Enteroaggregative and enterotoxigenic Escherichia coli among isolates from patients with diarrhea in Austria

Identification of Subsets of Enteroaggregative Escherichia coli Associated with Diarrheal Disease among Under 5 Years of Age Children from Rural Gambia

Enteroaggregative Escherichia coli (EAEC) cause acute and persistent diarrhea, mostly in children worldwide. Outbreaks of diarrhea caused by EAEC have been described, including a large outbreak caused by a Shiga toxin expressing strain. This study investigated the association of EAEC virulence factors with diarrhea in children less than 5 years. We characterized 428 EAEC strains isolated from stool samples obtained from moderate-to-severe diarrhea cases (157) and healthy controls (217) children aged 0–59 months recruited over 3 years as part of the Global Enteric Multicenter Study (GEMS) in The Gambia. Four sets of multiplex polymerase chain reaction were applied to detect 21 EAEC-virulence genes from confirmed EAEC strains that target pCVD432 (aatA) and AAIC (aaiC). In addition, Kirby-Bauer disc diffusion antimicrobial susceptibility testing was performed on 88 EAEC strains following Clinical Laboratory Standard Institute guidelines. We observed that the plasmid-encoded enterotoxin [odds ratio (OR): 6.9, 95% confidence interval (CI): 2.06–29.20, P < 0.001], aggregative adherence fimbriae/I fimbriae (aggA) [OR: 2.2, 95% CI: 1.16–4.29, P = 0.008], and hexosyltransferase (capU) [OR: 1.9, 95% CI 1.02–3.51, P = 0.028] were associated with moderate-to-severe diarrhea among children < 12 months old but not in the older age strata (> 12 months). Our data suggest that some EAEC-virulent factors have age-specific associations with moderate-to-severe diarrhea in infants. Furthermore, our study showed that 85% and 72% of EAEC strains tested were resistant to sulphamethoxazole-trimethoprim and ampicillin, respectively. Sulphamethoxazole-trimethoprim and ampicillin are among the first-line antibiotics used for the treatment of diarrhea in The Gambia.

Enteric Bacteria Isolated from Diarrheal Patients in Korea in 2014

OBJECTIVES

The aim of this study was to characterize the pathogens responsible for causing diarrhea according to season, region of isolation, patient age, and sex as well as to provide useful data for the prevention of diarrheal disease.

METHODS

Stool specimens from 14,886 patients with diarrhea were collected to identify pathogenic bacteria from January 2014 to December 2014 in Korea. A total of 3,526 pathogenic bacteria were isolated and analyzed according to season, region of isolation, and the age and sex of the patient.

RESULTS

The breakdown of the isolated pathogenic bacteria were as follows: Salmonella spp. 476 (13.5%), pathogenic Escherichia coli 777 (22.0%), Vibrio parahaemolyticus 26 (0.74%), Shigella spp. 13 (0.37%), Campylobacter spp. 215 (6.10%), Clostridium perfringens 508 (14.4%), Staphylococcus aureus 1,144 (32.4%), Bacillus cereus 356 (10.1%), Listeria monocytogenes 1 (0.03%), and Yersinia enterocolitica 10 (0.3%). The isolation rate trend showed the highest ratio in the summer season from June to September for most of the pathogenic bacteria except the Gram-positive bacteria. The isolation rate of most of the pathogenic bacteria by patient age showed highest ratio in the 0-19 year age range. For isolation rate by region, 56.2% were isolated from cities and 43.8% were isolated from provinces.

CONCLUSION

Hygiene education should be addressed for diarrheal disease-susceptible groups, such as those younger than 10 years, aged 10-19 years, and older than 70 years, and monitoring for the pathogens is still required. In addition, an efficient laboratory surveillance system for infection control should be continued.

A study on the epidemiology and aetiology of acute gastroenteritis in adult patients presenting at the infectious diseases hospital in tirana, Albania

BACKGROUND

Acute gastroenteritis remains a common cause of hospital emergency room visits in Albania. However, the aetiology of severe gastroenteritis leading to hospitalization in adults frequently remains unclear.

AIMS

Our objective was to study the epidemiology and causes of community-acquired, acute gastroenteritis in adult patients presenting to hospital.

STUDY DESIGN

Cross sectional study.

METHODS

A prospective study was conducted from January 2010 to January 2012, among patients ≥15 years old with community-acquired gastroenteritis presenting to the emergency room of the University Hospital "Mother Theresa" in Tirana, Albania. Stool samples and rectal swabs were collected from the patients for microbiological testing.

