Elevated levels of enteric IgA in an unimmunised mouse model of Hyper IgM syndrome derived from gut-associated secondary lymph organs even in the absence of germinal centres

Introduction

Patients with Human Hyper IgM syndromes (HIGM) developed pulmonary and gastrointestinal infections since infancy and most patients have mutations in the CD40 ligand (CD40L) gene. Most HIGM patients compared to healthy subjects have higher/similar IgM and lower IgG, and IgA serum concentrations but gut antibody concentrations are unknown. CD40L on activated T-cells interacts with CD40 on B-cells, essential for the formation of germinal centres (GCs) inside secondary lymphoid organs (SLOs), where high-affinity antibodies, long-lived antibody-secreting plasma cells, and memory B-cells, are produced. C57BL6-CD40 ligand deficient mice (C57BL6-cd40l ^-/-), are a model of HIGM, because serum immunoglobulin concentrations parallel levels observed in HIGM patients and have higher faecal IgA concentrations. In mice, TGFβ and other cytokines induce IgA production.

Aims

To compare and evaluate B-cell populations and IgA-producing plasma cells in peritoneal lavage, non-gut-associated SLOs, spleen/inguinal lymph nodes (ILN), and gut-associated SLOs, mesenteric lymph nodes (MLN)/Peyer´s patches (PP) of unimmunised C57BL6-cd40l ^-/- and C57BL6-wild-type (WT) mice.

Material and methods

Peritoneal lavages, spleens, ILN, MLN, and PP from 8-10 weeks old C57BL6-cd40l ^-/- and WT mice, were obtained. Organ cryosections were analysed by immunofluorescence and B-cell populations and IgA-positive plasma cell suspensions by flow cytometry.

Results

In unimmunised WT mice, GCs were only observed in the gut-associated SLOs, but GCs were absent in all C57BL6-cd40l ^-/- SLOs. PP and MLN of C57BL6-cd40l ^-/- mice exhibited a significantly higher number of IgA-producing cells than WT mice. In the spleen and ILN of C57BL6-cd40l^{- /-} mice IgA-producing cells significantly decreased, while IgM-positive plasma cells increased. C57BL6-cd40l ^-/- B-1 cells were more abundant in all analysed SLOs, whereas in WT mice most B-1 cells were contained within the peritoneal cavity. C57BL6-cd40l ^-/- B-cells in MLN expressed a higher TGFβ receptor-1 than WT mice. Mouse strains small intestine microvilli (MV), have a similar frequency of IgA-positive cells.

Discussion

Together our results confirm the role of PP and MLN as gut inductive sites, whose characteristic features are to initiate an IgA preferential immune response production in these anatomical sites even in the absence of GCs. IgA antibodies play a pivotal role in neutralising, eliminating, and regulating potential pathogens and microorganisms in the gut.

Differential virome composition and richness between children's diarrheagenic stools kept at ultra-low temperatures for long-term

INTRODUCTION

Diarrhoeal illness is the second cause of morbidity/mortality among children from less-developed regions worldwide. Nonetheless, there is scarce information regarding their gut microbiome.

AIM

Microbiome characterization, with an emphasis on the virome, of children's stools with diarrhoea, by a commercial microbiome array.

METHODOLOGY

Nucleic acids extraction, optimised for viral identification, of stool samples from 20 Mexican children with diarrhoea (10 children < 2 and 10 ≥ 2-years-old), collected 16 years ago and kept at -70 °C, were analysed for the presence of viruses, bacteria, archaea, protozoa, and fungi species sequences.

RESULTS

Only viral and bacterial species sequences were identified among children's stools. Most stool samples harboured species belonging to the bacteriophages (95%), anellovirus (60%), diarrhoeagenic viruses (40%), and non-human pathogens viruses (45% avian virus and 40% plant viruses) groups. Among the children's stools, virome inter-individual species composition was observed, even in presence of illness. The < 2-years-old children group has significantly higher viral richness (p = 0.01), conferred mainly by bacteriophages and diarrheagenic-viruses (p = 0.01) species, in comparison with the ≥ 2-years-old group.

CONCLUSIONS

The virome of stools of children with diarrhoea revealed inter-individual viral species composition. Similarly, to the few virome studies in healthy young children, the bacteriophages group was the most abundant. A significantly higher viral richness, conferred by bacteriophages and diarrheagenic-viral species, was observed among < 2-years-old children in comparison with older children. Stools preserved at -70 °C for long term can successfully be used for microbiome studies.

Isolation of Staphylococcus aureus, Uropathogenic Escherichia coli, and Nontuberculous Mycobacteria Strains from Pasteurized Cheeses and Unpasteurized Cream Sold at Traditional Open Markets in Mexico City

ABSTRACT

Fresh cheeses and cream are important garnishes of traditional Mexican food, often purchased at street or itinerant open markets or tianguis. However, there is scarce information regarding the microbiological quality of cheeses and cream sold in tianguis. For 2 years, three dairy stalls from three tianguis in Mexico City were visited once each season, trading practices were registered, and 96 dairy products were purchased. In total 72 fresh pasteurized cheeses that were hand-cut to order (24 Panela, 24 Canasto, and 24 Doble Crema) and 24 unpasteurized Crema de Rancho samples were collected. All dairy products remained without refrigeration for 8 h. Based on the National Guidelines limits, 87.5% of cheeses and 8% of Crema de Rancho samples were of low microbiological quality, and 1 sample of each type of cheese and 3 samples of Crema de Rancho exceeded the guidelines limits for Staphylococcus aureus. All dairy products were negative for Salmonella, Listeria monocytogenes, and all diarrheagenic Escherichia coli pathotypes, including Shiga toxin-producing E. coli. Among the 96 dairy samples, the prevalence of uropathogenic E. coli (UPEC) and of mycobacteria strains were determined because food items contaminated with these strains have been associated with urinary tract infections and mycobacteriosis, respectively. UPEC strains were isolated from 43% of cut-to-order cheeses and 29% of Crema de Rancho samples. Nontuberculous mycobacteria (NTM) strains were identified in 12.5% of Doble Crema cheese samples and 21% of Crema de Rancho samples. From the eight NTM-positive samples, 10 strains were identified (3 strains of Mycolicibacterium fortuitum, 2 of Mycobacteroides abscessus, 2 of Mycobacteroides chelonae, 2 of Mycolicibacterium porcinum, and 1 of Mycolicibacterium rhodesiae). All produced biofilms, and 70% had sliding motility (both virulence traits). Trading practices of cut-to-order pasteurized cheeses and unpasteurized Crema de Rancho in tianguis increase the risk of microbiological contamination of these products, including with human pathogens, and their consumption may cause human illness.

