Evaluation of protocol using gene capture and PCR for detection of Helicobacter pylori DNA in feces

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori.

OBJECTIVES

To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started.

SEARCH METHODS

We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as 13C or 14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities.

MAIN RESULTS

We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons.

AUTHORS' CONCLUSIONS

In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions.

Intrafamilial transmission of Helicobacter pylori: genotyping of faecal samples

BACKGROUND

After more than 20 years of research, there is a little information about the detailed routes of Helicobacter pylori transmission. The aim of this study was to explore intrafamilial transmission of H. pylori in children who had indication for upper gastrointestinal endoscopy and their parents.

METHODS

Children (aged up to 15 years) were studied during September 2012 to October 2013. The parents of those with positive urea breath test results were asked to provide faecal and blood samples after giving informed consent. Non-invasive tests such as immunoassay for serological antibodies against H. pylori and detection of its antigen in faeces were measured. The genetic similarity of the family strains was investigated by the random amplification of polymorphic DNA (RAPD-PCR) genotyping method.

RESULTS

According to the genotyping results of 30 families, in 10 (33.3%) children related H. pylori genotypes to their mothers were found, while only 2 children (6.7%) had similar genotypes to their fathers. Interestingly, children with similar H. pylori genotype with their mothers had higher IgA (35.7 ± 10.8) and IgM antibody titres (87.23 ± 19.15) than other children. In addition, in these children, lower titres of IgG antibodies (9.93 ± 3.31) were found rather than children who had no H. pylori in their faeces or had no similarities with their parents (30.28 ± 6.15).

CONCLUSIONS

In conclusion, mother-to-child transmission is the main route of intrafamilial transmission of H. pylori in Iranian families. Molecular typing of H. pylori can be useful in identifying a high-risk population.

Gastrointestinal Infections

Establishing a specific etiology for gastrointestinal infections can be challenging because of the common clinical features and wide variety of causative microorganisms. In many cases, the etiologic agent cannot be determined using traditional diagnostic methods and may result in unnecessary antibiotic use or prolonged periods of illness. Molecular tests provide many advantages over traditional laboratory methods but, with the exception of a few analytes, are still largely in the developmental phase for gastrointestinal pathogens and are not widely used. The main advantages of molecular tests include increased sensitivity and the ability to detect agents which will not grow in culture. To test for all possible gastrointestinal pathogens at one time would require a large panel that would include a variety of bacterial, viral and parasitic agents. Challenges inherent in developing diagnostic molecular panels include ensuring that all variants of a particular microorganism can be detected as well as the rapid evolution of pathogens. In this chapter, the diagnostic merit of molecular tests as well as available tests will be presented for the major groups of gastrointestinal pathogens.

Loop-Mediated Isothermal Amplification as a Fast Noninvasive Method of Helicobacter pylori Diagnosis

BACKGROUND

Helicobacter pylori infection is etiologically associated with some important health problems such as gastric cancer. Because of the high clinical importance of H. pylori infection, development of a noninvasive test for the detection of H. pylori is desirable.

METHODS

In this study, a loop-mediated isothermal amplification (LAMP) targeted ureC of H. pylori was evaluated on 100 stool specimens and compared with a stool antigen test. Culture and rapid urease test were considered as gold standards.

RESULTS

The overall detection rate of the fecal antigen test and LAMP was 58% and 82%, respectively. The analytical sensitivity of the fecal antigen test and LAMP was 500 and 10 H. pylori cells/g and 10 fg DNA/reaction, which is equal to six H. pylori genome.

CONCLUSION

LAMP technique has been characterized by high sensitivity and low detection limit for the detection of H. pylori in stool specimen. Clinical diagnostic performance of LAMP was better than the stool antigen test.

Accuracy of stool antigen test for the diagnosis of Helicobacter pylori infection in children: a meta-analysis

INTRODUCTION

Helicobacter pylori (H. pylori) is regarded as a major pathogen in gastrointestinal diseases and the infection rate is still at a high level in children. Therefore, the diagnosis is of great clinical importance. The objective was to perform a meta-analysis on H. pylori stool antigen test (SAT) for the diagnosis of the infection in children.

METHODS

Published information on the sensitivity and specificity of stool antigen test in each study was collected to assess the accuracy of the test for the diagnosis of H. pylori infection. Forty-five eligible studies were selected for analysis. Data on the publication year, H. pylori prevalence, eradication rate and gold standard of each study were summarized.

