Incidence, clinical implications and impact on public health of infections with Shigella spp. and entero-invasive Escherichia coli (EIEC): results of a multicenter cross-sectional study in the Netherlands during 2016-2017

Recent Advances in Electrochemical Biosensors for the Detection of Foodborne Pathogens: Current Perspective and Challenges

Foodborne pathogens cause many diseases and significantly impact human health and the economy. Foodborne pathogens mainly include Salmonella spp., Escherichia coli, Staphylococcus aureus, Shigella spp., Campylobacter spp. and Listeria monocytogenes, which are present in agricultural products, dairy products, animal-derived foods and the environment. Various pathogens in many different types of food and water can cause potentially life-threatening diseases and develop resistance to various types of antibiotics. The harm of foodborne pathogens is increasing, necessitating effective and efficient methods for early monitoring and detection. Traditional methods, such as real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and culture plate, are time-consuming, labour-intensive and expensive and cannot satisfy the demands of rapid food testing. Therefore, new fast detection methods are urgently needed. Electrochemical biosensors provide consumer-friendly methods to quickly detect foodborne pathogens in food and the environment and achieve extensive accuracy and reproducible results. In this paper, by focusing on various mechanisms of electrochemical transducers, we present a comprehensive overview of electrochemical biosensors for the detection of foodborne pathogens. Furthermore, the review introduces the hazards of foodborne pathogens, risk analysis methods and measures of control. Finally, the review also emphasizes the recent research progress and solutions regarding the use of electrochemical biosensors to detect foodborne pathogens in food and the environment, evaluates limitations and challenges experienced during the development of biosensors to detect foodborne pathogens and discusses future possibilities.

Shigella is common in symptomatic and asymptomatic men who have sex with men visiting a sexual health clinic in Amsterdam

INTRODUCTION

Shigellosis is a reportable infectious disease. It can present as a severe bloody diarrhoea but is often asymptomatic. Shigella can be sexually transmissible. We performed a study among symptomatic and asymptomatic men who have sex with men (MSM) to assess the prevalence of Shigella, Salmonella and Campylobacter.

METHODS

From March to June 2020, MSM attending the Amsterdam centre for sexual health were consecutively included. Predefined minimal numbers of inclusion of 150, 100 and 50 were determined, respectively, for MSM who reported no diarrhoea, diarrhoea during last month or diarrhoea on the day of visit to clinic. Anal samples were tested for the presence of Shigella, Salmonella and Campylobacter. During the same period, the frequency of these bacteria was assessed in routinely tested samples requested by general physicians or nursing home physicians. Characteristics of included MSM were compared between the men with different diarrhoea anamnesis, and the prevalence of shigellosis was estimated in each group.

RESULTS

We included 212 MSM without diarrhoea, 109 MSM who recently had diarrhoea and 68 MSM who reported diarrhoea on the day of clinic visit. Thirteen (3.3%, 95% CI 1.7% to 5.6%) MSM were infected with Shigella, none with Salmonella and 7 (1.8%, 95% CI 0.7% to 3.7%) with Campylobacter. Shigella prevalence was 2.8% (95% CI 1.0% to 6.1%) in asymptomatic men, 3.7% (95% CI 1.0% to 9.1%) in men who recently had diarrhoea and 4.4% (95% CI 0.9% to 12.4%) in men with current diarrhoea (p=0.799). Shigella was more frequently found in MSM who had used pre-exposure prophylaxis (PrEP) in the preceding 3 months (10/151), compared with those not having used PrEP (2/146) or being HIV positive (1/75) (p=0.038). Shigella was significantly more often detected among MSM compared with routinely obtained faecal samples being 11/770 (1.4%) (p=0.031).

