Analysis of the survival of H. pylori within a laboratory-based aquatic model system using molecular and classical techniques

Potential Role of Biofilm Formation in the Development of Digestive Tract Cancer With Special Reference to Helicobacter pylori Infection

Bacteria are highly social organisms that communicate via signaling molecules and can assume a multicellular lifestyle to build biofilm communities. Until recently, complications from biofilm-associated infection have been primarily ascribed to increased bacterial resistance to antibiotics and host immune evasion, leading to persistent infection. In this theory and hypothesis article we present a relatively new argument that biofilm formation has potential etiological role in the development of digestive tract cancer. First, we summarize recent new findings suggesting the potential link between bacterial biofilm and various types of cancer to build the foundation of our hypothesis. To date, evidence has been particularly convincing for colorectal cancer and its precursor, i.e., polyps, pointing to several key individual bacterial species, such as Bacteroides fragilis, Fusobacterium nucleatum, and Streptococcus gallolyticus subsp. Gallolyticus. Then, we further extend this hypothesis to one of the most common bacterial infection in humans, Helicobacter pylori (Hp), which is considered a major cause of gastric cancer. Thus far, there has been no direct evidence linking in vivo Hp gastric biofilm formation to gastric carcinogenesis. Yet, we synthesize the information to support an argument that biofilm associated-Hp is potentially more carcinogenic, summarizing biological characteristics of biofilm-associated bacteria. We also discuss mechanistic pathways as to how Hp or other biofilm-associated bacteria control biofilm formation and highlight recent findings on Hp genes that influence biofilm formation, which may lead to strain variability in biofilm formation. This knowledge may open a possibility of developing targeted intervention. We conclude, however, that this field is still in its infancy. To test the hypothesis rigorously and to link it ultimately to gastric pathologies (e.g., premalignant lesions and cancer), studies are needed to learn more about Hp biofilms, such as compositions and biological properties of extracellular polymeric substance (EPS), presence of non-Hp microbiome and geographical distribution of biofilms in relation to gastric gland types and structures. Identification of specific Hp strains with enhanced biofilm formation would be helpful not only for screening patients at high risk for sequelae from Hp infection, but also for development of new antibiotics to avoid resistance, regardless of its association with gastric cancer.

Helicobacter pylori: A foodborne pathogen?

Helicobacter pylori (H. pylori) is an organism that is widespread in the human population and is sometimes responsible for some of the most common chronic clinical disorders of the upper gastrointestinal tract in humans, such as chronic-active gastritis, duodenal and gastric ulcer disease, low-grade B-cell mucosa associated lymphoid tissue lymphoma of the stomach, and gastric adenocarcinoma, which is the third leading cause of cancer death worldwide. The routes of infection have not yet been firmly established, and different routes of transmission have been suggested, although the most commonly accepted hypothesis is that infection takes place through the faecal-oral route and that contaminated water and foods might play an important role in transmission of the microorganism to humans. Furthermore, several authors have considered H. pylori to be a foodborne pathogen because of some of its microbiological and epidemiological characteristics. H. pylori has been detected in drinking water, seawater, vegetables and foods of animal origin. H. pylori survives in complex foodstuffs such as milk, vegetables and ready-to-eat foods. This review article presents an overview of the present knowledge on the microbiological aspects in terms of phenotypic characteristics and growth requirements of H. pylori, focusing on the potential role that foodstuffs and water may play in the transmission of the pathogen to humans and the methods successfully used for the detection of this microorganism in foodstuffs and water.

Effects of ozone and chlorine disinfection on VBNC Helicobacter pylori by molecular techniques and FESEM images

Helicobacter pylori is a pathogen bacteria associated with chronic gastritis, peptic ulceration, and gastric carcinoma. H. pylori has a spiral morphology, which under certain conditions of stress becomes a coccoid form. This type of morphology has been linked to a viable but non-culturable (VBNC) state, which is thought to allow its persistence in the environment. Membrane damage in VBNC H. pylori in water as a mechanism for inactivation using ozone (O₃) and chlorine disinfection has not been reported in the literature. In this paper, disinfection assays with ozone and chlorine were conducted to evaluate their effects on VBNC H. pylori cells. The use of fluorescent dyes such as propidium monoazide (PMA) coupled with quantitative real-time polymerase chain reactions produced results necessary to assess the viability of the microorganism and demonstrate the effect of each disinfectant on the bacterial count. Applying ozone showed a 5-log bacterial reduction using a disinfectant concentration and exposure time (CT) of 4 mg min/L. Chlorine disinfection for the same 5-log reduction required a higher CT value. Field emission scanning electron microscope images of ozone-treated VBNC H. pylori also showed severe cell damage. The use of PMA revealed that chlorine produced physical damage in the membrane in addition to the known inhibiting effect on cell enzymatic processes. These findings are important for the detection and control of VBNC H. pylori cells in drinking water systems.

