Age-specific prevalence of Escherichia coli with localized and aggregative adherence in Venezuelan infants with acute diarrhea

Escherichia coli on colorectal cancer: A two-edged sword

Escherichia coli (E. coli) is a ubiquitous symbiotic bacterium in the gut, and the diversity of E. coli genes determines the diversity of its functions. In this review, the two-edged sword theory was innovatively proposed. For the question 'how can we harness the ambivalent nature of E. coli to screen and treat CRC?', in terms of CRC screening, the variations in the abundance and subtypes of E. coli across different populations present an opportunity to utilise it as a biomarker, while in terms of CRC treatment, the natural beneficial effect of E. coli on CRC may be limited, and engineered E. coli, particularly certain subtypes with probiotic potential, can indeed play a significant role in CRC treatment. It seems that the favourable role of E. coli as a genetic tool lies not in its direct impact on CRC but its potential as a research platform that can be integrated with various technologies such as nanoparticles, imaging methods, and synthetic biology modification. The relationship between gut microflora and CRC remains unclear due to the complex diversity and interaction of gut microflora. Therefore, the application of E. coli should be based on the 'One Health' view and take the interactions between E. coli and other microorganisms, host, and environmental factors, as well as its own changes into account. In this paper, the two-edged sword role of E. coli in CRC is emphasised to realise the great potential of E. coli in CRC screening and treatment.

Enteroaggregative Escherichia coli in mid-Norway: A prospective, case control study

BACKGROUND

The use of molecular methods has led to increased detection of Enteroaggregative Escherichia coli (EAEC) in faecal samples. Studies have yielded conflicting results regarding the clinical relevance of this finding. The objective of this study was to investigate the prevalence of EAEC in faecal samples from patients with diarrhoea and healthy controls and describe characteristics of EAEC positive persons.

METHODS

From March 1st, 2017 to February 28th, 2019, we investigated all consecutive faecal samples from patients with diarrhoea received at the laboratory and collected faecal samples from randomly invited healthy controls from mid-Norway. Real-time multiplex PCR was used for detection of bacterial, viral, and parasitic pathogens. We registered sex, age, urban versus non-urban residency, and travel history for all participants. Statistical analyses were performed with Pearson chi-squared test, Kruskal-Wallis test, and Mann-Whitney U test.

RESULTS

We identified EAEC in 440 of 9487 (4.6%) patients with diarrhoea and 8 of 375 (2.2%) healthy controls. The EAEC prevalence was 19.1% among those with diarrhoea and recent foreign travel and 2.2% in those without travel history independent of diarrhoea. Concomitant pathogens were detected in 64.3% of EAEC-positive patients with diarrhoea. The median age was 28.5 in those with EAEC-positive diarrhoea and 38 in those with EAEC-negative diarrhoea (p <0.01). In patients with diarrhoea, travel was reported in 72% of those with EAEC and concomitant pathogens, and 54% and 12% in those with only EAEC and no EAEC, respectively (p <0.01).

CONCLUSIONS

EAEC was a common detection, particularly in patients with diarrhoea and recent international travel, and was found together with other intestinal pathogens in the majority of cases. Our results suggest that domestically acquired EAEC is not associated with diarrhoea. Patients with EAEC-positive diarrhoea and concomitant pathogens were young and often reported recent travel history compared to other patients with diarrhoea.

Enteroaggregative Escherichia coli as etiological agent of endemic diarrhea in Spain: A prospective multicenter prevalence study with molecular characterization of isolates

Background

Enteroaggregative Escherichia coli (EAEC) is increasingly associated with domestically acquired diarrheal episodes in high-income countries, particularly among children. However, its specific role in endemic diarrhea in this setting remains under-recognized and information on molecular characteristics of such EAEC strains is limited. We aimed to investigate the occurrence of EAEC in patients with non-travel related diarrhea in Spain and molecularly characterize EAEC strains associated with illness acquired in this high-income setting.

Methods

In a prospective multicenter study, stool samples from diarrheal patients with no history of recent travel abroad (n = 1,769) were collected and processed for detection of EAEC and other diarrheagenic E. coli (DEC) pathotypes by PCR. An additional case–control study was conducted among children ≤5 years old. Whole-genome sequences (WGS) of the resulting EAEC isolates were obtained.

Results

Detection of DEC in the study population. DEC was detected in 23.2% of patients aged from 0 to 102 years, with EAEC being one of the most prevalent pathotypes (7.8%) and found in significantly more patients ≤5 years old (9.8% vs. 3.4%, p &lt; 0.001). Although not statistically significant, EAEC was more frequent in cases than in controls. WGS-derived characterization of EAEC isolates. Sequence type (ST) 34, ST200, ST40, and ST10 were the predominant STs. O126:H27, O111:H21, and O92:H33 were the predominant serogenotypes. Evidence of a known variant of aggregative adherence fimbriae (AAF) was found in 89.2% of isolates, with AAF/V being the most frequent. Ten percent of isolates were additionally classified as presumptive extraintestinal pathogenic E. coli (ExPEC), uropathogenic E. coli (UPEC), or both, and belonged to clonal lineages that could be specifically associated with extraintestinal infections.

Conclusion

EAEC was the only bacterial enteric pathogen detected in a significant proportion of cases of endemic diarrhea in Spain, especially in children ≤5 years old. In particular, O126:H27-ST200, O111:H21-ST40, and O92:H33-ST34 were the most important subtypes, with all of them infecting both patients and asymptomatic individuals. Apart from this role as an enteric pathogen, a subset of these domestically acquired EAEC strains revealed an additional urinary/systemic pathogenic potential.

Identification of enteropathogenic Escherichia coli in children with acute diarrheic syndrome from Sucre State, Venezuela

INTRODUCTION

Diarrheagenic Escherichia coli is an important causative agent of acute diarrheic syndrome. 

OBJECTIVE

To identify clonal groups of enteropathogenic E. coli (EPEC), in 485 children with acute diarrhea aged 0 to 10 years attending health care centers in Arismendi, Benítez and Sucre municipalities, Sucre state, Venezuela, from March to December, 2011. 

MATERIALS AND METHODS

After obtaining the informed consent, stool samples were collected. Escherichia coli was identified using standard coproculture methods and serology with polyvalent and monovalent antisera. DNA was isolated, and eae (intimin) and bfpA (bundlin) genes were amplified through two multiplex polymerase chain reactions (PCR). 

