Seroepidemiological study of the immune response to Campylobacter pylori in potential risk groups

Helicobacter pyloriInfection: A Global Occupational Risk for Healthcare Workers?

The occupational risks from Helicobacter pylori, a major cause of gastroduodenal diseases, were reviewed for selected groups of healthcare workers (HCWs). A literature search was performed using Medline/Pubmed, 1983 to June 2003. Additional manual searches were made using reference lists from the selected articles. Current knowledge implies various pathways of agent transmission, favoring person-to-person transmission. The risks are highest for gastroenterologists, some nurses, and employees caring for persons with mental disability. Results for other groups are conflicting.

The occupational risk of Helicobacter pylori infection among gastroenterologists and their assistants

BACKGROUND

Helicobacter pylori is a widely spread bacterium that mainly inhabits the gastric mucosa and can lead to serious illnesses such as peptic ulcer disease, gastric carcinoma and gastric MALT lymphoma. The oral-oral route seems to be the main transmission route. The fact that endoscopes are contaminated after being used to perform a gastroscopy leads one to question whether gastroenterologists and endoscopy nurses and assistants run a higher risk of infection.

METHODS

A systematic search for literature was conducted in the MEDLINE and EMBASE databases and further publications were found in reference lists of relevant articles. Epidemiological studies on the occupational exposure of endoscopy personnel were collected and their quality was assessed. Pooled effect estimates were identified in a meta-analysis.

RESULTS

Of the 24 studies included in the analysis, 15 were considered to be methodologically good. Of these 15 studies, eight single studies showed a statistically significant increased risk of infection for gastroenterologists, and five for their assistants. Meta-analysis across all methodologically good studies found a statistically significant risk of 1.6 (95%CI 1.3-2.0) for doctors. The pooled effect estimates also indicated a statistically significant risk of Helicobacter pylori infection (RR 1.4; 95%CI 1.1-1.8) for assistants too.When studies are stratified by medical and non-medical control groups, statistically significant risks can only be recognised in the comparison with non-medical controls.

CONCLUSIONS

In summary, our results demonstrated an increased risk of Helicobacter pylori infection among gastroenterological personnel. However, the choice of control group is important for making a valid assessment of occupational exposure risks.

Are endoscopy nurses at risk of infection with Helicobacter pylori from their work?

BACKGROUND

In response to studies suggesting risk of occupational transmission of Helicobacter pylori (HP) to endoscopy staff, this cross-sectional study of seroprevalence to HP in gastroscopy nurses working in West of Scotland hospitals (an area of high endemicity of HP infection) was performed to determine if they were at excess risk relative to peers working in surgical specialities but without gastroscopy exposure. The study aimed to fulfil employer's duties to carry out a suitable risk assessment required by health and safety legislation.

METHOD

This cross-sectional study compares the seroprevalence of HP in gastroscopy nurses and comparators drawn from orthopaedic and trauma units in 10 hospitals during 1998. A directly administered questionnaire collated exposure information on occupational and non-occupational risk factors for infection. Venepuncture was performed for latex agglutination test for IgG to HP. Confounding by socio-economic factors was controlled for by multivariate analysis.

RESULTS

Of the 222 participants, 74 were endoscopy staff (84% response) and 148 (59%) were comparators. Of these, 32.4% of gastroscopy and 33% of comparators were seropositive for HP (OR 0.97, P > 0.9, 95% CI 0.5-1.8). No association was found between gastroscopy exposure variables (frequency, years) or exposure to all endoscopy procedures and HP. Significant associations were found for age, childhood deprivation and greater number of siblings.

CONCLUSION

No excess HP infection was found in gastroscopy nurses. Duties imposed by the health and safety legislation appear discharged by normal infection control procedures. Socio-economic factors are key determinants of HP status.

