, the total number of bacteria in the upper jejunum were 100-1000 times higher in patients with enteropathogenic E. coli (EPEC) or enterotoxigenic E. coli (ETEC). In another 11 cases with diarrhoea caused by Shigella, rotavirus or of unknown aetiology, the total viable counts of bacteria were similar to those of the controls. Five patients with severe EPEC diarrhoea received antibodies for 5 days. The patients improved clinically, and the EPEC strain had disappeared from the upper jejunum when they were reexamined. In conclusion, in EPEC diarrhoea a colonization of the upper jejunum by the causative organism seemed to take place, while in ETEC diarrhoea, there appeared to be a nonspecific contamination by enteric bacteria.

Host defense mechanisms in protein energy malnutrition

This review has focused on effects of protein energy malnutrition on immune responses in the human host. These studies document major impairment of the T-cell and complement systems in severe PEM, and less profound, but probably significant, effects upon B-cells and immunoglobulins, particularly SIgA. While mild-moderate malnutrition also alters the T-cell system and may predispose to infection, there is less evidence to suggest that complement is similarly affected. Indeed, some data suggest that the host with mild to moderate malnutrition is still able to respond to stress with an acute phase serum protein response and to boost serum levels of complement and complement activity. This may be a functionally significant distinction, serving to separate the more from the less severely ill. Because many other factors alter immune responses, including vitamins, calories, and trace metals, and few clinical studies have examined these parameters, it is uncertain how much of the problem in malnutrition is due to protein, to energy intake, to iron, to other micronutrients and trace minerals, to vitamin E or to other vitamins alone or in combination with deficiencies in protein and energy. Other chapters in this volume attempt to sort out these questions in animal studies, but the relevance of these data for the human situation will remain uncertain until the investigations are carried out in humans as well.

Bacteriostasis of Escherichia coli by milk. VI. The in-vitro bacteriostatic property of Gambian mothers' breast milk in relation to the in-vivo protection of their infants against diarrhoeal disease

A one-year field-study has been carried out in a diarrhoea-endemic area in West Africa to determine the relationship between the bacteriostatic activity of fresh human milk for Escherichia coli in vitro and freedom from diarrhoea of the infant recipients of the milk. The specific contribution of E. coli gastroenteritis to gastrointestinal diseases of infants in general is not known, nor is its particular role in the Gambian infants studied. During the study period, however, both enteropathogenic and toxigenic strains of E. coli were isolated. The incidence of diarrhoea in Gambian infants of seven age-groups from 2 days to 12 months was not significantly correlated with the bacteriostatic activity of milk. This was due rather to absence of diarrhoea in babies fed on low-activity milk than illness in those receiving highly bacteriostatic milk. Indeed, very active milk appeared to protect recipients almost completely, including seven babies of over 3 months of age, five of them during the rainy season, when the risk was high. Babies receiving lower-activity milk experienced more diarrhoea. In a situation where diarrhoeal disease is multifactorial, field evaluation of the protective action by one antibacterial property of milk is difficult. A better understanding of in vivo protection is important, and the factors which have to be taken into account are discussed.

Effects of salicylate on intestinal absorption: in vitro and in vivo studies with enterotoxigenic micro-organisms

This study was done to determine whether salicylate could affect alterations in intestinal absorption induced by preparations of enterotoxigenic micro-organisms. It was found in rats that salicylate increased intestinal monosaccharide uptake in vitro and reversed the inhibitory effects induced by cell-free preparations of Staphylococcus sp., Candida sp. and Klebsiella sp. In vivo, salicylates increased net water absorption in rat jejunum exposed to cell-free preparations of various micro-organisms. Increase in net fluid flux occurred after subcutaneous injection only with bacteria which stimulate adenylate cyclase activity. These observations suggest that the absorptive and anti-secretory effects of aspirin are cyclic nucleotide dependent. The potential clinical role of salicylates as anti-secretory agents in diarrhoeal diseases, particularly in children, requires further investigation.

Immunoglobulin-containing cells in jejunal mucosa of children with protein-energy malnutrition and gastroenteritis

Jejunal biopsies from 20 well nourished children (average age 12.8 months) with gastroenteritis, and 20 children (average age 20 months) with protein-energy malnutrition were examined by immunofluorescent technique for immunoglobulins A, G, M, E, and D, and for epithelial glycoprotein secretory component. Compared with previous studies on normal infants, the children with gastroenteritis showed a moderate increase in IgA-containing cells, a large increase in IgM-containing cells, and no change in IgG-containing cells. These findings are similar to previously recorded findings on adults with gastroenteritis. In contrast there was a pronounced and highly significant decrease in IgA-containing cells in the jejunal mucosa of the children with protein-energy malnutrition. No significant differences were noted between the populations of IgG-, IgM-, IgE-, and IgD-containing cells in the two groups. It is suggested that this selective deficiency in mucosal IgA results from a delay in maturation of the secretory IgA system, and the mechanisms of such a deficiency are discussed.

The use of oral glucose electrolyte solution prepared with untreated well water in acute non-specific childhood diarrhoea

When untreated bacterially contaminated well water was used to constitute an oral glucose electrolyte solution, bacterial multiplication was significantly greater in the solution than in the well water. A controlled prospective trial in a West African village, comparing this solution with one prepared from clean drinking water, found no significant differences in the effects of the solutions when they were given to children suffering from acute diarrhoea. The intake of potentially pathogenic organisms from the well water solution was small compared to that from the local weaning foods. In remote areas of developing countries, where general and food hygiene is poor, it may prove possible to use such untreated water in the preparation of therapeutic glucose electrolyte solutions.