RESULTS

The presence of bacterial infection was determined in 39.6% of coprocultures. The prevalence of E. coli was 54.7%; 82.9% of these isolates were positive by serology for the evaluated serogroups and serotypes, which were mostly identified in children between 0 and 2 years (37.9%); 48.6% of E. coli strains amplified the eae gene; of these, 58.8% were classified as typical EPEC (eae+ y bfp+). EPEC II was the most common serogroup (38.7%), with predominance of typical EPEC (60%). In positive strains for eae gene, the β intimin allele was the most frequently identified (74.5%). Only four strains with O157:H7 serotype were identified, which showed no PCR amplification of the eae and bfpA genes. 

CONCLUSION

This study showed the importance of molecular tests to identify diarrheagenic E. coli strains causing clinical conditions of varying severity.

A comparative study of bacterial and parasitic intestinal infections in India

BACKGROUND

Infectious diarrhea causes a major health problem in developing countries with significant morbidity and mortality. Very often, rehydration therapy alone does not suffice, mandating the use of antimicrobial agents. However, rapidly decreasing antimicrobial susceptibility is complicating the matters.

MATERIALS AND METHODS

The study aimed to determine the prevalent bacterial and parasitic agents of diarrhea in India. A cross-sectional study was done at Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, during 2012-14. Stool samples were received from patients of all age groups and processed for bacteriological and parasitological identification by microscopy, bacterial culture, biochemical identification, serotyping and antimicrobial susceptibility tests. The study also aimed to identify the recent papers (after year 2000) reporting aetiology of infectious diarrhea in India involving the general population as a whole and compare them with present findings.

RESULTS

Out of 6527 samples, 581 (8.90%) were positive for bacterial pathogens. A total of 280 samples (of 3823 under-five year children) were positive for diarrheagenic Escherichia coli. Other organisms like Vibrio cholera were found in 159 (2.44%) cases, Shigella spp. in 126 (1.93%), Salmonella Typhi in 7 (0.11%), Salmonella Typhimurium in 6 (0.10%), Aeromonas hydrophila in 3 (0.05%) cases. Levels of resistance to nalidixic acid, amoxicillin and ciprofloxacin were alarmingly high. Third generation cephalosporins were seen to be moderately active except against E. coli. Parasites were identified in 312 (4.78%) cases. Giardia intestinalis, Ascaris lumbricoides and Entamoeba histolytica were identified in 2.27%, 1.15% and 0.64% cases respectively.

CONCLUSION

Analysis of recent nationwide studies revealed V. cholerae was the most common bacterial/parasitic agent of diarrhea across all populations, being followed by diarrheagenic E. coli and Giardia intestinalis. Periodic laboratory monitoring of antimicrobial susceptibility pattern is essential, as is formulation of effective antibiotic use policy.

Characterization of Shiga toxin-producing Escherichia coli isolated from healthy pigs in China

Background

Shiga toxin-producing Escherichia coli (STEC) is recognized as an important human diarrheal pathogen. Swine plays an important role as a carrier of this pathogen. In this study we determined the prevalence and characteristics of STEC from healthy swine collected between May 2011 and August 2012 from 3 cities/provinces in China.

Results

A total of 1003 samples, including 326 fecal, 351 small intestinal contents and 326 colon contents samples, was analyzed. Two hundred and fifty five samples were stx-positive by PCR and 93 STEC isolates were recovered from 62 stx-positive samples. Twelve O serogroups and 19 O:H serotypes including 6 serotypes (O100:H20/[H20], O143:H38/[H38], O87:H10, O172:H30/[H30], O159:H16, O9:H30/[H30]) rarely found in swine and ruminants were identified. All 93 STEC isolates harbored stx₂ only, all of which were stx_2e subtype including 1 isolate being a new variant of stx_2e. 53.76%, 15.05% and 2.15% STEC isolates carried astA, hlyA and ehxA respectively. Four STEC isolates harbored the high-pathogenicity island. Of the 15 adherence-associated genes tested, 13 (eae, efa1, iha, lpfA_O113, lpfA_O157/OI-154, lpfA_O157/OI-141, toxB, saa, F4, F5, F6, F17 or F41) were all absent while 2 (paa and F18) were present in 7 and 4 STEC isolates respectively. The majority of the isolates were resistant to tetracycline (79.57%), nalidixic acid (78.49%), trimethoprim-sulfamethoxazole (73.12%) and kanamycin (55.91%). The STEC isolates were divided into 63 pulsed-field gel electrophoresis patterns and 21 sequence types (STs). Isolates of the same STs generally showed the same or similar drug resistance patterns. A higher proportion of STEC isolates from Chongqing showed multidrug resistance with one ST (ST3628) resistant to 14 antimicrobials.

Conclusions

Our results indicate that swine is a significant reservoir of STEC strains in China. Based on comparison by serotypes and sequence types with human strains and presence of virulence genes, the swine STEC may have a low potential to cause human disease.

Enteropathogenic Escherichia coli prevalence in laboratory rabbits

Rabbit-origin enteropathogenic Escherichia coli (EPEC) causes substantial diarrhea-associated morbidity and has zoonotic potential. A culture-based survey was undertaken to ascertain its prevalence. EPEC was isolated from 6/141 (4.3%) commercially-acquired laboratory rabbits. Three of these did not have diarrhea or EPEC-typical intestinal lesions; they instead had background plasmacytic intestinal inflammation. Asymptomatically infected rabbits may function as EPEC reservoirs.

Incidence of diarrhoeagenic Escherichia coli isolated from young children with diarrhoea in the west of Iran

Diarrhoeagenic Escherichia coli (DEC) represents a main group of enteric pathogens that cause human diarrhoea. Because it is not simply distinguished from normal flora by simple laboratory methods, modern molecular diagnostic assays are necessary. Although it is neither necessary nor applicable to perform PCR for all patients, it is of many advantages to verify the prevalence of DEC in different areas by this method. Knowing the prevalence of DEC in an area, we can focus on few pathogens and narrow our antimicrobial treatment. The aim of this study is to evaluate the contribution of the different DEC categories in children diarrhoea in the west of Iran.The stool specimens of 251 children with diarrhoea were collected from June to September 2007. Polymerase chain reaction (PCR) was performed to determine the presence of enteropathogenic (EPEC), enterotoxigenic (ETEC), entero-invasive (EIEC), Shiga toxin-producing (STEC) and entero-aggregative (EAEC) strains. ETEC strains were isolated from 13 and EAEC strains from 16 children. STEC was detected in 7 children, and no EIEC was isolated. Finally, EPEC strains were isolated in 41 cases. EAEC and EPEC are the most frequent DECs in children less than 10 years of age in West of Iran.

