Etiology and epidemiology of diarrhea in children in Hanoi, Vietnam

An exploration of spatial patterns of seasonal diarrhoeal morbidity in Thailand

Studies of temporal and spatial patterns of diarrhoeal disease can suggest putative aetiological agents and environmental or socioeconomic drivers. Here, the seasonal patterns of monthly acute diarrhoeal morbidity in Thailand, where diarrhoeal morbidity is increasing, are explored. Climatic data (2003-2006) and Thai Ministry of Health annual reports (2003-2009) were used to construct a spatially weighted panel regression model. Seasonal patterns of diarrhoeal disease were generally bimodal with aetiological agents peaking at different times of the year. There is a strong association between daily mean temperature and precipitation and the incidence of hospitalization due to acute diarrhoea in Thailand leading to a distinct spatial pattern in the seasonal pattern of diarrhoea. Model performance varied across the country in relation to per capita GDP and population density. While climatic factors are likely to drive the general pattern of diarrhoeal disease in Thailand, the seasonality of diarrhoeal disease is dampened in affluent urban populations.

Prevalence of gastrointestinal pathogens in Sub-Saharan Africa: systematic review and meta-analysis

A significant proportion of vulnerable people in sub-Saharan Africa (SSA) remain at risk for contracting diarrhoeal diseases due to the presence of many risk factors facilitating their transmission. A systematic review of published articles from the SSA region was done to determine the prevalence and types of diarrhoeal pathogens in circulation, based on a search of databases, including EBSCO host, PubMed, Scopus, Science Direct, Google scholar and Web of Science was done between September 2009 and December 2010. Data were summarized from 27 studies, with pooled data analysed and reported. Pathogens were isolated from between 26.8–65.6% of cases, with an overall isolation rate of 55.7% (95% CI, 48.2–62.9%). Isolation rates were highest amongst adult cases followed by children, and the odds of isolating a pathogen was greater in diarrhoeal cases (Odds Ratio 4.93 (95% CI, 1.99 to 12.23), than in asymptomatic controls. Overall isolation ranged from 8% to 99%; and heterogeneity testing suggests differences between age groups (Q=5.806; df=2, P=0. 055). Mixed E. coli spp., (29.95%), Cryptosporidium (21.52%), Cyclospora (18%), Entamoeba. (13.8%), Shigella spp. (10.49%), Salmonella spp. (8.36%), and Campylobacter spp. (8.33%), were most commonly reported, and rotavirus was the most common virus isolated. This is the first review to look at the range of enteric pathogens circulating in SSA, and has confirmed high rates of isolation of pathogens from diarrhoeal cases. Public health practitioners can use this information to understanding the challenges related to diarrhoeal illness and set priorities for their prevention and control.

Spatio-temporal patterns of diarrhoeal mortality in Mexico

Diarrhoeal mortality rates in Mexican children dramatically declined during the 1980s and 1990s, concomitant with a temporal shift in peak deaths from summer to autumn-winter. The spatial dynamics of these patterns have not previously been studied. We first describe the seasonal features of paediatric diarrhoeal mortality in Mexico as a whole, then across individual states. While no geographical gradients in the magnitude of diarrhoeal mortality rates have been detected in recent years, we identified a distinct spatial pattern in the timing of peak mortality rate. In the 1980s the summer peak mortality was earliest around Mexico's capital and later in states to the southeast and northwest. Our results suggest that the direction and timing of those annual waves are related to the mean monthly precipitation and mean daily temperature. This pattern has disintegrated in recent years as the summer peak has diminished.

Etiology of diarrhea in young children and patterns of antibiotic resistance in Cambodia

BACKGROUND

Little is known about diarrhea etiology and antibiotic resistance in developing countries where diarrhea is a major public health problem.

METHODS

To describe diarrhea etiology and antibiotic resistance patterns in Cambodia, 600 children aged 3 months to 5 years with acute diarrhea (cases) and 578 children without diarrhea (controls) were enrolled from a hospital in Phnom Penh. Stool samples were collected, and pathogens and antibiotic resistance patterns were described.

