Pathogenic intestinal bacteria: adhesion and invasion

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

Laboratory diagnosis of monoclonal gammopathies. Prospective study of 14 cases in Dakar, Senegal]

BACKGROUND: Short-chain fatty acids (SCFA), produced in the normal colon by bacterial fermentation, are decreased in acute diarrhoea. This may have deleterious effects on epithelial function in the colon. METHODS: The ability of several diarrhoeal pathogens to produce SCFA when incubated with starch in vitro was studied. Isolated pathogens were incubated for 24 h with either no added substrate, glucose, or starch under anaerobic conditions, and SCFA were quantitated by gas-liquid chromatography. RESULTS: Unlike the normal colonic flora, the pathogens produced acetate but not propionate or butyrate. D-Lactate was also produced by all the pathogens studied. When the pathogens were incubated in anaerobic medium containing starch, significantly greater amounts of acetate and significantly lesser amounts of lactate were produced. CONCLUSIONS: The inability of enteric pathogens to produce butyrate may impair epithelial cell function, whereas production of D-lactate may enhance mucosal damage in diarrhoeal disease. The presence of luminal starch may be helpful in shifting the fermentation profile to a more favourable pattern.     

Aetiology of acute diarrhoea in hospitalized children in Hong Kong

To determine the role of enteric pathogens in acute childhood diarrhoea in Hong Kong, 388 children with diarrhoea and 306 children of similar age without diarrhoea were evaluated in a hospital-based study during a one-year period from August 1994 to July 1995. Of the diarrhoeal cases, 55% were under 1 year and 95% were below 5 years of age. On admission, 22% had some dehydration but none was severely dehydrated. All children were well nourished. Oyer 60% of children with diarrhoea had one or more pathogens in their stool. Rotavirus was the most commonly isolated pathogen (34.6%), followed by Salmonella (23.3%), Campylobacter (4.7%) and Shigella (2.1%). Rotavirus was not assessed in the controls and was detected mainly during the winter months December to February. Bacterial pathogens were identified more commonly in diarrhoea patients (30%) than in controls (5.6%) (P < 0.001). Despite rapid recent socioeconomic development in Hong Kong, non-typhoidal Salmonella diarrhoea remains a significant local problem in infants under 1 year. Further detailed assessment of the transmission and prevention of this infection is required.     

Isolation and identification of Aeromonas species from human stools

One thousand and three diarrhoeal stool samples were processed in our laboratory during the period 1996/1997 for the presence of enteric pathogens especially Aeromonas spp., which has emerged as a new agent causing diarrhoea. Ampicillin sheep blood agar was found to be the best medium for the isolation of Aeromonas spp. from stool specimens. Enteric pathogens were found in 200 (20%) stools, of which Aeromonas spp. was the second commonest pathogen isolated amounting to 21% of isolates. This study clearly indicates that Aeromonas spp. must be looked for in every diarrhoeal stool samples, specially in children below 10 years of age. Isolation and identification is cost effective and easy, if the given protocol is observed.     

Enteropathogenic and enterohaemorrhagic Escherichia coli: more subversive elements

Enteropathogenic (EPEC) and enterohaemorrhagic Escherichia coli (EHEC) constitute a significant risk to human health worldwide. Both pathogens colonize the intestinal mucosa and, by subverting intestinal epithelial cell function, produce a characteristic histopathological feature known as the 'attaching and effacing' (A/E) lesion. Although EPEC was the first E. coli to be associated with human disease in the 1940s and 1950s, it was not until the late 1980s and early 1990s that the mechanisms and bacterial gene products used to induce this complex brush border membrane lesion and diarrhoeal disease started to be unravelled. During the past few months, there has been a burst of new data that have revolutionized some basic concepts of the molecular basis of bacterial pathogenesis in general and EPEC pathogenesis in particular. Major breakthroughs and developments in the genetic basis of A/E lesion formation, signal transduction, protein translocation, host cell receptors and intestinal colonization are highlighted in this review.     