Molecular characterization of diarrheagenic Escherichia coli from Libya

Diarrheagenic Escherichia coli (DEC) are important enteric pathogens that cause a wide variety of gastrointestinal diseases, particularly in children. Escherichia coli isolates cultured from 243 diarrheal stool samples obtained from Libyan children and 50 water samples were screened by polymerase chain reaction (PCR) for genes characteristic of enteroaggregative E. coli (EAEC), enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enterohemorrhagic E. coli (EHEC), and enteroinvasive E. coli (EIEC). The DEC were detected in 21 (8.6%) children with diarrhea; 10 (4.1%) cases were identified as EAEC, 3 (1.2%) as EPEC, and 8 (3.3%) were ETEC; EHEC, and EIEC were not detected. All DEC were grouped phylogenetically by PCR with the majority (> 70%) identified as phylogenetic groups A and B1. The EAEC isolates were also tested for eight genes associated with virulence using PCR. Multi-virulence (≥ 3 virulence factors) was found in 50% of EAEC isolates. Isolated EAEC possessed different virulence traits and belonged to different phylogenetic groups indicating their heterogeneity.

Enzootic enteropathogenic Escherichia coli infection in laboratory rabbits

Enteropathogenic Escherichia coli (EPEC) is the most important cause of persistent diarrhea in children, particularly in developing countries. Animals serve as pathogenic E. coli reservoirs, and compelling evidence for cross-species EPEC transmission exists. In this report, enzootic EPEC infection associated with up to 10.5% diarrhea-associated morbidity in a large laboratory Dutch Belted rabbit colony was investigated. These rabbits were obtained from a commercial vendor and had acute diarrhea following shipment. Fecal culture of 20 rabbits yielded 48 E. coli isolates, 83% of which were eae positive. Repetitive sequence-based PCR (REP-PCR) and serologic analysis identified a single disease-associated EPEC O145:H2 strain. In sampled rabbits, EPEC-positive culture and the presence of diarrhea were significantly associated. This strain displayed a localized adherence-like HEp-2 cell adherence pattern, as seen in diarrheic human infant EPEC isolates. Treatment was instituted with the fluoroquinolone antibiotic enrofloxacin, to which all isolates were susceptible. Preshipment parenteral enrofloxacin administration reduced diarrhea-associated morbidity 22-fold and mortality 12-fold in subsequent deliveries. This report emphasizes the zoonotic potential of animal EPEC strains and the need for virulence determinant-based screening of E. coli isolates from diarrheic animals.

Phenotypic and genotypic characterization of Escherichia Coli O111 serotypes

AIM

The purpose of this study was to characterize phenotypically and genotypically the serotypes of the E. coli O111 associated with diarrheal disease and assess the variation among serotypes in terms of specific virulence factors and HeLa cells adherence patterns.

BACKGROUND

Escherichia coli O111 serogroups are prevalent in endemic or sporadic cases of diarrhea, especially in developing areas.

PATIENTS AND METHODS

A total of 54 strains of E. coli O111 isolated from diarrheal and healthy cases were included in this study. Flagella antigens of motile and non-motile strains were identified by fliC-RFLP method (H types) and confirmed with agglutination test using H-specific antisera. All strains were tested for the presence of 5 different gene regions associated with virulence (eaeA, eaeB, bfpA, sxt and EAF plasmid) by PCR and the patterns of bacterial attachment to HeLa cells was assayed in cell culture.

RESULTS

Of 54 E. coli O111 strains, 89% were typeable with standard H antisera and the remaining 11% of strains were non-motile (H -). Twenty-three different H type were distinguished among the O111 strains by PCR-RFLP. The most common serotypes included H21, H9, H2, H6 and H12 (48%). Serotypes O111:H9 were represented by strains with 2 patterns of virulence genes (eaeA (+) /bfpA (+) /EAE(+), and eaeA (+) /bfpA (-) /EAE(-) ) and serotype H14 was represented by strains with the single eaeA (+) /bfpA (+) /EAE(-) combination. Four distinct patterns of adherence were distinguished: LA, LLA, AA and DA. All of serotypes with the eaeA (+) /bfpA (+) /EAE(+), or eaeA(+)/bfpA(+)/EAE(-), combination isolated from children with diarrhea exhibited the LA pattern, and serotypes with eaeA(+)/bfpA(-)/EAF(-) showed the LLA, while the majority of the strains isolated from healthy cases exhibited the DA, AA and NA patterns.

CONCLUSION

Strains of this O serogroup represented a diverse of serotypes with a variety of virulence factors and mechanisms of pathogenesis.

Pathogenic microorganisms associated with childhood diarrhea in low-and-middle income countries: case study of Yaoundé - Cameroon

Notwithstanding significant advancement in the understanding of pathogenesis and management, diarrheal illnesses remain one of the principal causes of global childhood mortality and morbidity. Infections account for most illnesses, with pathogens employing ingenious mechanisms to establish disease. In 2002, an interdisciplinary program "Populations et al. Espaces à Risques SANitaires" (PERSAN) was set up under the patronage of the Development Research Institute (IRD). Focused on health in Cameroon's urban environment, the program mainly sought to identify diarrhea risk factors in Yaoundé. So for, a cross-sectional epidemiological study in children aged 6-59 months was carried out using a standardized protocol. The survey was initiated in 2002 and conducted during April to June in the year 2005. 3,034 stool samples were collected from children in twenty neighbourhoods in Yaoundé and examined at the Epidemiology and Public Health Laboratory of the Cameroon Pasteur Institute. About 60% of the patients were aged less than two years and 52% were male. Among the 437 patients with the diarrheal disease, 260 were found to be of infectious etiology, i.e. micro organism was detected in 59.5% of the cases. Out of which, 10 (03.8%), 96 (36.9%), and 154 (59.2%) were respectively caused by pathogenic viruses, pathogenic bacteria and pathogenic parasites. Higher prevalence was found in overcrowded and under supply spontaneous settlement (78.4%) than in less crowded and formal residential settlement (21.5%). Etiologic data on diarrheal diseases and their spatial distribution are important tools for public health management and control strategic planning.

Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 87/D2 and international type strains from E. coli O128

The O-antigen of the lipopolysaccharide (LPS) from the enteroaggregative Escherichia coli strain 87/D2 has been determined by component analysis together with NMR spectroscopy. The polysaccharide has pentasaccharide repeating units in which all the residues have the galacto-configuration. The repeating unit of the O-antigen, elucidated using the O-deacylated LPS, is branched with the following structure: Analysis of the 1H NMR spectrum of the LPS revealed O-acetyl groups (approximately 0.7 per repeating unit) distributed over two positions. Subsequent analysis showed that the galactose residue carries acetyl groups at either O-3 or O-4 in a ratio of approximately 2:1. The international reference strain from E. coli O128ab was investigated and the repeating unit of the O-antigens has the following structure: Analysis of the 1H NMR spectrum of the LPS revealed O-acetyl groups (approximately one per repeating unit) distributed over two positions. The integrals of the resonances for the O-acetyl groups indicated similarities between the O-antigen from E. coli O128ab and that of E. coli strain 87/D2, whereas the O-acetyl substitution pattern in the E. coli O128ac O-antigen differed slightly. Enzyme immunoassay using specific anti-E. coli O128ab and anti-E. coli O128ac rabbit sera confirmed the results.

Two or more enteropathogens are associated with diarrhoea in Mexican children

BACKGROUND

Diarrhoeal diseases constitute a major public health problem, particularly in the developing world, where the rate of mortality and morbidity is very high. The purpose of this study was to conduct a 2 years and 3 months study in order to determine the prevalence of five enteropathogen diarrheogenic agents in Mexico City.

METHODS

Faecal samples were obtained from 300 Mexican children diagnosed as positive for diarrhoea, aged > 2 to < 12 years old, and from 80 children matched for age but with no symptoms of the disease (control group). Two multiplex PCR were used to detect Escherichia coli, Salmonella spp., and Shigella spp. In addition, the two protozoan parasites Entamoeba histolytica/Entamoeba dispar and Giardia intestinalis were detected by conventional methods.

RESULTS

All diarrhoeal samples were positive for one or more enteropathogens. The most common enteropathogens in diarrhoeal samples were E. histolytica/E. dispar (70.3%), Salmonella (ohio 28.3%; typhimurium 16.3%; infantis 8%; anatum 0.6%; Newport 0.3%), G. intestinalis (33%), E. coli (ETEC 13.3%; EPEC 9.3%; VTEC 8.6%; EIEC 1%) and Shigella spp. (flexneri 1.6%, sonnei 1%). Infections by two (24%) three (16%) and four (12%) pathogens were observed.

CONCLUSION

This study revealed that 52% of the patients were infected by more than one enteropathogen, notably E. histolitica/E. dispar and Salmonella ohio. These results are useful for clinicians to improve the empiric treatment used in such cases.

Identification of diarrheagenic Escherichia coli isolated from infants and children in Dar es Salaam, Tanzania

Background

Relatively few studies have been done in Tanzania to detect and classify diarrheagenic Escherichia coli (DEC) strains among children with diarrhea. This study aimed at investigating DEC among children in Dar es Salaam aged less than five years hospitalized due to acute/persistent diarrhea.

Methods

DEC were isolated from stool samples collected from two hundred and eighty children with acute/persistent diarrhea at Muhimbili National Hospital and Ilala and Mwananyamala Municipal Hospitals in Dar es Salaam. A multiplex PCR system method was used to detect a species specific gene for E.coli and ten different virulence genes for detection of five pathogroups of DEC namely enteroaggregative- (EAEC), enteropathogenic- (EPEC), enterotoxigenic- (ETEC), enteroinvasive- (EIEC) and enterohemorghagic- Escherichia coli (EHEC).

Results

Sixty-four patients (22.9%) harbored DEC. Forty-one of them (14.6%) were categorized as EAEC. Most of the EAEC (82.9%) were classified as typical EAEC possessing the aggR gene, and 92.6% carried the aat gene. Isolates from thirteen patients were EPEC (4.6%) and most of these (92.3%) were typical EPEC with both eae and bfpA genes. Ten isolates were identified as ETEC (3.6%) with only the heat stable toxin; either st1a or st1b but not both. Age wise, EAEC and EPEC were significantly more prevalent among the age group 0–6 months (p < 0.05). Genes for EHEC (stx₁ and stx₂) and EIEC (ial) were not detected in this study group.

Conclusion

The results show a high proportion of DEC among Tanzanian children with diarrhea, with typical EAEC and typical EPEC predominating. The use of primers for both variants of ST1 (st1a and st1b) increased the sensitivity for detection of ETEC strains.

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.

Urban dust fecal pollution in Mexico City: Antibiotic resistance and virulence factors of Escherichia coli

Fecal pollution of settled dust samples from indoor and outdoor urban environments, was measured and characterized by the presence of fecal coliforms (FC), and by the characterization of Escherichia coli virulence genes, adherence and antibiotic resistance traits as markers. There were more FC indoors than outdoors (mean values 1089 and 435MPN/g). Among indoor samples, there were more FC in houses with carpets and/or pets. Using a PCR-based assay for six enteropathogenicity genes (belonging to the EAEC, EHEC and EPEC pathotypes) on randomly selected E. coli isolates, there was no significant difference between isolates from indoors and outdoors (60% and 72% positive to at least one gene). The serotypes commonly associated with pathogenic strains, such as O86 and O28, were found in the indoor isolates; whereas O4, O66 and O9 were found amongst outdoor isolates. However, there were significantly more outdoor isolates resistant to at least one antibiotic (73% vs. 45% from indoors) among the strains positive for virulence factors, and outdoor isolates were more commonly multiresistant. There was no relationship between the presence of virulence genes and resistance traits. These results indicate that outdoor fecal bacteria were more likely from human sources, and those found indoors were related to pets and maintained in carpets. This study illustrates the risk posed by fecal bacteria from human sources, usually bearing virulence and resistance traits. Furthermore, the high prevalence of strains carrying genes associated to EAEC or EHEC pathotypes, in both indoor and outdoor environments, adds to the health risk.

