GASTROENTEROLOGY
ALIMENTARY
1991;100:1495-1501
TRACT
Epidemiology of Helicobacter PyIori in an Asymptomatic Population in the United States Effect of Age, Race, and Socioeconomic
Status
DAVID Y. GRAHAM, HODA M. MALATY, DOLORES G. EVANS, DOYLE J. EVANS, Jr., PETER D. KLEIN, and ERVIN ADAM Departments of Medicine and Pediatrics and Division of Molecular Virology, United States Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine: and Veterans Affairs Medical Center, Houston, Texas
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, hut 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 [‘“Cl 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 l%lyr for the overall population. The frequency of H. pylori infection was higher in blacks (70%) than whites (34%) (P < 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 hut 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 Socioeconomic factors seem to determine acquisition.
H
pathway. the age of
elicobacter
pylori is now accepted as the major cause of type B gastritis, and H. pylori gastritis is strongly associated with duodenal ulcer and gastric ulcer disease (1). There is a considerable body of information concerning gastritis, and studies specifically linking epidemiological data on H. pylori with older observations on gastritis are beginning to appear. These preliminary studies have reported that the prevalence of H. pylori infection increases with age (2-13), 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. Most studies reported to date have involved small numbers of subjects or have surveyed poorly characterized populations. As a result, specific correlations of H. pylori infection with epidemiological factors such as race or socioeconomic class have not been possible. The present study was designed to study [a) the prevalence of H. pylori infection in a defined asymptomatic population, (b) the age-distribution pattern of H. pylori infection, and (c) the possible relationships between H. pylori infection and factors such as race, gender, socioeconomic status, alcohol consumption,
Abbreviations usedin thispaper: ELISA, enzyme-linked immunosorbent assay; HM-CAP, high-molecular-weight, cell associated proteins; UBT, urea breath test. o 1991 by the American Gastroenterological Association 0016-5085/91/$3.00
GASTROENTEROLOGYVol. lOO,No.6
1496 GRAHAM ETAL.
of nonsteroidal antiinflammatory smoking, and ownership of pets.
use
drugs (NSAIDs),
Subjects and Methods Study Population Volunteers between the ages of 15 and 80 years were eligible for enrollment. Entry criteria were: both subjects and their parents were born in the United States: the enrollees planned to reside in the Houston metropolitan area for the next 4 years; and they considered themselves to be in good health and denied symptoms referable to the upper gastrointestinal tract. Each potential volunteer completed a self-administered screening questionnaire, and the results were reviewed by a trained interviewer. In addition to demographic information, the instrument asked the volunteers: (a) did they consider themselves to be in good health; (b) had they had any serious illness or surgery in the past 2 months; (c) had they ever had gastric surgery or a peptic ulcer, or had anyone in their immediate family had a peptic ulcer; and (d) did they have arthritis and if yes, what medication were they taking and for how long? Each individual was questioned about the presence and the frequency of symptoms referable to the upper gastrointestinal tract, including indigestion, heartburn, sour stomach, nausea/vomiting, and burning pain in the stomach area and/or in the chest. In addition, enrollees were questioned about the use of any medications during the preceding 2 months, specifically antibiotics, bismuth-containing compounds, or NSAIDs. All enrollees were also questioned about smoking and alcohol use and whether they kept pets at home. Subjects were excluded if they had a history of peptic ulcer, frequent (defined as occurring more than once a month) symptoms referable to the upper gastrointestinal tract, or if they used antacids or antibiotics regularly. Demographic information was obtained directly from each participant through the self-administered questionnaire and included race, age, gender, weight, height, marital status, highest educational level, place of birth, occupation, and family income.
Methods of Enrollment The primary method of recruitment was by advertisement in local and public newspapers and by flyers placed in the various facilities in the Texas Medical Center Houston, TX. Teenagers aged 15-18 years were recruited from schools through contacts with the school’s principal and nurse. Short explanatory talks were given to the children, and letters were sent to the parents explaining the aims of the project, the breath test procedure, and the procedure of blood drawing. Many elderly subjects were recruited from senior citizens’ homes and churches. Elderly subjects were required to maintain an active lifestyle. No more than eight individuals were accepted from any one school, senior citizens’ home, or church. The study was approved by the Institutional Review Board for the VA Medical Center, Baylor College of Medicine, The Methodist Hospital, and the Clinical Research Center. A consent form was signed by each individual
before participating in the study. Both the subjects under 18 years of age and their parents certified their assent by their signatures before participating in the study. A serum sample was obtained from each subject for evaluation of immunoglobulin G (IgG) antibody to the high-molecular-weight, cell-associated proteins (HM-CAP) of H. pylori (14); the sera were stored at -70” C. A ‘C-urea breath test (UBT) was also done to assess whether urease activity was present in the stomach (15,161.