Helicobacter pylori in intensive care: why we should be interested

Helicobacter pylori is estimated to infect over 50% of the world's population, the majority of whom are asymptomatic. Although most research to date has focused on local gastroduodenal disease manifestations, the potential impact of H. pylori infection and the associated chronic active inflammation on systemic disease processes is now being explored. This review addresses three aspects of emerging importance regarding H. pylori in intensive care medicine: acute gastric stress ulceration, nosocomial infection, and the potential modulatory effect on the systemic stress response. The role of H. pylori in acute stress ulceration remains uncertain, but it is unlikely to have the same major aetiological role as in peptic ulcer disease. The pathogenesis of both acute stress ulceration and H. pylori gastritis suggest overlapping mechanisms of gastric mucosal damage and H. pylori may augment stress ulceration incidence and severity. Nosocomial infection of both staff and patients with H. pylori has been suggested by serological studies, and increased H. pylori infection has been reported in intensive care staff. This has significant short- and long-term health implications and also raises questions regarding the efficacy and implementation of routine infection control precautions in intensive care. Finally, H. pylori infection has been linked with the pathogenesis of many extra-intestinal diseases, but the evidence is weak and the relationship between H. pylori and systemic diseases remains controversial. However, the potential for H. pylori to modulate systemic disease processes, particularly the systemic stress response in critical illness, is both theoretically plausible and therapeutically tantalising and requires further investigation.

Diagnostic value of detection of IgM antibodies to Helicobacter pylori

This report describes the diagnostic value of anti-Helicobacter pylori IgM detection. Serum samples from 9043 symptomatic and asymptomatic individuals were evaluated with ELISA for the presence of anti-H. pylori IgG, IgM, and IgA. The specificity of detected IgM was confirmed by inhibition and cross-reactivity assays. Treatment of IgM-positive specimens with 1% 2-mercaptoethanol resulted in approximately 90% inhibition. Our data suggest a low level of cross-reactivity (5%) between H. pylori and four different enteropathogenic bacteria tested. The specificity of anti-H. pylori IgM was also demonstrated by Western blot and linearity studies. Data show that the detected IgM is highly specific. Western blot analysis revealed a variable IgM response to H. pylori antigens among patients, with the most reactive antigenic fractions being in the range of 55- to 100-kDa. Overall, the data confirm the diagnostic value of anti-H. pylori IgM detection. The prevalence of IgM antibodies to H. pylori in tested sera was significantly higher in symptomatic patients (10.4%) than in asymptomatic individuals (1.1%). Likewise, the percentage of sera positive for IgM alone was higher in symptomatic than in asymptomatic groups (3.8 vs 0.22%). About 5% of sera were positive only for IgA. We concluded that ELISA can be used for the detection of specific IgM to H. pylori and that the presence or absence of IgM antibodies to H. pylori may reflect whether or not an acute infection exists.

High risk of Helicobacter pylori infection in young Japanese dentists

BACKGROUND AND AIM

The route of person-to-person transmission of Helicobacter pylori may be either fecal-oral or oral-oral, because the bacterium is found in both dental plaque and feces. We assessed the prevalence of H. pylori seropositivity, which reflects present or past infection, in Japanese dentists exposed occupationally to dental plaque.

METHODS

We examined the sera of 60 dentists (34 who were 20-29 years or older, and 26 who were over 30 years of age) and 60 age-matched controls by using quantitative ELISA for antibodies of the immunoglobulin G class to H. pylori.

RESULTS

The proportion of dentists seropositive for H. pylori (42 of 60, 70%) was higher than in controls (23 of 60, 38%). The odds ratio for H. pylori seropositivity (3.8; 95% CI, 1.76-8.02) was high in the dentists. When dentists were classified in terms of the length of their practice, the odds ratio for seropositivity (10.4; 95% CI, 3.26-32.85) was high in the dentists practising for fewer than 4 years. The proportion of dentists in their 20s who were seropositive was greater than that in the group of age-matched controls.

CONCLUSION

Japanese young dentists are at a high risk for H. pylori infection, with the oral-oral transmission route being possibly the most common.

Helicobacter pylori and endoscopy

Helicobacter pylori is possibly the most common bacterial infection of humans and is now recognized as the most important acquired cause of peptic ulceration. Epidemiological evidence also recently implicated this bacterium in the pathogenesis of gastric cancer. The mechanism of spread of the organism, by either the faecal-oral or oral-oral route, raises the possibility of transmission of this organism from infected patients to hospital staff particularly those involved in endoscopy. The evidence for an increased risk to endoscopists is contradictory, varying from none to a five-fold increase. This review summarizes the evidence for mode of transmission and risk to hospital staff from this important bacterium.

Seroprevalence of immunoglobulin G antibodies against Helicobacter pylori among endoscopy personnel in Japan

BACKGROUND

The seroprevalence of immunoglobulin G antibodies against Helicobacter pylori in endoscopy personnel was determined to investigate whether gastrointestinal endoscopists and endoscopy nurses in Japan are at an increased risk for H. pylori infection and to clarify risk factors for H. pylori infection during endoscopy.