The structures ofEscherichia coliO-polysaccharide antigens

Escherichia coli is usually a non-pathogenic member of the human colonic flora. However, certain strains have acquired virulence factors and may cause a variety of infections in humans and in animals. There are three clinical syndromes caused by E. coli: (i) sepsis/meningitis; (ii) urinary tract infection and (iii) diarrhoea. Furthermore the E. coli causing diarrhoea is divided into different 'pathotypes' depending on the type of disease, i.e. (i) enterotoxigenic; (ii) enteropathogenic; (iii) enteroinvasive; (iv) enterohaemorrhagic; (v) enteroaggregative and (vi) diffusely adherent. The serotyping of E. coli based on the somatic (O), flagellar (H) and capsular polysaccharide antigens (K) is used in epidemiology. The different antigens may be unique for a particular serogroup or antigenic determinants may be shared, resulting in cross-reactions with other serogroups of E. coli or even with other members of the family Enterobacteriacea. To establish the uniqueness of a particular serogroup or to identify the presence of common epitopes, a database of the structures of O-antigenic polysaccharides has been created. The E. coli database (ECODAB) contains structures, nuclear magnetic resonance chemical shifts and to some extent cross-reactivity relationships. All fields are searchable. A ranking is produced based on similarity, which facilitates rapid identification of strains that are difficult to serotype (if known) based on classical agglutinating methods. In addition, results pertinent to the biosynthesis of the repeating units of O-antigens are discussed. The ECODAB is accessible to the scientific community at http://www.casper.organ.su.se/ECODAB/.

Phenotypic and genotypic characterisation of Escherichia coli strains serogrouped as enteropathogenic E. coli (EPEC) isolated from pasteurised milk

Fifty-six Escherichia coli strains, serogrouped as EPEC, isolated from three different brands of pasteurised milk commercialised in Rio de Janeiro, Brazil, were tested for enteropathogenicity markers. Most of the strains (71.4%) were adherent to HEp-2 cells. The adherent strains were distributed among 7 EPEC serogroups (O26, O55, O111, O114, O125, O127, O128, O158). Although almost half of these strains (33.9%) presented unrecognisable adherence phenotypes, classical adherence patterns (localised-like, aggregative and diffuse adherence) described for E. coli and epidemiologically associated with diarrheagenic strains were observed. None of the strains showed typical localised adherence, usually associated with EPEC strains, but 4 of them displayed a localised-like adherence (LAL) phenotype, characterised by fewer and less compact microcolonies but that is still associated with diarrheagenic strains as well as strains of non-human origin. Indeed, 3 of these 4 strains were able to elicit the attaching-effacing lesion (FAS-positive), the central feature of EPEC pathogenesis, and hybridised with bfpA and eae DNA probes. The other LAL-positive strain hybridised with the bfpA probe but gave negative results for the eae probe and FAS assays. Interestingly, all LAL-positive strains produced amplicons of 200 bp in the PCR for bfpA, instead of the expected 326 bp fragment. PCR reactions for stx1 and stx2, two shiga-toxin-encoding genes, gave negative results. Typing of LEE-associated genes by PCR showed the profile eae (beta), tir (beta), espA (alpha) and espB (alpha) for one of the LAL-positive strain. The most prevalent adherence phenotype was the aggregative pattern which is observed in strains epidemiologically associated with persistent diarrhea. Additionally, one strain promoted complete detachment of the Hep-2 cell monolayer after 3 h of infection which might be related to the production of citotoxins, a feature that has been increasingly observed in clinical strains. The possession of EPEC-related O and H antigens is no longer deemed an essential characteristic of true pathogenic EPEC strains, emphasising the importance of routinely screen for virulence markers in E. coli strains isolated from foods. Our results are in accordance with data from the literature that demonstrate that environmental strains display atypical features but yet are capable of eliciting the classical A/E lesion and thus must be considered as potentially pathogenic. Further, our results demonstrate the potential of pasteurised milk as a vehicle for transmission of diarrheagenic E. coli in Brazil.

Detection and characterization of diarrheagenic Escherichia coli from young children in Hanoi, Vietnam

Diarrhea continues to be one of the most common causes of morbidity and mortality among infants and children in developing countries. Escherichia coli is an emerging agent among pathogens that cause diarrhea. The development of a highly applicable technique for the detection of different categories of diarrheagenic E. coli is important. We have used multiplex PCR by combining eight primer pairs specific for enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli, enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). This facilitates the identification of five different categories of diarrheagenic E. coli from stool samples in a single reaction simultaneously. The prevalences of diarrheagenic E. coli were 22.5 and 12% in the diarrhea group and the control group, respectively. Among 587 fecal samples from Vietnamese children under 5 years of age with diarrhea, this technique identified 132 diarrheagenic E. coli strains. This included 68 samples (11.6%) with EAEC, 12 samples (2.0%) with EIEC, 39 samples (6.6%) with EPEC, and 13 samples (2.2%) with ETEC. Among the 249 age-matched controls, 30 samples were positive for diarrheagenic E. coli. The distribution was 18 samples (7.2%) with EAEC, 11 samples (4.4%) with EPEC, and 1 sample (0.4%) with ETEC.

Prevalence of diarrheagenic Escherichia coli in acute childhood enteritis: a prospective controlled study

OBJECTIVE

Since diarrheagenic E. coli are not identified by common clinical laboratory techniques, we hypothesized that these organisms might be an unrecognized cause of enteritis in children in the U.S.

STUDY DESIGN

1327 children with acute gastroenteritis were identified prospectively by active surveillance in the Emergency Department (ED) and the inpatient units at Cincinnati Children's Hospital Medical Center. Stool samples were evaluated for diarrheagenic E. coli using a panel of DNA probes and adherence pattern to HEp-2 cells. Stool samples from a reference group of 555 well children were studied for comparison.

RESULTS

Gene probe studies, but not HEp-2 cell adherence, demonstrated that enteroaggregative, diffusely adherent and enteropathogenic E. coli were associated with clinical illness. Each was isolated significantly more often from study subjects in the ED than controls. In children <1 year of age, enteroaggregative E. coli were isolated significantly more often from both inpatients (4.7%, Odds Ratio = 3.4, 95% confidence intervals 1.3-9.1, p <0.03) and ED patients (10.0%, Odds Ratio = 7.2, 95% confidence intervals 2.9-18.2, p <0.001) than from well children (1.4%).

CONCLUSIONS

Diarrheagenic E. coli , especially enteroaggregative E. coli , may be an important, unrecognized cause of childhood diarrhea in the U.S.

Enteroaggregative Escherichia coli: An emerging pathogen in children

Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen that causes enteric and food-borne infectious diseases. Children throughout the world appear to be susceptible to EAEC infection. EAEC pathogenesis involves the following three stages: 1) adherence to the intestinal mucosa; 2) increased production and deposition of a mucus biofilm; and 3) mucosal toxicity due to inflammation and cytokine release. The HEp-2 cell adherent assay allows identification of EAECs characteristic aggregative or "stacked brick" adherence pattern. Antimicrobial treatment of children who develop an EAEC infection should be individually based. All children with EAEC diarrhea should receive adequate oral fluid hydration. For children who have persistent diarrhea and severe dehydrating illness despite having received adequate oral rehydration, antimicrobials may be initiated. Azithromycin and rifaximin have been shown to shorten the course of EAEC diarrhea in adults and probably represent the recommended antimicrobials of choice for children with severe or persistent illness. The objective of this review is to increase awareness of this important emerging pathogen and to discuss the epidemiology, pathogenesis, and pathogen and host factors associated with EAEC infection in children.

