Helicobacters of possible zoonotic origin: a review

Since the isolation of Helicobacter pylori, many new Helicobacter species have been identified from the gastrointestinal tract in humans and animals. In humans, a spiral organism different from H. pylori and provisionally named "Helicobacter heilmannii", has been associated with gastritis, gastric ulceration and to a lesser degree, gastric cancer. In addition Helicobacter cinaedi, Helicobacter fennelliae, Helicobacter pullorum and "Flexispira rappini" have been isolated from cases of enteric disease, bacteremia and pneumonic illness. In the biliary tract, the presence of Helicobacter bilis, Helicobacter pullorum and "Flexispira rappini" has been demonstrated. Morphological, epidemiological and genotypic data suggest the involvement of animal helicobacters in these infections. In this paper, a review of the literature addressing the current knowledge about epidemiology, diagnosis, pathogenesis and therapy of these infections is given.

[Epidemiology, acquisition and transmission of Helicobacter pylori]

Helicobacter pylori infection is a chronic infection essentially acquired during childhood. Its prevalence in developed countries like France has decreased according to the year of birth all along the twentieth century, reflecting the progressive improvement of socio-economic and environmental conditions. The incidence of acquisition in adulthood is lower than 0.5% per year. In developing countries, the prevalence is still very high, even in early childhood. H. pylori is a strictly human bacterium. Its reservoir is essentially the stomach. Transmission most likely occurs between humans by an oro-oral or a gastro-oral transmission. Faeco-oral transmission, either direct or via the environment, is possible but seems to be rare in France.

High prevalence of Helicobacter heilmannii-associated gastritis in a small, predominantly rural area: further evidence in support of a zoonosis?

BACKGROUND

Primary hosts of Helicobacter heilmannii are domestic animals--cats, dogs and pigs, but rarely is it detected in gastric biopsies from humans. We found H. heilmannii in gastric biopsies obtained from patients living in a predominantly rural area.

METHODS

We evaluated geographic and demographic data from the area and calculated both the total prevalence and the prevalence in each community in this area. Chi-squared test and exploratory data analysis were used for statistical evaluation. Histologic and clinical data were recorded.

RESULTS

Forty-three communities, mostly rural, were identified in the area, the size of which is about 200 km2. H. heilmannii was detected in 33 patients (prevalence 2%) living in 20 communities. The prevalence of H. heilmannii statistically significantly varied in those communities from 0.06%-1.1%. It was possible to infer that there is a negative correlation between prevalence and community size. Chronic active gastritis was diagnosed in all patients. The active inflammation became inactive after eradication of H. heilmannii via common anti-Helicobacter therapy.

CONCLUSION

A high prevalence of H. heilmannii-associated gastritis in a small, predominantly rural area and statistically significant differences in prevalence from one community to the next, i.e. highest in the smallest village and lowest in a small town with a rather urban lifestyle, were found. In our opinion, these prevalence rates may be a consequence of transmission of the infection from domestic animals, because animal-human contact is generally more common in villages than in towns.

Transmission of Helicobacter pylori from challenged to nonchallenged nude mice kept in a single cage

To determine the transmission route of Helicobacter pylori, one nude mouse was challenged by H. pylori, and then raised with nonchallenged nude mice in a single cage in a sterilized environment with and without exposure to their feces. After coraising for two and four weeks, all mice were killed to determine H. pylori in the stomach, saliva, and feces and to assess gastritis grade. Natural transmission of H. pylori occurred in 50% (2/4) and 70% (7/10) of mice after two weeks and four weeks of coraising when they were exposed to their feces. H. pylori was detected not only in the stomach but also in saliva and feces by PCR of all challenged and transmitted mice. However, no transmission occurred in mice not exposed to feces of a challenged mouse, while sharing food and water in a single cage. These findings suggest that the fecal-oral transmission route is important, at least in the animal model. Serum levels of anti-H. pylori urease IgG of the H. pylori-transmitted mice increased after coraising, and gastritis was observed in the stomach of both challenged and transmitted mice. We conclude that H. pylori bacteria are transmitted through the fecal-oral route from challenged to nonchallenged nude mice, resulting in gastritis.

Monitoring sentinel mice for Helicobacter hepaticus, H rodentium, and H bilis infection by use of polymerase chain reaction analysis and serologic testing

BACKGROUND AND PURPOSE

Natural infection of research mice with enterohepatic Helicobacter spp. is common and may confound experimental studies from intercurrent disease. We evaluated a protocol of dirty bedding exposure for transmission of Helicobacter infection from colony mice to female Tac:(SW)fBR sentinel mice over 6 months.