CONCLUSION

Shigella infections are relatively common in both symptomatic and asymptomatic MSM. Future studies should focus on the risk of onward transmission via asymptomatic persons. Samenvatting Introductie Shigellose is een meldingsplichtige infectieziekte. Het kan zich presenteren als een ernstige bloederige diarree, maar is vaak asymptomatisch. Shigella kan seksueel overdraagbaar zijn. We hebben een onderzoek uitgevoerd onder symptomatische en asymptomatische mannen die seks hebben met mannen (MSM) om de prevalentie van Shigella, Salmonella en Campylobacter te bepalen. Methoden Van maart tot juni 2020 werden achtereenvolgens MSM van het Amsterdamse centrum voor seksuele gezondheid opgenomen. Vooraf gedefinieerde minimale aantallen van inclusie van respectievelijk 150, 100 en 50 waren bepaald voor MSM die geen diarree, diarree in de afgelopen maand of diarree op de dag van bezoek aan de kliniek meldden. Anale monsters werden getest op de aanwezigheid van Shigella, Salmonella en Campylobacter. In dezelfde periode werd de frequentie van deze bacteriën bepaald in routinematig geteste monsters aangevraagd door huisartsen of verpleeghuisartsen. Kenmerken van geïncludeerde MSM werden vergeleken tussen mannen met verschillende diarree anamnese, en de prevalentie van shigellose werd in elke groep geschat. Resultaten We includeerden 212 MSM zonder diarree, 109 MSM die onlangs diarree hadden en 68 MSM die diarree meldden op de dag van het bezoek aan de kliniek. Dertien (3,3%, 95% CI 1,7-5,6%) MSM waren geïnfecteerd met Shigella, geen enkele met Salmonella, en 7 (1,8%, 95% CI 0,7-3,7%) met Campylobacter. De prevalentie van Shigella was 2,8% (95%CI 1,0-6,1%) bij asymptomatische mannen, 3,7% (95%CI 1,0-9,1%) bij mannen die recent diarree hadden en 4,4% (95%CI 0,9-12,4%) bij mannen met huidige diarree (P=0,799). Shigella werd vaker gevonden bij MSM die in de voorgaande drie maanden (10/151) PrEP hadden gebruikt dan bij mensen die geen PrEP hadden gebruikt (2/146) of hiv-positief waren (1/75) (p=0,038). Shigella werd significant vaker gedetecteerd bij MSM in vergelijking met routinematig verkregen fecale monsters, namelijk 11/770 (1,4%) (p=0,031). Conclusie Shigella infecties komen relatief vaak voor bij zowel symptomatische als asymptomatische MSM. Toekomstige studies moeten zich richten op het risico van verdere overdracht via asymptomatische personen.

The Antibacterial Effects of Cocktail and Single Forms of Lytic Phages Belonging to Podoviridae and Myoviridae Families from Sewage against Shigella sonnei and Shigella flexneri

BACKGROUND

Diarrhea caused by bacterial pathogens such as Shigella spp. is one of the prominent public health concerns. The evolution of vast antibiotic resistance by these pathogens, leading to failure in the infections eradication, has made an impetus to seek and develop novel approaches. Recently, some alternative therapies such as phage therapy have been investigated. Bacteriophages are viruses that target specific bacterial species. The objective of this study was to assess the therapeutic effect of phages obtained from hospital sewage against Shigella sonnei (S. sonnei) ATCC® 9290 and S. flexneri ATCC 12022 standard and clinical strains.

METHODS

Four various lytic bacteriophages were isolated from animal fecal and sewage samples and propagated using S. sonnei and S. flexneri as host organisms. The phages' morphology was determined using transmission electron microscopy (TEM). The lytic potential and host specificity of isolated phages were evaluated using double layer plaque assay and spot test. Moreover, bacterial turbidity values were evaluated in coculture with phages in the Luria Bertani (LB) medium for 24 hours at time intervals of 30 min.

RESULTS

Phage cocktails (Shs1, Shs2, Shf1, and Shf2) exhibited higher antimicrobial activity than single phage application against S. sonnei and S. flexneri standard strains. The phages belonged to Podoviridae and Myoviridae families according to TEM-assisted morphological features analysis. In addition, the phages exhibited host specificity using the spot test against 18 Shigella clinical isolates.