Enteroaggregative Escherichia coli: an emerging enteric pathogen

Enteroaggregative Escherichia coli (EAEC) represents an emerging pathogen that causes enteric and food-borne infectious diseases. Subgroups in many populations throughout the world are susceptible to EAEC infection. EAEC pathogenesis involves adherence to the intestinal mucosa; increased production and deposition of a mucus biofilm; and mucosal toxicity due to inflammation and cytokine release. Due to the heterogeneity of EAEC strains and differing host immune responses, not all EAEC infections are symptomatic. Recent data suggest that individuals with a homozygous genotype -251 AA single nucleotide polymorphism (SNP), in the IL-8 promoter region, are more susceptible to EAEC diarrhea. The HEp-2 cell adherent assay allows identification of EAEC's characteristic aggregative or "stacked brick" adherence pattern. Antimicrobial treatment of individuals who develop EAEC diarrhea should be individually based. Ciprofloxacin and rifaximin, compared to placebo, have been shown to significantly shorten the course of diarrhea in patients who developed EAEC infection. The objective of this review is to increase awareness of this important emerging pathogen and to discuss the epidemiology, pathogenesis, and host-pathogen factors associated with EAEC infection.

Enteroaggregative and cell-detachingEscherichia coli strains among polish children with and without diarrhea

To determine the association of enteroaggregative (EAEC) and cell-detaching (CDEC) Escherichia coli with diarrhea of unknown origin among children from Wrocław (Poland), E. coli strains isolated from stool specimens of children with diarrhea were examined for mannose-resistant adherence to HEp-2 cells. EAEC were isolated from 10 of 39 (26%) children examined with diarrhea and 4 of 20 (20%) age-matched controls. CDEC were present in 14 (36%) cases of diarrhea and 7 (35%) healthy subjects. Cell-detaching activity was distinctly associated with hemolysin production. Among hemolytic CDEC strains cytotoxic necrotizing factor 1 (CNF1) synthesis prevailed among isolates obtained from cases of diarrhea (57%) in comparison with isolates obtained from healthy controls (14.3%). Although neither EAEC nor CDEC E. coli strains were associated with diarrhea of children in this setting, there were differences among EAEC and CDEC strains isolated from children with and without diarrhea.

Screening the enteroaggregative Escherichia coli activity and detection of the aggA, aafA, and astA genes with novel PCR primers for the Escherichia coli isolates from diarrhea cases in Taiwan

Enteroaggregative Escherichia coli (EAggEC) are emerging enteropathogens associated with human diarrhea diseases and food poisoning cases. They show distinctive aggregative pattern of adherence to cultured human epithelial cells. However, EAggEC strains are diverse and not all of them have the aggregative adherence fimbria I (AAF/I), AAF/II and heat-stable enterotoxin 1 (EAST1) genes. We attempted to determine the incidence of EAggEC in E. coli isolates from diarrhea patients in Taiwan and to characterize these EAggEC strains. We used three activity assays including HeLa cell adhesion, human blood hemagglutination and bacterial clumping tests and polymerase chain reaction (PCR) primers designed from an aggregative adherence pattern associated plasmid (pCVD432) to screen the EAggEC strains in 403 E. coli isolates including 63 laboratory isolates and 340 clinical isolates obtained from diarrheal disease cases. All these 403 E. coli strains were also assayed with novel PCR primers designed from AAF/I (aggA), AAF/II (aafA) and EAST1 (astA) genes. Results showed that except for the three EAggEC reference strains, only three clinical isolates were identified as EAggEC strains. Including the reference strains, all the E. coli strains with EAggEC activity generated positive PCR results to the aggA gene based primers, but not to the aafA and astA gene targeted primers.

Prevalence of enteroaggregative Escherichia coli among children with and without diarrhea in Switzerland

In a prospective study between July 1999 and September 2000, stool specimens of children below the age of 16 years with (n = 187) and without (n = 137) diarrhea were tested for the presence of enterovirulent bacteria by standard culture methods and by PCR. Targets for the PCR were the plasmid pCVD432 for enteroaggregative Escherichia coli (EAEC), the verotoxin 1 and verotoxin 2 genes for enterohemorrhagic E. coli, ipaH for enteroinvasive E. coli (EIEC) and Shigella spp., genes coding for heat-stable and heat-labile toxins for enterotoxigenic E. coli (ETEC), and the eaeA gene for enteropathogenic E. coli. The following bacteria could be associated with diarrhea: Salmonella enterica (P = 0.001), Campylobacter spp. (P = 0.036), ETEC (P = 0.012), and EAEC (P = 0.006). The detection of EAEC, ETEC, and S. enterica was strongly associated with a history of recent travel outside of Switzerland. EAEC isolates were found in the specimens of 19 (10.2%) of 187 children with diarrhea and in those of 3 (2.2%) of 137 children without diarrhea (P = 0.006) and were the most frequently detected bacteria associated with diarrhea. Among the children below the age of 5 years, the specimens of 18 (11.9%) of 151 with diarrhea were positive for EAEC, while this agent was found in the specimens of 2 (2.2%) of 91 controls (P = 0.007). Enteropathogenic E. coli isolates were found in the specimens of 30 (16.4%) of the patients and in those of 15 (10.9%) of the controls, with similar frequencies in all age groups (P > 0.05). We conclude that EAEC bacteria are involved in a significant proportion of diarrhea cases among children. Children younger than 5 years of age are more often affected by EAEC than older children.

