Detection of free and plankton-associated Helicobacter pylori in seawater

An ultrasensitive J-shaped optical fiber LSPR aptasensor for the detection of Helicobacter pylori

The development of label-free and sensitive detection of pathogenic bacteria is of great significance for disease prevention and public health protection. In this study, an originally bent structure, named as J-shaped optical fiber probe, was first designed to engineer a localized surface plasmon resonance (LSPR) aptamer biosensor for the rapid and ultrasensitive detection of Helicobacter pylori (H. pylori). The J-shaped optical fiber probe exhibited a significant improvement in refractive index sensitivity (RIS) and LSPR signal response. Meantime, the original sequence of aptamer was truncated in order to effectively capture H. pylori on the optical fiber surface. Besides, a spacer nucleic acid with short stem-loop structure was adopted to control the aptamer density on gold nanoparticles (AuNPs) on the surface of the J-shaped optical fiber probe, which displayed a further enhancement in LSPR signal response. Benefitting from these creative designs, the proposed LSPR biosensor can realize label-free and sensitive detection of H. pylori with a detection limit as low as 45 CFU/mL and a wide linear range from 1.0 × 102 CFU/mL to 1.0 × 108 CFU/mL. At the same time, the sensing strategy can detect the pathogenic bacteria from actual water samples in one step just in 30 min without any sample pretreatment. Due to the advantages of ease-to-preparation, high sensitivity, and rapid analysis, this proposed J-shaped optical fiber LSPR aptasensor can provide a potential strategy for point-of-caring detection of pathogenic bacteria in environmental monitoring and disease diagnosis.

Socioeconomic indices guided linear mixed-effects and meta-regression modelling of the temporal, global and regional prevalence of Helicobacter pylori in environmental waters: A class I carcinogen

Environmental waters (EW) substantially lend to the transmission of Helicobacter pylori (Hp). But the increase in Hp infections and antimicrobial resistance is often attributed to socioeconomic status. The connection between socioeconomic status and Hp prevalence in EW is however yet to be investigated. This study aimed to assess the impacts of socioeconomic indices (SI: continent, world bank region (WBR), world bank income (WBI), WHO region, Socio-demographic Index (SDI quintile), Sustainable Development Index (SuDI), and Human Development Index (HDI)) on the prevalence of Hp in EW. Hp-EW data were fitted to a generalized linear mixed-effects model and SI-guided meta-regression models with a 1000-resampling test. The worldwide prevalence of Hp in EW was 21.76% [95% confidence interval [CI]: 10.29-40.29], which declined significantly from 59.52% [43.28-74.37] in 1990-99 to 19.36% [3.99-58.09] in 2010-19 and with increasing trend in 2020-22 (33.33%, 22.66-45.43). Hp prevalence in EW was highest in North America (45.12%, 17.07-76.66), then Europe (22.38%, 5.96-56.74), South America (22.09%, 13.76-33.49), Asia (2.98%, 0.02-85.17), and Africa (2.56%, 0.00-99.99). It was negligibly different among sampling settings, WBI, and WHO regions demonstrating highest prevalence in rural location [42.62%, 3.07-94.56], HIEs [32.82%, 13.19-61.10], and AMR [39.43%, 19.92-63.01], respectively. However, HDI, sample size, and microbiological method robustly predict Hp prevalence in EW justifying 26.08%, 21.15%, and 16.44% of the true difference, respectively. In conclusion, Hp is highly prevalence in EW across regional/socioeconomic strata and thus challenged the uses of socioeconomic status as surrogate for hygienic/sanitary practices in estimating Hp infection prevalence.