Rotavirus vaccines against diarrhoeal disease

Rotaviruses are responsible for more diarrhoeal disease-associated mortality than any other single agent. Vaccination may therefore hold the key to combating diarrhoeal disease worldwide. Natural immunity to rotavirus infection indicates that rather than protection from reinfection such immunity gives rise to less severe and less frequent attacks of diarrhoea. Early attempts to design a rotavirus vaccine with bovine rotavirus failed because of poor efficacy in some developing countries. Research into rhesus rotavirus, particularly the high-titre rhesus rotavirus tetravalent (RRV-TV) vaccine, has given slightly better results. A stumbling block to truly effective oral vaccines seems to be immunogenicity in developing countries. If efficacy can be ensured by trials in the developing countries, money spent on rotavirus vaccines will be well spent.     

Fontanel ultrasonography of purulent meningitis in children in Abidjan (Ivory Coast)

Reactive arthritis (ReA) is one of the most common arthritides affecting young adults. In most cases it follows urogenital or enteric bacterial infection, but its pathogenesis is not fully understood. It is generally considered a sterile arthritis which appears to involve immune response to bacterial organisms and genetic host susceptibility associated with the presence of HLA-B27 antigen. New findings suggest that in some ReA cases, viable bacteria are present inside the joints, and these organisms may cause the disease and trigger the inflammatory response. ReA manifests clinically as a rheumatoid factor negative oligoarthritis associated with enthesopathy and certain mucosal and skin lesions. Laboratory findings in ReA are non-specific. Although concepts of its pathogenesis are still evolving, so-called ReA remains an important condition to be distinguished from rheumatoid arthritis. Prognosis is generally better. Treatments with known effects in some cases include non-steroidal anti-inflammatory drugs, intra-articular corticosteroids, oral tetracyclines and sulphasalazine. The occasional chronic and severe ReA may be very difficult to treat.     

Heart signal recognition by Hidden Markov Models: the ECG case

From December 1989 to May 1990, 315 faecal samples from children under 5 years old with diarrhoea (215) and without diarrhoea (100) seen at paediatric clinics were investigated for bacterial, viral and parasitic enteropathogens. Standard and recently described methods were used for the investigations, which revealed that 74.9% of children with diarrhoea were infected with enteropathogens compared with 28% of controls. In the diarrhoeal group, 59.1% had a bacterial, 26.5% a viral and 2.3% a parasitic aetiology. Rotavirus was the pathogen most frequently detected, accounting for 22.3% of positive findings in the group with diarrhoea versus 9% in the control group. Other important agents were: enterotoxigenic Escherichia coli (ETEC) (14.4 versus 6%), enteropathogenic E. coli (EPEC) (10.7 versus 5%), enteroadherent E. coli (EAEC) (9.3 versus 4%), enterohaemorrhagic E. coli (EHEC) (5.1 versus 3%) and Salmonella spp. (3.3 versus 1%). The following enteropathogens were detected exclusively in the diarrhoeal stools: Shigella spp. (5.1%), Yersinia enterocolitica (0.9%), Aeromonas hydrophila (1.4%), Entamoeba histolytica (0.5%), Giardia lamblia (0.5%), Trichomonas hominis (0.5) and Trichuris trichiura (0.9%). The detection rates of rotavirus, EPEC and EAEC were much greater in the diarrhoeal than in the control patients. No Vibrio cholerae, enteroinvasive E. coli (EIEC), Plesiomonas spp. or Cryptosporidium spp. were detected in this study. Our data suggest that both the traditional and newly recognised diarrhoeal agents are important causes of diarrhoea in the children under 5 years old in Lagos, Nigeria.     

Hygiene behaviour and hospitalized severe childhood diarrhoea: a case-control study

The relationship between personal and domestic hygiene behaviour and hospitalized childhood diarrhoea was examined in a case-control study of 356 cases and 357 controls from low-income families in metropolitan Manila. Indices of hygiene behaviour were defined for overall cleanliness, kitchen hygiene, and living conditions. Only the indices for overall cleanliness and kitchen hygiene were significantly associated with diarrhoea. An increasing excess risk of hospitalization with severe diarrhoea was noted as the ratings for standards of hygiene became lower, and this excess risk persisted even after controlling for confounding variables. The implications of our findings for the control of diarrhoeal disease are discussed.     