HIGHLIGHTS

A Novel Adult Murine Model of Typical Enteroaggregative Escherichia coli Infection Reveals Microbiota Dysbiosis, Mucus Secretion, and AAF/II-Mediated Expression and Localization of β-Catenin and Expression of MUC1 in Ileum

Typical enteroaggregative Escherichia coli (tEAEC) is a diarrheagenic E. coli pathotype associated with pediatric and traveler’s diarrhea. Even without diarrhea, EAEC infections in children also lead to increased gut inflammation and growth shortfalls. EAEC strain’s defining phenotype is the aggregative adherence pattern on epithelial cells attributable to the aggregative adherence fimbriae (AAF). EAEC only causes diarrhea in humans; therefore, not much is known of the exact intestinal region of infection and damage or its interactions with intestinal enterocytes in vivo and in situ. This study aimed to develop a new tEAEC mouse model of infection, characterize the microbiota of infected mice, and evaluate in situ the expression of host adherence and surface molecules triggering EAEC infection and the role of the EAEC AAF-II in adherence. Six-week-old C57BL/6 mice, without previous antibiotic treatment, were orally challenged with EAEC 042 strain or EAEC 042 AAF-II mutant (ΔAAF/II) strain, or DAEC-MXR strain (diffusely adherent E. coli clinical isolate), and with saline solution (control group). Paraffin sections of the colon and ileum were stained with H&E and periodic acid-Schiff. ZO-1, β-catenin, MUC1, and bacteria were analyzed by immunofluorescence. EAEC-infected mice, in comparison with DAEC-MXR-infected and control mice, significantly lost weight during the first 3 days. After 7 days post-infection, mucus production was increased in the colon and ileum, ZO-1 localization remained unaltered, and morphological alterations were more pronounced in the ileum since increased expression and apical localization of β-catenin in ileal enterocytes were observed. EAEC-infected mice developed dysbiosis 21 days post-infection. At 4 days post-infection, EAEC strain 042 formed a biofilm on ileal villi and increased the expression and apical localization of β-catenin in ileal enterocytes; these effects were not seen in animals infected with the 042 ΔAAF/II strain. At 3 days post-infection, MUC1 expression on ileal enterocytes was mainly detectable among infected mice and colocalized with 042 strains on the enterocyte surface. We developed a novel mouse model of EAEC infection, which mimics human infection, not an illness, revealing that EAEC 042 exerts its pathogenic effects in the mouse ileum and causes dysbiosis. This model is a unique tool to unveil early molecular mechanisms of EAEC infection in vivo and in situ.

Bacteriostatic effect of Echeveria extracts on diarrheagenic E. coli pathotypes and non-cytotoxicity on human Caco-2 cells

INTRODUCTION

Diarrheagenic Escherichia coli pathotypes are important aetiological agents of diarrhoeal illness among children from less developed areas, worldwide. Diarrheagenic E. coli pathotypes strains are increasingly becoming drug resistant, thus effective and accessible therapeutic alternatives are required for their treatment; herbal extracts may be a potential alternative.

AIMS

to evaluate Echeveria craigiana, E. kimnachii, and E. subrigida methanol extracts antibacterial effect on six diarrheagenic E. coli reference strains and on human colorectal adenocarcinoma cells viability and cytokine production.

METHODOLOGY

Diarrheagenic E. coli pathotypes reference strains: typical enteropathogenic E2348/69, enterotoxigenic H10407, enterohaemorrhagic O157:H7/EDL933, enteroinvasive E11, diffusely adherent C18451-A, and enteroaggregative 042 E. coli. E craigiana, E. kimnachii, and E. subrigida leaves, collected at Sinaloa, Mexico, were freeze-dried and macerated in methanol solvent. Antibacterial activity was determined by a novel method developed in our laboratory, bacterial oxygen consumption by polarographic oxygen electrode technique and membrane integrity by two methods (live/dead and protein leakage assays). Colorectal adenocarcinoma cells viability by MTT assay and cytokine production using a Cytometric Bead Array kit.

RESULTS

Extracts concentrations of 100 μg/mL and 5-hour incubation, reduced more than 93% the growth of all diarrheagenic E. coli pathotypes tested strains and significantly decreased bacterial oxygen consumption, like bacteriostatic antibiotics. After 24-hour incubation methanol extracts had a differential antibacterial effect on each diarrheagenic E. coli pathotypes strain. Echeveria extracts did not have any effect on viability and cytokine production of colorectal adenocarcinoma cells.

CONCLUSIONS

Echeveria methanol extracts have a bacteriostatic effect on all diarrheagenic E. coli pathotypes strains, thus potentially they could be used as antibacterial agents on diarrheagenic E. coli pathotypes-contaminated products and on patients with diarrheagenic E. coli pathotypes infections.