Virulence markers of enteroaggregative Escherichia coli isolated from children and adults with diarrhea in Brasília, Brazil

Escherichia coli strains isolated from sporadic cases of acute diarrhea in children and adults and from children without diarrhea were investigated for the presence of the pAA plasmid. Strains harboring the pAA plasmid were isolated at similar frequencies from children with (19.6%) and without (10.8%) diarrhea and from adults with diarrhea (11.8%). The genotypic and phenotypic virulence markers of these strains were further analyzed. Most of the strains were positive for EAST1 (73%), and this toxin was detected significantly more frequently in strains from children with diarrhea than in strains from adults with diarrhea (P < 0.05). Likewise, pic sequences were detected significantly more frequently in strains from children with diarrhea than in strains from adults with diarrhea (P < 0.005) and controls (P < 0.025). Furthermore, the association of pAA positivity (pAA(+)) and pic positivity (pic(+)) was more frequently found for strains from children with diarrhea than for strains from controls, indicating that pAA(+) pic(+) strains may represent a subset of pAA(+) strains associated with disease in children. Most of the strains (82.5%) adhered to cells presenting the typical aggregative pattern. The frequency of occurrence of enteropathogenic E. coli (EPEC) serogroups in the strains from children with diarrhea was very high (56%), while none of the strains from adults with diarrhea belonged to EPEC serogroups. Extraintestinal virulence markers were very commonly found in strains from adults with diarrhea. The frequencies of occurrence of the adhesins AFA and SFA were significantly higher in strains from adults with diarrhea than in strains from children with diarrhea. More than one extraintestinal virulence marker was found in 58% of the strains from adults with diarrhea but in only 7.7% of the strains from children with diarrhea. Our results show that pAA(+) strains isolated from children and adults with diarrhea present very different profiles when enteroaggregative E. coli virulence markers, serotypes, and extraintestinal virulence markers are considered.

Rotavirus type A and other enteric pathogens in stool samples from children with acute diarrhea on the Colombian northern coast

The present study, conducted from March 1998 to July 2000, determined the etiology of acute diarrhea in 253 young children and infants from Cartagena and Sincelejo, Colombia. In 253 stool samples, the following enteric pathogens were recovered: rotavirus type A (36.6%) as the major agent, Salmonella spp (9.0%), Shigella spp (8.0%), enteric pathogenic Escherichia coli (6.0%), enteric hemorragic Esc. coli (2.8%), Providencia alcalifaciens (2.8%), Aeromonas hydrophila (2.0%), Yersinia enterocolitica (0.8%), Entamoeba hystolitica (10%), Giardia lamblia (4%), Endolimax nana (3.2%), Ascaris lumbricoides (2.8%), Ent. coli (1.2%), Balantidium coli (0.8%), Blastocystis hominis (0.8%), Dypilidium caninum (0.4%) and hook worm sp. (0.4%). Infection with more than one pathogen occurred in 96 (37.9%) patients. Rotavirus and enteric pathogenic Esc. coli were frequent. Concurrent infection by more than one parasite occurred in 18.6% of the infants. Most rotavirus infections (76.7%) occurred in infants under 12 months. Vomiting, severe dehydration and fever were frequent in children with rotavirus infection. At least one fecal marker of inflammatory diarrhea was registered in patients with bacterial infection. To our knowledge, this is first report of P. alcalifaciens associated with infantile diarrhea in Colombia and the first description of Esc. coli O157:H7 and Y. enterocolitica in our region.

Enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC) are an increasingly important cause of diarrhoea. E. coli belonging to this category cause watery diarrhoea, which is often persistent and can be inflammatory. EAEC have been implicated in sporadic diarrhoea in children and adults, in both developing and developed countries, and have been identified as the cause of several outbreaks worldwide. EAEC are defined by their ability to adhere to epithelial cells in a characteristic "stacked-brick" pattern but are otherwise highly heterogeneous. Genes that could contribute to the pathogenicity of EAEC encode adhesins, toxins, and other factors, all of which are only partially conserved. Practicable tools are needed to improve diagnosis and identify risk factors. EAEC-infected individuals can be treated with fluoroquinolones but there is a need to examine alternative treatment protocols.

Asymptomatic infections by diarrheagenic Escherichia coli in children from Misiones, Argentina, during the first twenty months of their lives

Diarrheagenics Escherichia coli are the major agents involved in diarrheal disease in developing countries. The aim of this study was to evaluate the time of appearance of the first asymptomatic infection by the different categories of diarrheagenic E. coli in 44 children since their birth and during the first 20 months of their lives. In all of the children studied, we detected at least one category of diarrheagenic E. coli through the 20 months of the study. 510 diarrheagenic E. coli (33.5%) were obtained from the 1,524 samples collected from the 44 children during the time of the study (31.4% EAggEC, 28.8% EPEC, 27.1% DAEC, and 12.7% ETEC). Neither EHEC nor EIEC were identified. The median age for diarrheagenic E. coli colonization was 7.5 months. The mean weaning period was 12.8 months and the mean age for introduction of mixed feeding (breast fed supplemented) was 3.8 months. A significantly lower incidence of diarrheal disease and asymptomatic infections was recorded among the exclusively breast-fed rather than in the supplemented and non breast-fed infants. For ETEC, EPEC and EAggEC the introduction of weaning foods and complete termination of breast-feeding were associated with an increase of asymptomatic infections.

Identification of copper-zinc superoxide dismutase gene from enteroaggregative Escherichia coli

We describe here the identification of sodC gene from enteroaggregative Escherichia coli (EAggEC). A 294 bp gene-specific fragment was amplified from the organism by DNA as well as RT-PCR using primers from bacterial sodC sequences. The metal co-factor present in the protein was confirmed by running samples in native gels and inhibiting with 2 mM potassium cyanide. However, the nonpathogenic E. coli possesses the gene but does not express it. Thus, the presence of copper-zinc superoxide dismutase encoded by sodC was demonstrated for the first time in EAggEC, which means it could be a novel candidate for a virulence marker.

A localized adherence-like pattern as a second pattern of adherence of classic enteropathogenic Escherichia coli to HEp-2 cells that is associated with infantile diarrhea

Escherichia coli strains that cause nonbloody diarrhea in infants are known to present three distinct patterns of adherence to epithelial cells, namely, localized (LA), diffuse (DA), and aggregative (AA) adherence. Strains with LA (typical Enteropathogenic Escherichia coli [EPEC]) are well recognized as a cause of secretory diarrhea, but the role of strains with DA (DAEC) is controversial, and strains with AA (EAEC) have been more frequently related to persistent diarrhea whereas its relationship with acute diarrhea is not well defined. To determine the relationship of the different types of E. coli adherence patterns with acute diarrhea (lasting less than 14 days) and persistent diarrhea (lasting more than 14 days) in São Paulo, Brazil, we studied stool specimens from 40 infants under 1 year of age with diarrhea and 40 age-matched control infants without any gastrointestinal symptoms. Twenty-eight (35.0%) of eighty cases yielded adherent E. coli (HEp-2 cells). Strains with localized and aggregative adherence were associated with acute and persistent diarrhea. A total of 11.2% of the adherent strains were typical EPEC serotypes and hybridized with the enteroadherence factor probe; 5.0% were EAEC and hybridized with the EAEC probe. DAEC strains were isolated from 10.0% of patients and 7.5% of controls and did not hybridize with the two probes used (daaC and AIDA-I). Strains with a localized adherence-like pattern (atypical EPEC) were found significantly more frequently (P = 0.028) in cultures from children with diarrhea (17.5%) than in controls (2.5%).