RESULT

Forty-five studies, including 5931 patients, evaluated the accurancy of H. pylori SAT. Pooled sensitivity, specificity, LR+ and LR- were: 92.1%, 94.1%, 17.01, 0.085, respectively. Subgroup analyses were conducted to evaluate the sensitivity and specificity of H. pylori SAT in different situations and found that sensitivity and specificity were significantly higher when monoclonal H. pylori SAT and two or more reference methods were used.

CONCLUSIONS

Detection of H. pylori antigen in stools with ELISA monoclonal antibodies is a non-invasive efficient test for the diagnosis of infection in children. However, the available one-step and polyclonal SAT tests are still unreliable.

The first 1000 cultured species of the human gastrointestinal microbiota

The microorganisms that inhabit the human gastrointestinal tract comprise a complex ecosystem with functions that significantly contribute to our systemic metabolism and have an impact on health and disease. In line with its importance, the human gastrointestinal microbiota has been extensively studied. Despite the fact that a significant part of the intestinal microorganisms has not yet been cultured, presently over 1000 different microbial species that can reside in the human gastrointestinal tract have been identified. This review provides a systematic overview and detailed references of the total of 1057 intestinal species of Eukarya (92), Archaea (8) and Bacteria (957), based on the phylogenetic framework of their small subunit ribosomal RNA gene sequences. Moreover, it unifies knowledge about the prevalence, abundance, stability, physiology, genetics and the association with human health of these gastrointestinal microorganisms, which is currently scattered over a vast amount of literature published in the last 150 years. This detailed physiological and genetic information is expected to be instrumental in advancing our knowledge of the gastrointestinal microbiota. Moreover, it opens avenues for future comparative and functional metagenomic and other high-throughput approaches that need a systematic and physiological basis to have an impact.

Preliminary examination of herbal extracts on the inhibition of Helicobacter pylori

BACKGROUND

This work aims at describing the traditional uses, to determine the antimicrobial potential of two different extracts hexane, acetone of the leaves of Citrus unshiu, Citrus sinensis, Citrus limon, Laurus nobilis, Citrus paradisi on clinical strain of H. pylori in a bid to identify potential sources of cheap starting materials for the synthesis of new drugs. H. pylori strain was a culture collection of Hacettepe University, Turkey.

METHODS

The activity was quantitatively assessed on the basis of the inhibition zone, and their activity index was also calculated along with the MIC method.

RESULTS

All the plants demonstrated antimicrobial activity against H. pylori with zone of inhibition diameters ranging from 0 - 30 mm and minimum inhibitory concentration (MIC) values ranging from 1:512-1:4096 dilutions.

CONCLUSION

The results may serve as scientific validation of the ethnomedicinal uses of the Citrus unshiu, Citrus sinensis, Citrus limon, Laurus nobilis, and Citrus paradisi in the treatment of H. pylori-related infections. However, further investigations would be necessary to determine their toxicological properties, in-vivo potencies and mechanism of action against H. pylori.

Non-invasive genotyping of Helicobacter pylori cagA, vacA, and hopQ from asymptomatic children

BACKGROUND

Helicobacter pylori infection is usually acquired in childhood, but little is known about its natural history in asymptomatic children, primarily due to the paucity of non-invasive diagnostic methods. H. pylori strains harboring cagA and specific alleles of hopQ and vacA are associated with increased risk for gastric cancer. Many studies of H. pylori virulence markers in children have the bias that symptomatic subjects are selected for endoscopy, and these children may harbor the most virulent strains. Our aim is to genotype cagA, hopQ, and vacA alleles in stool DNA samples of healthy Colombian children residing in an area with high incidence of gastric cancer, to avoid selection bias resulting from endoscopy.

METHODS

H. pylori status of 86 asymptomatic children was assessed by (13) C-urea breath test (UBT) and PCR. H. pylori 16S rRNA, cagA, hopQ, and vacA genes were amplified from stool DNA samples and sequenced.

RESULTS

UBT was positive in 69 (80.2%) of 86 children; in stool DNA analysis, 78.3% were positive by 16S rRNA PCR. cagA, vacA, and hopQ were detected in 66.1%, 84.6%, and 72.3% of stool DNA samples from 16S rRNA-positive children. Of the children's DNA samples, which revealed vacA and hopQ alleles, 91.7% showed vacA s1 and 73.7% showed type I hopQ. Type I hopQ alleles were associated with cagA positivity and vacA s1 genotypes (p < 0.0001).

