Development of a groEL gene-based species-specific multiplex polymerase chain reaction assay for simultaneous detection of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus

An Integrated Approach to Hygiene, Sanitation, and Storage Practices for Improving Microbial Quality of Drinking Water Treated at Point of Use: A Case Study in Makwane Village, South Africa

This study assessed the impact of sanitation practices, hygienic and storage conditions on the quality of drinking water treated at point-of-use in Makwane Village. Subsequent to implementation of low-cost Household Water Treatment Devices which are the biosand filter with zeolite-silver (BSZ-SICG) and silver-impregnated porous pot (SIPP) filters in Makwane village, a structured questionnaire was designed to collect the following information: age of caretakers, number of children under the age of five, water storage conditions, sanitation amenities, and hygiene practices. Water quality from the sources to household level was assessed using culture-based and molecular techniques. The results revealed a significant association between the presence of Escherichia coli in treated drinking water with the age group of caregivers and the number of children ofless than the age of five [OR (95% CI) = 8.4737 (0.147–3.3497), p = 0.0141923 and OR (95% CI) = 9.1667 (0.1848–3.0159); p = 0.0165830, respectively]. Moreover, significant association was noted between hygiene practices (washing of hands with/without soap) and water quality in storage containers [OR (95% CI) = 16.000 (0.6763–3.9495), p = 0.0000125]. These findings further prove that there is still a dire need for reconsidering hygiene education in rural areas as the health benefits of water treated at point of use (POU) coupled with safe-storage condition interventions might not be guaranteed without proper hygiene. The results further highlighted the importance of washing hands in improving microbial quality of drinking water, which is the key factor for fighting against infectious diseases.

Quantification of Human Oral and Fecal Streptococcus parasanguinis by Use of Quantitative Real-Time PCR Targeting the groEL Gene

Two pairs of species-specific PCR primers targeting the housekeeping groEL gene, Spa146f-Spa525r and Spa93f-Spa525r, were designed to quantify human oral and fecal Streptococcus parasanguinis. Blast analysis against reference sequences of NCBI nucleotide collection database and the Chaperonin Sequence Database showed the forward primers Spa146f and Spa93f 100% matched only with S. parasanguinis, and the in silico Simulated PCR algorithm showed both primer pairs hit only S. parasanguinis groEL gene in Chaperonin Sequence Database. The two primer pairs were respectively used to perform PCR with saliva DNA of each of 6 human subjects, and the amplicons of individual PCR reactions were cloned. The phylogenetic analysis showed cloned sequences were all affiliated to S. parasanguinis, which further validates the specificity of two primer pairs, and that individual subjects harbored multiple genotypes of S. parasanguinis in saliva. By spiking S. parasanguinis into human fecal samples, we found the quantification limit of quantitative real-time PCR (qPCR) assays for both primer pairs was 5-6 log₁₀ groEL copies/g feces. Human fecal S. parasanguinis amounts quantified with qPCR using each of the two primer pairs correlated well with those determined with metagenomic sequencing. qPCR with either primer pair showed periodontitis patients had significantly lower level of saliva S. parasanguinis than healthy people. In both feces and saliva, the S. parasanguinis abundances quantified with two primer pairs exhibited strong and significant correlation. Our results show that the two S. parasanguinis-specific primer pairs can be used to quantify and profile human saliva and fecal S. parasanguinis.

Molecular detection of Vibrio cholerae from human stool collected from SK Hospital, Mymensingh, and their antibiogram

Objective:

Vibrio spp., particularly, Vibrio cholerae is a major etiology of diarrhea in humans worldwide. In this study, we isolated and identified V. cholerae from the human stool of suspected cases along with antibiogram.

Materials and Methods:

In total, 25 stool samples from cholera suspected patients were analyzed. Isolation and molecular detection of Vibrio species were performed based on staining, motility, cultural and biochemical characteristics followed by polymerase chain reaction (PCR) using groEL gene-specific primers.

Results:

Among the 25 samples, seven showed growth of yellow color colonies on Thiosulfate-Citrate-Bile salts-Sucrose agar plates. The isolates were Gram-negative, curved shaped, and motile. Biochemically, they were found positive for indole and Methyl Red tests and negative for Voges–Proskauer test. Out of the seven positive samples, only three isolates were confirmed as Vibrio spp. using genus-specific primers. Subsequently, these three isolates were confirmed as V. cholerae by PCR using V. cholerae groEL gene-specific primers. Antibiotic sensitivity test revealed these three isolates as highly sensitive to azithromycin, chloramphenicol, gentamicin, and norfloxacillin while resistant to streptomycin, tetracycline, and oxacillin.