Antimicrobial and Antibiofilm Activities of Carvacrol, Amoxicillin and Salicylhydroxamic Acid Alone and in Combination vs. Helicobacter pylori: Towards a New Multi-Targeted Therapy

The World Health Organization has indicated Helicobacter pylori as a high-priority pathogen whose infections urgently require an update of the antibacterial treatments pipeline. Recently, bacterial ureases and carbonic anhydrases (CAs) were found to represent valuable pharmacological targets to inhibit bacterial growth. Hence, we explored the underexploited possibility of developing a multiple-targeted anti-H. pylori therapy by assessing the antimicrobial and antibiofilm activities of a CA inhibitor, carvacrol (CAR), amoxicillin (AMX) and a urease inhibitor (SHA), alone and in combination. Minimal Inhibitory (MIC) and Minimal Bactericidal (MBC) Concentrations of their different combinations were evaluated by checkerboard assay and three different methods were employed to assess their capability to eradicate H. pylori biofilm. Through Transmission Electron Microscopy (TEM) analysis, the mechanism of action of the three compounds alone and together was determined. Interestingly, most combinations were found to strongly inhibit H. pylori growth, resulting in an additive FIC index for both CAR-AMX and CAR-SHA associations, while an indifferent value was recorded for the AMX-SHA association. Greater antimicrobial and antibiofilm efficacy of the combinations CAR-AMX, SHA-AMX and CAR-SHA against H. pylori were found with respect to the same compounds used alone, thereby representing an innovative and promising strategy to counteract H. pylori infections.

Zooplankton act as cruise ships promoting the survival and pathogenicity of pathogenic bacteria

Bacteria in general interact with zooplankton in aquatic ecosystems. These zooplankton-bacterial interactions help to shape the bacterial community by regulating bacterial abundances. Such interactions are even more significant and crucially in need of investigation in the case of pathogenic bacteria, which cause severe diseases in humans and animals. Among the many associations between a host metazoan and pathogenic bacteria, zooplankton provide nutrition and protection from stressful conditions, promote the horizontal transfer of virulence genes, and act as a mode of pathogen transport. These interactions allow the pathogen to survive and proliferate in aquatic environments and to endure water treatment processes, thereby creating a potential risk to human health. This review highlights current knowledge on the contributions of zooplankton to the survival and pathogenicity of pathogenic bacteria. We also discuss the need to consider these interactions as a risk factor in water treatment processes.

Acanthamoeba castellanii supports extracellular survival of Helicobacter pylori in co-culture

This study aimed to demonstrate whether Helicobacter pylori is able to survive in co-culture with a protozoan, Acanthamoeba castellanii, in order to further investigate a possible aqueous environmental mode of transmission. Numbers of H. pylori in co-culture with A castellanii were assessed by colony forming unit (CFU) assay and cell morphology was observed by electron microscopy. Viable and intact H. pylori in co-culture were detected and the number of H. pylori in co-culture with A. castellanii was significantly higher than in bacterial single culture. It was also shown that co-culture of H. pylori with A. castellanii physically separated by a filter membrane negated this survival effect, suggesting that adherence of H. pylori to A. castellanii affects its survival. Scanning electron microscopy revealed helical forms of H. pylori in co-culture with A. castellanii, but not in single culture. These results imply that mutual interaction between H. pylori and A. castellanii in the environment is critical for survival of H. pylori. In addition, the H. pylori gene expression profile was found to differ between single and co-cultured cells using RNA-sequence analysis.

Helicobacter pylori: Survival in cultivable and non-cultivable form in artificially contaminated Mytilus galloprovincialis

Several studies report the presence of Helicobacter pylori (H. pylori) in seawater either free or attached to planktonic organism. After considering the role played by plankton in the food chain of most aquatic ecosystems and the possible role that seafood products can assume in the transmission of H. pylori to humans, the aim of this study was to assess the survival of H. pylori in artificially contaminated Mytilus galloprovincialis (M. galloprovincialis). A traditional culture method and a reverse transcriptase-PCR (RT-PCR) assay were employed to detect the mRNA of known virulence factor (VacA) which can be considered use a marker of bacterial viability. The obtained results clearly show that H. pylori is able to survive in artificially contaminated mussels for 6 days (2 days in a cultivable form and 4 days in a non-cultivable form).

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.