CONCLUSION

In this study, phage cocktail of Podoviridae and Myoviridae families from sewage conferred substantial antibacterial effects against S. sonnei and S. flexneri. However, single phage effects were unstable in the LB coculture. Moreover, the phages had host specificity using the spot test performed against Shigella spp. clinical isolates.

Discrimination of Escherichia coli, Shigella flexneri, and Shigella sonnei using lipid profiling by MALDI-TOF mass spectrometry paired with machine learning

Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has become a staple in clinical microbiology laboratories. Protein-profiling of bacteria using this technique has accelerated the identification of pathogens in diagnostic workflows. Recently, lipid profiling has emerged as a way to complement bacterial identification where protein-based methods fail to provide accurate results. This study aimed to address the challenge of rapid discrimination between Escherichia coli and Shigella spp. using MALDI-TOF MS in the negative ion mode for lipid profiling coupled with machine learning. Both E. coli and Shigella species are closely related; they share high sequence homology, reported for 16S rRNA gene sequence similarities between E. coli and Shigella spp. exceeding 99%, and a similar protein expression pattern but are epidemiologically distinct. A bacterial collection of 45 E. coli, 48 Shigella flexneri, and 62 Shigella sonnei clinical isolates were submitted to lipid profiling in negative ion mode using the MALDI Biotyper Sirius® system after treatment with mild-acid hydrolysis (acetic acid 1% v/v for 15 min at 98°C). Spectra were then analyzed using our in-house machine learning algorithm and top-ranked features used for the discrimination of the bacterial species. Here, as a proof-of-concept, we showed that lipid profiling might have the potential to differentiate E. coli from Shigella species using the analysis of the top five ranked features obtained by MALDI-TOF MS in the negative ion mode of the MALDI Biotyper Sirius® system. Based on this new approach, MALDI-TOF MS analysis of lipids might help pave the way toward these goals.

Virulence plasmid pINV as a genetic signature for Shigella flexneri phylogeny

Shigella flexneri is a major health burden in low- and middle-income countries, where it is a leading cause of mortality associated with diarrhoea in children, and shows an increasing incidence among travellers and men having sex with men. Like all Shigella spp., S. flexneri has evolved from commensal Escherichia coli following the acquisition of a large plasmid pINV, which contains genes essential for virulence. Current sequence typing schemes of Shigella are based on combinations of chromosomal genetic loci, since pINV-encoded virulence genes are often lost during growth in the laboratory, making these elements inappropriate for sequence typing. By performing comparative analysis of pINVs from S. flexneri strains isolated from different geographical regions and belonging to different serotypes, we found that in contrast to plasmid-encoded virulence genes, plasmid maintenance genes are highly stable pINV-encoded elements. For the first time, to our knowledge, we have developed a S. flexneri plasmid multilocus sequence typing (pMLST) method based on different combinations of alleles of the vapBC and yacAB toxin–antitoxin (TA) systems, and the parAB partitioning system. This enables typing of S. flexneri pINV plasmids into distinct ‘virulence sequence types’ (vSTs). Furthermore, the phylogenies of vST alleles and bacterial host core genomes suggests an intimate co-evolution of pINV with the chromosome of its bacterial host, consistent with previous findings. This work demonstrates the potential of plasmid maintenance loci as genetic characteristics to study as well as to trace the molecular phylogenesis of S. flexneri pINV and the phylogenetic relationship of this plasmid with its bacterial host.

A duplex droplet digital PCR assay for Salmonella and Shigella and its application in diarrheal and non-diarrheal samples

OBJECTIVES

To evaluate a duplex droplet digital polymerase chain reaction (ddPCR) assay targeting Salmonella fimY and Shigella ipaH genes.

METHODS

The linear range, precision, analytical sensitivity, and analytical specificity of the ddPCR assay were analyzed. The ddPCR assay was compared with quantitative real-time PCR (qPCR) using 362 stool samples from 187 children with mild diarrhea and 175 children without diarrhea.