Conclusion:

Vibrio cholerae were isolated from the stool of diarrheic human patients and confirmed by PCR targeting the groEL gene. The isolates were found resistant to streptomycin, tetracycline and oxacillin, and need further characterization to reveal the molecular basis of their origin and resistance.

Detection of Vibrio anguillarum and Vibrio alginolyticus by Singleplex and Duplex Loop-Mediated Isothermal Amplification (LAMP) Assays Targeted to groEL and fklB Genes

Singleplex and duplex loop-mediated isothermal amplification (LAMP) assays were developed for detecting Vibrio anguillarum, a major bacterial pathogen of fish, and Vibrio alginolyticus, a pathogen of fish and humans, separately and simultaneously from contaminated seawater by targeting the groEL gene of V. anguillarum, which encodes a molecular chaperone protein, and the fklB gene of V. alginolyticus, which encodes a 22 kilodalton (kDa) peptidyl prolyl isomerase. The optimal reaction conditions to produce consistent results were 65 °C for 30 min, 63 °C for 30 min, and 63 °C for 40 min for the groEL (singleplex for V. anguillarum), fklB (singleplex for V. alginolyticus), and groEL + flkB (duplex) LAMP assays, respectively, analyzed via visual detection methods (use of calcein, and SYBR Green I) and agarose gel electrophoresis. The assays were found to be species-specific, as closely related Vibrio spp. were not detected. The limits of detection (LoDs) of the LAMP assays for DNA template from pure culture and artificially contaminated seawater were 10 and 14 fg (groEL assay; for V. anguillarum), 12.5 and 17 fg (fklB assay; for V. alginolyticus), and 50 and 70 fg (duplex assay) per reaction, respectively, which were much better than the LoDs of conventional polymerase chain reaction (PCR). Singleplex and duplex LAMP assays were found to be rapid, species-specific, and sensitive for the detection of V. anguillarum and V. alginolyticus and are applicable to laboratory and field diagnostics.

Multiple etiologies of infectious diarrhea and concurrent infections in a pediatric outpatient-based screening study in Odisha, India

BACKGROUND

There are multiple etiologies responsible for infectious gastroenteritis causing acute diarrhea which are often under diagnosed. Also acute diarrhea is one of the major causes of morbidity and mortality among children less than 5 years of age.

METHODS

In our study, fecal samples (n = 130) were collected from children (<5 years) presenting with symptoms of acute diarrhea. Samples were screened for viral, bacterial, and parasitic etiologies. Rotavirus and Adenovirus were screened by immunochromatographic tests. Diarrheagenic Escherichia coli (EPEC, EHEC, STEC, EAEC, O157, O111), Shigella spp., Salmonella spp., Vibrio cholera, Cryptosporidium spp., and Giardia spp. were detected by gene-specific polymerase chain reaction.

RESULTS

Escherichia coli was detected to be the major etiological agent (30.07%) followed by Rotavirus (26.15%), Shigella (23.84%), Adenovirus (4.61%), Cryptosporidium (3.07%), and Giardia (0.77%). Concurrent infections with two or more pathogens were observed in 44 of 130 (33.84%) cases with a predominant incidence particularly in <2-year-old children (65.90%) compared to children of 2-5 years age group (34.09%). An overall result showed significantly higher detection rates among children with diarrhea in both combinations of two as well as three infections concurrently (p = 0.004915 and 0.03917, respectively).

CONCLUSION

Suspecting possible multiple infectious etiologies and diagnosis of the right causative agent(s) can aid in a better pharmacological management of acute childhood diarrhea. It is hypothesized that in cases with concurrent infections the etiological agents might be complementing each other's strategies of pathogenesis resulting in severe diarrhea that could be studied better in experimental infections.

gbpA as a Novel qPCR Target for the Species-Specific Detection of Vibrio cholerae O1, O139, Non-O1/Non-O139 in Environmental, Stool, and Historical Continuous Plankton Recorder Samples