New Insights Into DAEC and EAEC Pathogenesis and Phylogeny

Diarrheagenic E. coli can be separated into six distinct pathotypes, with enteroaggregative (EAEC) and diffusely-adherent E. coli (DAEC) among the least characterized. To gain additional insights into these two pathotypes we performed whole genome sequencing of ten DAEC, nine EAEC strains, isolated from Mexican children with diarrhea, and one EAEC plus one commensal E. coli strains isolated from an adult with diarrhea and a healthy child, respectively. These genome sequences were compared to 85 E. coli genomes available in public databases. The EAEC and DAEC strains segregated into multiple different clades; however, six clades were heavily or exclusively comprised of EAEC and DAEC strains, suggesting a phylogenetic relationship between these two pathotypes. EAEC strains harbored the typical virulence factors under control of the activator AggR, but also several toxins, bacteriocins, and other virulence factors. DAEC strains harbored several iron-scavenging systems, toxins, adhesins, and complement resistance or Immune system evasion factors that suggest a pathogenic paradigm for this poorly understood pathotype. Several virulence factors for both EAEC and DAEC were associated with clinical presentations, not only suggesting the importance of these factors, but also potentially indicating opportunities for intervention. Our studies provide new insights into two distinct but related diarrheagenic organisms.

Longitudinal Analysis of the Microbiological Quality of Raw Cow's Milk Samples Collected from Three Small Family Dairy Farms in Mexico over a 2-Year Period

In Mexico, the total milk production that family dairy farms (FDF) contribute is ca. 35%, but this milk is not evaluated for microbiological quality. Forty percent of the milk and dairy products consumed by Mexicans is unpasteurized. In total, 24 raw cow's milk samples from three FDF (one sample per each season from each FDF for two sequent years) were characterized for the presence of food quality indicator organisms, Staphylococcus aureus, Salmonella enterica, Listeria monocytogenes, and Mycobacterium spp., by standard procedures. Escherichia coli presence was also evaluated by a direct count method and diarrheagenic E. coli (DEC) by molecular methods. On the basis of Mexican guidelines for raw milk entering production, 42% of samples exceeded the aerobic mesophilic bacteria limits. A total of 83% raw milk samples were positive for total coliforms, 54% for fecal coliforms, and 46% for E. coli. Forty-three E. coli isolates were selected and characterized for the presence of 11 DEC loci; of theses, 40 isolates were negative for all DEC loci, and 3 isolates, all collected from the same sample, were Shiga toxin 2 (stx₂) positive and O157 antigen negative, and one stx₂ isolate was resistant to 6 of the 16 antibiotics tested. None of the 24 raw milk samples were positive for Salmonella enterica, L. monocytogenes, or staphylococcal enterotoxin. S. aureus was isolated from nine samples, of which only three samples harbored resistant isolates. From three samples, four nontuberculous mycobacterial isolates were recovered (Mycobacteroides chelonae, Mycobacteroides porcinum, and two Mycobacteroides abscessus). All four isolates produced biofilm and had sliding motility, and three isolates (M. porcinum and two M. abscessus) were resistant to the two antibiotics tested (clarithromycin and linezolid). FDF provide raw milk to a large proportion of the Mexican population, but its consumption could be harmful to health, emphasizing the need to implement national microbiological quality guidelines for raw milk intended for direct human consumption.

Cytolethal distending toxin-producing Escherichia coli strains causing severe diarrhoea in young Mexican children

Introduction. Cytolethal distending toxins (CDTs), encoded by cdt genes, have DNase activity leading to cellular and nuclear distension, resulting in irreversible cell cycle arrest and apoptosis of target cells. cdt-positive Escherichia coli strains have been isolated from children with diarrhoea. There is, however, scant information on the prevalence and clinical presentation of diarrhoeal disease caused by these strains. Furthermore, toxin production of cdt-positive strains is rarely confirmed. We report five young children with diarrhoea caused by CDT-producing E. coli in whom stools were negative for other bacterial or enteric pathogens.

Case presentation. On admission to hospital, all children presented watery diarrhoea with high stool output (range 7–20 stools/24 h); five had fever of 38 °C or more and four presented vomiting. Dehydration was present in four patients, one of whom had hypovolaemic shock; one child also presented hyponatraemia and hypokalaemia. In two children, cdt-positive strains were classified as typical and atypical enteropathogenic E. coli, and the remaining three harboured cdt-positive strains that did not belong to any diarrhoeagenic pathogroup. One cdt-positive strain from each case was characterized by a CDT cytotoxic assay and a cdt type-specific PCR. All strains produced the characteristic cellular intoxication due to CDT. Two strains carried the cdt-I, one cdt-III, one cdt-IV, and one concurrently had cdt-I, cdt-II and cdt-III genes.

Conclusion. Our results suggest that CDT-producing E. coli strains are an infrequent, albeit significant, cause of severe diarrhoeal illness in children. Future research should measure the true burden of cdt-positive E. coli diarrhoea among children.

Blood transcriptional profiling of childhood diarrheal diseases identifies gene signatures of Shigella and rotavirus infections

Globally, diarrheal diseases are a leading cause of death in children under five and disproportionately affect children in developing countries. To identify changes in gene expression associated with diarrheal disease, we performed RNA sequencing on whole blood of 192 children less than 10 years of age with acute diarrhea at the Hospital General O’Horan, and 47 age-matched healthy controls from Yucatan, Mexico. We found strong transcriptional signatures associated with rotavirus and Shigella infections relative to other diarrheal infections. The other organisms in our study (Salmonella, E. coli, norovirus, and adenovirus) did not produce transcriptional changes that could be detected in whole blood. Weighted gene correlation network analysis was used to generate modules of genes with similar expression patterns that could be linked to biological functions. In the case of Shigella and rotavirus infections, differentially expressed genes with increased expression were grouped in modules associated with immune system functions. In Shigella infections, modules enriched for genes in adaptive immunity, especially in lymphocyte activation, showed decreased expression while modules enriched for innate immunity, including genes involved in complement activation, an inflammatory response and a response to bacteria, had increased expression. In rotavirus, but not other viral infections, the expression of a module containing genes involved in a type 1 interferon response was increased. Our data suggest that immune gene expression in peripheral blood may distinguish diarrheal diseases caused by Shigella and rotavirus infections from diseases caused by other organisms.