METHODS

Cecal scrapings from culled colony mice and associated sentinel mice were tested for H. hepaticus, H. rodentium, and H. bilis using polymerase chain reaction analysis (PCR). These results were correlated with the results of sentinel serum IgG responses measured by ELISA.

RESULTS

In 9 colony rooms, 43 of 45 mice were infected with H. hepaticus; in 14 rooms, 58 of 70 mice were infected with H. rodentium; and in 2 rooms, 2 of 10 mice were infected with H. bilis. Concurrence of Helicobacter infection between colony and sentinel mice was 82% for H. hepaticus, 88% for H. rodentium, and 94% for H. bilis. Concurrence of Helicobacter infection status of sentinel cagemates was 98% for H. hepaticus, 86% for H. rodentium, and 95% for H. bilis. Fecal samples pooled by sentinel cage had positive PCR results for H. hepaticus and H. rodentium at 1 month in 60 and 44%, respectively, of the cages that contained test-positive mice at necropsy (6 months). By 3 months, detection rates were 100 and 81% for H. hepaticus and H. rodentium, respectively, and H. bilis was not detected until 4 months. Newly acquired infections with H. rodentium and H. bilis were evident throughout the 6-month study period. Seroconversion was coincident with positive PCR results in sentinel mice, and serum IgG values continued to increase until necropsy. The serum IgG ELISA was 98 to 100% sensitive, but was low in specificity (34 to 44%), most likely attributable to common coinfection with H. hepaticus and H. rodentium.

CONCLUSION

Sentinel mice acquire infection with Helicobacter spp. through dirty bedding exposure. Combined use of PCR analysis and serologic testing of sentinel mice was predictive of Helicobacter infection status of mouse colonies used for biomedical research.

Eradication of infection with Helicobacter spp. by use of neonatal transfer

BACKGROUND AND PURPOSE

Efficient methods for detection and elimination of Helicobacter spp. infections are needed to facilitate the development of Helicobacter-free mouse colonies. We developed an inexpensive, high-throughput method for preparation of fecal DNA for Helicobacter polymerase chain reaction (PCR) assays.

METHODS

Fecal DNA was prepared by heating fecal pellets to 95 degrees C for 10 minutes in an alkaline solution, then adjusting the pH by addition of Tris buffer. This solution is used for PCR assays without purification of DNA. We then tested fostering as a method of generating Helicobacter-free mice. Litters born to Helicobacter-positive dams were transferred to Helicobacter-negative foster dams on the first day of life.

RESULTS

Fostered pups tested Helicobacter negative up to 89 days of age, whereas pups raised by Helicobacter-positive dams were all test positive by 19 days of age.

CONCLUSION

These simple methods provide an efficient system for the development of Helicobacter-free mouse colonies.

Comparative analysis of the Helicobacter pylori status in patients with gastric MALT-type lymphoma and their respective spouses

Helicobacter pylori is of major importance for the development and progression of gastric MALT-type lymphoma. In case of localized low grade lymphoma successfully treated by Helicobacter pylori eradication reinfection by the bacterium may involve the risk of lymphoma reoccurrence.

AIMS

To assess the frequency and type of Helicobacter pylori infection among patients with gastric MALT-type lymphoma and their respective spouses as potential sources of person to person spread of the infection.

SUBJECTS

35 patients with gastric MALT-type lymphoma and their cohabiting spouses.

METHODS

We investigated serum IgG titers in response to the infection by Helicobacter pylori and to its virulence factors CagA and VacA by enzyme linked immunosorbent assay (ELISA) and by Western blot.

RESULTS

Seropositivity of Helicobacter pylori, Cag A and Vac A was found to be 100/89/69% and 97/86/66% in patients and respective partners, respectively. The seroprevalence rates of the latter group by far exceed those of the German population.

CONCLUSION

These data provide evidence for a high Helicobacter pylori infection rate in both patients with gastric MALT-type lymphoma and their respective spouses. Considering the latter as a potential source of reinfection with the risk of lymphoma reoccurrence for the successfully treated patient with gastric MALT-type lymphoma careful follow-up seems highly reasonable to decide on the necessity of a future test-and-treat strategy of this population.

[Helicobacter pylori and its role in pathology]

The review deals with modern data on the main cultural and biochemical properties, pathogenicity factors and their possible role in pathogenesis. Information on the methods of the diagnostics of diseases associated with H. pylori is given. The routes of the transmission of this infective agent are discussed. The results of experimental data on the genetics and immunochemistry of H. pylori are presented.