Helicobacter pylori isolated from Iranian drinking water: vacA, cagA, iceA, oipA and babA2 genotype status and antimicrobial resistance properties

Despite the clinical importance of Helicobacter pylori in human gastric disorders, its exact route of transmission is still uncertain. Based on the contentious hypothesis and findings of previous investigations, water may play an important role in the transmission of H. pylori to humans. This study was carried out to investigate the vacA, cagA, oipA, iceA and babA2 genotype status and antimicrobial resistance properties of H. pylori strains isolated from the drinking water samples of four major provinces in Iran. A total of 400 drinking water samples were cultured and tested. H. pylori-positive strains were analyzed for the presence of various genotypes and antimicrobial resistance. Twelve of 400 (3%) water samples were positive for H. pylori. Samples from Isfahan province had the highest, while those from Shiraz had the lowest prevalence of H. pylori. The seasonal distribution was also determined, with the highest prevalence of bacteria in the summer season (7.36%). H. pylori strains harbored the highest levels of resistance against ampicillin (100%), erythromycin (75%), clarithromycin (75%), and trimethoprim (58.3%). The most commonly detected genotypes were vacAs1a (83.3%), vacAm1a (66.6%), vacAs2 (50%) and cagA (50%). The presence of similar genotypes in the H. pylori strains of drinking water and those of human clinical samples suggest that contaminated water maybe the sources of bacteria. Spiramycin and furazolidone are suggested for the treatment of cases of H. pylori infection.

Methods for Detecting the Environmental Coccoid Form of Helicobacter pylori

Helicobacter pylori is recognized as the most common pathogen to cause gastritis, peptic and duodenal ulcers, and gastric cancer. The organisms are found in two forms: (1) spiral-shaped bacillus and (2) coccoid. H. pylori coccoid form, generally found in the environment, is the transformed form of the normal spiral-shaped bacillus after exposed to water or adverse environmental conditions such as exposure to sub-inhibitory concentrations of antimicrobial agents. The putative infectious capability and the viability of H. pylori under environmental conditions are controversial. This disagreement is partially due to the fact of lack in detecting the coccoid form of H. pylori in the environment. Accurate and effective detection methods of H. pylori will lead to rapid treatment and disinfection, and less human health damages and reduction in health care costs. In this review, we provide a brief introduction to H. pylori environmental coccoid forms, their transmission, and detection methods. We further discuss the use of these detection methods including their accuracy and efficiency.

Detection of Helicobacter pylori in city water, dental units' water, and bottled mineral water in Isfahan, Iran

Helicobacter pylori infection in human is one of the most common infections worldwide. However, the origin and transmission of this bacterium has not been clearly explained. One of the suggested theories is transmission via water. This study was conducted to determine the prevalence rate of H. pylori in tap water, dental units' water, and bottled mineral water in Iran. In the present study, totally 200 water samples were collected in Isfahan province and tested for H. pylori by cultural method and polymerase chain reaction (PCR) by the detection of the ureC (glmM) gene. Using cultural method totally 5 cultures were positive. Two out of 50 tap water samples (4%), 2 out of 35 dental units' water (5.8%) samples, and 1 out of 40 (2.5%) from water cooler in public places were found to be contaminated with H. pylori. H. pylori ureC gene was detected in 14 (7%) of water samples including 5 tap water (10%), 4 dental units' water (11.4%), 1 refrigerated water with filtration, and 4 (10%) water cooler in public places samples. This may be due to the coccoid form of bacteria which is detected by PCR method.

Specific detection of cultivable Helicobacter pylori cells from wastewater treatment plants

BACKGROUND

Helicobacter pylori is present in surface water and wastewater, and biofilms in drinking water systems have been reported as possible reservoirs of H. pylori. However, its ability to survive in an infectious state in the environment is hindered because it rapidly loses its cultivability. The aim of this study was to determine the presence of cultivable and therefore viable H. pylori in wastewater treatment plants to understand the role of wastewater in the pathogen's transmission.

MATERIALS AND METHODS

A modified filter technique was used to obtain a positive H. pylori culture, and specific detection of this pathogen was achieved with FISH and PCR techniques.

RESULTS

A total of six positive H. pylori cultures were obtained from the water samples, and molecular techniques positively identified H. pylori in 21 culture-negative samples.