RESULTS

The duplex ddPCR assay showed good linearity in the range of 5.3 × 10⁰ to 1.24 × 10⁵ copies/reaction for Salmonella and 1.9 × 10⁰ to 1.84 × 10⁵ copies/reaction for Shigella. When analyzed with spiked stool samples, the limit of detection and limit of quantification were 550 and 5500 colony-forming units per mL of stool sample for Shigella, respectively, whereas both were 1.0 × 10⁴ colony-forming units per mL of stool sample for Salmonella. Among 362 stool samples, more samples were detected as positive by ddPCR than by qPCR. Salmonella load was significantly higher in diarrheal samples than in non-diarrheal samples. Determined by receiver-operating characteristic analysis, the optimal cut-off value was 1.25 × 10⁴ copies/mL of stool sample to distinguish between symptomatic and asymptomatic Salmonella infections.

CONCLUSION

Salmonella and Shigella prevalence may have been underestimated in the past.

Symptoms and PCR testing interval for bacterial pathogens in patients with diarrhoea

Introduction . Acute diarrhoea can be caused by Salmonella species, Shigella species, Yersinia enterocolitica, Campylobacter species and Plesiomonas shigelloides (SSYCP). In clinical practice, however, polymerase chain reaction (PCR) for SSYCP is frequently performed as part of the diagnostic work-up for patients with chronic diarrhoea and gastrointestinal complaints.Hypothesis. This study postulates that PCR for SSYCP is of limited clinical use in patients with chronic diarrhoea and gastrointestinal complaints.Aim. The primary aim of this study is to evaluate whether testing for SSYCP remains sensible in patients with chronic diarrhoea and gastrointestinal symptoms and if earlier testing leads to more positive PCR results.Methodology. Between January 2017 and December 2018, data on PCR results, culture results, symptoms, symptom to testing interval (STI) and immune status were retrospectively collected from the medical records of patients with gastrointestinal symptoms for whom PCR results for SSYCP were available. The STIs of PCR-positive patients and PCR-negative patients were compared.Results. In total, 146 PCR-positive and 149 PCR-negative patients were included. STIs of <7 days occurred in 55 % of all PCR-positive patients compared to 38 % in PCR-negative patients. PCR-positive patients were more often tested within 7 days after onset of gastrointestinal symptoms or diarrhoea. A third of PCR-positive patients had an STI of >7 days. Immunocompromised patients had a shorter STI. Admitted patients had a shorter STI. Eighty-six PCR-positive patients had a positive culture (58 %). Antibiotic use 3 months prior to PCR testing was correlated with negative PCR results.Conclusions . This study shows that early testing correlates with more positive PCR results and underlines that PCR for SSYCP is of lesser importance in the diagnostic workup of chronic diarrhoea and/or gastrointestinal symptoms. The shorter STI found in immunocompromised patients is possibly due to a lower threshold for testing in this population. It is also important to take recent antibiotic use into consideration when interpreting PCR results, given the correlation between negative PCR results and antibiotic use. Careful and precise documentation of symptoms in medical records is essential for clinical practice and research.

ECTyper: in silico Escherichia coli serotype and species prediction from raw and assembled whole-genome sequence data

Escherichia coli is a priority foodborne pathogen of public health concern and phenotypic serotyping provides critical information for surveillance and outbreak detection activities. Public health and food safety laboratories are increasingly adopting whole-genome sequencing (WGS) for characterizing pathogens, but it is imperative to maintain serotype designations in order to minimize disruptions to existing public health workflows. Multiple in silico tools have been developed for predicting serotypes from WGS data, including SRST2, SerotypeFinder and EToKi EBEis, but these tools were not designed with the specific requirements of diagnostic laboratories, which include: speciation, input data flexibility (fasta/fastq), quality control information and easily interpretable results. To address these specific requirements, we developed ECTyper (https://github.com/phac-nml/ecoli_serotyping) for performing both speciation within Escherichia and Shigella, and in silico serotype prediction. We compared the serotype prediction performance of each tool on a newly sequenced panel of 185 isolates with confirmed phenotypic serotype information. We found that all tools were highly concordant, with 92-97 % for O-antigens and 98-100 % for H-antigens, and ECTyper having the highest rate of concordance. We extended the benchmarking to a large panel of 6954 publicly available E. coli genomes to assess the performance of the tools on a more diverse dataset. On the public data, there was a considerable drop in concordance, with 75-91 % for O-antigens and 62-90 % for H-antigens, and ECTyper and SerotypeFinder being the most concordant. This study highlights that in silico predictions show high concordance with phenotypic serotyping results, but there are notable differences in tool performance. ECTyper provides highly accurate and sensitive in silico serotype predictions, in addition to speciation, and is designed to be easily incorporated into bioinformatic workflows.