Human hepatitis B virus and hepatocellular carcinoma. I. Experimental infection of tree shrews with hepatitis B virus

A cross-sectional study involving 771 children under the age of one year, was carried out in a traditional area of urban Ilorin, Nigeria, to determine how socio-economic conditions and feeding practices relate to diarrhoeal disease among infants. After adjustment has been made (through logistic regression) for covariates, five factors had significant association with diarrhoeal disease. These are the age of the child, parity, mother's education, availability of household kitchen and the feeding of semi-solid food to the infants. The lowest diarrhoeal rate occurred in infants aged 0-3 months while the highest rate occurred among infants seven to nine months old (Odds Ratio = 4.2). Children who were of the fifth or higher birth order had significantly higher risk of diarrhoea when compared with those who were of the first or second birth order (OR = 1.62; P < 0.05). Children of mothers with secondary education had significantly higher risk of diarrhoea compared with children of illiterates (OR = 1.9; P < 0.05). Households that had no kitchen had significantly higher risk of infantile diarrhoea than households with kitchen facilities (P < 0.01). Finally, infants receiving semi-solid food had higher risk of diarrhoea compared to those children not receiving semi-solid food (P < 0.05). Diarrhoeal disease awareness campaign to educate mothers on the dangers of childhood diarrhoea and how to prevent it, through proper hygiene, especially, food hygiene, is advocated.     

The molecular basis of intractable diarrhoea of infancy

The intractable diarrhoeas of infancy present very major problems of clinical management. However, the conceptual importance of these conditions lies in the information that they may provide about normal small-intestinal function in humans: among such infants will be found the human equivalents of the 'knock-out' mice, in which targeted gene disruption allows sometimes unexpected insight into the regulation of intestinal function. The challenge posed by the intractable diarrhoeal syndromes, of working backwards from an apparently common phenotype to probably multiple genotypes, is, however, immense. Very few of these conditions have been described at the genetic level, although the molecular basis of pathogenesis has been better explored in recent years. The two major groups of intractable diarrhoea are due to (1) primary epithelial abnormalities (which usually present within the first few days of life) and (2) immunologically mediated (which generally present after the first few weeks). The high prevalence of autoimmune enteropathy among infantile autoimmune disease, in contrast to adult autoimmunity, is intriguing and may reflect constitutive abnormality of extrathymic lymphocyte maturation. The use of potent immunosuppressive drugs and increasing expertise with parenteral nutrition are improving the outlook of these previously fatal conditions. Viewed globally, however, the pressing problem is to treat effectively the millions of infants who die from severe persistent diarrhoea and wasting, which would certainly not be considered intractable in wealthy countries.     

Enteric pathogens in severe forms of acute gastroenteritis in Ghanaian children

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

A case-control study of diarrhoea in children caused by Escherichia coli producing heat-stable enterotoxin (EAST-1)

Escherichia coli strains associated with diarrhoeal disease have been classified into several types according to the pathogenic mechanism. Among these, enteroaggregative E. coli strains (EAggEC) have been associated with persistent childhood diarrhoea. Some strains of EAggEC produce a heat-stable toxin (EAST-1) that differs from others described previously. The main goal of this case-control study was to determine the prevalence of EAggEC and EAST-1-producing E. coli strains as a cause of diarrhoea in children in Spain and to study their in-vitro susceptibility to 21 antimicrobial agents. In the case group (115 children) 22 (19%) isolates and four (3.5%) isolates were EAST-1-producing E. coli and EAggEC, respectively, whereas in the control group (79 children) four (5%) isolates produced EAST-1 (p = 0.005) and three (3.8%) isolates were EAggEC. The present study suggests that EAST-1-producing E. coli strains are associated with diarrhoeal diseases in Spanish children, whereas EAggEC strains are not. Moreover, EAST-1-producing E. coli strains showed a high susceptibility to all the antimicrobial agents tested except for ampicillin.     