RESULTS

The most frequently isolated pathogens in these cases were enteroaggregative Escherichia coli (20%) and rotavirus (26%). Enterotoxigenic E. coli, enteroaggregative E. coli, Shigella, Aeromonas, rotavirus, and adenovirus were statistically significantly associated with diarrhea. Among cases, vomiting was associated with viral infections, whereas bloody stool was associated with Shigella. Enterotoxigenic E. coli isolates were highly resistant to ampicillin, sulfonamides, and tetracycline. Approximately 50% of Campylobacter coli and 30% of Campylobacter jejuni isolates were resistant to nalidixic acid and ciprofloxacin. Over 33% of Salmonella isolates were resistant to ampicillin and tetracycline, and almost 100% of Shigella isolates were resistant to trimethoprim/sulfamethoxazole.

CONCLUSIONS

These data on the etiology of diarrhea and antibiotic resistance patterns in Cambodia will have significant effect on local public health policies and on local resource prioritization practices.

Bacterial enteropathogens and risk factors associated with childhood diarrhea

OBJECTIVE

To investigate the etiology of bacterial enteropathogens causing diarrhea among children; to elucidate the risk factors, sign and symptoms involved in developing of infection; and to identify the antimicrobial susceptibility pattern.

METHODS

Stool samples from diarrheal cases with clinical diagnosis of gastroenteritis compared to matched controls, were examined for detection of bacterial enteropathogens by conventional cultural method from February 2006 through January 2007.

RESULTS

Ninety three of diarrheal cases comprising enteropathogen isolates. A recognized bacterial enteric pathogen was identified in 31% of the cases and 8% of the control group. The frequency of isolated enteropathogens from faeces of diarrheal cases was recorded in the following order, Enterohemorrhagic E. coli 8.3%, Shigella spp. 6.7%, Campylobacter jejuni 5%, Salmonella spp. 4%, Yersinia enterocolitica 2.7%, Aeromonas spp. 4.7%, and Plesiomonas spp. 1.3%. E.H.E coli, Shigella and Salmonella had shown a significant statistical association with diarrhea (p<0.05). Compared to matched uninfected control, multivariate analysis revealed that malnutrition status (OR adjusted 8.37; p<0.001) was the only independent factor associated with infection. Antibiotic susceptibility profile indicated that enteropathogens were generally susceptible to meropenem, ceftriaxone, followed by amikacin and ciprofloxacin. Almost all enteropathogens were resistant to ampicillin and amoxicillin.

CONCLUSIONS

The results of this study emphasize the importance of bacterial enteropathogens in causing severe diarrhea in children. E.H.E. coli was the most predominant pathogen. Malnutrition was identified as the main independent risk factor associated with developing of infection. Ampicillin and amoxicillin should not be used as empirical treatment in acute diarrhea.

Case-control study of diarrheal disease etiology in a remote rural area in Western Thailand

The objective was to assess the association of enteric pathogens in diarrheal disease in a remote rural area in Thailand. Stool specimens were collected from 236 children aged 3 months to 5 years with acute diarrhea (cases) and from 236 asymptomatic controls. Standard microbiologic methods, and enzyme immunoassay for viral pathogens, Giardia, and Cryptosporidium, were used to identify enteric pathogens with susceptibility testing by disk diffusion. Campylobacter, Plesiomonas, Salmonella, and enterotoxigenic Escherichia coli were commonly isolated from cases and controls (22% versus 25%, 10% versus 11%, 6% versus 9%, and 10% versus 6%, respectively). Only Shigella, rotavirus, and adenovirus were identified significantly more frequently in cases than controls (9% versus 0%, 18% versus 3%, and 16% versus 2%, respectively), whereas Giardia lamblia was detected less often in cases than controls. Most pre-school children were infested with enteric pathogens; laboratory-based studies are important to understand the epidemiology of enteric pathogens in remote areas among marginal populations.

