Simultaneous detection and quantification of 19 diarrhea-related pathogens with a quantitative real-time PCR panel assay

First recorded food-borne outbreak of gastroenteritis caused by enteroinvasive Escherichia coli serotype O8:H19 in Thailand

An enteroinvasive Escherichia coli (EIEC) outbreak affecting 154 individuals was identified among attendees at a wedding in Loei Province, Thailand. The median time to symptom onset was 18 h (range: 7-72 h). The epidemiological evidence suggested that larb-neua-dib (spicy minced raw beef salad) was the probable source of the outbreak. The O8:H19 isolates identified in this study closely resemble the O8:H19 strains from the United States and the United Kingdom, but not the O96:H19 strains from Europe. This is the first EIEC outbreak documented in Thailand. Complexities in identifying EIEC contribute to its underreporting.

Guidelines for Antibiotics Prescription in Critically Ill Patients

How to cite this article: Khilnani GC, Tiwari P, Mittal S, Kulkarni AP, Chaudhry D, Zirpe KG, et al. Guidelines for Antibiotics Prescription in Critically Ill Patients. Indian J Crit Care Med 2024;28(S2):S104-S216.

Development of a rapid homogeneous immunoassay for detection of rotavirus in stool samples

Rotavirus is the main pathogen causing acute viral gastroenteritis. Accurate and rapid diagnosis of rotavirus infection is important to determine appropriate treatment, prevention of unnecessary antibiotics use and control of infection spread. In this study, we established a rapid, accurate, and sensitive amplified luminescent proximity homogeneous assay linked immunosorbent assay (AlphaLISA) for detecting rotavirus and evaluated its efficacy in human stool samples. Our results demonstrated that the sensitivity of AlphaLISA (5⁻⁸) significantly exceeded that of the immunochromatographic assay (ICA, 5⁻⁴) for rotavirus antigen detection. The intra-assay and inter-assay coefficients of variation were 2.99–3.85% and 5.27–6.51%, respectively. Furthermore, AlphaLISA was specific for rotavirus and did not cross-react with other common diarrhea viruses. AlphaLISA and real-time reverse transcription polymerase chain reaction (RT-qPCR, which is considered a gold standard for detecting diarrhea viruses) tests showed consistent results on 235 stool samples, with an overall consistency rate of 97.87% and a kappa value of 0.894 (P < 0.001). The overall consistency rate of ICA compared with RT-qPCR was 95.74%. AlphaLISA showed better consistency with RT-qPCR than the routinely used ICA for rotavirus detection in stool samples. The AlphaLISA method can be used in clinical practice for the rapid, accurate, and sensitive detection of rotavirus infection.

Viral Eco-Genomic Tools: Development and Implementation for Aquatic Biomonitoring

Enteric viruses (EVs) occurrence within aquatic environments varies and leads to significant risk on public health of humans, animals, and diversity of aquatic taxa. Early and efficacious recognition of cultivable and fastidious EVs in aquatic systems are important to ensure the sanitary level of aquatic water and implement required treatment strategies. Herein, we provided a comprehensive overview of the conventional and up-to-date eco-genomic tools for aquatic biomonitoring of EVs, aiming to develop better water pollution monitoring tools. In combination with bioinformatics techniques, genetic tools including cloning sequencing analysis, DNA microarray, next-generation sequencing (NGS), and metagenomic sequencing technologies are implemented to make informed decisions about the global burden of waterborne EVs-associated diseases. The data presented in this review are helpful to recommend that: (1) Each viral pollution detection method has its own merits and demerits; therefore, it would be advantageous for viral pollution evaluation to be integrated as a complementary platform. (2) The total viral genome pool extracted from aquatic environmental samples is a real reflection of pollution status of the aquatic eco-systems; therefore, it is recommended to conduct regular sampling through the year to establish an updated monitoring system for EVs, and quantify viral peak concentrations, viral typing, and genotyping. (3) Despite that conventional detection methods are cheaper, it is highly recommended to implement molecular-based technologies to complement aquatic ecosystems biomonitoring due to numerous advantages including high-throughput capability. (4) Continuous implementation of the eco-genetic detection tools for monitoring the EVs in aquatic ecosystems is recommended.