RESULTS

The median age of the study patients was 33 (15-88) years and 577 (58%) were females. The median age of males was 35 (15-87) years. The vast majority of cases occurred in urban area (849, 85%), p<0.01. Patients were admitted throughout the year with peak admissions for patients infected by bacterial pathogens in summer and those affected by viral pathogens in autumn. A total of 917 (91.7%) patients underwent a laboratory examination. The overall isolation rate was 51%. Bacterial pathogens were found in 29%, viral pathogens in 19% and protozoal pathogens in 2.5% of patients. No aetiological agent or other cause of acute diarrhoea was found in 449 (49%) patients. Twenty-nine (3.2%) patients were hospitalized.

CONCLUSION

Despite extensive laboratory investigations, enteropathogens were detected in only 51% of adult patients who presented to the hospital ER with acute gastroenteritis. Viral infections ranked as the second most common cause of gastroenteritis in adults.

Enteroaggregative Escherichia coli: An Emerging Enteric Food Borne Pathogen

Enteroaggregative Escherichia coli (EAEC) are quite heterogeneous category of an emerging enteric pathogen associated with cases of acute or persistent diarrhea worldwide in children and adults, and over the past decade has received increasing attention as a cause of watery diarrhea, which is often persistent. EAEC infection is an important cause of diarrhea in outbreak and non-outbreak settings in developing and developed countries. Recently, EAEC has been implicated in the development of irritable bowel syndrome, but this remains to be confirmed. EAEC is defined as a diarrheal pathogen based on its characteristic aggregative adherence (AA) to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa with a “stacked-brick” adherence phenotype, which is related to the presence of a 60 MDa plasmid (pAA). At the molecular level, strains demonstrating the aggregative phenotype are quite heterogeneous; several virulence factors are detected by polymerase chain reaction; however, none exhibited 100% specificity. Although several studies have identified specific virulence factor(s) unique to EAEC, the mechanism by which EAEC exerts its pathogenesis is, thus, far unknown. The present review updates the current knowledge on the epidemiology, chronic complications, detection, virulence factors, and treatment of EAEC, an emerging enteric food borne pathogen.

Enteric bacteria isolated from acute diarrheal patients in the Republic of Korea between the year 2004 and 2006

In an epidemiological survey of human enterobacterial infections in the Republic of Korea during three years from 2004 to 2006, we isolated 1,784 (6.2%, isolation rate of enteropathogens from stool samples) in 2004, 2,547 (9.5%) in 2005 and 3,506 bacteria (12.3%) from people who visited clinics. Among the isolated bacteria, pathogenic Escherichia coli, especially, EAEC was the most frequently identified pathogen in both urban and rural regions followed by Staphylococcus aureus, Salmonella species, Bacillus cereus, Vibrio parahaemolyticus, Campylobacter jejuni, Clostridium perfringens, and Shigella species. Distinct seasonality was found in V. parahaemolyticus species, while this pathogen showed no age-specific patterns. However, other bacteria, i.e., pathogenic E. coli, S. aureus, Salmonella spp., and B. cereus showed similar seasonality throughout the year, showing a slight increase in the infection rate during the summer months and high prevalence among children under 10 years of age and elder-age people. The antibiotic susceptibility patterns of pathogenic E. coli, Salmonella spp., and S. aureus showed high resistance to penicillins. However, both pathogenic E. coli and Salmonella spp. were susceptible to several cephems, imipenem, and amikacin. Moreover, S. aureus strains resistant to vancomycin were not found. In conclusion, these surveillances can play an important role for the control and prevention to the diseases originated by enteritis bacteria.

High incidence of enteroaggregative Escherichia coli among food handlers in three areas of Kenya: a possible transmission route of travelers' diarrhea

BACKGROUND

Contaminated food and water are acknowledged vehicles for the transmission of travelers' diarrhea (TD). Importance of food handlers as reservoirs of enteroaggregative Escherichia coli (EAEC), enteropathogenic E coli (EPEC), and Shiga toxin-producing E coli (STEC) causing TD has not been clearly demonstrated.

METHODS

We undertook a 1-year prospective study to determine the presence and selected risk factors of carriage of EAEC, EPEC, and STEC by 1,399 food handlers working in tourist hotels in three popular tourist destinations of Kenya. Enterotoxigenic E coli (ETEC) was not sought in this study.