Distribution, detection of enterotoxigenic strains and antimicrobial drug susceptibility patterns of bacteroides fragilis group in diarrheic and non-diarrheic feces from brazilian infants

Despite the importance of gastrointestinal diseases and their global distribution, affecting millions of individuals around the world, the role and antimicrobial susceptibility patterns of anaerobic bacteria such as those in the Bacteroides fragilis group (BFG) are still unclear in young children. This study investigated the occurrence and distribution of species in the BFG and enterotoxigenic strains in the fecal microbiota of children and their antimicrobial susceptibility patterns. Diarrheic (n=110) and non-diarrheic (n=65) fecal samples from children aged 0-5 years old were evaluated. BFG strains were isolated and identified by conventional biochemical, physiological and molecular approaches. Alternatively, bacteria and enterotoxigenic strains were detected directly from feces by molecular biology. Antimicrobial drug susceptibility patterns were determined by the agar dilution method according to the guidelines for isolated bacteria. BFG was detected in 64.3% of the fecal samples (55% diarrheic and 80.4% non-diarrheic), and 4.6% were enterotoxigenic. Antimicrobial resistance was observed against ampicillin, ampicillin/sulbactam, piperacillin/tazobactam, meropenem, ceftriaxone, clindamycin and chloramphenicol. The data show that these bacteria are prevalent in fecal microbiota at higher levels in healthy children. The molecular methodology was more effective in identifying the B. fragilis group when compared to the biochemical and physiological techniques. The observation of high resistance levels stimulates thoughts about the indiscriminate use of antimicrobial drugs in early infancy. Further quantitative studies are needed to gain a better understanding of the role of these bacteria in acute diarrhea in children.

Ancestral lineages of human enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a common cause of diarrhea among children living in and among travelers visiting developing countries. Human ETEC strains represent an epidemiologically and phenotypically diverse group of pathogens, and there is a need to identify natural groupings of these organisms that may help to explain this diversity. Here, we sought to identify most of the important human ETEC lineages that exist in the E. coli population, because strains that originate from the same lineage may also have inherited many of the same epidemiological and phenotypic traits. We performed multilocus sequence typing (MLST) on 1,019 ETEC isolates obtained from humans in different countries and analyzed the data against a backdrop of MLST data from 1,250 non-ETEC E. coli and eight ETEC isolates from pigs. A total of 42 different lineages were identified, 15 of which, representing 792 (78%) of the strains, were estimated to have emerged >900 years ago. Twenty of the lineages were represented in more than one country. There was evidence of extensive exchange of enterotoxin and colonization factor genes between different lineages. Human and porcine ETEC have probably emerged from the same ancestral ETEC lineage on at least three occasions. Our findings suggest that most ETEC strains circulating in the human population today originate from well-established, globally widespread ETEC lineages. Some of the more important lineages identified here may represent a smaller and more manageable target for the ongoing efforts to develop effective ETEC vaccines.

Comparison of clinical associations and laboratory abnormalities in children with moderate and severe dehydration

OBJECTIVES

To search for possible early clinical associations and laboratory abnormalities in children with severe dehydration in northern Jordan.

PATIENTS AND METHODS

We prospectively evaluated 251 children with acute gastroenteritis. Dehydration assessment was done following a known clinical scheme. Probable clinical associations and laboratory abnormalities were examined against the preassigned dehydration status.

RESULTS

Children with severe dehydration had significantly more hypernatremia and hyperkalemia, less isonatremia, and higher mean levels of urea, creatinine, and glucose (P < 0.005). Receiver operating characteristic curves showed statistically significant area under the curve values for laboratory variables. These area under the curve values were 0.991 (95% confidence interval [CI] 0.980-1.001) for serum urea, 0.862 (95% CI 0.746-0.978) for sodium, 0.850 (95% CI 0.751-0.949) for creatinine, 0.69 (95% CI 0.555-0.824) for potassium, and 0.684 (95% CI 0.574-0.795) for glucose (P < 0.05 for all). Certain independent serum cutoff levels of urea, creatinine, sodium, glucose, and potassium had high negative predictive value (100%), whereas other cutoff values for each, except potassium, had high positive predictive value (100%) for severe dehydration. Historic clinical characteristics of patients did not correlate to dehydration degree.