CONCLUSIONS

The combination of a culturing procedure after sample filtration followed by the application of a molecular method, such as PCR or FISH, provides a specific tool for the detection, identification, and direct visualization of cultivable and therefore viable H. pylori cells from complex mixed communities such as water samples.

Sociocultural and dietary practices among Malay subjects in the north-eastern region of Peninsular Malaysia: a region of low prevalence of Helicobacter pylori infection

BACKGROUND AND AIM

The prevalence of Helicobacter pylori infection is exceptionally low among the Malays in the north-eastern region of Peninsular Malaysia. The reasons are unknown. Our aim was to compare environmental factors that differed in relation to H. pylori prevalence among Malays born and residing in Kelantan.

METHODS

A case-control study was conducted among Malays in Kelantan who underwent upper endoscopy between 2000 and 2008. Helicobacter pylori status was determined by gastric histology. Sociocultural and dietary factors were assessed using a validated investigator-directed questionnaire administered after 2008, and the data were analyzed using logistic regression analysis.

RESULTS

The study group consisted of 161 subjects (79 H. pylori positive and 82 controls). Univariable analysis identified five poor sanitary practices associated with an increased prevalence of H. pylori infection: use of well water, use of pit latrine, less frequent boiling of drinking water, and infrequent hand wash practice after toilet use and before meals. Multivariable logistic regression analysis identified three variables inversely associated with H. pylori infection: frequent consumption of tea (OR: 0.023, 95% CI: 0.01-0.07), frequent use of "budu" or local anchovy sauce (OR: 0.09, 95% CI: 0.1-0.7), and frequent use of "pegaga" or centenella asiatica (OR: 0.25, 95% CI: 0.1-0.65).

CONCLUSIONS

Under the assumption that sanitary, sociocultural, and dietary habits have not changed over the years, we can conclude that an increased risk of H. pylori was associated with unsanitary practices whereas protection was associated with consumption of tea and locally produced foods, "pegaga" and "budu." These dietary factors are candidates for future study on the effects on H. pylori transmission.

Feasibility of methods based on nucleic acid amplification techniques to fulfil the requirements for microbiological analysis of water quality

Molecular methods based on nucleic acid recognition and amplification are valuable tools to complement and support water management decisions. At present, these decisions are mostly supported by the principle of end-point monitoring for indicators and a small number of selected measured by traditional methods. Nucleic acid methods show enormous potential for identifying isolates from conventional culture methods, providing data on cultivable and noncultivable micro-organisms, informing on the presence of pathogens in waters, determining the causes of waterborne outbreaks, and, in some cases, detecting emerging pathogens. However, some features of water microbiology affect the performance of nucleic acid-based molecular techniques and thus challenge their suitability for routine water quality control. These features include the variable composition of target water samples, the generally low numbers of target micro-organisms, the variable water quality required for different uses and the physiological status or condition of such micro-organisms. The standardization of these molecular techniques is also an important challenge for its routine use in terms of accuracy (trueness and precision) and robustness (reproducibility and reliability during normal usage). Most of national and international water regulations recommend the application of standard methods, and any new technique must be validated respect to established methods and procedures. Moreover, molecular methods show a high cost-effectiveness value that limits its practicability on some microbial water analyses. However, new molecular techniques could contribute with new information or at least to supplement the limitation of traditional culture-based methods. Undoubtedly, challenges for these nucleic acid-based methods need to be identified and solved to improve their feasibility for routine microbial water monitoring.

Temporal study of Helicobacter pylori presence in coastal freshwater, estuary and marine waters

Helicobacter pylori, a gastric pathogen, is believed to be transmitted via the fecal-oral route as well as the oral-oral route. Its presence and viability in environmental waters is not well characterized. The goals of this study were to test H. pylori presence via molecular methods in freshwater, estuarine and beach sites in Delaware over both short and long time scales and to establish whether fecal indicator bacteria, including total Enterococcus and human-specific Bacteroidetes species, are predictive of the pathogen in these waters. The presence of Helicobacter pylori was initially tested by PCR with newly designed 23S rRNA gene primers against Helicobacter spp. and confirmed by sequencing. Two coastal beach sites were repeatedly positive in 2007. Clone library analysis indicated the persistence of one operational taxonomic unit (OTU) over time at one site. Detection of H. pylori was also determined by PCR assays from DNA and RNA for the 16S rRNA gene, as well as DNA for the ureA and cagA genes. Approximately 21% of the samples were positive for H. pylori 16S rRNA gene and 80% of those were also positive for H. pylori 16S rRNA, indicating that this potential pathogen is not only present in natural waters, but also probably viable. There was no correlation between the occurrence of H. pylori and fecal indicator bacteria, suggesting that standard water quality tests are ineffective in predicting the presence of this pathogen in natural waters. These results demonstrate the widespread presence of potentially viable H. pylori in coastal marine and estuarine waters. Additionally, the repeatedly positive samples indicate either a continual contamination source or persistence of H. pylori in marine waters.