RESULTS

During the period April 2003 to May 2004, EAEC harboring the aggR gene were detected from 29 (2.1%) subjects and EPEC harboring the eaeA gene and STEC harboring the stx2 gene were detected from 11 (0.8%) and 2 (0.1%) of the study subjects, respectively. Mean age of subjects with EAEC was significantly lower (24.6 y) than the rest of the study population (28.2 y) (p < 0.05). Pit latrines usage was significantly associated with the isolation of EAEC (<0.001) but not with EPEC and STEC. Four of the 29 EAEC isolates were sensitive to all antibiotics tested, and 19 (65.5%) were multidrug resistant (MDR). Antibiotic resistance varied from 6.9% for cefuroxime to 72.4% for co-trimoxazole. Six EPEC isolates (6/13, 46.2%) showed multidrug resistance. Cluster analysis of the pulsed-field gel electrophoresis (PFGE) profiles showed that the EAEC isolates belonged to two clonally unrelated genotypes.

CONCLUSIONS

We conclude that food handlers working in tourist hotels are important carriers of EAEC that could cause TD and a high proportion of the EAEC are MDR. The isolation of MDR EAEC from food handlers working in tourist hotels is of potential public health importance. There is a need for a study employing molecular methods including PFGE to examine carriage of similar pathogens in food handlers, processed foods, and travelers consuming the food who develop diarrhea.

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.

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.

Structure-function analysis of the enteroaggregative Escherichia coli plasmid-encoded toxin autotransporter using scanning linker mutagenesis

The plasmid-encoded toxin (Pet) from enteroaggregative Escherichia coli is a cytopathic serine protease, which is prototypical of a large family of bacterial autotransporter toxins. To further elucidate the structure-function relationships of this toxin, we employed transposon-based scanning linker mutagenesis. A subset of insertions throughout the Pet mature toxin (passenger) domain reduced secretion to the extracellular space. Many of these mutants were undetectable, but secretion of a subset of mutants with insertions in the N-terminal half of the toxin could be restored to wild type secretion levels if cultured in the presence of 0.1% Triton X-100. Secretion of two mutants with insertions at the extreme C terminus was partially restored when co-expressed with a minimal clone of EspP, a related autotransporter protein. Several well secreted mutants with insertions in the N-terminal third of the molecule reduced protease activity over 20-fold, suggesting that the protease domain is located within this N-terminal region of Pet. We have also identified two insertional mutants in the middle of the passenger domain that were proteolytic but no longer cytopathic; these mutants displayed decreased binding and internalization upon incubation with HEp-2 cells. Our data suggest the existence of separate functional domains mediating Pet proteolysis, secretion, and cell interaction.

The multiplex-PCR-based detection and genotyping of diarrhoeagenic Escherichia coli in diarrhoeal stools

In several hospitals in Beirut, Lebanon, 77 isolates of Escherichia coli were successfully derived from the stools of patients with diarrhoeal diseases, by culture on MacConkey or MacConkey-sorbitol agar. When the isolates were screened, using a multiplex PCR, 14 (from 14 different patients) were each found positive for one of the various genes defining the enterotoxigenic (five), enteroinvasive (four), enteroaggregative (three) or enteropathogenic (two) groups. Genotyping of these 14 diarrhoeagenic isolates, by pulsed-field gel electrophoresis, indicated that all were genomically distinct with the exception of two of the enteroaggregative isolates (which were of the same genotype). The E. coli apparently involved in diarrhoeal disease in Beirut therefore belong to at least four different diarrhoeagenic groups and show strain variation within each group. Diarrhoea in the absence of diarrhoeagenic E. coli may be the result of infection with bacteria other than E. coli or viral or parasitic enteropathogens.

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.

Enteropathogens in adult patients with diarrhea and healthy control subjects: a 1-year prospective study in a Swedish clinic for infectious diseases

A 1-year prospective study was conducted to identify enteropathogens in adults with diarrhea (n=851) and in healthy control subjects (n=203) by use of conventional laboratory methods. Virulence factor genes for diarrheagenic Escherichia coli were detected by polymerase chain reaction. Enteropathogens were identified in 56% of patients and 16% of control subjects. The isolation rate was 65% for patients with symptoms for <1 week and for travelers; >1 pathogen was found in 11% of patients. The most frequent enteropathogens were Campylobacter (13% of patients), Clostridium difficile (13%), enterotoxigenic Escherichia coli (8%), Salmonella (7%), Shigella (4%), Blastocystis hominis (4%), calicivirus (3%), rotavirus (3%), enteroaggregative E. coli (2%), Aeromonas (2%), Giardia intestinalis (2%), Cryptosporidium (2%), and astrovirus (2%). Less frequently isolated (< or =1% of patients) were verotoxigenic E. coli, enteropathogenic E. coli, enteroinvasive E. coli, Entamoeba histolytica/Entamoeba dispar, microsporidia, and adenovirus. Fifty percent of the patients were hospitalized, and 43% needed intravenous fluids. The median duration of diarrhea was 14 days. Clinical features were not helpful for predicting the etiology of diarrhea.