CONCLUSIONS

Serum urea, creatinine, sodium, potassium, and glucose were useful independently in augmenting clinical examination to diagnose the degree of dehydration status among children presenting with gastroenteritis. Serum urea performed the best among all. On the contrary, none of the examined historical clinical patterns could be correlated to the dehydration status. Larger and multicenter studies are needed to validate our results and to examine their impact on final outcomes.

Coculture fermentations of Bifidobacterium species and Bacteroides thetaiotaomicron reveal a mechanistic insight into the prebiotic effect of inulin-type fructans

Four bifidobacteria, each representing a cluster of strains with specific inulin-type-fructan degradation capacities, were grown in coculture fermentations with Bacteroides thetaiotaomicron LMG 11262, a strain able to metabolize both oligofructose and inulin. In a medium for colon bacteria with inulin as the sole added energy source, the ability of the bifidobacteria to compete for this substrate reflected phenotypical variation. Bifidobacterium breve Yakult, a strain that was not able to degrade oligofructose or inulin, was outcompeted by B. thetaiotaomicron LMG 11262. Bifidobacterium adolescentis LMG 10734, a strain that could degrade oligofructose (displaying a preferential breakdown mechanism) but that did not grow on inulin, managed to become competitive when oligofructose and short fractions of inulin started to accumulate in the fermentation medium. Bifidobacterium angulatum LMG 11039(T), a strain that was previously shown to degrade all oligofructose fractions simultaneously and to be able to partially break down inulin, was competitive from the beginning of the fermentation, consuming short fractions of inulin from the moment they appeared. Bifidobacterium longum LMG 11047, representing a cluster of bifidobacteria that shared both high fructose consumption and oligofructose degradation rates and were able to perform partial breakdown of inulin, was the dominating strain in a coculture with B. thetaiotaomicron LMG 11262. These observations indicate that distinct subgroups within the large-intestinal Bifidobacterium population will be stimulated by different groups of prebiotic inulin-type fructans, a variation that could be reflected in differences concerning their health-promoting effects.

Fever in Common Infectious Diseases

#x203A; Infection of the respiratory tract is the most common reason for seeking medical advice and hospital admission in children. A viral upper respiratory tract infection (URTI) is the most common infection of the respiratory tract.

› In developing countries, acute respiratory infection remains a leading cause of childhood mortality, causing an estimated 1.5–2 million deaths annually in children younger than 5 years of age.

› In developed countries, viruses are responsible for most upper and lower respiratory tract infections, including pharyngitis and pneumonia.

› Although the degree of fever cannot differentiate between viral and bacterial diseases, high fever is associated with a greater incidence of serious bacterial diseases such as pneumonia or meningitis.

› Worldwide, diarrheal disease is the leading cause of childhood deaths under 5 years of age.

› If the fever does not have an evident source, urinary tract infection (UTI) should be considered, particularly if the fever is greater than 39.0°C and persists for longer than 24–48 h.

› Widespread vaccinations against bacteria causing meningitis, such as Hib, and vaccines against meningococci and pneumococci have dramatically reduced the incidence of meningitis.

› A child with fever and nonblanching rash should be promptly evaluated to exclude meningococcal diseases.

› Young children with malaria may present with irregular fever and not with typical paroxysms of fever, occurring particularly in early falciparum infection or as a consequence of previous chemoprophylaxis, which modifies the typical pattern of fever.