Diarrheagenic Escherichia coli carrying supplementary virulence genes are an important cause of moderate to severe diarrhoeal disease in Mexico

Diarrheagenic Escherichia coli (DEC) cause acute and persistent diarrhoea worldwide, but little is known about their epidemiology in Mexico. We determined the prevalence of bacterial enteropathogens in 831 children with acute diarrhoea over a four-year period in Yucatan, Mexico. Six DEC supplementary virulence genes (SVG), mainly associated with enteroaggregative E. coli (EAEC), were sought in 3100 E. coli isolates. DEC was the most common bacterial enteropathogen (28%), surpassing Salmonella (12%) and Shigella (9%). Predominant DEC groups were diffusely adherent E. coli (DAEC) (35%), EAEC (24%), and enteropathogenic E. coli (EPEC) (19%). Among children with DEC infections, 14% had severe illness mainly caused by EPEC (26%) and DAEC (18%); 30% had moderate diarrhoea mainly caused by DAEC (36%), mixed DEC infections (33%) and EAEC (32%). DAEC was most prevalent during spring, while ETEC, EAEC and EPEC predominated in summer. EAEC was more frequent in children 6–24 months old than in those younger than 6 months of age (P = 0.008, OR = 4.2, 95% CI, 1.3–13.9). The presence of SVG dispersin, (aatA), dispersin-translocator (aatA), enteroaggregative heat-stable toxin 1 (astA), plasmid encoded toxin (pet), cytolethal distending toxin (cdt) was higher in DEC than non-DEC strains, (36% vs 26%, P <0.0001, OR = 1.5, 95% CI, 1.3–1.8). 98% of EAEC-infected children harboured strains with SVG; 85% carried the aap-aatA gene combination, and 33% of these also carried astA. 28% of both EPEC and ETEC, and 6% of DAEC patients had strains with SVG. 54% of EPEC patients carried pet-positive strains alone or in combination with astA; only this DEC group harboured cdt-positive isolates. All ETEC patients carried astA- or astA-aap-positive strains. astA and aap were the most common SVG in DAEC (3% and 2%) and non-DEC strains (21% and 13%). DEC carrying SVG are an important cause of moderate to severe bacterial diarrhoea in Mexican children.

Diarrhoea is an important cause of illness and death among young children in low- and middle-income countries. Nonetheless, very few epidemiological studies of diarrhoea have been conducted in Mexico during the last two decades. In recent years, a group of bacteria known as diarrheagenic Escherichia coli (DEC) have been recognized as a major cause of diarrheal illness worldwide. This group cannot be identified by the conventional biochemical methods used for other diarrhoeal pathogens such as Salmonella or Shigella, which limits its identification. We conducted a study in Yucatan, Mexico, to identify the bacterial causes of acute diarrhoea in children less than five years of age who required hospitalization. All DEC strains were further characterized for the presence of six E. coli supplementary virulence genes (SVG). Of the 831 children with acute diarrhoea, a bacterial pathogen was found in 56%. DEC was the most prevalent (28%) pathogen, surpassing Salmonella and Shigella. Among children with DEC diarrhoea, 44% were moderately or severely ill. Thirty-six percent of the DEC strains had one or more SVG, which were more common in older children. Our results strongly suggest that DEC carrying SVG are an important cause of moderate to severe bacterial diarrhoeal disease in Mexico.

Enteroaggregative coli: A Pathogen Bridging the North and South

Enteroaggregative Escherichia coli (EAEC) is a heterogeneous emerging enteric pathogen. Identified during the 1980's when EAEC strains where isolated from cases of acute and persistent diarrhea among infants from developing countries and of traveler's diarrhea. Subsequently, EAEC strains were linked with foodborne outbreaks and diarrhea illness in adults and children from industrialized countries, HIV-infected subjects and stunting of malnourished poor children. Nowadays, EAEC is increasingly recognized as a major cause of acute diarrhea in children recurring hospitalization and of traveler's diarrhea worldwide. EAEC strains defining phenotype is the aggregative adherence (AA) pattern on epithelial cells. AggR a transcriptional regulator of several EAEC virulence genes has been a key factor in both understanding EAEC pathogenesis and defining typical EAEC (tEAEC) strains. EAEC virulence genes distribution among these strains is highly variable. Present challenges are the identification of key virulence genes and how they coordinately function in the setting of enteric disease.

Occurrence of potentially pathogenic nontuberculous mycobacteria in Mexican household potable water: a pilot study

Background

Nontuberculous mycobacteria (NTM) are environmental opportunistic pathogens found in natural and human-engineered waters, including drinking water distribution systems and household plumbing. This pilot study examined the frequency of occurrence of NTM in household potable water samples in Mexico City. Potable water samples were collected from the “main house faucet” and kitchen faucet. The presence of aerobic-mesophilic bacteria (AMB), total coliforms (TC), fecal coliforms (FC) and NTM species were determined. Mycobacteria species were identified by PCR restriction enzyme pattern analysis (PRA) of the 65-kDa heat shock protein gene (hsp65) and sequencing of the hypervariable region 2 (V2) of the 16S rRNA gene and of the rpoB gene.

Results

AMB (<100 CFU/ml) were present in 118 out of 120 samples; only two samples were outside guidelines ranges (>100 CFU/ml). TC and FC were detected in four and one samples, respectively. NTM species were recovered from 16% samples (19/120) and included M. mucogenicum (nine), M. porcinum (three), M. avium (three), M. gordonae (one), M. cosmeticum (one), M. fortuitum (one), and Mycobacterium sp (one). All household water samples that contained NTM complied with the standards required to grade the water as “good quality” potable water.

Conclusion

Household potable water may be a potential source of NTM infection in Mexico City.