Comparison of assay of coliform enterotoxins by conventional techniques versus in vivo intestinal perfusion

Thirty-six strains of coliform bacteria were tested for enterotoxigenicity both by conventional assays, including the Y-1 adrenal and Chinese hamster ovary cell assays for heat-labile toxin and the suckling mouse assay for heat-stable toxin, and by determining the ability of graded concentrations of ultrafiltrate high- or low-molecular-weight toxin preparations to induce water secretion during in vivo perfusion in the rat jejunum. The ultrafiltrates of all 18 strains isolated from persons with infectious diarrheal disease, including seven of Escherichia coli, seven of Klebsiella pneumoniae, and four of Enterobacter cloacae, contained one (nine strains) or two (nine strains) potent toxin fractions (resembling either heat-labile or heat-stable toxin in terms of apparent molecular weight and heat lability characteristics) that induced water secretion at perfusion concentrations of 10 ng/ml or less. Unconcentrated broth filtrates of five of the E. coli strains and two of Klebsiella reacted positively in one or more of the conventional assay systems. Concentrated ultrafiltrates from two strains that were negative in the in vitro assays for heat-labile toxin were tested and also proved to be inactive in these test systems. None of 18 strains isolated from control sources produced, in the ultrafiltrates, enterotoxins capable of inducing water secretion at low concentrations, and none reacted positively in the conventional assays. These results indicate that some strains of coliform bacteria elaborate potent toxin materials that are capable of inducing water secretion and can be detected by perfusion of concentrated ultrafiltrates but not by conventional assay systems for enterotoxigenicity. Whether this represents quantitative or qualitative differences between the toxin materials that stimulate these different test systems remains to be established.

Gastroenteritis in London and Jamaica: a clinical and bacteriological study

The flora of both faeces and small bowel lumen was studied in children with gastroenteritis from London, England, and Kingston, Jamaica. Clinical and laboratory differences between these two groups are described. All bacterial groups in the faeces were greatly altered during gastroenteritis and this particularly affected anaerobic organisms. These changes generally reverted rapidly to normal after the illness. The small bowel flora was also altered during gastroenteritis; there was a tendency for a wider range of organisms including anaerobes to be isolated from the children in Jamacia than from those in England.

Faecal pollution of surface waters in Jakarta

Profuse numbers of Enterobacteriaceae were found in samples of surface waters from the Ciliwung River and adjoining canals which criss-cross metropolitan Jakarta and are used widely for domestic purposes by the poorer sections of its population. 15 of the 20 specimens gres E. coli, Klebsiella were isolated from seven and Citrobacter from four. Using enrichment culture procedures, Salmonella sp. were grown from 10 (48%) of 21 water samples examined, and 12 (63%) of aquatic sediments collected at the same sites. Altogether 14 serotypes and 37 Salmonella isolations were recorded. This high degree of faecal contamination of the environment is a major cause of the immense problem of gastro-intestinal infections in that city and probably in many similar cities in developing countries in the tropics.

The human rumen

The cow is a ruminant, and cow's milk has evolved to promote bacterial growth in the upper small bowel; whereas human milk has evolved to discourage bacterial growth. Examination of the constituents of the two milks shows that their differences can be accounted for in terms of this difference in function. Children who are fed a calf's diet tend to develop a rumen. This may lead to chronic diarrhoea and malnutrition and may be a factor in diarrhoea ascribed to cow's-milk-protein allergy and lactose intolerance.

Immunological interrelationships between cholera toxin and the heat-labile and heat-stable enterotoxins of coliform bacteria

Cholera toxin (CT) and the heat-labile (LT) toxin of Escherichia coli are known to share antigenic properties. The present study examined the immunological relationship of CT and the LT and heat-stable (ST) toxins of E. coli, Klebsiella pneumoniae, and Enterobacter cloacae. The neutralizing capacity of equine CT antiserum and of antiserum raised in rabbits to the LT toxin of the three species of coliform bacteria was evaluated by determining their capacity to inhibit the action of purified CT and semipurified ultrafiltration preparations of the coliform LT and ST toxins in inducing water secretion as assayed by the in vivo marker perfusion technique in the rat jejunum. One milliliter of antiserum to CT and to E. coli and Klebsiella LT completely neutralized the secretory action of each of these three toxins; effective serial dilutions of CT antiserum extended to 1 to 4, whereas those of the antisera to LT were limited to 1 to 2 in most instances. One milliliter of antiserum to E. cloacae LT partially neutralized each of the three coliform LT toxins; serial dilutions were inactive. Antiserum to E. cloacae LT did not neutralize CT. Antiserum to CT and to each of the three coliform LT toxins also had a weak neutralizing effect on the ST toxins of E. coli and Klebsiella, but they did not affect E. cloacae ST. Adsorption of the antiserum to CT and to each of the three LT toxins by incubation with a heat-inactivated preparation of either the homologous or a heterologous LT toxin completely abolished the neutralizing capacity of the antisera towards both LT and ST. These observations indicate that the immunological interrelationship of CT and E. coli LT extends to the LT toxins of Klebsiella and E. cloacae and, further, that these immunological properties are shared to a lesser extent by the ST toxins of E. coli and Klebsiella.