Helicobacter pylori Biofilm Formation and Its Potential Role in Pathogenesis

Despite decades of effort, Helicobacter pylori infections remain difficult to treat. Over half of the world's population is infected by H. pylori, which is a major cause of duodenal and gastric ulcers as well as gastric cancer. During chronic infection, H. pylori localizes within the gastric mucosal layer, including deep within invaginations called glands; thanks to its impressive ability to survive despite the harsh acidic environment, it can persist for the host's lifetime. This ability to survive and persist in the stomach is associated with urease production, chemotactic motility, and the ability to adapt to the fluctuating environment. Additionally, biofilm formation has recently been suggested to play a role in colonization. Biofilms are surface-associated communities of bacteria that are embedded in a hydrated matrix of extracellular polymeric substances. Biofilms pose a substantial health risk and are key contributors to many chronic and recurrent infections. This link between biofilm-associated bacteria and chronic infections likely results from an increased tolerance to conventional antibiotic treatments as well as immune system action. The role of this biofilm mode in antimicrobial treatment failure and H. pylori survival has yet to be determined. Furthermore, relatively little is known about the H. pylori biofilm structure or the genes associated with this mode of growth. In this review, therefore, we aim to highlight recent findings concerning H. pylori biofilms and the molecular mechanism of their formation. Additionally, we discuss the potential roles of biofilms in the failure of antibiotic treatment and in infection recurrence.

Review of Research on Routes of Helicobacter pylori Infection

In recent years, many scholars conducted in-depth research onHelicobacter pyloriand identified it as an important pathogen of chronic gastritis and peptic ulcer.H. pylorialso causes also and contributes to precancerous lesions (atrophic gastritis and intestinal metaplasia) and is closely related to occurrence and development of gastric adenocarcinoma and gastric mucosa-associated lymphoma. This study summarizes biological characteristics, epidemic status, and infection route ofH. pyloriand reviews research on roles of natural environments, especially drinking water, during 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.

The frequency of Helicobacter pylori in dental plaque is possibly underestimated

OBJECTIVE

The commonest bacteria, causing infection across the world is Helicobacter pylori, which colonizes the human stomach. This bacteria has also been detected in some extra-gastric ecological niches such as the oral cavity and water. However, the results of H. pylori detection in extra-gastric ecological niche are controversial. The improvement of the sensitivity and the specificity of the detection methods appear to be some of the main bottleneck issues in providing compelling evidence. The aim of this study was to detect the presence of this organism in dental plaque samples using an analytically sensitive and specific Polymerase Chain Reaction (PCR) as well as a new nucleic acid detection method termed the Loop-mediated Isothermal Amplification (LAMP).

DESIGN

In a descriptive cross-sectional study 45 participants enrolled and dental plaque samples were collected from at least two teeth surfaces (one anterior and one posterior tooth) using a sterile periodontal curette. The DNA content was extracted from the samples and the presence of H. pylori was determined by PCR and LAMP reactions.

RESULTS

The frequency of detection of H. pylori in the dental plaque samples were 44% (20/45), 66.67% (30/45) and 77.78% (35/45) using PCR, LAMP and positivity for both tests, respectively.

CONCLUSION

The high frequency of H. pylori was detected in the dental plaque samples of the participants, which concurs with the high prevalence of this bacteria in the population. This is one of the highest reported rates around the world. The results reveal that dental plaque can be one of the main causes of re-infection and also be the cause of oral-oral transmission.

Environmental risk factors associated with Helicobacter pylori seroprevalence in the United States: a cross-sectional analysis of NHANES data