CONCLUSIONS

Using stool DNA samples, virulence markers of H. pylori were successfully genotyped in a high percentage of the asymptomatic infected children, revealing a high prevalence of genotypes associated with virulence. Type I hopQ alleles were associated with the presence of cagA and the vacA s1 genotype.

In vivo measurement of Helicobacter pylori infection

Helicobacter pylori is a well-recognized gastroduodenal pathogen (National Institute of Health Consensus Conference, JAMA 272:65-9, 1994) and a class I carcinogen (International Agency for Research on Cancer, IARC Monograph on the Evaluation of Carcinogenic Risk to Humans 61:177-240, 1994) which successfully colonizes the harsh acidic environment of the stomach. H. pylori is the causative factor for peptic ulcer disease (PUD) and an independent risk factor for gastric adenocarcinoma development. Therefore, accurate detection of infection is crucial for devising proper eradication regimens and preventing the more severe GI complications.Detection of H. pylori in the gastric mucosa can be performed via (1) direct detection of the bacterium; culture, histology and polymerase chain reaction (PCR) or (2) indirect detection of its enzymatic products particularly urease as well as serum H. pylori-specific antibody responses, which can be detected by rapid urease test (RUT) and serology, respectively.The accuracy of these diagnostic tests is reported as follows: 98.1% for bacterial culture, 98.1% for histology, 94.3% for PCR, 96.2% for RUT, and 84.9% for serology (Ni et al, J Pediatr 136(6):823-7, 2000).

Intrafamilial Genotyping of Helicobacter pylori from Faecal DNA

Helicobacter pylori infection, often acquired in early childhood, is a global cause of undernutrition, gastritis, peptic ulcer disease and gastric carcinoma. This study tested the feasibility of using H. pylori shed in the faeces as a source of DNA for non-invasive epidemiological studies. H. pylori DNA was chemically recovered and isolated using a specific biotinylated oligonucleotide probe with magnetic capture from 28 H. pylori positive faecal samples obtained from children attending hospital for the investigation of suspected H. pylori infection, together with close family members. Random amplification of polymorphic DNA (RAPD) was subsequently used to discriminate each isolate. 93% of stool samples selected were typeable. Parent, child and sibling samples were compared and similarities determined. Phylogenetic analysis showed that H. pylori DNA obtained from the faeces can be used to genotype individual strains, offering a means of studying intrafamilial transfer of this microorganism.

Utility of stool sample-based tests for the diagnosis of Helicobacter pylori infection in children

OBJECTIVE

Helicobacter pylori antigen or DNA in stool are meant to detect the bacteria; however, in children the colonization of the gastric mucosa by H pylori is usually weak and fecal excretion of antigen or DNA varies considerably, challenging the utility of these tests in this age group. The aim of the present study was to carry out a systematic review and meta-analysis to evaluate the performance of stool H pylori DNA and antigen tests for the diagnosis of infection in children.

METHODS

We conducted a systematic review and meta-analysis to assess the accuracy of stool tests for diagnosis of H pylori infection in children. We searched PubMed, EMBASE, and LILACS databases. Selection criteria included participation of at least 30 children and the use of a criterion standard for H pylori diagnosis. In a comprehensive search, we identified 48 studies.

RESULTS

Regarding antigen-detection tests, enzyme-linked immunosorbent assay (ELISA) monoclonal antibodies showed the best performance, with sensitivity and specificity of 97%, positive likelihood ratio (LR+) of 29.9, and negative likelihood ratio (LR-) of 0.03. ELISA polyclonal antibodies had sensitivity of 92%, specificity of 93%, LR+ of 16.2, LR- of 0.09, and high heterogeneity (P < 0.0001). One-step monoclonal antibody tests demonstrated sensitivity of 88%, specificity of 93%, LR+ of 10.6, and LR- of 0.11. For DNA detection, polymerase chain reaction-based test showed sensitivity of 80.8%, specificity of 98%, LR+ of 17.1, and LR- of 0.18.

CONCLUSIONS

Detection of H pylori antigen in stools with ELISA monoclonal antibodies is a noninvasive efficient test for diagnosis of infection in children. One-step tests showed low accuracy and more studies are needed to obtain a useful office-based screening test. The available molecular tests are still unreliable.