Persistent bloody diarrhoea without fever associated with diffusely adherent Escherichia coli in a young child

Diffusely adherent Escherichia coli (DAEC) is thought to cause diarrhoea in children, and so too are other diarrhoeagenic E. coli (DEC); however, the evidence base is inconclusive. DEC pathotypes are differentiated on the basis of their pathogenic features, and thus cannot be quickly identified on selective culture media. Molecular techniques, not readily available in most clinical laboratories, are required to differentiate DEC strains from non-pathogenic E. coli in the stool flora. We report a case of persistent bloody diarrhoea, without fever, in a previously healthy 21-month infant from whom we isolated five DAEC strains. The child’s stools movements were loose, with gross blood and mucus; fresh mount analysis revealed numerous faecal leukocytes and erythrocytes. Response to antimicrobial treatment with trimethoprim-sulfamethoxazole was poor despite susceptibility in vitro. Although the patient improved with azithromycin, blood was present in the patient’s stools for over 30 days. The severe diarrhoea in this patient might be explained by the fact that these DAEC isolates harboured a siderophore receptor, which allows the bacteria to use iron derived from haem compounds that promote its multiplication. The isolates also induced in vitro secretion of several immunomodulatory cytokines that may account for the patient’s loose stools and faecal leukocytes. DAEC may play a greater role than suspected in afebrile children with bloody diarrhoea.

C57-CD40 ligand deficient mice: a potential model for enterotoxigenic Escherichia coli (H10407) colonization

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrheal disease in humans, calves and pigs. In humans, these infections mainly occur in developing countries leading to a high diarrheal morbidity and infant mortality and to travellers' diarrhea. ETEC strains constitute a phenotypically and genetically diverse pathotype with as common characteristics the production of heat-labile (LT) and/or heat-stable enterotoxins (ST) as well as of one or more fimbrial colonization factors. Despite the global importance of these pathogens, a broadly ETEC protective vaccine is not yet available, partially due to the lack of a suitable animal model for human ETEC. Such model would allow to test more ETEC molecules as potential vaccine candidates. The C57-CD40 ligand deficient (C57-cd40l(-/-)) mouse has been successfully used to develop infection models of intestinal pathogens, but little is known about its humoral immune response. Therefore, the aims of this study were to characterize the humoral immune response of C57 and C57-cd40l(-/-) mice and to determine the persistence of ETEC H10407 and two of its variants after oral inoculation. The serum IgM, IgG and IgA and faecal IgG and IgA concentrations, of twelve mice per mouse strain (C57 and C57-cd40l(-/-)), were determined by ELISA. All serum immunoglobulins and the faecal IgG concentration were significantly lower in C57-cd40l(-/-) than in C57 mice. In contrast the faecal IgA concentration was significantly higher in the C57-cd40l(-/-) mice. This high intestinal IgA concentration might be a compensatory T cell-independent production of IgA production. Both mouse strains were orally inoculated with 5×10(8) ETEC H10407 (LT(+), ST-colonization factor antigen I (CFA/I)(+)) and ETEC in animal faeces was established by culture followed by st and lt loci identification by PCR until day 14 post infection. Most C57 mice eliminated the strain within 3 days whereas infection remained in C57-cd40l(-/-) mice until day 14. Subsequently both mouse strains were inoculated with ETEC H10407 variants and followed up until day 113. Likewise C57 mice eliminated both ETEC variants within 4 days. All C57-cd40l(-/-) mice had eliminated the LT(-) variant at day 31, whereas the ST-CFA/I(-) variant remained in mice stools until day 113. These observations suggest that C57-cd40l(-/-) mice are permissive for ETEC H10407 colonization.

Antimicrobial-resistant Campylobacter in the food chain in Mexico

We describe prevalence and antimicrobial susceptibility results for thermophilic Campylobacter isolates collected from humans, food, and food-animals in an integrated food chain surveillance network in Mexico. From 2003 to 2006, stool samples were collected from children with diarrhea at state sentinel hospitals. Concurrently, fecal samples from asymptomatic children in kindergartens, as well as raw chicken, pork and beef from retail outlets, and food-animal intestines from slaughterhouses were all collected in 65 cities from four different states. C. jejuni was identified with a standardized hippurate test. Hippurate negative, indoxyl acetate positive isolates were classified as Campylobacter spp. Susceptibility testing was performed by agar dilution according to Clinical and Laboratory Standards Institute guidelines. A total of 1,259 C. jejuni and 1,797 Campylobacter spp. isolates were recovered from 11,811 samples. Chicken was significantly more contaminated for both intestinal samples (93.6%) and meat products (58.3%), compared with swine (71.4%)/pork (14.6%) samples, and cattle (25.1%)/beef (5.3%) samples (p<0.001). Campylobacter was recovered from 5.1% of children with diarrhea and from 3.2% of asymptomatic children. Chicken was significantly more likely to harbor ciprofloxacin-resistant C. jejuni (85.8%) than swine (62.5%, OR=3.6), cattle (39.8%, OR=9.3), or humans (58.2%, OR=4.4). No significant differences were found for ciprofloxacin-resistant Campylobacter spp. among food-animals, but the rate in food-animals was significantly higher than in humans (84% vs. 56.7%, OR=4.0). Swine was significantly more likely to harbor erythromycin-resistant C. jejuni (14.8%) than chicken (3.5%, OR=4.9), cattle (1.8%, OR=9.3), or humans (3.0%, OR=5.7), and was associated with higher rates of erythromycin-resistant Campylobacter spp. (41.9%) than chicken (10.5%, OR=6.1) and humans (11.9%, OR=5.3). The high resistance rates to ciprofloxacin preclude the use of fluoroquinolones for treatment of campylobacteriosis in Mexico. Our results emphasize the need for ongoing and integrated surveillance of antimicrobial usage and antimicrobial susceptibility in humans and animals.