Helicobacter pylori imparts a considerable burden to public health. Infections are mainly acquired in childhood and can lead to chronic diseases, including gastric ulcers and cancer. The bacterium subsists in water, but the environment's role in transmission remains poorly understood. The nationally representative National Health and Nutrition Examination Survey (NHANES) was examined for environmental risk factors associated with H. pylori seroprevalence. Data from 1999–2000 were examined and weighted to represent the US population. Multivariable logistic regression estimated adjusted odds ratios (aOR) and 95% confidence intervals (CI) for associations with seropositivity. Self-reported general health condition was inversely associated with seropositivity. Of participants aged <20 years, seropositivity was significantly associated with having a well as the source of home tap water (aOR 1·7, 95% CI 1·1–2·6) and living in a more crowded home (aOR 2·3, 95% CI 1·5–3·7). Of adults aged ⩾20 years, seropositivity was not associated with well water or crowded living conditions, but adults in soil-related occupations had significantly higher odds of seropositivity compared to those in non-soil-related occupations (aOR 1·9, 95% CI 1·2–2·9). Exposures to both well water and occupationally related soil increased the effect size of adults' odds of seropositivity compared to non-exposed adults (aOR 2·7, 95% CI 1·3-5·6). Environmental exposures (well-water usage and occupational contact with soil) play a role in H. pylori transmission. A disproportionate burden of infection is associated with poor health and crowded living conditions, but risks vary by age and race/ethnicity. These findings could help inform interventions to reduce the burden of infections in the United States.

Helicobacter pylori: A chameleon-like approach to life

Helicobacter pylori (H. pylori) is widely adaptable for colonization in human stomachs in more than half of the world’s population. The microorganism is characterized by an unusual capability of arranging itself in both genotypic and phenotypic ways. Stressing conditions, including antimicrobial agents in sub-inhibitory concentrations, facilitate entering the viable but nonculturable state in which bacterial cells acquire the coccoid form. This morphotype represents an important strategy for bacterial survival in unsuitable conditions and also allows escape from the immune system. H. pylori is capable of forming biofilm outside and inside the host. For the bacterial population, the sessile growth mode represents an ideal environment for gene rearrangement, as it allows the acquiring of important tools aimed to improve bacterial “fitness” and species preservation. Biofilm formation in H. pylori in the human host also leads to recalcitrance to antibiotic treatment, thus hampering eradication. These lifestyle changes of H. pylori allow for a “safe haven” for its survival and persistence according to different ecological niches, and strongly emphasize the need for careful H. pylori surveillance to improve management of the infection.

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.

Waterborne Pathogens

A variety of microorganisms occur in the marine environment which are capable of infecting humans. This chapter, focused on waterborne pathogens, summarizes the types of pathogens that are a threat to human health, as well as the fecal indicator bacteria that are commonly used as surrogates for pathogens in regulatory and research applications. Limitations and alternatives to traditional fecal indicator bacteria are explored, highlighting challenges and policy implications for protecting public health. Methodological advances and challenges are also reviewed, with an emphasis on research designed to fill gaps and provide scientific support for management of marine resources, particularly bathing beaches. Accordingly, recent and previous epidemiology studies linking microbial measures of water quality to health outcomes are discussed in detail. As an alternative to the measurement of individual water samples, modeling of pathogens in marine waters is introduced. Overall, this chapter provides an overview of the pathogens, microbial measures and policy implications important for protecting humans from exposure to pathogens in marine waters.

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.

Detection of Helicobacter pylori in biofilms by real-time PCR

Helicobacter pylori is a cause of peptic ulcer disease and a causative agent of gastric cancer. Currently, a possible waterborne route of transmission or a possible survival in drinking water biofilms is discussed. H. pylori, like many other bacterial strains, has the ability to enter the viable but nonculturable state (vbnc) in case of unfavorable conditions. Therefore it is necessary to develop new analysis tools for vbnc bacteria. We established a fast and reliable method to detect H. pylori in drinking water biofilms by quantitative real-time PCR which makes it redundant to use difficult cultivation methods for nonculturable bacteria. With this method it was possible to identify water biofilms as a niche for H. pylori. The real-time PCR analysis targets the ureA subunit of the Helicobacter pylori urea gene which showed high specificity and sensitivity. The quantitative real-time PCR was used to detect H. pylori in biofilms of different age, unspiked and spiked with predetermined levels of cells. The drinking water biofilms were generated in a silicone-tube model. The DNA-sequences for probe and primers showed no cross-homologies to other related bacteria and it was possible to detect less than 10 genomic units of H. pylori. This novel method is a useful tool for a fast screening of drinking water biofilms for H. pylori. The results suggest that drinking water biofilms may act as a reservoir for H. pylori which raises new concerns about the role of biofilms as vectors for pathogens like Helicobacter pylori.