An African perspective on Helicobacter pylori: prevalence of human infection, drug resistance, and alternative approaches to treatment

Helicobacter pylori is a Gram-negative, micro-aerophilic, motile, curved rod that inhabits the gastric mucosa of the human stomach. It chronically infects thousands of millions of people world-wide, and is one of the most genetically diverse of bacterial species. Infection with the bacterium leads to chronic gastritis, peptic ulceration, gastric cancers and gastric mucosa-associated lymphoid-tissue (MALT) lymphoma. The prevalence of infection appears to be partly determined by geographical and socio-demographic factors, being higher in Africa than elsewhere. Current treatment, based on potent combinations that each consist of a proton-pump inhibitor and two antibiotics, is successful in 80%-90% of patients. Some undesirable side-effects, poor patient compliance and drug resistance are, however, associated with significant levels of treatment failure and with contra-indications for some patients. Antibiotic resistance in H. pylori is a growing global concern that merits the urgent attention of public-health authorities. Numerous pieces of clinical evidence have revealed that eradication of the organism from a patient results in improvement of gastritis and drastically decreases the frequency of relapse of gastric and duodenal ulcers. Natural products, including medicinal plants and honey, may offer useful alternatives in the treatment of H. pylori-related infections.

Real-time PCR/RFLP assay to detect Giardia intestinalis genotypes in human isolates with diarrhea in Egypt

Two major genotypic assemblages of Giardia intestinalis infect humans; the nested real-time polymerase chain reaction (PCR) was used for targeting the triose phosphate isomerase (tpi) gene to detect and genotype G. intestinalis in human feces in Egypt. Among 97 fecal samples, 30 (31%) were diagnosed as giardiasis by saline wet mount microscopy after staining with Lugol's iodine. The tpi gene was amplified from 41 (42.3%) fecal samples, of which 11 were microscopy-negative specimens. Of the total samples, 24 (58.5%) contained assemblage A group I, and 7 (17.1%) were assemblage A group II from the group of patients complaining of intermittent diarrhea. Eight (19.5%) samples contained assemblage B from patients with persistent diarrhea. Two (5%) samples had a mixture of assemblage A group II and assemblage B. The technique was able to detect as few as 20 trophozoites per PCR on fecal DNA-isolated, microscopy-negative, and quantitative (q)PCR-positive specimens; there was a higher average cycle threshold value than microscopy-positive and qPCR-positive specimens, suggesting that they represented true, low-burden infections. In conclusion, we could genotype G. intestinalis from fresh stool samples in Egypt; in infections commonly presented with intermittent diarrhea, the most prevalent genotype was assemblage A group I. The most vulnerable age group included 10- to 20-yr-old individuals.

Application of Stool-PCR test for diagnosis of Helicobacter pylori infection in children

AIM: To evaluate the usefulness of stool-PCR test for diagnosis of Helicobacter pylori (H pylori) infection in pediatric populations.

METHODS: Based on endoscopic features (including nodular gastritis, erosive duodenitis and ulcer) and/or a positive rapid urease test (RUT) obtained during endoscopy, 28 children from a group of children admitted to the Children's Medical Center of Tehran for persistent upper gastrointestinal problems were selected to compare biopsy-based tests with stool-PCR. Their gastric activity and bacterial density were graded by the updated Sydney system, and their first stool after endoscopy was stored at -70°C. Biopsies were cultured on modified campy-blood agar plates and identified by gram-staining, biochemical tests, and PCR. Two methods of phenol-chloroform and boiling were used for DNA extraction from H pylori isolates. Isolation of DNA from stool was performed using a stool DNA extraction kit (Bioneer Inc, Korea). PCR was performed using primers for detection of vacA, cagA, and 16srRNA genes in both isolates and stool.

RESULTS: Sixteen out of 28 child patients (57%) were classified as H pylori positive by biopsy-based tests, of which 11 (39%) were also positive by stool-PCR. Sensitivity and specificity of stool-PCR was 62.5% and 92.3% respectively. H pylori was observed in histological sections for 10 out of 11 stool-positive patients. Association was observed between higher score of H pylori in histology and positivity of stool-PCR. Also association was observed between the more severe form of gastritis and a positive stool-PCR.

CONCLUSION: Association between higher score of H pylori in histology and a positive stool-PCR make it a very useful test for detection of H pylori active infection in children. We also suggest that a simple stool-PCR method can be a useful test for detection of H pylori virulence genes in stool.