The role of hygienic bathing after defecation in the transmission of Schistosoma mansoni

Transmission of Schistosoma mansoni depends on fecal eggs reaching water, but the way this happens is poorly understood. We studied the role of hygienic bathing after defecation in the contamination of water with S. mansoni eggs. Individuals in an endemic community in Northern Senegal (n=991) were examined for S. mansoni infection and a random sample (22%) was interviewed about stool disposal practices and hygienic behavior. We assessed the presence and viability of S. mansoni eggs adhering to the peri-anal region of 13 infected volunteers, by counting the miracidia in the water they had used for hygienic washing; for 10 of them (77%) miracidia were demonstrated. From the population infection distribution, average number of defecations per day, proportion of individuals bathing after defecation, and association between miracidial counts and infection intensity, we calculated a daily population miracidial output of approximately 30,000 through hygienic bathing. For comparison, one complete stool reaching the water was calculated to yield approximately 2500 miracidia. Thus, 12 individuals in this population should defecate into the water every day to produce the same number of miracidia as through hygienic bathing. Our results suggest a major role of hygienic bathing after defecation in the transmission of S. mansoni.

Safety of raw meat and shellfish in Vietnam: an analysis of Escherichia coli isolations for antibiotic resistance and virulence genes

This study was conducted to examine a current baseline profile of antimicrobial resistance and virulence of Escherichia coli isolated from foods commonly sold in the market place in Vietnam. E. coli were isolated from 180 samples of raw meat, poultry and shellfish and also isolated from 43 chicken faeces samples. Ninety-nine E. coli isolates recovered from all sources were selected for the investigation of their susceptibility to 15 antimicrobial agents by the disk diffusion method. Eighty-four percent of the isolates were resistant to one or more antibiotics, and multi-resistance, defined as resistance to at least 3 different classes of antibiotics, was detected in all sources. The rates of multi-resistance were up to 89.5% in chicken, 95% in chicken faeces and 75% in pork isolates. Resistance was most frequently observed to tetracycline (77.8%), sulfafurazole (60.6%), ampicillin (50.5%), amoxicillin (50.5%), trimethoprim (51.5%), chloramphenicol (43.4%), streptomycin (39.4%), nalidixic acid (34.3%) and gentamicin (24.2%). In addition, the isolates also displayed resistance to fluoroquinolones (ciprofloxacin 16.2%, norfloxacin 17.2%, and enrofloxacin 21.2%), with chicken isolates showing the highest rates of resistance to these antibiotics (52.6-63.2%). Thirty-eight multi-resistant isolates were selected for further the examination of antibiotic resistance genes and were also evaluated for virulence gene profiles by multiplex and uniplex polymerase chain reaction. The beta-lactam TEM gene and tetracycline resistance tetA, tetB genes were frequently detected in the tested isolates (84.2% and 89.5% respectively). Genes which are responsible for resistance to streptomycin (aadA) (68.4%), chloramphenicol (cmlA) (42.1%), sulfonamides (sulI) (39.5%), trimethoprim (dhfrV) (26.3%) and kanamycin (aphA-1) (23.7%) were also widely distributed. Plasmid-mediated ampC genes were detected in E. coli isolates from chicken and pork. The isolates were tested for the presence of 58 virulence genes for adhesins, toxins, capsule synthesis, siderophores, invasins and others from different E. coli pathotypes. All of the tested isolates contained at least one virulence gene and there were 16 genes detected. Virulence genes detected were fimH (92.1%), bmaE (84.2%), TSPE4.C2 (42.1%), aidA AIDA-I (orfB) (31.6%), east1 (26.3%), traT (23.7%), and others including fyuA, iutA, chuA, yjaA, iss, iroN(E. coli), ibeA, aah (orfA), iha and papG allele III (10.5-2.6%). Typical toxin genes produced by enterohemorrhagic and enterotoxigenic E. coli pathotypes (a heat-stable toxin (ST), heat-labile toxin (LT) and Shiga toxin stx1, stx2) were not detected in any of these 38 isolates. The study has revealed that E. coli in raw foods is a significant reservoir of resistance and virulence genes.