Enteroaggregative Escherichia coli pathotype: a genetically heterogeneous emerging foodborne enteropathogen

Until now, a common feature that defines the enteroaggregative Escherichia coli (EAEC) strains is the ability to produce a 'stacked-brick' appearance on epithelial cells, but it does not distinguish between pathogenic and nonpathogenic strains. Numerous adhesins, toxins, and proteins associated with virulence have been described, as well as multiple factors contributing to EAEC-induced inflammation. None of these factors are found in all EAEC isolates, and no single factor has ever been implicated in EAEC virulence. The European outbreak of Shiga-toxin-producing EAEC raises its pathogenic potential and interest on finding the true pathogenic factors that may define this pathotype. EAEC were first associated with persistent diarrhea in infants from developing countries, since then they have increasingly been linked as a cause of acute and persistent diarrhea in young infants and children in developing and industrialized countries, individuals infected with human immunodeficiency virus, as a cause of acute diarrhea in travelers from industrialized regions, and with foodborne outbreaks. A major effect of EAEC infection is on the malnourished children in developing countries. Here, we will discuss the EAEC public health relevance and their complexity because of the strain heterogeneity regarding their pathogenesis, identification, diagnosis, lineage, epidemiology, and clinical manifestations.

Presence of faecal coliforms, Escherichia coli and diarrheagenic E. coli pathotypes in ready-to-eat salads, from an area where crops are irrigated with untreated sewage water

Consumption of ready-to-eat (RTE) salads has increased worldwide. Consequently, the number of outbreaks caused by food-borne pathogens, including diarrheagenic E. coli pathotypes (DEPs), associated with the consumption of RTE-salads has increased. DEPs include enterotoxigenic (ETEC), typical and atypical enteropathogenic (tEPEC, aEPEC), enteroinvasive (EIEC), enteroaggregative (EAEC), diffuse adherent (DAEC) and Shiga toxin-producing (STEC) E. coli. In less-developed areas of the world, fresh crops continue to be irrigated with untreated sewage water. The aims of this study were to evaluate the microbiological quality and prevalence of DEPs in RTE-salads of raw vegetables, purchased from restaurants at Pachuca-City, Hidalgo, Mexico, where most locally consumed vegetables are irrigated with untreated sewage water. A total of 130 salads were purchased from restaurants of three categories: A) national chain restaurants and B) local restaurants, both with the H distinctive (a recognition that the Secretary of Tourism grants to restaurants that manage supplies with high levels of hygiene); and C) local small inexpensive restaurants without H distinctive. A total of 6 restaurants were included, 2 per category (A(1-2), B(1-2), C(1-2)). Each sample was tested for the presence of faecal coliforms (FC) and E. coli by standard procedures. E. coli strains were further characterized for the presence of DEPs loci by two multiplex polymerase chain reactions. Among the 130 salad samples 99% (129) were contaminated with FC; 85% (110/129) harboured E. coli and 7% (8/110) DEPs. The amount of positive salad samples for FC and E. coli was similar between restaurants and categories. The FC mean (571 FC/g) of all samples was significantly higher (p<0.001) than the E. coli mean (63 E. coli/g). A weak correlation of 7.7% (r(2)=0.077, p=0.003) between median FC and E. coli MPN (most probable number) per sample was found. Of the 8 salad samples contaminated with DEPs, 2 were spinach salads from restaurant A(2) and 3 were (Mixed salad) samples from each C restaurant. Three samples harboured non-O157 STEC strains, 2 EIEC, 1 ETEC and 2 samples had non-O157 STEC and EIEC strains, simultaneously. A significant difference (p=0.008) between the prevalence of E. coli vs. DEPs was observed. Independently of the restaurants' overall hygienic status, most RTE-salads had a poor microbiological quality and some harboured DEPs that have been associated with illness in Mexico. Health authorities should focus on implementing DEPs screening in raw vegetables and enforcing the legislation that forbids irrigation with untreated sewage water of both root and leafy vegetables.

Correlation between circulating adhesion molecules and resistin levels in hypertensive type-2 diabetic patients

BACKGROUND

Endothelial dysfunction, a common feature among hypertensive and type-2 diabetic patients, has been associated with inflammation and increased concentrations of serum soluble adhesion molecules and resistin, a monocyte-macrophage- and adipocyte-derived cytokine.

THE AIM OF THIS STUDY

To determine if there is a correlation between the serum concentrations of ICAM-1, VCAM-1, Eselectin and resistin in hypertensive type-2 diabetic patients.

METHODS

Thirty hypertensive type-2 diabetic patients were enrolled in the study. Serum ICAM-1, VCAM-1, E-selectin and resistin concentrations were determined by ELISA and correlated with the Spearman correlation coefficient.

RESULTS

The patients' serum resistin concentrations significantly correlated with VCAM-1 (r = 0.31, p= 0.05) concentrations but not with ICAM-1 (r = 0.29, p = >0.05) and E-selectin (r = 0.10, p = 0.24) concentrations.

CONCLUSION

VCAM-1 and resistin may participate in the pathophysiology of vascular damage in hypertensive type-2 diabetic patients. Serum resistin concentrations may be a marker of endothelial dysfunction.

Vitamin A supplementation modifies the association between mucosal innate and adaptive immune responses and resolution of enteric pathogen infections

BACKGROUND

The efficacy of vitamin A supplementation on diarrheal disease morbidity may reflect the divergent effects that supplementation has on pathogen-specific immune responses and pathogen-specific outcomes.

OBJECTIVE

We examined how vitamin A supplementation modified associations between gut-cytokine immune responses and the resolution of different diarrheal pathogen infections.

DESIGN

Stools collected from 127 Mexican children who were 5-15 mo old and enrolled in a randomized, placebo-controlled vitamin A supplementation trial were screened for enteropathogenic Escherichia coli (EPEC), enterotoxigenic E. coli (ETEC), and Giardia lamblia. Fecal concentrations of interleukin (IL)-6, IL-8, IL-4, IL-5, IL-10, monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) were measured by using an enzyme-linked immunosorbent assay. Hazard models that incorporated categorized cytokine variables (ie, nondetectable, less than the median of detectable concentrations, and at least the median of detectable concentrations) were fit to the length of pathogen infections stratified by treatment group.

RESULTS

Vitamin A-supplemented children with fecal MCP-1 or IL-8 concentrations less than the median of detectable concentrations and IL-10 concentrations of at least median concentrations had longer durations of EPEC infection than did children in the placebo group. In supplemented children, detectable fecal TNF-α or IL-6 concentrations were associated with shorter ETEC infection durations, whereas MCP-1 concentrations of at least the median were associated with longer infection durations. Children in this group who had IL-4, IL-5, or IFN-γ concentrations of at least median detectable concentrations had shorter durations of G. lamblia infection.