Evidence favouring the gastro-oral route in the transmission of Helicobacter pylori infection in children

OBJECTIVE

Several studies support the view that Helicobacter pylori is acquired in early life and within families. However, the exact route of transmission remains unknown. Given that H. pylori colonizes only the human gastric mucosa, the hypothesis that history of vomiting in siblings may be a relevant risk factor was tested in a paediatric setting.

METHODS

One hundred urban children (age range 0.8-16.6 years, median 9), 44% with evidence of active H. pylori infection, were recruited. A structured questionnaire dealing with socio-economic issues was completed. Vomiting siblings and siblings of vomiting index children were screened for H. pylori by means of (13)C-urea breath test. Serum samples from index children were assayed for immunoglobulin G to hepatitis A (HAV) and Epstein-Barr virus (EBV) in order to check for faecal-oral and oral-oral exposure, respectively.

RESULTS

Vomiting siblings of H. pylori-infected index children and siblings of H. pylori-infected vomiting index children had a high rate of active H. pylori infection (60 and 67%, respectively). History of vomiting in siblings was positively associated with active H. pylori infection in the index children (multivariate odds ratio 2.4, 95% confidence interval 1.3-4.3). Seropositivity for HAV and EBV was found in 1 and 68 index children, respectively. The agreement between active H. pylori infection and EBV seropositivity was not significant (kappa = 0.26).

CONCLUSIONS

History of vomiting in siblings is an independent risk factor for H. pylori. Nowadays, transmission of H. pylori in urban children may involve the gastro-oral route more than the faecal-oral or oral-oral pathways.

How come I've got it? (A review of Helicobacter pylori transmission)

Numerous epidemiological studies have shown the two main risk factors for Helicobacter pylori acquisition: childhood and low socio-economic level both in developing and developed countries. Nevertheless, in the absence of ubiquitous extra-human reservoir(s), the route(s) for person-to-person transmission remains undetermined. Very recent data favour the oro-oral route: besides gastric mucosa, mouth might be a sanctuary site and the oro-oral transmission hypothesis seems applicable worldwide. Nevertheless, the gastro-oral route (vomiting, gastro-oesophageal reflux) is still possible and deserves further research. In developing countries, feco-oral transmission (perhaps through the water supply) might be a significant mechanism of human contamination both for primary infection in children and perhaps, reinfection in adults.

Evidence from a nine-year birth cohort study in Japan of transmission pathways of Helicobacter pylori infection

We examined the longitudinal changes of Helicobacter pylori infection within 46 families with children and 48 couples without children living in Japan. The study cohort was monitored from 1986 to 1994. H. pylori status was assessed by the presence of anti-H. pylori immunoglobulin G antibodies. At study entry, H. pylori prevalence in children with positive mothers was 23% versus 5% in children with negative mothers (odds ratio = 5.3; 95% confidence interval = 0.6 to 42.8). Seroconversion (rate of 1.5%/year) was evident only among children living with positive mothers and did not differ among adults living with or without children. These data strongly support the cluster phenomenon of H. pylori infection among families, the key role of the infected mothers in the transmission within families, and the importance of adult-child transmission and not vice versa.

Prevalence of Helicobacter pylori infection in Kenyan schoolchildren aged 3-15 years and risk factors for infection

OBJECTIVES

To determine the prevalence of Helicobacter pylori (Hp) infection in Kenyan schoolchildren aged 3-15 years and the risk factors for infection.

DESIGN

A cross-sectional survey and study of risk factors.

SUBJECTS

Primary-school children in Trans Nzoia district, Kenya.

METHODS

Hp status was determined using the 13C-urea breath test. Risk factors were assessed using a structured interview schedule.

RESULTS

Of 205 children interviewed, valid breath test results were obtained for 192 (93.7%), of whom 155 (80.7% (95% CI 75.2-86.3)) were infected. Univariate analysis showed weak associations between Hp infection and rural areas (location of home, Relative Risk (RR)= 1.2 (1.0-1.4); location of school, RR = 1.2 (1.0-1.3)) and lower socio-economic status (RR = 1.2 (1.0-1.4)). Access to only a pit-latrine in the home (RR = 1.2 (1.0-1.4)) and plate-sharing with other family members in the home also increased the likelihood of Hp infection (RR = 1.3 (1.1 -1.6)). However, after logistic regression modelling only plate-sharing in the home remained as an independent risk factor (odds ratio (OR) = 2.8 (1.3-6.3)).