Diarrheagenic Escherichia coli and Shigella strains isolated from children in a hospital case-control study in Hanoi, Vietnam

This case-control study detected and characterized Shigella and diarrheagenic Escherichia coli (DEC) types among Vietnamese children less than 5 years old. In 249 children with diarrhea and 124 controls, Shigella spp. was an important cause of diarrhea (P < 0.05). We used multiplex PCR and DNA probes to detect enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAggEC), enteropathogenic E. coli (EPEC), attaching and effacing E. coli (A/EEC), verocytotoxin-producing E. coli (VTEC), and enterotoxigenic E. coli (ETEC). The prevalences of DEC in the diarrhea and control groups were 25.7 and 10.5%, respectively. In 62 children with diarrhea, 64 DEC strains included 22 EAggEC (8.8%), 2 EIEC (0.8%), 23 A/EEC (9.2%), 7 EPEC (2.8%), and 10 ETEC strains (4.0%). Among controls, 13 DEC strains included 5 EAggEC strains (4.0%), 7 A/EEC strains (5.6%), and 1 EPEC strain. The characterization of DEC by serotypes, antimicrobial susceptibility patterns, virulence genes, and pulsed-field gel electrophoresis showed the occurrence of many different and highly heterogenic DEC subtypes, but common serotypes were found among ETEC, EIEC and EPEC, respectively. Serotyping was used to distinguish between A/EEC and EPEC. However, A/EEC, EPEC, and EAggEC were isolated at high frequency from both cases and controls. Further in-depth studies are needed to better understand important virulence factors of DEC, especially A/EEC, EPEC, and EAggEC.

Role of Escherichia coli in acute diarrhoea in tribal preschool children of central India

Five hundred and eighty preschool children belonging to tribal areas of Madhya Pradesh were followed up daily for the presence of diarrhoea for a period of 1 year. In all, 1236 episodes of diarrhoea were recorded with an average of 2.13 episodes per child per year. Stool samples were collected during 780 episodes. They were cultured to isolate Escherichia coli as well as non-E. coli enteropathogens. Ten different genes were detected to identify all diarrhoeagenic E. coli using multiplex polymerase chain reaction. Enteroaggregative E. coli was the commonest diarrhoeagenic E. coli and was isolated from 64 children, followed by enteropathogenic E. coli (27), enterotoxigenic E. coli (10) and enterohaemorrhagic E. coli (2). Other enteropathogens detected were bacteria such as Shigella sp, Vibrio cholerae and Salmonella sp, parasites such as Giardia lamblia and Entameba histolytica, and rotavirus. Most of the bacterial pathogens were multi-drug resistant. The study shows that diarrhoeagenic E. coli contribute significantly to the burden of acute diarrhoea in tribal preschool children.

Diarrhoeagenic Escherichia coli and other causes of childhood diarrhoea: a case-control study in children living in a wastewater-use area in Hanoi, Vietnam

A case-control study was conducted to identify the aetiology of diarrhoeal diseases in pre-school children in a suburban area of Hanoi where the use of untreated wastewater in agriculture and aquaculture is a common practice. Stool specimens and clinical information were collected from 111 pairs of children with diarrhoea and healthy controls. A total of 73 cases (66 %) and 41 controls (36 %) had an enteric pathogen. The pathogens most often associated with diarrhoea were rotavirus (17 % of cases) and Entamoeba histolytica (15 %), followed by Shigella (5 %). Diarrhoeagenic Escherichia coli (DEC) was found in 23 % of both patients and controls. Characterization of DEC by serotyping, antimicrobial susceptibility test and PFGE showed that DEC represented by different pathotypes belonged to various serotypes. Except for three enterotoxigenic E. coli strains, typing by PFGE revealed no correlation between pathotype and serotype of DEC strains. This suggests a high prevalence of a variety of DEC subtypes in this area. For this particular region, vaccine development strategies targeting rotavirus and Shigella are likely to be of public health benefit, whereas the role of DEC and preventive measures need to be further elaborated.