METHODS

One hundred twenty-one gastrointestinal endoscopists and endoscopy nurses provided personal information, including their observance of infection-control measures, by means of self-administered questionnaire. One hundred one age-matched healthy individuals undergoing routine physical examinations served as controls. Serum samples from each subject were examined with enzyme-linked immunosorbent assay for the presence of IgG antibodies against H. pylori.

RESULTS

Among younger subjects (< 40 years old), endoscopists and endoscopy nurses had higher seropositive rates than did control subjects (p < 0.05). Among older subjects (> or = 40 years old), the seropositive rate did not differ between endoscopy personnel and control subjects (p = 0.2174). However, among older seropositive subjects, endoscopy personnel had significantly higher antibody titers than did control subjects (p < 0.01). Older seropositive endoscopists performed significantly more examinations per month than did their seronegative colleagues (p < 0.05). Furthermore, younger seropositive endoscopy nurses performed significantly more examinations per month than did seronegative nurses (p < 0.05).

CONCLUSIONS

Gastrointestinal endoscopists and endoscopy nurses in Japan are at high risk for H. pylori infection. The risk of H. pylori infection is correlated with the frequency of endoscopic examinations, especially in older gastrointestinal endoscopists and younger endoscopy nurses.

Heterogeneity of immunoglobulin G response to Helicobacter pylori measured by the unweighted pair group method with averages

The heterogeneity of the immune response to Helicobacter pylori has always been noticed but has never been evaluated by obtaining a quantitative measure. For this purpose, sera were tested by enzyme-linked immunosorbent assay, and 207 positive serum specimens were subsequently tested by immunoblotting. The presence or absence of six specific bands was noted. The homology of the different profiles of bands was measured by calculating the Dice coefficient, and a dendrogram was constructed. Thirty-four profiles were found, with each profile containing from 1 to 43 serum specimens. At a level of 72% similarity, 115 of the serum specimens studied fell into eight profiles. At a level of 48% similarity, 186 of the serum specimens studied fell into 22 profiles. The difference in immunoblot profiles was probably linked to the host immune response, but infection with strains carrying different antigens cannot be ruled out.

High seroprevalence of IgG against Helicobacter pylori among endoscopists in Taiwan

A prospective survey to investigate the seroprevalence of IgG against Helicobacter pylori among endoscopists in Taiwan was conducted by analyzing blood samples of 70 study subjects and 64 nonendoscopist physicians with quantitative ELISA. Personal information and the practices of infection control related to gastroscopy examination were obtained by a self-administered questionnaire. Significant differences were detected in the IgG prevalence between study and control subjects (80.0% vs 51.6%; P < 0.05). The serum level of antibody in endoscopists (385.2 +/- 36.1 unit/ml) was significantly higher than that of nonedoscopists (211.8 +/- 33.0 unit/ml; P = 0.018). Endoscopists performing 30 or more sessions of gastroscopy per week had higher seroprevalence than those performing less than 30 sessions (90.9% vs 70.3%; P = 0.0126). In conclusion, endoscopists in Taiwan had a high prevalence of H. pylori infection. The cause might be related to the frequency of gastroscopies performed.

Prevention of Helicobacter pylori infection

A gastroenterologist, treating a patient with H. pylori, must decide whether the unit of treatment is only the ill individual, or the family, perhaps including close contacts. If it is the family and close contacts, is it all family members and contacts, or are there some ages, relationships, or clinical characteristics that increase the risk of transmission to the patient after successful treatment of their infection? In preventing reinfection, the available data suggest: the natural infectious dose has not been determined infection may occur from oral or faecal shedding children are more infectious than adults socio-economic factors are important in any comparison of infection rates food and water seem unlikely vehicles in the developed world travel in the third world may increase risk of infection seropositivity in adults predominantly reflects exposure in childhood infection is frequently with more than one strain reinfections are not more frequent in families with other members infected reinfections are infrequent with strains different from the original strain reinfection might be more frequent in developing countries no need for all family members to be treated to reduce reinfection rates. In considering vaccine, the available data suggest: breast milk IgA can reduce infection rate antibodies induced by vaccine may reduce infection in animals late benefit of childhood vaccination in developed countries probable early benefit of childhood vaccination in developing countries vaccination of already infected adults would have cost-benefit.