Transmission pathway of Helicobacter pylori: does food play a role in rural and urban areas?

Helicobacter pylori is a Gram-negative microaerophilic bacterium that has colonized the human gastric mucosa. This infection is very common and affects more than half of the human population. The prevalence is however unbalanced between rural developing areas (more than 80%) and urban developed areas (less than 40%). H. pylori is responsible for several pathologies, such as gastritis, peptic ulcer and gastric cancer but its transmission pathway is still not clear. The risk factors for H. pylori infection include poor social and economic development; poor hygienic practices; absence of hygienic drinking water; and unsanitary prepared food. There is evidence supporting a gastro-oral, oral-oral and faecal-oral transmission, but no predominant mechanism of transmission has been yet identified. Transmission may occur in a vertical mode (e.g. from parents to child) or in a horizontal mode (across individuals or from environmental contamination). In either case, the involvement of water and food cannot be excluded as vehicles or sources of infection. Indirect evidence of presence of H. pylori in water and food, namely the detection of its DNA and survival studies after artificial contamination of food and water has been described. This paper reviews data both favourable and against the role of water and food in the transmission of H. pylori, exploring their role as a potential transmission vehicle for person-to-person and food-chain transmission. The likelihood of the transmission pathway in developing rural and developed urban areas appears to be different. In developed areas, person-to-person transmission within families appears to be dominant, while in the rural developing areas the transmission pathway appears to be more complex. In this later case, the transmission by contaminated food, water, or via intensive contact between infants and non-parental caretakers may have a greater influence than within-family transmission.

Failure to detect Helicobacter pylori DNA in drinking and environmental water in Dhaka, Bangladesh, using highly sensitive real-time PCR assays

The main transmission pathway of Helicobacter pylori has not been determined, but several reports have described detection of H. pylori DNA in drinking and environmental water, suggesting that H. pylori may be waterborne. To address this possibility, we developed, tested, and optimized two complementary H. pylori-specific real-time PCR assays for quantification of H. pylori DNA in water. The minimum detection level of the assays including collection procedures and DNA extraction was shown to be approximately 250 H. pylori genomes per water sample. Using our assays, we then analyzed samples of drinking and environmental water (n = 75) and natural water biofilms (n = 21) from a high-endemicity area in Bangladesh. We could not identify H. pylori DNA in any of the samples, even though other pathogenic bacteria have been found previously in the same water samples by using the same methodology. A series of control experiments were performed to ensure that the negative results were not falsely caused by PCR inhibition, nonspecific assays, degradation of template DNA, or low detection sensitivity. Our results suggest that it is unlikely that the predominant transmission route of H. pylori in this area is waterborne.

Quantitative PCR monitoring of antibiotic resistance genes and bacterial pathogens in three European artificial groundwater recharge systems

Aquifer recharge presents advantages for integrated water management in the anthropic cycle, namely, advanced treatment of reclaimed water and additional dilution of pollutants due to mixing with natural groundwater. Nevertheless, this practice represents a health and environmental hazard because of the presence of pathogenic microorganisms and chemical contaminants. To assess the quality of water extracted from recharged aquifers, the groundwater recharge systems in Torreele, Belgium, Sabadell, Spain, and Nardò, Italy, were investigated for fecal-contamination indicators, bacterial pathogens, and antibiotic resistance genes over the period of 1 year. Real-time quantitative PCR assays for Helicobacter pylori, Yersinia enterocolitica, and Mycobacterium avium subsp. paratuberculosis, human pathogens with long-time survival capacity in water, and for the resistance genes ermB, mecA, blaSHV-5, ampC, tetO, and vanA were adapted or developed for water samples differing in pollutant content. The resistance genes and pathogen concentrations were determined at five or six sampling points for each recharge system. In drinking and irrigation water, none of the pathogens were detected. tetO and ermB were found frequently in reclaimed water from Sabadell and Nardò. mecA was detected only once in reclaimed water from Sabadell. The three aquifer recharge systems demonstrated different capacities for removal of fecal contaminators and antibiotic resistance genes. Ultrafiltration and reverse osmosis in the Torreele plant proved to be very efficient barriers for the elimination of both contaminant types, whereas aquifer passage followed by UV treatment and chlorination at Sabadell and the fractured and permeable aquifer at Nardò posed only partial barriers for bacterial contaminants.