Advances in defining etiology and new therapeutic approaches in acute diarrhea

Defining etiology of acute diarrhea is critical to disease therapy and prevention. In this review we look at recent developments in etiologic agents of acute diarrhea and advances in therapy and prevention of the illness. Newly appreciated agents include enterotoxigenic Bacteroides fragilis, Klebsiella oxytoca and Laribacter hongkongensis. Atypical enteropathogenic E. coli (EPEC) strains lacking the gene for epithelial attachment appear to be more important as causes of diarrhea than traditional EPEC strains. Enterotoxigenic E. coli and enteroaggregative E. coli diarrhea known to be important abroad, have recently been shown to occur in the United States. Non-O157:H7 strains of Shiga toxin-producing E. coli are increasing and infrequently are being sought. There is currently a serious epidemic of nosocomial diarrhea due to a fluoroquinolone-resistant and more virulent and difficult to treat strain of C. difficile. Rotavirus vaccine development should lead to reduction of infant gastroenteritis mortality in infants living in developing regions. Noroviruses produce outbreaks of water- and food-borne disease but show broad genetic diversity. Reduced osmolarity oral rehydration treatment (ORT) and recombinant human lactoferrin/lysozyme plus rice-based ORT effectively treat acute diarrhea. Probiotics were shown to be effective in preventing antibiotic associated- and C. difficile-diarrhea. Rifaximin prevents and azithromycin effectively treats travelers' diarrhea.

Dipstick for rapid diagnosis of Shigella flexneri 2a in stool

BACKGROUND

Shigellosis or bacillary dysentery, an acute bloody diarrhoea, is a major public health burden in developing countries. In the absence of prompt and appropriate treatment, the infection is often fatal, particularly in young malnourished children. Here, we describe a new diagnostic test for rapid detection, in stool, at the bedside of patients, of Shigella flexneri 2a, the most predominant agent of the endemic form of the disease.

METHODOLOGY/PRINCIPAL FINDINGS

The test is based on the detection of S.flexneri 2a lipopolysaccharide (LPS) using serotype 2a-specific monoclonal antibodies coupled to gold particles and displayed on one-step immunochromatographic dipstick. A concentration as low as 20 ng/ml of LPS is detected in distilled water and in reconstituted stools in under 15 minutes. The threshold of detection corresponds to a concentration of 5x10(7) CFU/ml of S. flexneri 2a, which provides an unequivocal positive reaction in three minutes in distilled water and reconstituted stools. The specificity is 100% when tested with a battery of Shigella and unrelated strains, in culture. When tested in Vietnam, on clinical samples, the specificity and sensitivity were 99.2 and 91.5%, respectively. A decrease of the sensitivity during the evaluation on stool samples was observed after five weeks at room temperature and was due to moistening of the dipsticks caused by the humidity of the air during the fifth week of the evaluation. This drawback is now overcome by improving the packaging and providing dipsticks individually wrapped in waterproof bags.

CONCLUSION

This simple dipstick-bases test represents a powerful tool for case management and epidemiological surveys.

Enteroaggregative Escherichia coli: epidemiology, virulence and detection

Enteroaggregative Escherichia coli (EAEC) is a subgroup of diarrhoeagenic E. coli (DEC) that during the past decade has received increasing attention as a cause of watery diarrhoea, which is often persistent. EAEC have been isolated from children and adults worldwide. As well as sporadic cases, outbreaks of EAEC-caused diarrhoea have been described. The definition of EAEC is the ability of the micro-organism to adhere to epithelial cells such as HEp-2 in a very characteristic ‘stacked-brick’ pattern. Although many studies searching for specific virulence factor(s) unique for this category of DEC have been published it is still unknown why the EAEC cause persistent diarrhoea. In addition, the aggregative property of EAEC causes a lot of problems in serotyping due to the cells auto-agglutinating. The gold standard for identification of EAEC includes isolation of the agent and an adherence assay using tissue culture, viz. HEp-2 cells. This assay is in most cases reliable; however, emergence of ‘atypical’ EAEC has been described in several publications. In addition, the HEp-2 assay is time consuming, demands a tissue culture lab and trained staff. Several molecular biological assays have been described, however, none show 100 % specificity.