The Vibrio cholerae N-acetyl glucosamine-binding protein A (GbpA) is a chitin-binding protein involved in V. cholerae attachment to environmental chitin surfaces and human intestinal cells. We previously investigated the distribution and genetic variations of gbpA in a large collection of V. cholerae strains and found that the gene is consistently present and highly conserved in this species. Primers and probe were designed from the gbpA sequence of V. cholerae and a new Taq-based qPCR protocol was developed for diagnostic detection and quantification of the bacterium in environmental and stool samples. In addition, the positions of primers targeting the gbpA gene region were selected to obtain a short amplified fragment of 206 bp and the protocol was optimized for the analysis of formalin-fixed samples, such as historical Continuous Plankton Recorder (CPR) samples. Overall, the method is sensitive (50 gene copies), highly specific for V. cholerae and failed to amplify strains of the closely-related species Vibrio mimicus. The sensitivity of the assay applied to environmental and stool samples spiked with V. cholerae ATCC 39315 was comparable to that of pure cultures and was of 102 genomic units/l for drinking and seawater samples, 101 genomic units/g for sediment and 102 genomic units/g for bivalve and stool samples. The method also performs well when tested on artificially formalin-fixed and degraded genomic samples and was able to amplify V. cholerae DNA in historical CPR samples, the earliest of which date back to August 1966. The detection of V. cholerae in CPR samples collected in cholera endemic areas such as the Benguela Current Large Marine Ecosystem (BCLME) is of particular significance and represents a proof of concept for the possible use of the CPR technology and the developed qPCR assay in cholera studies.

Detection of major diarrheagenic bacterial pathogens by multiplex PCR panels

Diarrheal diseases remain a major threat to the youngest population in low- and middle-income countries. The main bacterial pathogens causing diarrhea are diarrheagenic Escherichia coli (DEC) that consists of enteroaggregative (EAEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), enterohemorrhagic EHEC and enteroinvasive E. coli (EIEC), Salmonella, Shigella spp. (S. dysenteria, S. sonnei, S. flexneri) Campylobacter (C. coli, C. jejuni), Vibrio (V. vulnificus, V. parahaemolyticusm, V. cholerae), Yersinia enterocolitica and Aeromonas hydrophila. The aim of this study was to set up rapid multiplex PCR (mPCR) panels to identify these diarrheagenic pathogens based on their specific virulence genes. Primers against specific target genes were combined into three mPCR panels: one for diarrheal E. coli, one for pathogens causing mainly bloody diarrhea, and the third for the remaining pathogens. The panels were tested against a set of stool samples from Swedish children with diarrhea and controls and the analysis identified bacterial pathogens in 14/54 (26%) of the samples. These results show that our three developed mPCR panels can detect main bacterial diarrheagenic pathogens in clinical samples.

PCR-restriction fragment length polymorphism analysis using groEL gene to differentiate pathogenic Vibrio species

Important pathogenic Vibrio species were differentiated by PCR-restriction fragment length polymorphism analysis. A 1117-bp groEL gene product was amplified using universal primers and digested using the restriction enzymes NruI or XbaI, revealing unique digestion patterns for each of the 10 Vibrio species, of which 7 were pathogenic in humans, along with 2 other species pathogenic in fish.

Multiplex PCR for the detection and differentiation of Vibrio parahaemolyticus strains using the groEL, tdh and trh genes

Vibrio parahaemolyticus is a significant cause of human gastrointestinal disorders worldwide, transmitted primarily by ingestion of raw or undercooked contaminated seafood. In this study, a multiplex PCR assay for the detection and differentiation of V. parahaemolyticus strains was developed using primer sets for a species-specific marker, groEL, and two virulence markers, tdh and trh. Multiplex PCR conditions were standardised, and extracted genomic DNA of 70 V. parahaemolyticus strains was used for identification. The sensitivity and efficacy of this method were validated using artificially inoculated shellfish and seawater. The expected sizes of amplicons were 510 bp, 382 bp, and 171 bp for groEL, tdh and trh, respectively. PCR products were sufficiently different in size, and the detection limits of the multiplex PCR for groEL, tdh and trh were each 200 pg DNA. Specific detection and differentiation of virulent from non-virulent strains in shellfish homogenates and seawater was also possible after artificial inoculation with various V. parahaemolyticus strains. This newly developed multiplex PCR is a rapid assay for detection and differentiation of pathogenic V. parahaemolyticus strains, and could be used to prevent disease outbreaks and protect public health by helping the seafood industry maintain a safe shellfish supply.