Adherence patterns and adherence-related DNA sequences in Escherichia coli isolates from children with and without diarrhea in São Paulo city, Brazil

The correlation between various adherence patterns and adherence-related DNA sequences in Escherichia coli isolates from 1- to 4-year-old children with and without diarrhea in São Paulo, Brazil, was evaluated. A total of 1,801 isolates obtained from 200 patients and 200 age-matched controls were studied. The adherence patterns found were classified as diffuse, aggregative, aggregative in a 6-h assay, aggregative predominantly in coverslips, localized, localized-like, and noncharacteristic. In general, the DNA sequences used as probes showed excellent specificities (>93%), but their sensitivities varied. Thus, the results of bioassays and assays with DNA probes normally used to search for adherent E. coli did not correlate well, and the best method for the identification of these organisms in the clinical research setting remains controversial. Isolates presenting diffuse adherence or hybridizing with the related daaC probe, or both, were by far the most frequent in patients (31.5, 26.0, and 23.0%, respectively), followed by isolates presenting aggregative adherence or hybridizing with the related EAEC probe, or both (21.5, 13.0, and 10.5%, respectively). None of the different combinations of adherence patterns and adherence-related DNA sequences found were associated with acute diarrhea.

Etiological study of diarrheal patients in Vientiane, Lao People's Democratic Republic

The etiological agents of diarrhea in Vientiane, Lao People's Democratic Republic (Lao PDR), were studied in the period from October 1996 to August 1997. A total of 880 patients with diarrhea visiting medical facilities were examined for Shigella, Salmonella, diarrheagenic Escherichia coli, vibrio, Aeromonas, Campylobacter, and rotavirus. Shigella spp., heat-stable enterotoxin (ST)-producing E. coli, and serogroup-based enteropathogenic E. coli were found to be the main organisms causing diarrhea in Vientiane, with frequencies of 16.8% (148 of 880), 17.2% (111 of 645), and 11.0% (97 of 880), respectively. Relatively low incidences were observed in the cases of Salmonella spp., (0.6%; 5 of 880), Campylobacter spp. (4.4%; 39 of 880), and rotavirus (6.1%; 9 of 148), and no isolates of V. cholerae O1 or O139 or Aeromonas were recovered. An analysis of the incidences of enteropathogens with respect to age and seasonal variations demonstrated that the frequencies of isolation of Shigella spp. and heat-labile enterotoxin-producing E. coli were significantly higher in those aged 1 to 5 years than in those younger than 1 year of age and those older than 5 years of age (P < 0.0001 and P < 0.05, respectively) and that the frequencies of isolation of Shigella spp. and ST-producing E. coli were significantly higher in the rainy season than in the dry season (P < 0.005 and P < 0.001, respectively). Almost all strains of Shigella spp. tested were resistant to ampicillin, tetracycline, and erythromycin and were susceptible to cefdinir and ofloxacin. This is the first intensive and longitudinal study to define the etiologic agents of diarrheal diseases in Lao PDR.

Enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC), an increasingly recognized cause of diarrhea in children in developing countries, has been particularly associated with persistent diarrhea (more than 14 days), a major cause of illness and death. Recent outbreaks implicate EAEC as a cause of foodborne illness in industrialized countries. The pathogenesis of EAEC infection is not well understood, but a model can be proposed in which EAEC adhere to the intestinal mucosa and elaborate enterotoxins and cytotoxins, which result in secretory diarrhea and mucosal damage. EAEC's ability to stimulate the release of inflammatory mediators may also play a role in intestinal illness.

Diarrheagenic Escherichia coli

Escherichia coli is the predominant nonpathogenic facultative flora of the human intestine. Some E. coli strains, however, have developed the ability to cause disease of the gastrointestinal, urinary, or central nervous system in even the most robust human hosts. Diarrheagenic strains of E. coli can be divided into at least six different categories with corresponding distinct pathogenic schemes. Taken together, these organisms probably represent the most common cause of pediatric diarrhea worldwide. Several distinct clinical syndromes accompany infection with diarrheagenic E. coli categories, including traveler's diarrhea (enterotoxigenic E. coli), hemorrhagic colitis and hemolytic-uremic syndrome (enterohemorrhagic E. coli), persistent diarrhea (enteroaggregative E. coli), and watery diarrhea of infants (entero-pathogenic E. coli). This review discusses the current level of understanding of the pathogenesis of the diarrheagenic E. coli strains and describes how their pathogenic schemes underlie the clinical manifestations, diagnostic approach, and epidemiologic investigation of these important pathogens.

Efficacy of the rhesus rotavirus-based quadrivalent vaccine in infants and young children in Venezuela

BACKGROUND

Rotaviruses are the principal known etiologic agents of severe diarrhea among infants and young children worldwide. Although a rhesus rotavirus-based quadrivalent vaccine is highly effective in preventing severe diarrhea in developed countries, in developing countries its efficacy has been less impressive. We thus conducted a catchment study in Venezuela to assess the efficacy of the vaccine against dehydrating diarrhea.

METHODS

In this randomized, double-blind, placebo-controlled trial, 2207 infants received three oral doses of the quadrivalent rotavirus vaccine (4x10(5) plaque-forming units per dose) or placebo at about two, three, and four months of age. During approximately 19 to 20 months of passive surveillance, episodes of gastroenteritis were evaluated at the hospital.

RESULTS

The vaccine was safe, although 15 percent of the vaccinated infants had febrile episodes (rectal temperature, > or =38.1 degrees C) during the six days after the first dose, as compared with 7 percent of the controls (P<0.001). However, the vaccine gave 88 percent protection against severe diarrhea caused by rotavirus and 75 percent protection against dehydration, and produced a 70 percent reduction in hospital admissions. Overall, the efficacy of the vaccine against a first episode of rotavirus diarrhea was 48 percent. Horizontal transmission of vaccine virus was demonstrated in 15 percent of the vaccine recipients and 13 percent of the placebo recipients with rotavirus-positive diarrhea.

CONCLUSIONS

In this study in a developing country, the quadrivalent rhesus rotavirus-based vaccine induced a high level of protection against severe diarrheal illness caused by rotavirus.