Training doctors for tomorrow

Enterotoxaemia of sheep and goats occurs worldwide, but the condition in goats is poorly understood. The disease in goats is mostly caused by Clostridium perfringens type D, although the role of the toxins of this microorganism in the pathogenesis of the disease is not fully understood. The disease occurs in three forms, peracute, acute and chronic, the cardinal clinical sign of the acute and chronic forms being diarrhoea. The main biochemical alterations are hyperglycaemia and glycosuria, while at necropsy the disease is often characterized by haemorrhagic colitis. The typical histological changes observed in the brain of sheep with enterotoxaemia are not considered to be a common feature of enterotoxaemia in goats. Although the pathogenesis of caprine enterotoxaemia has not yet been properly defined, it is usually accepted that the presence of C. perfringens type D in the small bowel, together with a sudden change to a diet rich in carbohydrates, is the main predisposing factor for the disease. Vaccination seems to be poorly effective in preventing caprine enterotoxaemia, which might be due to the fact that the enteric form of the disease is partially independent of circulating C. perfringens toxin. More studies are needed on caprine enterotoxaemia, especially of its pathogenesis and immunity, in order to develop more efficient control measures for this disease.     

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

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

Mechanism and treatment of diarrhoea due to Vibrio cholerae and Escherichia coli: roles of drugs and prostaglandins

The primary objectives of these studies were to determine the clinical efficacy and safety of the potential antisecretory and antimicrobial drugs in the treatment of diarrhoea due to Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC). The drugs evaluated were chlorpromazine (CPZ), nicotinic acid, berberine, indomethacin, chloroquine, tetracycline, furazolidone, and bioflorin. Additionally, the role of prostaglandins (PGs) in the pathogenesis of cholera diarrhoea has been studied. The drug studies were carried out as placebo-controlled, randomized clinical trials in patients with active diarrhoea due to vibrio cholerae and ETEC. All patients received intravenous (i.v.) or oral rehydration solutions (ORS), but no other medications except the study drugs. Results indicate that CPZ (1 mg/kg or 4 mg/kg), berberine (200 mg), and nicotinic acid (2 g) all reduced stool volumes from 30% to more than 50% in diarrhoeal patients without significant side effects. It appeared that berberine was more effective in ETEC diarrhoea than in cholera. However, chloroquine, indomethacin, clonidine, and bioflorin had no clinically useful effects. Among the antimicrobial agents, a single dose of tetracycline was found to be effective in cholera, because the drug significantly (p < 0.05) reduced the total stool volume from 20.9 +/- 15.9 to 10.5 +/- 8.6 (liters in 6-days, mean +/- SD) compared to furazolidone. Drugs other than antimicrobial and antisecretory agents were also evaluated in the treatment of cholera. It has been shown that treatment with bioflorin, which is a bacterial preparation of lyophilized Streptococcus faecium, did not significantly (p > 0.05) reduce fluid-loss in cholera. Additional studies in animals indicated that treatment with short chain glucose polymers, alone or in combination with a chloride blocking agent, anthracene-9-carboxylic acid (A9C), significantly reduced intestinal secretion in a rat model of secretory diarrhoea. For the first time it was demonstrated that jejunal prostaglandin (PG) E2 concentrations were significantly increased during acute cholera and correlated with the volumes of stool and duration of diarrhoea. Furthermore, it was shown that treatment with indomethacin, a potent inhibitor of PG synthesis, significantly reduced jejunal PGE2 output in adults with acute cholera, in addition to net secretion of water and electrolytes. In summarizing the results, it is concluded that: (1) CPZ, berberine, and nicotinic acid are potential antidiarrhoeal agents, (2) PGs are involved in the pathogenesis of cholera, (3) tetracycline and furazolidone are effective antimicrobial agents in cholera, (4) and glucose short-chain polymers (used with the chloride blocking agent, anthracene-9-carboxylic acid) are better sources of carbohydrates in oral rehydration solutions.     