CONCLUSION

The effect of supplementation on associations between fecal cytokine concentrations and pathogen infection resolution depends on the role of inflammatory immune responses in resolving specific pathogen infections.

Impact of Vitamin A on Selected Gastrointestinal Pathogen Infections and Associated Diarrheal Episodes among Children in Mexico City, Mexico

BACKGROUND

The overall effect of vitamin A supplementation on diarrheal disease in community trials may result from its effect on specific diarrheal pathogens.

METHODS

We conducted a placebo-controlled, double-blind trial of the prophylactic effect of vitamin A on gastrointestinal pathogen infections and clinical symptoms among 188 children in Mexico City, Mexico, from January 1998 to May 1999. Children 6-15 months of age were randomly assigned to receive either a vitamin A supplement (for children <12 months of age, 20,000 international units [IU] of retinol; for children > or =12 months of age, 45,000 IU of retinol) every 2 months or a placebo and were followed for up to 15 months. Stool samples, collected semimonthly, were screened for enteropathogenic Escherichia coli (EPEC), enterotoxigenic E. coli (ETEC), Shiga toxin-producing E. coli (STEC), enteroinvasive E. coli (EIEC), and Giardia lamblia.

RESULTS

Vitamin A supplementation reduced the prevalence of EPEC infections (rate ratio [RR], 0.52 [95% confidence interval {CI}, 0.23-0.86]) and led to shorter durations of both EPEC and ETEC infections. Supplementation also reduced the prevalence of EPEC-associated diarrhea (RR, 0.41 [95% CI, 0.16-1.00]), EPEC-associated fever (RR, 0.15 [95% CI, 0.02-0.98]), and G. lamblia-associated fever (RR, 0.27 [95% CI, 0.13-0.80]). Finally, children who received vitamin A supplementation had shorter durations of EPEC-associated diarrhea than did children who did not receive supplementation but had longer durations of G. lamblia-associated diarrhea.

CONCLUSIONS

These results suggest that the effect of vitamin A supplementation on clinical outcomes may be pathogen dependent.

Enteroinvasive Escherichia coli severe dysentery complicated by rotavirus gastroenteritis

Enteroinvasive Escherichia coli (EIEC) is an important agent of pediatric diarrhea and dysentery in developing countries. We report a life-threatening severe dysentery case due to EIEC in a malnourished 4-month-old male, native Indian infant co-infected with rotavirus. The severe gastrointestinal bleeding anemia and hypovolemic shock was successfully treated with IV blood transfusions, rehydration and antibiotic therapy.

The effect of vitamin A supplementation on the intestinal immune response in Mexican children is modified by pathogen infections and diarrhea

Vitamin A supplementation has consistently reduced infant mortality and the severity of pathogen-induced diarrhea. The mechanism by which vitamin A modulates the mucosal immune response to produce these effects remains poorly defined. To address this issue, stools collected during the summer months from 127 Mexican children 5-15 mo old enrolled in a larger, randomized, double-blind, placebo-controlled, vitamin A supplementation trial were screened for interleukin (IL)-4, IL-6, interferon-gamma (IFN-gamma), and gastrointestinal pathogens. Fecal cytokine values were categorized into 3 levels (undetectable, <median, > or =median). Multinomial regression models were used to determine the probability that vitamin A-supplemented children had higher categorical values of a cytokine than children in the placebo group. Differences in categorical values were also analyzed after stratification by gastrointestinal pathogen infections and diarrheal symptoms. Overall, fecal cytokine categorical levels did not differ between children randomized to the 2 arms. Vitamin A-supplemented children infected with enteropathogenic E. coli (EPEC) had reduced IL-4 and IFN-gamma levels [odds ratio (OR) = 0.3, 95% CI 0.13-0.67 and OR = 0.34, 95% CI 0.14-0.83, respectively] compared with children in the placebo group. Vitamin A-supplemented children had increased IL-4 levels when infected with A. lumbricoides (OR = 12.06, 95% CI 0.95-153.85). In contrast, IL-4 levels increased (OR = 2.14, 95% CI 0.94-4.87) and IFN-gamma levels decreased (OR = 0.51, 95% CI 0.26-0.99) among vitamin A-supplemented children with diarrhea compared with children in the placebo group. These findings suggest that the regulation of the mucosal immune response by vitamin A may depend on the type of enteric pathogen infecting the child and the presence of clinical symptoms.

Network of dendritic cells within the muscular layer of the mouse intestine

Dendritic cells (DCs) are located at body surfaces such as the skin, respiratory and genital tracts, and intestine. To further analyze intestinal DCs, we adapted an epidermal sheet separation technique and obtained two intestinal layers, facing the lumen and serosa. Unexpectedly, immunolabeling of the layer toward the serosa revealed a regular, dense, planar network of cells with prominent dendritic morphology within the external muscular layer and with increasing frequency along the length of the intestine. Direct examination of the serosal-disposed layers showed a significant fraction of the DCs to express DEC-205/CD205, CD11c, Langerin/CD207, Fcgamma receptor/CD16/32, CD14, and low levels of activation markers, CD25, CD80, CD86, and CD95. By more sensitive FACS analyses, cells from this layer contained two CD11c(+) populations of CD45(+) CD205(+), CD19(-) leukocytes, MHC II(+) and MHC II(-). When ovalbumin conjugated to an anti-DEC-205 antibody was injected into mice, the conjugate targeted to these DCs, which upon isolation were able to stimulate ovalbumin-specific, CD4(+) and CD8(+) T cell antigen receptor-transgenic T cells. In vivo, these DCs responded to two microbial stimuli, systemic LPS and oral live bacteria, by up-regulating CD80, CD86, DEC-205, and Langerin within 12 h. This network of DCs thus represents a previously unrecognized antigen-presenting cell system in the intestine.