Helicobacter pylori in children

Helicobacter pylori is the major cause of antral gastritis in children, however, it is not always associated with symptoms. The exception to this occurs in duodenal ulcer disease with which H. pylori is linked in children albeit less strongly than in adults. Duodenal ulcers do not recur in older children following eradication of H. pylori. The importance of asymptomatic carriage of H. pylori in children, particularly in relation to the duration of this infection and the subsequent development of gastric cancer, remain to be established. Helicobacter pylori is associated with both hypochlorhydria and persistent diarrhoea in children in developing countries, but the significance of this association is still unknown. Although there is no consensus on the optimal regimen for treating H. pylori infection in children, dual therapy with amoxycillin and bismuth subcitrate for 2 weeks followed by monotherapy with bismuth subcitrate for a further 6 weeks will eradicate H. pylori infection in the majority of children. Those who relapse may be treated with a repeat course plus metronidazole for 4 weeks. Compliance with such regimens is a problem and shorter treatment courses that are equally effective in children need to be defined. Similarly, studies are required on the influence of the intrafamilial reservoir of H. pylori infection on relapse after treatment and the need for whole family eradication therapy.

Helicobacter pylori in the oral cavity. A critical review of the literature

Helicobacter pylori is now generally accepted as a key etiologic agent in peptic ulcer disease as well as in gastric cancer. Dental plaque has been implicated as a possible source of H. pylori by studies that used culture, biochemical, nucleic acid, and immunologic analyses. Variation in the sensitivities of detection by these different reported assays may reflect the methods used, technical difficulties, microbiota complexes, geographic distribution, and host response. The finding of H. pylori in dental plaque also suggested that dental workers may be at increased risk of acquiring H. pylori infection from occupational exposure. We review the available data concerning the presence of this important pathogen in the oral cavity and its potential to be acquired by dental workers. Knowledge of this organism's route of transmission may aid in the development of therapeutic procedures to stop its potential spread.

Transmission and acquisition of Helicobacter pylori infection: evidences and hypothesis

The role of Helicobacter pylori in gastroduodenal diseases has been established, but many ecological and epidemiological features remain unclear. Although H pylori infection is one of the most common infections in the world, the mode of transmission remains unknown. Uncommon extra-endoscopic isolation raises obstacles to a good understanding of epidemiological patterns, and no rational basis exists for a prophylaxis strategy. This work reviews the data on the reservoir of the bacteria and its ecological niche, the method of excretion from the site of infection and the possible circumstances of acquisition. Many features are completely unknown or still controversial, and interpretation is often speculative. At the present time, it can be assumed that the most likely mode of spread would be from saliva in childhood. However, further works are required to establish, whether or not, fecal transmission co-occurs in low hygiene conditions.

Helicobacter pylori infection in dentists--a case-control study

To test the null hypothesis that frequent and multiple salivary exposure is not a risk factor for developing H. pylori infection, serum anti-H. pylori IgG from 179 dentists and dental students and 179 age-, sex- and socioeconomic-matched controls were assayed using an ELISA. Seroprevalence in dentists was 16% (11/70); clinical dental students 6% (3/47); and pre-clinical dental students 10% (6/62). There were no differences in H. pylori seropositivity between cases and controls. There was an increase in H. pylori seropositivity with age (chi (trend)2 9.04, p = 0.003). These data provide evidence that adults are not at high risk of developing H. pylori infection as a result of exposures to saliva from multiple sources.

Helicobacter pylori seroepidemiology in risk groups

Helicobacter pylori is associated with peptic ulcer and chronic active gastritis. The response to infection can be determined by measuring serum titers of anti-H. pylori antibodies. We compared antibody titers in 612 serum samples from 570 individuals considered at risk for H. pylori infection, 170 of them are control sera from 110 adults and 60 children with no gastric alterations. The study groups were 93 institutionalized mentally handicapped children, 40 heterosexual couples, 101 HIV-sero-positive patients, 86 patients with chronic renal failure and 40 individuals (20 adults and 20 children) with symptoms associated with gastritis or gastroduodenal ulcer disease. In the adult and child control groups, 33.5% and 11.6% of the individuals had circulating anti-H. pylori antibodies. Significantly more adults (80%) and children (75%) with gastric symptoms had detectable circulating antibody titers. Elevated titers were also found in institutionalized children and in adults with renal failure.

Helicobacter pylori and gastric cancer

This review focuses on the similarities between the epidemiology of gastric cancer and the epidemiology of Helicobacter pylori. Their demographic patterns and the results of studies regarding familial and environmental risk factors are described. The association of gastric cancer and H. pylori infection with both gastric ulcer and chronic atrophic gastritis is also characterized and the possibility that a H. pylori infection could lead to gastric cancer is discussed.