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.

Helicobacter pylori-coccoid forms and biofilm formation

Electron microscopic studies have shown that Helicobacter pylori occurs in three stages: spiral forms, coccoid forms and degenerative forms. The spiral forms are viable, culturable, virulent and can colonize experimental animals and induce inflammation. The coccoid forms may also be viable but are nonculturable, less virulent and are less likely to colonize and induce inflammation in experimental animals than the spiral forms. The degenerative forms are pyknotic, nonculturable, coccoid forms of dead H. pylori. These forms cannot be cultured and the cell membrane has disintegrated but gene material can be detected by PCR in water supplies. There is no substantial evidence for viable H. pylori persisting in water supplies. Epidemiological studies suggest that environmental water is a risk factor for H. pylori infection when compared with tap water, and formation of H. pylori biofilm cannot be excluded. Helicobacter pylori does not seem to take part in biofilm formation in the oral cavity even though the bacterium may be detected.

Quantitative detection of Helicobacter pylori in water samples by real-time PCR amplification of the cag pathogenicity island gene, cagE

AIMS

A new real-time PCR assay that simultaneously amplifies a 102-bp fragment of the cagE gene from Helicobacter pylori and a new internal positive control containing a specific sequence of the gyrB gene from Aeromonas hydrophila, was developed and validated for the detection of H. pylori in environmental samples.

METHODS AND RESULTS

The specificity, limits of detection and quantification, repeatability, reproducibility, and accuracy of the method were calculated. The resulting values confirmed the applicability of the method for the quantitative detection of H. pylori. The feasibility of the method was also evaluated by testing 13 pyloric antrum-positive biopsies and 69 water samples, including potable (10), surface (19) and wastewater (40) matrices. The results showed that all the biopsies and 3 of the 40 wastewater samples analysed were positive.

CONCLUSIONS

This real-time PCR method provides a sensitive, specific, and accurate method for the rapid quantification of H. pylori in environmental samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PCR diagnostic system proposed in this work, provides a suitable tool for the quantitative detection of H. pylori in environmental samples and can be useful for verifying the role of water as a potential route of its transmission.

Protection of waterborne pathogens by higher organisms in drinking water: a review

Higher organisms are ubiquitous in surface waters, and some species can proliferate in granular filters of water treatment plants and colonize distribution systems. Meanwhile, some waterborne pathogens are known to maintain viability inside amoebae or nematodes. The well-documented case of Legionella replication within amoebae is only one example of a bacterial pathogen that can be amplified inside the vacuoles of protozoa and then benefit from the protection of a resistant structure that favours its transport and persistence through water systems. Yet the role of most zooplankton organisms (rotifers, copepods, cladocerans) in pathogen transmission through drinking water remains poorly understood, since their capacity to digest waterborne pathogens has not been well characterized to date. This review aims at (i) evaluating the scientific observations of diverse associations between superior organisms and pathogenic microorganisms in a drinking water perspective and (ii) identifying the missing data that impede the establishment of cause-and-effect relationships that would permit a better appreciation of the sanitary risk arising from such associations. Additional studies are needed to (i) document the occurrence of invertebrate-associated pathogens in relevant field conditions, such as distribution systems; (ii) assess the fate of microorganisms ingested by higher organisms in terms of viability and (or) infectivity; and (iii) study the impact of internalization by zooplankton on pathogen resistance to water disinfection processes, including advanced treatments such as UV disinfection.

Characterization of an Helicobacter pylori environmental strain

AIMS

To investigate the main genotypic virulence markers and the phenotypic features of an environmental Helicobacter pylori strain, named MDC1.