Oral rehydration therapy in the management of diarrhea

Importance of oral rehydration solution in the treatment of diarrhoeal diseases in well-known. It can be applied in all types of diarrhoea, practically, without any side effects, complications, such hypernatraemia is avoidable. It has proved to be effective for the dehydration, caused by diarrhoea, and for the diarrhoea, too. The authors review the position of oralis rehydration liquid in the therapy of diarrhoea, the pathophysiology and epidemiology of diarrhoeal diseases. The therapeutic practices, suitable composition of oral rehydration solution, cost-benefit considerations, further possible indications of solution are discussed as well. The authors give background information about the modification of the composition of oral rehydration solution, recommended by the World Health Organization, and call the attention to the importance of the alteration of health officer's view about the oral rehydration therapy.     

Return from the tropics: relevant diagnosis and rational therapy

Gastrointestinal disorders, particularly diarrhoea, are the main reason to consult a physician after travelling to the tropics. Although mostly of infectious origin specific pathogens frequently cannot be demonstrated. As the majority of acute diarrhoeal episodes resolve without any specific therapy, bacterological and parasitological investigations should initially be ordered with reserve and economically. Fever after a stay in the tropics has to be always a matter of concern as it could be the expression of a potentially dangerous infection, e.g. falciparum malaria. The primary objective must be the exclusion of potentially life-threatening infections requiring a specific treatment. Numerous asymptomatic travellers returning from the tropics want their physicians to exclude an inapparent exotic infection. The value of such check-ups can be questioned, and there are just a few rational investigations in this particular context.     

Bacterial pathogens associated with diarrhoea on the island of Crete

Stool specimens from 3,600 diarrhoeal patients from the island of Crete, Greece, were examined for bacterial pathogens, during a three-year period (1992-1994). One or more pathogens were identified in 826 patients (22.9%), more often from children. Salmonella spp. were the most frequently isolated organisms in 13.6% of the patients, followed by Campylobacter in 4.7%, and enteropathogenic Escherichia coli (EPEC) in 3.9%. Yersinia enterocolitica was found in 0.7%, Shigella spp. in 0.7% and Aeromonas hydrophila in 0.05%. Vibrio spp. and enterohaemorragic E. coli were not identified in the stools tested. Resistance to ampicillin was observed in 36% of the Salmonella, 62% of the Shigella, and 27% of the EPEC isolates. Cotrimoxazole resistance was observed in 42% of the Shigella and 12% of the EPEC isolates, while tetracycline and the quinolones were inactive against almost half and erythromycin against 20% of the Campylobacter isolates. This is the first study investigating bacterial pathogens associated with diarrhoea on the island of Crete.     

The experience with neutron irradiation in locally advanced adenocarcinoma of the prostate

The protective effect of breastfeeding against infantile diarrhoea may be less pronounced in areas with modern water supply and sanitation facilities. This finding raises the question whether protection by breastfeeding against infantile diarrhoea in developing countries will decline with improvement in water supply and sanitation. To address this question a historical cohort study of the associations between feeding modes and diarrhoea incidence and severity in children aged 0-14 months at baseline was done in Al Ain city, United Arab Emirates. In this city in a newly developed country, modern water supply and sanitation facilities have become available to everyone during the last two decades. During three months of follow-up of 249 children, the nonbreastfed had more diarrhoea than did the partly breastfed, who in turn had more diarrhoea than did the fully breastfed. After multivariate adjustment, this dose-response effect was consistent for three measures of diarrhoeal morbidity in each child: occurrence or non-occurrence of incidence episodes, number of episodes, and total severity score. However, significant differences were seen only between the nonbreastfed and fully breastfed subgroups. These results indicate that in Al Ain, despite the universal access to modern water supply and sanitation facilities, breastfeeding plays an important role in reducing the incidence and severity of infantile diarrhoea. This observation is particularly important given the growing concern that, as an unwanted effect of 'modernisation', breastfeeding is on the decline in Al Ain and comparable populations elsewhere.