Serodiagnosis of Helicobacter pylori infections with an enzyme immunoassay using the chromatographically purified 120 kilodalton protein

A membrane-associated 120 kDa protein of Helicobacter pylori with known species-specificity was isolated and used in an enzyme immunoassay (EIA) for the detection of Helicobacter pylori-specific IgG antibodies in patient sera. The EIA was compared with two other methods used for serodiagnosis of Helicobacter pylori infections: an EIA using sonicated whole Helicobacter pylori cell antigen and Western immunoblot. In a prospective study 127 unselected patients (76 patients with antrum gastritis, 51 patients without gastritis) who underwent gastroscopy were studied histologically and serologically. The EIA using the purified 120 kDa protein had the highest specificity (92%) compared with the EIA using a whole cell sonicate of a single Helicobacter pylori strain as antigen (60.7%) and the immunoblot (90.2%). The sensitivity was 96%, 100% and 92%, respectively. Sera of three control patients reacted strongly in all three methods, indicating possible Helicobacter pylori infection with negative histological findings. The EIA using the 120 kDa protein as antigen was shown to be a specific and sensitive technique for the serodiagnosis of Helicobacter pylori infections.

Serodiagnosis of Helicobacter pylori infections by detection of immunoglobulin G antibodies using an immunoblot technique and enzyme immunoassay

A transferable solid phase enzyme immunoassay (TSP-EIA) and an immunoblot technique were evaluated for the detection of IgG antibodies against Helicobacter pylori. Using the biopsy urease test as reference method, the sensitivity and specificity of the EIA were 96% and 100%, respectively. Immunoblot analysis was carried out by testing sera from patients with a positive urease test who suffered from type B gastritis, gastric and duodenal ulcers, and a negative control group. The immunoblotted Helicobacter pylori proteins showed reproducible immunoreactive bands at molecular weights of 130, 93, 75 and 67 kDa. The molecular weight protein fractions of Helicobacter pylori of 180 kDa and higher were found to be of minor immunological significance. Proteins of less than 60 kDa exhibited wide serum-specific variations in reactivity after immunostaining. No correlation between specific immunoblot patterns and clinical signs induced by Helicobacter pylori infection was observed.

Immunoglobulin G antibodies to Helicobacter pylori in patients with dyspeptic symptoms investigated by the western immunoblot technique

Helicobacter pylori is a gram-negative, curved, rod-shaped bacterium known to cause gastritis and to be an important factor in the pathogenesis of peptic ulcers. Serological testing has recently been proposed as an aid in diagnosis of H. pylori infections. In this study, we used the Western immunoblot technique to evaluate the possibility of using one or more of the antigens from H. pylori for this purpose. Thirteen major bands and about 30 minor bands could be identified by Western blotting when sera from 53 consecutive dyspeptic patients, 27 healthy children, and 25 blood donors were evaluated. Antibodies against most of the major bands were found significantly more frequently in patients with H. pylori infections than in patients without such infections. However, antibodies against a single polypeptide were not produced by all patients with H. pylori infection. Polypeptides with molecular masses of 120, 50, and between 19 and 36 kDa seem to be the most specific polypeptides for the diagnosis of H. pylori infections. This study showed only minor differences in antigenic composition between different clinical isolates of H. pylori, and serological cross-reactions with other bacteria were limited. Major serological cross-reactions were found only with Campylobacter jejuni and with bacterial lipopolysaccharide. However, one band at 60 kDa reacted with antiserum to the Legionella micdadei common antigen, which may indicate a cross-reaction with common antigen from several other bacteria. This study demonstrates that a number of bands may be useful as antigens in serological tests after isolation and purification.

Elevated risk of Helicobacter pylori infection in submarine crews

In a prospective study designed to elucidate the route of transmission of Helicobacter pylori, the seroprevalence and incidence of Helicobacter pylori infection was determined in the following branches of the armed forces presumed to be at increased risk of acquiring transmissible diseases by the fecal-oral or oral-oral route: German submarine crews (n = 64, mean age 26.2 years) and regular officers of the French infantry (n = 51, mean age 26.5 years) who had served for a minimum of three years. The submarine crews were compared with air force staff (n = 74, mean age 23.7 years), and the French officers with French infantry recruits (n = 135, mean age 20.5 years) who started their service at the beginning of the study. The frequency of IgG and IgA antibody responses to the 120, 88, 86 and 82 kDa proteins was determined by the immunoblot method. The frequency of a positive antibody response was strongly dependent on age (p less than 0.001). When results were controlled for age by the logistic regression analysis, the submarine crews revealed significantly increased frequencies of the IgG and IgA responses compared to air force staff. The antibody responses of French officers and recruits were not significantly different. It is concluded that submarine crews serving during their missions in an overcrowded space with extremely limited sanitary facilities must be considered a high-risk group for Helicobacter pylori infection. These results strongly suggest person-to-person transmission of Helicobacter pylori, by either the oral-oral or the fecal-oral route.