METHODS AND RESULTS

The H. pylori MDC1 genotypic status was evaluated by PCR amplification. The mosaicism in vacA alleles was expressed by the s1m1 allelic combination, as found in strains which are strong vacuolating cytotoxin producers; the number of cagA variable EPIYA motifs displayed P1P2P3P3 pattern and the iceA1 was recorded between the iceA allelic types and the babA2 gene found in strains causing more severe disease. The biofilm formation was evaluated on a polystyrene surface in static conditions by scanning electron microscopy and confocal scanning laser microscopy. Helicobacter pylori MDC1 displayed a dense mature biofilm with cells in a coccoid morphology persistent in time in which the expression of the luxS gene, related to the quorum-sensing signalling, was always detected.

CONCLUSIONS

Helicobacter pylori MDC1 strain had the main virulence markers closely related to gastric pathogenesis and displayed a well-structured biofilm which allowed this bacterium to be more protected in the environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

The persistence of the environmental virulent H. pylori strain in a clustered state suggests a long-term survival of this bacterial community outside of the host, enabling the bacterial transmission with important clinical repercussions.

High occurrence of Helicobacter pylori in raw goat, sheep and cow milk inferred by glmM gene: a risk of food-borne infection?

Helicobacter pylori is an organism widespread in humans and sometimes responsible for serious illnesses, such as gastric and duodenal ulcers, MALToma and even gastric cancer. It has been hypothesized that the infection route by H. pylori involves multiple pathways including food-borne transmission, as the microorganism has been detected from foods such as sheep and cow milk. This work reports the results of a survey conducted in order to investigate the presence of H. pylori in raw goat, sheep and cow milk produced in Southern Italy, employing a Nested Polymerase Chain Reaction (Nested-PCR) assay for the detection of the phosphoglucosamine mutase gene (glmM), as screening method followed by conventional bacteriological isolation. Out of the 400 raw milk samples examined, 139 (34.7%) resulted positive for the presence of glmM gene, but no strains were isolated. In this work H. pylori DNA has been firstly detected from 41 (25.6%) raw goat milk samples. The results deserve further investigations on the contamination source/s of the milk samples and on the major impact that it may have on consumers.

Survival of gastric and enterohepatic Helicobacter spp. in water: implications for transmission

Part of the reason for rejecting aquatic environments as possible vectors for the transmission of Helicobacter pylori has been the preference of this microorganism to inhabit the human stomach and hence use a direct oral-oral route for transmission. On the other hand, most enteric bacterial pathogens are well known for being able to use water as an environmental reservoir. In this work, we have exposed 13 strains of seven different Helicobacter spp. (both gastric and enterohepatic) to water and tracked their survival by standard plating methods and membrane integrity assessment. The influence of different plating media and temperatures and the presence of light on recovery was also assessed. There was good correlation between cultivability and membrane integrity results (Pearson's correlation coefficient = 0.916), confirming that the culture method could reliably estimate differences in survival among different Helicobacter spp. The species that survived the longest in water was H. pylori (>96 h in the dark at 25 degrees C), whereas H. felis appeared to be the most sensitive to water (<6 h). A hierarchical cluster analysis demonstrated that there was no relationship between the enterohepatic nature of Helicobacter spp. and an increased time of survival in water. This work assesses for the first time the survival of multiple Helicobacter spp., such has H. mustelae, H. muridarum, H. felis, H. canadensis, H. pullorum, and H. canis, in water under several conditions and concludes that the roles of water in transmission between hosts are likely to be similar for all these species, whether enterohepatic or not.

Adherence of Helicobacter pylori to abiotic surfaces is influenced by serum

Helicobacter pylori bacteria cultured in a chemically defined medium without serum readily adhere to a variety of abiotic surfaces. Growth produces microcolonies that spread to cover the entire surface, along with a planktonic subpopulation. Serum inhibits adherence. Initial attachment is protein mediated, but other molecules are responsible for more permanent attachment.

Use of HP selective medium to detect Helicobacter pylori associated with other enteric bacteria in seawater and marine molluscs

AIMS

This project investigated the utility of HP selective medium to isolate H. pylori cells from seawater and from marine molluscs.