A qPCR-based method for rapid quantification of six intestinal homeostasis-relevant bacterial genera in feces

Aim: Developing efficient methods for monitoring the complex microbial community to rapidly assess the health status. Materials & methods: The qPCR-based method was developed, verified and in situ applied in fecal samples. Results: Six primer pairs with high specificity were designed to perform qPCR assays under a unified reaction condition within 2.5 h. The limits of detection, amplification efficiency and feasibility of the qPCR-based method established here were verified. In situ application of 18 fecal samples showed that the amounts of Bacteroides, Streptococcus and Bifidobacterium in colorectal cancer patient feces were obviously lower than those of healthy volunteers. Conclusion: This qPCR-based method was a reliable tool for rapid quantification of the six intestinal homeostasis relevant bacterial genera in feces.

Updates on defining and detecting diarrheagenic Escherichia coli pathotypes

PURPOSE OF REVIEW

Several types of Escherichia coli cause acute diarrhea in humans and are responsible for a large burden of disease globally. The purpose of this review is to summarize diarrheagenic Escherichia coli (DEC) pathotype definitions and discuss existing and emerging molecular, genomic, and gut microbiome methods to detect, define, and study DEC pathotypes.

RECENT FINDINGS

DEC pathotypes are currently diagnosed by molecular detection of unique virulence genes. However, some pathotypes have defied coherent molecular definitions because of imperfect gene targets, and pathotype categories are complicated by hybrid strains and isolation of pathotypes from asymptomatic individuals. Recent progress toward more efficient, sensitive, and multiplex DEC pathotype detection has been made using emerging PCR-based technologies. Genomics and gut microbiome detection methods continue to advance rapidly and are contributing to a better understanding of DEC pathotype diversity and functional potential.

SUMMARY

DEC pathotype categorizations and detection methods are useful but imperfect. The implementation of molecular and sequence-based methods and well designed epidemiological studies will continue to advance understanding of DEC pathotypes. Additional emphasis is needed on sequencing DEC genomes from regions of the world where they cause the most disease and from the pathotypes that cause the greatest burden of disease globally.

High-Throughput Multiparallel Enteropathogen Detection via Nano-Liter qPCR

Quantitative molecular diagnostic methods can effectively detect pathogen-specific nucleic acid sequences, but costs associated with multi-pathogen panels hinder their widespread use in research trials. Nano-liter qPCR (nL-qPCR) is a miniaturized tool for quantification of multiple targets in large numbers of samples based on assay parallelization on a single chip, with potentially significant cost-savings due to rapid throughput and reduced reagent volumes. We evaluated a suite of novel and published assays to detect 17 enteric pathogens using a commercially available nL-qPCR technology. Amplification efficiencies ranged from 88 to 98% (mean 91%) and were reproducible across four operators at two separate facilities. When applied to fecal material, assays were sensitive and selective (99.8% of DNA amplified were genes from the target organism). Due to nanofluidic volumes, detection limits were 1-2 orders of magnitude less sensitive for nL-qPCR than an enteric TaqMan Array Card (TAC). However, higher detection limits do not hinder detection of diarrhea-causing pathogen concentrations. Compared to TAC, nL-qPCR displayed 99% (95% CI 0.98, 0.99) negative percent agreement and 62% (95% CI 0.59, 0.65) overall positive percent agreement for presence of pathogens across diarrheal and non-diarrheal fecal samples. Positive percent agreement was 89% among samples with concentrations above the nL-qPCR detection limits. nL-qPCR assays showed an underestimation bias of 0.34 log₁₀ copies/gram of stool [IQR -0.40, -0.28] compared with TAC. With 12 times higher throughput for a sixth of the per-sample cost of the enteric TAC, the nL-qPCR chip is a viable alternative for enteropathogen quantification for studies where other technologies are cost-prohibitive.