CONCLUSIONS

The prevalence of Hp infection in Kenyan schoolchildren aged 3-15 years is already high, suggesting that most acquisition occurs before age 3 years. Children who normally shared a plate with other family members during meals in the home had a higher prevalence of infection, suggesting that oro-oral transmission may be important in this population. Future studies in developing countries should focus on younger children (before age 3 years), and consider the possibility of adult-child, oro-oral transmission in order to establish likely modes of transmission.

Quantitative culture of Helicobacter pylori from gastric juice: the potential for transmission

The transmission of Helicobacter pylori may occur by spread of organisms from gastric juice which has been introduced into the mouth by gastro-oesophageal reflux. The aim of this study was to quantify the load of H. pylori present in gastric juice available for transmission. Gastric antral biopsy and gastric juice samples were collected from 108 adult dyspeptic patients undergoing routine upper gastroscopy and the presence of H. pylori was determined. In all, 54 (50%) of 108 patients gave positive results in the gastric antral biopsy rapid urease test and for H. pylori histology. The gastric juice of 40 (37%) of patients gave positive results for the urease A gene by PCR assay; 34 (31%) of patients were positive by these three tests and H. pylori was cultured from the gastric juice of 13 (38%) of these patients. The median count of H. pylori in gastric juice was 1.75 x 10(1) cfu/ml. Viable organisms in gastric juice may lead to transmission of H. pylori when refluxed or vomited into the mouth.

Helicobacter pylori infection occurs via close contact with infected individuals in early childhood

BACKGROUND

The manner in which Helicobacter pylori is transmitted is of fundamental importance when considering strategies for its control, yet, to date, the exact mode of transmission remains uncertain.

METHODS

The seroprevalence of H. pylori in a relatively isolated rural town in Japan (A-town) was examined to analyse the H. pylori infection route. The immunoglobulin G antibodies against H. pylori in 1684 subjects who had received public health examinations in A-town were determined with an enzyme-linked immunosorbent assay. The seroprevalence was compared in five areas according to the water source. The possibility and frequency of intrafamilial infection was analysed by comparing the seroprevalence among family members residing in the same home.

RESULTS

The seroprevalence of H. pylori did not differ significantly between the five areas examined. Seropositivity was significantly more common in the children whose mothers were seropositive (45.0%, 27/60) than in the children whose mothers were seronegative (10.0%, 2/20; odds ratio (OR) = 7.36, P = 0.0036, 95% confidence interval (CI) = 1.57-34.59). Seropositivity was significantly more common in the children whose older siblings were seropositive (55.0%, 22/40) than in the children whose older siblings were seronegative (23.5%, 20/85; OR = 3.97, P = 0.00051, 95% CI = 1.79-8.84). There was no significant relationship in seroprevalence between children and fathers, grandchildren and grandfathers, grandchildren and grandmothers, or within couples. Seropositivity was significantly more common in the adolescents who had attended a nursery school (44.4%, 20/45) than in the adolescents who had not attended a nursery school (25.6%, 109/426) (OR = 2.33, P = 0.0070, 95% CI = 1.24-4.36).

CONCLUSIONS

The acquisition of H. pylori infection occurs by close contact with infected individuals in early childhood, especially via contact with infected mothers and other infected children.

Increased risk of infection with Helicobacter pylori in spouses of infected subjects: observations in a general population sample from the UK

BACKGROUND/AIMS

To investigate risk factors for infection with Helicobacter pylori in a general population sample who accepted an invitation to be screened. In particular, to determine whether being the spouse of an infected subject is an independent risk factor for infection after adjustment for other risks.

METHODOLOGY

A serological screening test for Helicobacter pylori was offered to 4015 randomly selected subjects registered at a single general practice in Market Harborough, UK. Those invited were also asked to complete a questionnaire if attending for screening; this included information relating to possible risk factors for infection. Results were analyzed in the overall sample of attenders and a subset of married couples, using univariate and multivariate analyses.

RESULTS

Complete results were obtained for 1431 (36%) subjects. Age, childhood social class and household crowding in childhood were independent risk factors after adjustment for other variables. Positive status of spouse was an independent risk factor in a subset of 389 married couples (P = 0.005, Odds Ratio: 2.65, 95% Confidence Interval: 1.34-5.25).

CONCLUSIONS

Our study confirmed the correlation between childhood living conditions and infection with Helicobacter pylori. In the study population, having a Helicobacter pylori-positive spouse was associated with a significant increased risk of being infected.