Cluster-specific gene markers enhance Shigella and enteroinvasive Escherichia coli in silico serotyping

Shigella and enteroinvasive Escherichia coli (EIEC) cause human bacillary dysentery with similar invasion mechanisms and share similar physiological, biochemical and genetic characteristics. Differentiation of Shigella from EIEC is important for clinical diagnostic and epidemiological investigations. However, phylogenetically, Shigella and EIEC strains are composed of multiple clusters and are different forms of E. coli, making it difficult to find genetic markers to discriminate between Shigella and EIEC. In this study, we identified 10 Shigella clusters, seven EIEC clusters and 53 sporadic types of EIEC by examining over 17000 publicly available Shigella and EIEC genomes. We compared Shigella and EIEC accessory genomes to identify cluster-specific gene markers for the 17 clusters and 53 sporadic types. The cluster-specific gene markers showed 99.64% accuracy and more than 97.02% specificity. In addition, we developed a freely available in silico serotyping pipeline named Shigella EIEC Cluster Enhanced Serotype Finder (ShigEiFinder) by incorporating the cluster-specific gene markers and established Shigella and EIEC serotype-specific O antigen genes and modification genes into typing. ShigEiFinder can process either paired-end Illumina sequencing reads or assembled genomes and almost perfectly differentiated Shigella from EIEC with 99.70 and 99.74% cluster assignment accuracy for the assembled genomes and read mapping respectively. ShigEiFinder was able to serotype over 59 Shigella serotypes and 22 EIEC serotypes and provided a high specificity of 99.40% for assembled genomes and 99.38% for read mapping for serotyping. The cluster-specific gene markers and our new serotyping tool, ShigEiFinder (installable package: https://github.com/LanLab/ShigEiFinder, online tool: https://mgtdb.unsw.edu.au/ShigEiFinder/), will be useful for epidemiological and diagnostic investigations.

Historical, current, and emerging tools for identification and serotyping of Shigella

The Shigella genus includes serious foodborne disease etiologic agents, with 4 species and 54 serotypes. Identification at species and serotype levels is a crucial task in microbiological laboratories. Nevertheless, the genetic similarity between Shigella spp. and Escherichia coli challenges the correct identification and serotyping of Shigella spp., with subsequent negative repercussions on surveillance, epidemiological investigations, and selection of appropriate treatments. For this purpose, multiple techniques have been developed historically ranging from phenotype-based methods and single or multilocus molecular techniques to whole-genome sequencing (WGS). To facilitate the selection of the most relevant method, we herein provide a global overview of historical and emerging identification and serotyping techniques with a particular focus on the WGS-based approaches. This review highlights the excellent discriminatory power of WGS to more accurately elucidate the epidemiology of Shigella spp., disclose novel promising genomic targets for surveillance methods, and validate previous well-established methods.

Virulence Factors of Enteric Pathogenic Escherichia coli: A Review

Escherichia coli are remarkably versatile microorganisms and important members of the normal intestinal microbiota of humans and animals. This harmless commensal organism can acquire a mixture of comprehensive mobile genetic elements that contain genes encoding virulence factors, becoming an emerging human pathogen capable of causing a broad spectrum of intestinal and extraintestinal diseases. Nine definite enteric E. coli pathotypes have been well characterized, causing diseases ranging from various gastrointestinal disorders to urinary tract infections. These pathotypes employ many virulence factors and effectors subverting the functions of host cells to mediate their virulence and pathogenesis. This review summarizes new developments in our understanding of diverse virulence factors associated with encoding genes used by different pathotypes of enteric pathogenic E. coli to cause intestinal and extraintestinal diseases in humans.