Prevalence of Escherichia coli and Salmonella spp. in street-vended food of open markets (tianguis) and general hygienic and trading practices in Mexico City

Street-vendors in Mexico City provide ready-to-eat food to a high proportion of the inhabitants. Nevertheless, their microbiological status, general hygienic and trading practices are not well known. During spring and summer 2000, five tianguis (open markets) were visited and 48 vendors in 48 stalls interviewed. A total of 103 taco dressings were sampled for E. coli and Salmonella spp.: 44 (43%) contained E. coli and 5 (5%) Salmonella (2 S. Enteritidis phage type 8, 1 S. Agona, 2 S. B group). Both E. coli and salmonellas were isolated from three samples. Of Salmonella-positive stalls 80% (4/5) had three or more food-vendors and 80% of vendors were males, compared with 37.3% (16/43) and 46.4% (20/43) in the Salmonella-negative stalls respectively. Food-vendors kept water in buckets (reusing it all day), lacked toilet facilities, and prepared taco dressings the day before which remained at the tianguis without protection for 7.8 h on average. Consumption of street-vended food by local and tourist populations poses a health risk.

Multiplex PCR for detection of three plasmid-borne genes of enteroaggregative Escherichia coli strains

We developed a novel multiplex PCR assay for enteroaggregative Escherichia coli (EAEC) detection, by using three plasmid-borne genes (the aggregative adherence [AA] probe, aap, and aggR). One or more of the loci were detected in 24 (86%) of 28 patient isolates analyzed. The multiplex PCR assay is a fast, convenient, and sensitive molecular test to detect EAEC.

Faecal contamination and enterotoxigenic Escherichia coli in street-vended chili sauces in Mexico and its public health relevance

The street-vended food industry provides employment and cheap ready-to-eat meals to a large proportion of the population in developing countries like Mexico, yet little is known about its role in the transmission of food borne diseases (FBD). Because of its wide consumption, street-vended chili sauces in Mexico are potential vehicles of FBD. An observational study was performed in Mexico City collecting 43 street-vended chili sauces. These sauces were prepared under poor hygienic conditions of handling and selling. Consumers add 4-8 ml of chili sauce per taco, ingest 2-5 tacos per meal and on average, 50 consumers frequent a stall per day. Seventeen (40%) samples were faecally contaminated and 2(5%) sauces harboured sufficient enterotoxigenic Escherichia coli to cause disease. Weestimate that the consumption of only one of these chili sauces could result in ETEC disease inat least 21,000 consumers per year, making them important potential vehicles of FBD.

A fluorescence-based quantitative adhesion assay to study interactions between Entamoeba histolytica and human enterocytes. Effect of proinflammatory cytokines

In order to study the initial events during infection of target cells by the enteric pathogen Entamoeba histolytica, we developed a quantitative adhesion assay based on the use of a human colonic cell line (CaCo-2) and biotinylated amoebae tagged with fluorescein. To prevent the strong and rapid lytic activity of Entamoeba histolytica on colonic cells, which would otherwise impede the study of the primary adhesion steps, parasites were mildly fixed, biotinylated and labelled with streptavidin-FITC. After labelled parasites have bound to enterocytes, nonadhered amoebae are removed by washing and attached parasites quantified by means of an automated fluorescence plate reader. The bioassay is simple, nonhazardous and can be completed in 1.5 h. We were able to detect ranges from 200 to 20,000 fluorescent parasites per microwell in a 96-well plate, containing approximately 10(5) colonic cells. Fluorescence intensity (arbitrary units) increased in direct relationship to the number of parasites added per well, and was not limited by the size of the culture plate (96, 24 or six wells). As an example of the value of this assay, two proinflammatory cytokines (interleukin-1, (IL-1 beta) and interferon-gamma (IFN-gamma) known to influence the adhesion properties of endothelial and epithelial cells, were used to assess their effects upon enterocyte-entamoeba binding. The increase in amoebae binding revealed by cytokine treatment to enterocytes suggests that the parasite may take advantage of inflammatory stimuli in order to increase its binding to colonic epithelium. We believe this rapid, sensitive and simple method offers the potential for large scale screening assays to study the immunobiology of this protozoal infection by analysing the mechanisms involved in the primary interactions between Entamoeba histolytica and enterocytes.

A salt-activated inositol 1,3,4,5-tetrakisphosphate 3-phosphatase at the inner surface of the human erythrocyte membrane

The localization of the human erythrocyte membrane Ins(1,3,4,5)P4 3-phosphatase was investigated by saponin permeabilization of resealed 'isoionic' erythrocyte ghosts. This enzyme is active at the inner face of the plasma membrane, at the same site as a specific 5-phosphatase that degrades both Ins (1,4,5)P3 and Ins(1,3,4,5)P4. In the presence of EDTA, Ins(1,4,5)P3 was the only product of Ins(1,3,4,5)P4 metabolism. However, when Mg2+ was present both the 5-phosphatase and the 3-phosphatase attacked Ins (1,3,4,5)P4, directly forming Ins(1,3,4)P3 and Ins(1,4,5)P3;some Ins(1,4)P2 was also formed as a product of 5-phosphatase attack on the liberated Ins(1,4,5)P3. The Ins(1,3,4,5)P4 3-phosphatase was potently activated by KCl, thus making the route of metabolism of Ins(1,3,4,5)P4 by erythrocyte ghosts strikingly sensitive to variations in ionic strength: at 'cytosolic' K+ and Mg2+ levels, 3-phosphatase activity slightly predominated over 5-phosphatase. Ins(1,3,4,5)P4 3-phosphatase was potently inhibited by Ins-(1,3,4,5,6)P5 and InsP6 at levels lower than those often observed within cells. This leaves open the question as to whether the cellular function of inositol polyphosphate 3-phosphatase is to participate in a physiological cycle that interconverts Ins(1,3,4,5)P4 and Ins(1,4,5)P3 or to metabolize other inositol polyphosphates in the cytosol compartment of cells.