Acute Helicobacter pylori infection: clinical features, local and systemic immune response, gastric mucosal histology, and gastric juice ascorbic acid concentrations

The symptomatology of a case of acute infection with Helicobacter pylori is described, together with the accompanying changes in gastric mucosal histology, local and systemic humoral immune response, and gastric ascorbic acid concentration. The patient was an endoscopist, previously negative for the carbon-14 urea breath test, who had a week of epigastric pain and then became asymptomatic. H pylori was detected by culture of antral biopsy specimens and was still present after 74 days. Five days after infection the histological findings showed acute neutrophilic gastritis; by day 74 changes of chronic gastritis were evident. The patient seroconverted by IgG enzyme linked immunosorbent assay by day 74, but a mucosal IgM and IgA response was evident as early as day 14. Infection was accompanied by a transient hypochlorhydria but a sustained fall in gastric juice ascorbic acid concentration.

Transmission of Helicobacter pylori infection. Studies in families of healthy individuals

Helicobacter pylori is accepted as the commonest cause of type-B gastritis. Detailed information about the mode of transmission remains scanty. We investigated the frequency of H. pylori infection within families, defined as consisting of a husband and wife with at least one biologic child, all living in the same household. Inclusion criteria required that both the parents and the children had been born in the United States, had used no antibiotic or bismuth for the previous 2 months, had no recent major illness or surgical operation, and had no symptoms referable to the upper gastrointestinal tract. H. pylori infection was identified with a 13C-urea breath test and an enzyme-linked immunosorbent assay for anti-H. pylori IgG. Forty-one families (151 healthy individuals) were enrolled. Before the results of the H. pylori tests were known, one parent was selected as the index subject. H. pylori infection clustered; that is, 68% of spouses of H. pylori-infected index subjects were also H. pylori-infected, compared with 9% of spouses of H. pylori-negative index subjects (p less than 0.0001). The children of infected index parents were also more likely to be infected than children of uninfected index parents--40% versus 3%, respectively (p less than 0.0001)--and the results in the children were independent of whether the father or the mother was the index subject. Clustering of H. pylori infection within families suggests person-to-person transmission or common source exposure. The high frequency of H. pylori infection in spouses suggests that genetic factors are less important than living conditions for transmission of H. pylori infection.

Epidemiology of Helicobacter pylori in an asymptomatic population in the United States. Effect of age, race, and socioeconomic status

A causative role is now accepted for Helicobacter (formerly Campylobacter) pylori in type B gastritis, and evidence is accumulating that H. pylori infection plays a major contributory role in peptic ulcer disease. Preliminary studies have reported that the prevalence of H. pylori infection increases with age, but detailed information on the prevalence of the bacteria in any defined population and on the factors that may influence the pattern of distribution remains scanty. In the present study, a sensitive enzyme-linked immunosorbent assay and a [13C] urea breath test were used to investigate the prevalence of H. pylori infection among 485 healthy asymptomatic volunteers between the ages of 15 and 80 residing in the Houston metropolitan area. H. pylori infection was present in 52%. The prevalence of H. pylori infection increased rapidly with age at 1%/yr for the overall population. The frequency of H. pylori infection was higher in blacks (70%) than whites (34%) (P less than 0.001); this difference remained after adjustments were made for age, gender, educational level, income, and use of tobacco or alcohol. H. pylori infection was independent of gender but was closely correlated with socioeconomic class. There were significant inverse correlations between age-adjusted frequency of H. pylori infection and income and between educational level and H. pylori infection. There was no association between H. pylori infection and consumption of alcohol or nonsteroidal antiinflammatory drug use or smoking. Having pets was associated with a lower frequency of H. pylori infection, but this was highly associated with higher socioeconomic status. The mode(s) of transmission of H. pylori is unknown, but the social patterns of H. pylori infection are consistent with fecal-oral transmission as one important pathway. Socioeconomic factors seem to determine the age of acquisition.