Etiologic features of diarrheagenic microbes in stool specimens from patients with acute diarrhea in Thailand

Many microbial species have been recognized as enteropathogens for humans. Here, we predicted the causative agents of acute diarrhea using data from multiplex quantitative PCR (qPCR) assays targeting 19 enteropathogens. For this, a case-control study was conducted at eight hospitals in Thailand. Stool samples and clinical data were collected from 370 hospitalized patients with acute diarrhea and 370 non-diarrheal controls. Multiple enteropathogens were detected in 75.7% and 13.0% of diarrheal stool samples using multiplex qPCR and bacterial culture methods, respectively. Asymptomatic carriers of enteropathogens were found among 87.8% and 45.7% of individuals by qPCR and culture methods, respectively. These results suggested the complexity of identifying causative agents of diarrhea. An analysis using the quantification cut-off values for clinical relevance drastically reduced pathogen-positive stool samples in control subjects from 87.8% to 0.5%, whereas 48.9% of the diarrheal stool samples were positive for any of the 11 pathogens. Among others, rotavirus, norovirus GII, Shigella/EIEC, and Campylobacter were strongly associated with acute diarrhea (P-value < 0.001). Characteristic clinical symptoms, epidemic periods, and age-related susceptibility to infection were observed for some enteropathogens. Investigations based on qPCR approaches covering a broad array of enteropathogens might thus improve our understanding of diarrheal disease etiology and epidemiological trends.

Advances in Diagnostic Approaches for Viral Etiologies of Diarrhea: From the Lab to the Field

The applications of correct diagnostic approaches play a decisive role in timely containment of infectious diseases spread and mitigation of public health risks. Nevertheless, there is a need to update the diagnostics regularly to capture the new, emergent, and highly divergent viruses. Acute gastroenteritis of viral origin has been identified as a significant cause of mortality across the globe, with the more serious consequences seen at the extremes of age groups (young and elderly) and immune-compromised individuals. Therefore, significant advancements and efforts have been put in the development of enteric virus diagnostics to meet the WHO ASSURED criteria as a benchmark over the years. The Enzyme-Linked Immunosorbent (ELISA) and Polymerase Chain Reaction (PCR) are the basic assays that provided the platform for development of several efficient diagnostics such as real-time RT-PCR, loop-mediated isothermal amplification (LAMP), polymerase spiral reaction (PSR), biosensors, microarrays and next generation sequencing. Herein, we describe and discuss the applications of these advanced technologies in context to enteric virus detection by delineating their features, advantages and limitations.

An Origami Paper-Based Device Printed with DNAzyme-Containing DNA Superstructures for Escherichia coli Detection

Rapid detection of pathogenic bacteria is extremely important for public health and safety. Here, we describe for the first time an integrated origami paper-based analytical device (PAD) incorporating cell lysis, molecular recognition, amplification and visual detection of Escherichia coli (E. coli). The device features three components: paper for its ability to extract protein molecules nonspecifically from cells, DNA superstructures for their ability to immobilize RNA-cleaving DNAzymes (RCDs) but undergo target-induced RNA cleavage on paper, and isothermal rolling circle amplification (RCA) for its ability to amplify each cleavage event into repetitive sequence units that can be detected by naked eye. This device can achieve detection of E. coli K12 with a detection limit of as low as 103 CFU·mL-1 in a total turnaround time of 35 min. Furthermore, this device allowed the sensitive detection of E. coli in complex sample matrices such as juice and milk. Given that more specific RCDs can be evolved for diverse bacteria, the integrated PAD holds great potential for rapid, sensitive and highly selective detection of pathogenic bacteria in resource-limited settings.

High-Throughput Rapid and Inexpensive Assay for Quantitative Determination of Low Cell-Density Yeast Cultures

A procedure for microbial cell density determination with a high-throughput densitometric assay was developed to allow a precise quantification of both free and sessile cells, such as those of a biofilm, with a large range from low to high cell densities. Densitometry was chosen because it allows fast, rapid and cost-effective measures; it is non-disruptive; and has an easy learning curve. The method setup, and the further validation, was carried out with strains of Candida albicans, C. tropicalis and C. parapsilosis. Equations were developed at the level of the single strains, of the three species and finally a general one applicable to all three species. In the cross validation, with strains absent from the training set, the method was shown to be robust and flexible. The best results were obtained with species specific equations, although the global equation performed almost as well in terms of correlation between real and estimated density values. In all cases, a correlation around 0.98 between effective and predicted density was obtained with figures ranging from 10² to 10⁸ cells mL-1. The entire analytical part of the procedure can be accomplished with a MS Excel macro provided free of charge.