Characterization of the Luminal and Mucosa-Associated Microbiome along the Gastrointestinal Tract: Results from Surgically Treated Preterm Infants and a Murine Model

Environmental factors, including nutritional habits or birth mode, are known key determinants for intestinal microbial composition. Investigations of the intestinal microbiome in different species in a multiplicity of studies during recent decades have revealed differential microbial patterns and quantities along the gastrointestinal (GI) tract. Characterization of the microbial pattern in various aspects is a prerequisite for nutritional interventions. In this 16S rRNA amplicon-based approach, we present a characterization of the mucosa-associated microbiome in comparison with the luminal community of four infants at the time of the closure of ileostomies and perform a systematic characterization of the corresponding luminal and mucosal microbiome from jejunal, ileal and colonic regions, as well as collected feces in mice. The most dominant taxa in infant-derived samples altered due to individual differences, and in the mucosa, Enterococcus, Clostridiumsensustricto1, Veillonella, Streptococcus and Staphylococcus were the most abundant. Two less abundant taxa differed significantly between the mucosa and lumen. In murine samples, relative abundances differed significantly, mainly between the intestinal regions. Significant differences between mouse mucosa- and lumen-derived samples could be found in the observed species with a trend to lower estimated diversity in mucosa-derived samples, as well as in the relative abundance of individual taxa. In this study, we examined the difference between the mucosal and luminal bacterial colonization of the gastrointestinal tract in a small sample cohort of preterm infants. Individual differences were characterized and statistical significance was reached in two taxa (Cupriavidus, Ralstonia). The corresponding study on the different murine intestinal regions along the GI tract showed differences all over the intestinal region.

A Multifactorial Approach for Surveillance of Shigella spp. and Entero-Invasive Escherichia coli Is Important for Detecting (Inter)national Clusters

Shigella spp. and entero-invasive Escherichia coli (EIEC) can cause mild diarrhea to dysentery. In Netherlands, although shigellosis is a notifiable disease, there is no laboratory surveillance for Shigella spp. and EIEC in place. Consequently, the population structure for circulating Shigella spp. and EIEC isolates is not known. This study describes the phenotypic and serological characteristics, the phenotypic and genetic antimicrobial resistance (AMR) profiles, the virulence gene profiles, the classic multi-locus sequence types (MLST) and core genome (cg)MLST types, and the epidemiology of 414 Shigella spp. and EIEC isolates collected during a cross-sectional study in Netherlands in 2016 and 2017. S. sonnei (56%), S. flexneri (25%), and EIEC (15%) were detected predominantly in Netherlands, of which the EIEC isolates were most diverse according to their phenotypical profile, O-types, MLST types, and cgMLST clades. Virulence gene profiling showed that none of the isolates harbored Shiga toxin genes. Most S. flexneri and EIEC isolates possessed nearly all virulence genes examined, while these genes were only detected in approximately half of the S. sonnei isolates, probably due to loss of the large invasion plasmid upon subculturing. Phenotypical resistance correlated well with the resistant genotype, except for the genes involved in resistance to aminoglycosides. A substantial part of the characterized isolates was resistant to antimicrobials advised for treatment, i.e., 73% was phenotypically resistant to co-trimoxazole and 19% to ciprofloxacin. AMR was particularly observed in isolates from male patients who had sex with men (MSM) or from patients that had traveled to Asia. Furthermore, isolates related to international clusters were also circulating in Netherlands. Travel-related isolates formed clusters with isolates from patients without travel history, indicating their emergence into the Dutch population. In conclusion, laboratory surveillance using whole genome sequencing as high-resolution typing technique and for genetic characterization of isolates complements the current epidemiological surveillance, as the latter is not sufficient to detect all (inter)national clusters, emphasizing the importance of multifactorial public health approaches.