Helicobacter pylori in water sources: a global environmental health concern

Helicobacter pylori are Gram-negative micro-aerophilic motile curve rods that inhabit the gastric mucosa of the human stomach. The bacterium chronically infects billions of people worldwide and is one of the most genetically diverse of bacterial species. More than half of the world population in both developed and developing countries are infected with this organism. Infection usually occurs without overt clinical symptoms, particularly in poor communities. If untreated, the infection can last for decades without causing symptoms. In some communities, however, infection with the organism causes peptic and duodenal ulcers, gastritis, duodenitis, and gastric cancers. How H. pylori initially enters the stomach is not known, but contaminated food particles and water are suspected, with the former physically shielding it from stomach acid. Similarly, the route of transmission of this pathogen is unknown. Several reports have suggested the possibility of waterborne transmission as the organism can survive for a few days in fresh cold water, salt water, distilled water, and tap water. Knowledge of the epidemiology and mode of transmission of H. pylori is important to prevent its spread and may be useful in identifying high risk populations.

What is the role of the metabolic activity of the gut microbiota in inflammatory bowel disease? Probing for answers with stable isotopes

The pathogenesis of inflammatory bowel disease remains obscure. However, there has been increasing interest in the role of the gut microbiota, focusing in particular on the "unculturable majority" of luminal and mucosal bacteria, which until recently have been difficult to study owing to the technical challenges of identification and elucidating function. Bacterial components and metabolites have been implicated in signalling to host immune systems and regulating inflammatory responses. Although the rapid expansion in techniques of molecular microbiology has increased our understanding of bacterial diversity, the tools to assess bacterial metabolic activity, and to link the 2, lag behind. Stable isotope probing is a powerful technique to link the metabolic activity and diversity of "unculturable" bacteria through isotopic labelling of biomarkers such as DNA and RNA. Progression of current stable isotope probing methodology with high-resolution oligonucleotide 16s rRNA probe technology and high precision liquid chromatographic isotope ratio mass spectrometry may facilitate application in human microbial ecology. Progress towards stable isotope probing use in vivo, in concert with other advances in bacterial metabolome analysis, will lead to the development of a dynamic picture of the metabolic activity and diversity of intestinal bacteria in inflammatory bowel disease. Such insights will, over time, lead to fuller understanding of inflammatory bowel disease pathogenesis and the development of targeted therapies to reverse the "dysbiosis" that precedes disease relapse.

Prevalence of latent, neuropathogenic equine herpesvirus-1 in the Thoroughbred broodmare population of central Kentucky

REASON FOR PERFORMING STUDY

An emerging problem of equine herpesvirus-1 (EHV-1) infection in horses in the USA is a high-mortality myeloencephalopathy that commonly occurs where large numbers of horses are stabled. EHV-1 isolates recovered from recent neurological outbreaks represent a mutant virus strain that possesses enhanced neuropathogenicity. A central question of EHV-1 myeloencephalopathy is the latency carriage rate for these mutants of EHV-1 in USA horse populations.

OBJECTIVE

To estimate the prevalence of neuropathogenic strains of EHV-1 as latent infections in the Thoroughbred broodmare population of central Kentucky.

METHODS

Submandibular lymph nodes (SMLN) were collected during post mortem examination of 132 Thoroughbred broodmares. Total DNA purified from SMLN tissue was tested for the presence of latent EHV-1 DNA by an ultrasensitive magnetic bead-based, sequence-capture, nested PCR method. Differentiation of active from latent infections by EHV-1 was achieved by detection of transcripts of EHV-1 glycoprotein B by reverse transcription PCR.

RESULTS

Latent EHV-1 DNA was detected in the SMLN tissues of 71 (54%) of the 132 mares submitted for necropsy. Thirteen (18%) of the 71 latently infected horses harboured the neuropathogenic biovar of EHV-1. Of the 13 horses latently infected with an ORF30 mutant strain of EHV-1, 11 also carried a latent, wild-type strain of the virus in their SMLN tissues.

CONCLUSIONS

Neuropathogenic strains of EHV-1 have established a significant presence in the Thoroughbred broodmare population of central Kentucky as latently infected carrier horses. The data also indicate that a highly sensitive DNA detection method is required to identify many instances of EHV-1 latency.