METHODS AND RESULTS

Nested-PCR was performed to reveal the presence of Helicobacter genus. All samples were cultured in HP selective medium and 16 cultures were initially selected as putative Helicobacter. Helicobacter spp. DNA were detected in 9/16 cultures and three of them had 99-100% homology to H. pylori based on 16S RNA gene sequence. Helicobacter pylori isolation was unsuccessful. On the basis of 16S RNA gene sequences the contaminating organisms were shown to be Proteus mirabilis and Vibrio cholerae.

CONCLUSIONS

These results indicate the coexistence of three predominant bacterial genera in the cultures and that HP selective medium can grow other enteric bacteria besides Helicobacter. Additional assays will improve the HP selective medium formulation for marine samples avoiding P. mirabilis and V. cholerae interferents.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work shows the effectiveness of the selective HP medium for the Helicobacter culture from marine samples.

A conceptual model of water's role as a reservoir in Helicobacter pylori transmission: a review of the evidence

Helicobacter pylori infection plays a role in the development of chronic gastritis, peptic ulcer and gastric cancer, yet the route of transmission into susceptible hosts remains unknown. Studies employing microbiological techniques have demonstrated that H. pylori has the ability to survive when introduced into water and that H. pylori is present in water and other environmental samples all over the world. Epidemiological studies have shown that water source and exposures related to water supply, including factors related to sewage disposal and exposure to animals, are risk factors for infection. This review describes the microbiological and epidemiological evidence for, and proposes a model of, waterborne H. pylori transmission outlining important features in the transmission cycle. In the model, humans and animals shed the bacteria in their faeces and the mechanisms for entry into water, and for survival, ingestion and infection are dependent upon a range of environmental influences. Verification of the proposed model pathways has important implications for public-health prevention strategies.

A combination of direct viable count and fluorescent in situ hybridization for estimating Helicobacter pylori cell viability

The viable but non-culturable (VBNC) stage of Helicobacter pylori may represent a problem of public health concern, since these cells cannot be detected by traditional culture methods. In this study, the direct viable count method (DVC) was modified and adapted to H. pylori analysis by testing different times of incubation and concentrations of DNA-gyrase inhibitors. The DVC procedure was combined with fluorescent in situ hybridization (FISH) for the specific detection of viable cells of H. pylori (DVC-FISH). Incubation with 0.5 microg/ml of novobiocin for 24 h provided the optimal conditions for obtaining 3-5 times the original size of Helicobacter viable cells. Field work performed with various types of water (freshwater and seawater) using the DVC-FISH approach enabled us to confirm the presence of VBNC H. pylori cells in 16 of the 45 analyzed samples. The combination of the modified DVC procedure with FISH can provide a rapid and specific method to detect and identify viable cells of H. pylori in environmental samples.

Occurrence of Helicobacter pylori DNA in the coastal environment of southern Italy (Straits of Messina)

AIMS

The occurrence of Helicobacter pylori in the coastal zone of the Straits of Messina (Italy) as free-living and associated with plankton was studied.

METHODS AND RESULTS

Monthly sampling of seawater and plankton was carried out from April 2002 to March, 2003. All environmental samples analysed by cultural method, did not show the presence of H. pylori. The DNA extracted from all environmental samples was tested by PCR by using primers for H. pylori 16S rRNA, ureA and cagA. 16S rRNA PCR yielded amplified products of 522-bp in 15 of 36 (41.7%) of the environmental samples. By using the ureA primers to amplify the urea signal sequences, the predicted PCR products of 491-bp were obtained from eight (22.2%) of 36 environmental samples. PCR with cagA primers yielded amplified products of 349-bp in DNA extracted of seven of 36 (19.4%) of the environmental samples. When 16S rRNA, ureA and cagA amplified gene sequences were aligned with H. pylori 26695 and J99 genome sequences, we obtained a percentage of alignment over 90%.

CONCLUSIONS

The detection of H. pylori genes in marine samples allows us to consider the marine environment a possible reservoir for this pathogenic bacterium.

SIGNIFICANCE AND IMPACT OF THE STUDY

The direct detection of H. pylori genes may be relevant in order to consider the marine environment as significant reservoir for this bacterium.