High Prevalence of Intestinal Pathogens in Indigenous in Colombia

Background: Intestinal infections remain a major public health burden in developing countries. Due to social, ecological, environmental, and cultural conditions, Indigenous peoples in Colombia are at particularly high risk. Materials: 137 stool samples were analyzed by microscopy and real-time-Polymerase Chain Reaction (RT-PCR), targeting protozoan parasites (Giardia intestinalis, Entamoeba histolytica, Cryptosporidium spp., and Cyclospora cayetanensis), bacteria (Campylobacter jejuni, Salmonella spp., Shigella ssp./enteroinvasive E. coli (EIEC), Yersinia spp., enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), enterotoxin-producing E. coli (ETEC), enteroaggregative E. coli (EAEC), and Tropheryma whipplei), and helminths (Necator americanus, Strongyloides stercoralis, Ascaris lumbricoides, Ancylostoma spp., Trichuris. trichiura, Taenia spp., Hymenolepis nana, Enterobius vermicularis, and Schistosoma spp.). Microscopy found additional cases of helminth infections. Results: At least one pathogen was detected in 93% of the samples. The overall results revealed protozoa in 79%, helminths in 69%, and bacteria in 41%. G. intestinalis (48%), Necator/hookworm (27%), and EAEC (68%) were the most common in each group. Noteworthy, T. whipplei was positive in 7% and T. trichirua in 23% of the samples. A significant association of one infection promoting the other was determined for G. intestinalis and C. jejuni, helminth infections, and EIEC. Conclusions: The results illustrate the high burden of gastrointestinal pathogens among Indigenous peoples compared to other developing countries. Countermeasures are urgently required.

Determination of the Microbial and Chemical Loads in Rivers from the Quito Capital Province of Ecuador (Pichincha)-A Preliminary Analysis of Microbial and Chemical Quality of the Main Rivers

Contamination of natural water sources is one of the main health problems worldwide, which could be caused by chemicals, metals, or microbial agents. This study aimed to analyze the quality of 18 rivers located in Quito, the capital province of Pichincha, Ecuador, through physico-chemical and microbial parameters. The E. coli and total coliforms assessments were performed by a counting procedure in growth media. Polymerase chain reaction (PCR) was realized to detect several microbial genera, as well as Candida albicans, two parasites (Cryptosporidium and Giardia spp.) and E. coli pathotypes: enterohemorrhagic E. coli (EHEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC) and enteropathogenic E. coli (EPEC). Additionally, physico-chemical parameters and major and trace metals were analyzed in each surface water sample. Our results demonstrated that most of the rivers analyzed do not comply with the microbial, physico-chemical, and metal requirements established by the Ecuadorian legislation. In terms of microbial pollution, the most polluted rivers were Monjas, Machángara, Pisque, and Pita Rivers. Furthermore, three out of four analyzed E. coli pathotypes (EIEC, EHEC, and EAEC) were detected in certain rivers, specifically: Monjas River showed the presence of EIEC and EHEC; in the Machángara River, EAEC and EIEC were detected; and finally, EIEC was present in the Guayllabamba River. Several physico-chemical parameters, such as pH, CODtotal, and TSS values, were higher than the Ecuadorian guidelines in 11, 28, and 28% of the rivers, respectively. Regarding heavy metals, Zn, Cu, Ni, Pb, Cd, and Mn surpassed the established values in 94, 89, 61, 22, 22, and 17% of the rivers, respectively. Machangara River was the only one that registered higher Cr concentrations than the national guidelines. The values of Al and Fe were above the recommended values in 83 and 72% of the rivers. Overall, based on the physical-chemical and microbiological parameters the most contaminated rivers were Machángara and Monjas. This study revealed severe contaminations in Ecuadorean Rivers; further studies should evaluate the sources of contamination and their impact on public health.