POTENTIAL RELEVANCE

The presence of a relatively large biological reservoir of latent, neuropathogenic EHV-1 has the potential for posing emerging equine health and economic threats to the future prosperity of the USA horse industry.

In vitro anti-Helicobacter pylori activity of extracts of selected medicinal plants from North West Cameroon

ETHNOPHARMACOLOGICAL RELEVANCE

Helicobacter pylori, a gram negative microaerophilic bacterium is a major etiological agent in duodenal, peptic and gastric ulcers. The growing problem of antibiotic resistance by the organism demands the search for novel compounds from plant based sources.

AIM OF STUDY

The present study is aimed at evaluating the antimicrobial activity of some selected medicinal plants on clinical isolates of H. pylori circulating in Cameroon in a bid to identify potential sources of cheap starting materials for the synthesis of new drugs.

MATERIALS AND METHODS

Gastric biopsy samples were obtained from patients presenting with gastroduodenal complications. H. pylori was isolated from the specimens following standard microbiology procedures. The disk diffusion method was used to determine the susceptibility of 15 isolates to ten methanol plant extracts (Ageratum conyzoides, Scleria striatinux, Lycopodium cernua, Acanthus montanus, Eryngium foetidium, Aulutandria kamerunensis, Tapeinachilus ananassae, Euphorbia hirta, Emilia coccinea and Scleria verrucosa). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for the most active plant extracts were also determined by the agar dilution method. Results were analyzed statistically by the Fisher's exact test.

RESULTS

All the plants tested demonstrated antimicrobial activity with zone diameters of inhibition ranging from 0-30mm. Of these, A. conyzoides, S. striatinux and L. cernua showed very potent antibacterial activity on the isolates. The lowest MIC and MBC recorded were 0.032mg/mL and 0.098mg/mL respectively. However, the MIC of the extracts ranged from 0.032-1.0mg/mL for S. striatinux; 0.063-0.5mg/mL for L. cernua and 0.063-1.0mg/mL for A. conyzoides. The MBC of the extracts ranged from 0.098-15.0mg/mL for S. striatinux; 0.098-12.5mg/mL for A. conyzoides, and 0.195-12.5mg/mL for L. cernua. The extracts had a wide spectrum of activity. The three most potent extracts possessed significant (P<0.05) inhibitory activities.

CONCLUSION

The plant extracts may contain compounds with therapeutic activity.

Progress in developing accurate tests for the diagnosis of Helicobacter pylori infection

Helicobacter pylori is a chronic infectious agent as defined the major pathogen causing gastritis, gastric and duodenal ulcer, gastric carcinoma and mucosa-associated lymphoid tissue lymphoma, however little is known about its role in functional dyspepsia. H. pylori is the only microorganism known to inhabit the human stomach and the gastric mucosal cells. Chronic H. pylori infection of the stomach is increasingly recognized as a major risk factor for the development of gastroduodenal disease. H. pylori can be detected by non-invasive and invasive methods, the latter requiring endoscopy.

Culture of Helicobacter pylori from stool samples in children

We evaluated two protocols for isolation of Helicobacter pylori in stool from biopsied and nonbiopsied children. Twenty-three child patients whose presumptive positivity or negativity was diagnosed by endoscopy and a rapid urease test at site were used to compare biopsy-based tests with stool-based tests (H. pylori stool antigen test and stool culture). Their gastric activity and bacterial density were graded by the updated Sydney system. Biopsy and stool specimens were cultured on Campy-blood and Belo horizonte agar plates after enrichment in selective Campy-Thio medium. To compare two stool culture protocols, stools from 20 nonbiopsied children were tested by the HpSA test and cultured either as above or after treatment with cholestyramine. Grown colonies were screened by Gram staining, slide agglutination using anti-H. pylori monoclonal IgG; positive isolates were tested by biochemical tests and polymerase chain reaction for H. pylori-specific ureA gene. Coccoid H. pylori was isolated in stool samples from the biopsied patients whose bacterial density was two to four in histology. Their oxidase was slightly positive but became positive after two subcultures, while additional biochemical tests confirmed the isolation of H. pylori. Similar coccoid but oxidase positive H. pylori was isolated from three nonbiopsied children with the protocol of cholestyramine treatment only. The density of bacteria in the stomach may influence the recovery of H. pylori from stool; inactivation of bile with cholestyramine improves the yield in culture and favors isolation of an enhanced metabolic form of bacteria.