DNA-level diversity and relatedness of Helicobacter pylori strains in shantytown families in Peru and transmission in a developing-country setting

The efficiency of transmission of a pathogen within families compared with that between unrelated persons can affect both the strategies needed to control or eradicate infection and how the pathogen evolves. In industrialized countries, most cases of transmission of the gastric pathogen Helicobacter pylori seems to be from mother to child. An alternative model, potentially applicable among the very poor in developing countries, where infection is more common and the sanitary infrastructure is often deficient, invokes frequent transmission among unrelated persons, often via environmental sources. In the present study, we compared the genotypes of H. pylori from members of shantytown households in Peru to better understand the transmission of H. pylori in developing-country settings. H. pylori cultures and/or DNAs were obtained with informed consent by the string test (a minimally invasive alternative to endoscopy) from at least one child and one parent from each of 62 families. The random amplified polymorphic DNA fingerprints of 57 of 81 (70%) child-mother strain pairs did not match, nor did the diagnostic gene sequences (>1% DNA sequence difference), independent of the child's age (range, 1 to 39 years). Most strains from siblings or other paired family members were also unrelated. These results suggest that H. pylori infections are often community acquired in the society studied. Transmission between unrelated persons should facilitate the formation of novel recombinant genotypes by interstrain DNA transfer and selection for genotypes that are well suited for individual hosts. It also implies that the effective prevention of H. pylori infection and associated gastroduodenal disease will require anti-H. pylori measures to be applied communitywide.

Helicobacter pylori produces unique filaments upon host contact in vitro

Helicobacter pylori exists in 2 distinct morphological states, helicoid and coccoid. Both have been observed in in vitro culture and in gastric biopsies. We visualized H. pylori during AGS cell infections using immunofluorescence microscopy. Anti-H. pylori mouse serum as well as human serum from H. pylori-positive patients recognized long, thin bacterial filaments, which formed on helicoids and more frequently on coccoids. These filaments reached lengths of 59 microm and often connected bacteria. Periodate oxidation abolished antibody recognition, suggesting that carbohydrates compose a major antigenic component of the filaments. Similar to results obtained using immunofluorescence microscopy, scanning electron microscopy imaging revealed thin filamentous structures, which were absent on uninfected cells. Both coccoid conversion and filament development increased over the time course of infection with peak filament formation at 4 h. The number of visible filaments then decreased as bacteria clustered on the apical surface of AGS cells. Since the observed filaments were clearly distinct from previously described surface structures, including flagella and the cag type IV secretion system, our results demonstrate that these filaments represent a unique, previously unrecognized, organelle.

Diagnosis of Helicobacter pylori

The different invasive and noninvasive diagnostic tests for Helicobacter pylori have been applied mainly in emerging countries. Molecular methods have been developed, especially a test for detection of H. pylori and its clarithromycin resistance directly from stools. The long-term effects of eradication on histologic lesions have been studied in a meta-analysis and the prognostic value of post-treatment in gastric mucosa-associated lymphoid tissue lymphoma has been assessed. An operating link for gastritis assessment (the OLGA staging) has also been published. Attempts to simplify the urea breath test protocol have been made, and new stool antigen tests have been proposed and compared to those previously available.

Epidemiology of Helicobacter pylori infection

This review summarizes studies on the epidemiology of Helicobacter pylori published in peer-reviewed journals between April 2007 and March 2008. Infection with H. pylori often occurs in childhood, and once established, can persist lifelong if untreated. Prevalence of H. pylori infection is higher in developing countries when compared to developed countries, and can vary by ethnicity, place of birth, and socioeconomic factors even among persons living in the same country. Prevalence of infection is decreasing in many countries due to improvements in sanitation and living standards and the relatively recent movement of populations from rural to urban settings; however, post-treatment recurrence rates of H. pylori infection remain high in developing countries, and in given populations within developed countries. In addition, a number of recent studies have begun to explore the possible link between childhood infection with H. pylori and protection against asthma and allergy.

Epidemiology of Helicobacter pylori infection

Helicobacter pylori infection is typically acquired in early childhood in both low- and high-income regions of the world and, once established, commonly persists lifelong unless treated. Social and economic development decreases the prevalence both within and between countries. The epidemiology of H. pylori infection highlights the geographic, ethnic, and racial differences throughout the world.