Helicobacter pylori detection and antimicrobial susceptibility testing

The discovery of Helicobacter pylori in 1982 was the starting point of a revolution concerning the concepts and management of gastroduodenal diseases. It is now well accepted that the most common stomach disease, peptic ulcer disease, is an infectious disease, and all consensus conferences agree that the causative agent, H. pylori, must be treated with antibiotics. Furthermore, the concept emerged that this bacterium could be the trigger of various malignant diseases of the stomach, and it is now a model for chronic bacterial infections causing cancer. Most of the many different techniques involved in diagnosis of H. pylori infection are performed in clinical microbiology laboratories. The aim of this article is to review the current status of these methods and their application, highlighting the important progress which has been made in the past decade. Both invasive and noninvasive techniques will be reviewed.

Antemortem detection of latent infection with neuropathogenic strains of equine herpesvirus-1 in horses

OBJECTIVE

To evaluate a technique for identifying horses latently infected with neuropathogenic strains of equine herpesvirus-1 (EHV-1).

ANIMALS

36 adult mares, 24 of which were experimentally infected as weanlings with neuropathogenic or nonneuropathogenic EHV-1.

PROCEDURES

Mandibular lymph node (MLN) tissue was obtained from each horse via biopsy during general anesthesia. Purified DNA from MLNs was tested for EHV-1 DNA by use of a magnetic bead, sequencecapture, nested PCR assay. For MLNs that contained EHV-1 DNA, the 256-bp DNA fragments amplified via sequence-capture nested PCR were sequenced to determine the nucleotide at the polymorphic site that determines pathotype (ie, neuropathotype [G(2254)] or non-neuropathotype [A(2254)]).

RESULTS

Latent viral DNA was detected in 26 of the 36 (72%) mares tested. Neuropathogenic and nonneuropathogenic EHV-1 genotypes were detected in the latently infected horses. In each mare previously infected with known EHV-1 pathotypes, the open reading frame 30 genotype of latent EHV-1 was identical to that of the strain that had been inoculated 4 to 5 years earlier. Latent viral DNA was detected in 10 of the 12 mares that were inoculated as weanlings with neuropathogenic strains of EHV-1. The detection rate of the sequence-capture PCR method for EHV-1 latency was double that of conventional nested or realtime PCR assays performed on the same MLN DNA preparations.

CONCLUSIONS AND CLINICAL RELEVANCE

The magnetic bead, sequence-capture, nested PCR technique enabled low-threshold detection of DNA from latent neuropathogenic strains of EHV-1 in MLN specimens from live horses. The technique may be used to screen horses for latent neuropathogenic EHV-1 infection.

Novel therapeutic targets in Helicobacter pylori

The failure of current regimens to treat the gastric pathogen Helicobacter pylori is a growing problem. Responsible for gastritis and peptic ulcer disease, and designated as a Class 1 carcinogen, its presence in up to 90% of the population of the developing world makes its treatment a primary concern. The use of genomic, proteomic and transcriptomic data to determine essential gene products as targets for novel therapeutic agents is of key interest in this research. This review describes how such data can be obtained, evaluated and eventually used as a basis for the development of both vaccine and novel anti-helicobacter agents. It indicates both past successes and possible new avenues to exploit the increased availability of such data, whilst also examining the limitations of such approaches.

Multiplex real-time PCR assay using Scorpion probes and DNA capture for genotype-specific detection of Giardia lamblia on fecal samples

Two major genotypic assemblages of Giardia lamblia infect humans; the epidemiologic significance of this phenomenon is poorly understood. We developed a single-vessel multiplex real-time PCR (qPCR) assay that genotypes Giardia infections into assemblages A and/or B directly from fecal samples. The assay utilized Scorpion probes that combined genotype-specific primers and probes for the 18S rRNA gene into the same molecule. The protocol was capable of detecting as few as 20 trophozoites per PCR on fecal DNA isolated using a commercial method or 1.25 trophozoites per PCR on fecal DNA isolated using a G. lamblia-specific oligonucleotide capture technique. The assay was specific for fecal specimens, with no amplification of the discordant genotype with the opposite Scorpion probe. When 97 clinical specimens from Bangladesh were used, the multiplex PCR assay detected 95% (21 of 22) of Giardia microscopy-positive specimens and 18% (13 of 74) of microscopy-negative specimens. Microscopy-negative and qPCR-positive specimens had higher average cycle threshold values than microscopy-positive and qPCR-positive specimens, suggesting that they represented true low-burden infections. Most (32 of 35) infections were assemblage B infections. This single-reaction multiplex qPCR assay distinguishes assemblage A Giardia infections from assemblage B infections directly on fecal samples and may aid epidemiologic investigation.

Stool screening for colorectal cancer: molecular approaches

Assay of molecular markers in stool represents a promising noninvasive approach to screen colorectal cancer. Given that neoplasms exfoliate abundantly into the lumen and that DNA recovered from stool can be assayed with sensitive techniques, there is a strong biologic rationale to pursue this emerging technology. A challenge with DNA-based testing relates to the selection of markers. Because of the molecular heterogeneity of cancer, no single marker has yielded perfect sensitivity. Several combinations of markers in early stool assays have produced high detection rates of both colorectal cancer and advanced adenomas in selected patient groups, but observations from large representative populations are lacking at present. Potential expanded applications of stool DNA testing include detection of supracolonic aerodigestive cancers and of dysplasia in inflammatory bowel disease. Further marker discovery and technologic refinements should translate into improved test performance and fuel a continued evolution with this screening approach.

Diagnosis of Helicobacter pylori infection

While there are some attempts to improve culture of Helicobacter pylori, molecular methods have been the main focus of this interest. Their main application concerns the development of rapid tests also allowing the determination of bacterial resistance, i.e. real-time polymerase chain reaction (PCR) or fluorescence in situ hybridization (FISH), or to genotype the strains. Attempts to improve, simplify or explain the discrepancies of urea breath test results have been made and new generation of stool antigen test with monoclonal antibodies either using the standard ELISA format or rapid immunoenzymatic detection have confirmed their value. With regard to serology, studies have mainly focused on the distinction of infections with more pathogenic strains and the ability to diagnose atrophic gastritis with the Gastropanel.

Helicobacter pylori infection in pediatrics

The proposed route of Helicobacter pylori transmission appears to be fecal-oral, oral-oral and gastro-oral, yet, a number of studies challenged these hypotheses in 2003. The use of the stool antigen test and[13]-C urea breath testing were the tests of choice for diagnosis and 'test for cure' of H. pylori in Europe in 2003 but have not yet become accepted standard of care in North America. Pediatric H. pylori consensus guidelines are not yet revised; upper endoscopy and biopsy remain the gold standard for diagnosis of pediatric H. pylori infection. In addition to stronger evidence supporting the role of host influences of H. pylori-associated gastric cancer risk, compelling evidence was provided for the role of H. pylori in iron deficiency anemia of childhood. Antibiotic resistance remains a problem in conferring treatment failure and 2003 studies indicate that macrolide resistance is higher in children than in adults. Treatment with proton pump inhibitor-based triple therapy for 10-14 days remains the mainstay for eradication of H. pylori in childhood. Finally, multinational studies are needed to develop screening guidelines for childhood infection to avoid long-term severe gastroduodenal disease sequelae.

Detection of Helicobacter pylori DNA in feces and saliva by polymerase chain reaction: a review

The polymerase chain reaction (PCR), known for its high sensitivity and specificity, has been used for the detection of Helicobacter pylori DNA in bodily materials such as feces and saliva. Since fecal specimens contain PCR inhibitors, DNA before PCR amplification has been purified using various biochemical, immunological and physical pre-PCR steps. Several PCR protocols, differing from each other in the selection of genomic targets and primers, have produced varying degrees of specificity and sensitivity in detecting H. pylori DNA. PCR identified antimicrobial resistance of H. pylori in feces. It also detected virulence factor genes such as the cytotoxin-associated gene (cagA) and vacuolating cytotoxin gene (vacA) in feces and saliva. While the cagA gene was detected in 50-60% of fecal specimens, it was found in 25% of salivary specimens from patients. There was considerable variation in the detection rate of H. pylori DNA in salivary samples. The detection rate in saliva with the most effective primer pair was lower than that observed in feces, making saliva a less suitable specimen for the diagnosis of H. pylori infection. There is controversy regarding the permanent presence of H. pylori in saliva. Whether the salivary and gastric specimens of an individual harbor identical or different strains has not been resolved. PCR cannot distinguish between living and dead organisms. However, it can offer quick results on fecal and salivary specimens, which may contain fastidious and slow-growing H. pylori in low numbers.