Enzyme-finked
Anti-Helicobacter
lmmunosorbent Assay for pylori Zmmunoglobulin G
Specific details of the procedure are published elsewhere (14); the high-molecular-weight, cell-associated antigen preparation contains at least two proteins in the molecular-weight range of 400,000-700,000. The enzymelinked immunosorbent assay (ELISA) was done in 96-well Microtiter plates (Linbro, Scientific Co., Hamden, CT] coated with HM-CAP diluted with phosphate-buffered saline (PBS) to approximately 7 t.&mL. Sera diluted 1:50 and 1:lOO were added, and alkaline phosphatase-conjugated anti-human IgG (Southern Biotechnology, Birmingham, AL) was used as the detector. Each plate included HM-CAP ELISA-positive and -negative control sera. The test was scored positive for OD value ~0.20.The specificity and positive predictive value of the HM-CAP ELISA were each previously shown to be 100%; the sensitivity is 98.70/o, and the negative predictive value 98.6% (16). There is no cross-reactivity with Campylobacter jejuni.
Urea Breath Test The [“Cl-UBT exploits the existence of a target bond linking the [‘C]-labeled portion to the rest of the molecule. Scission of this bond by a specific enzyme results in the rapid formation of ‘“CO, and can be detected in respiratory CO,. In this instance, the high local concentration of H. pylori urease in the stomach acting on the [‘Qurea results in readily measurable increases in respiratory [‘“C] within 20 minutes of substrate administration. This action can be distinguished from that of colonic bacteria by the rapidity and extent of urea hydrolysis in H. pylori-infected individuals. The urea breath test result was positive if the urease activity was 2 0.500kmol kg-’ h-‘; the test duration was 1 hour.
Analyses H. pylori infection was defined as a positive ELISA test result. The data were analyzed by logistic regression and x2 using the SAS program (SAS Institute, Cary, NC]. We categorized subjects into seven age groups. The MantelHaenszel x2 analysis was used to examine relationships between H. pylori infection and age, gender, race, socioeconomic level, educational level, smoking, alcohol consumption, keeping pets, and use of NSAIDs. Logistic regression was used to evaluate the association of each independent variable of the study on the frequency of H. pylori infection with adjustment for the other variables. The analyses were done on the whole population and for each race separately.
June
1991
EPIDEMIOLOGY
Results
We enrolled 490 healthy asymptomatic volunteers residing in the Houston metropolitan area. In 441 of the enrollees, the results of both the ELISA and the UBT were concordant; in 44 the results of ELISA were positive and the UBT results negative. Five individuals had a positive UBT and a negative ELISA result and were excluded. The discordant findings were randomly spread, and inclusion or exclusion of those with discordant findings would not change any of the results obtained. H. pylori infection was present in 253 subjects or 52% of the population studied (Table 1). The subjects ranged in age from 15 to 80 years. The black population represented 35% of the total population in the geographic area. To compare the frequency of H. pylori infection between races, a similar number of persons from each of the two racial groups were enrolled. The male-female ratio was similar (1:0.84 and 1:0.99 for whites and blacks, respectively). Table 2 presents the results of logistic regression analysis with H. pylori infection as the dependent variable. The overall frequency of H. pylori infection was higher in blacks (70%) than whites (34%) (P < 0.001; Figure 1). The frequency of H. pylori infection among blacks remained greater than among whites after adjustment for all parameters evaluated (e.g., age, gender, educational level, and income). The frequency of H. pylori infection in men and women was similar when controlled for race and age (Table 1; P > 0.5). Thus, the data are presented (except where noted) according to race, with gender merged. Associations Between Study Variables and Helicobacter pylori Infection
There was a significant inverse correlation between age-adjusted frequency of H. pylori infection and income in the white population (P < 0.001) but not in the black population (Table 2 and Figure 2). A similar inverse correlation existed between educa-
Table 1. Study Population Black Age group
White
Men
Women
Men
Women 13
15-19
17
31
14
20-29
19
19
21
18
30-39
23
17
16
22
40-49
19
15
23
15
50-59
7
7
18
13
60-69
14
21
16
18
> 70
13
24
11
21
112
134
119
120
72
67
35
33
Total Infected
(%)
OF HELZCOBACTER I’Y’LOHI INFECTION
1497
tional level and H. pylori infection; those with the highest education showed the lowest rate of infection (P < 0.05; Figure 3). This association was significant among both blacks (P < 0.04) and whites (P < 0.02). The possible associations of alcohol consumption, NSAID or tobacco use, and pet ownership on the frequency of H. p_vlori infection was analyzed (Tables 2 and 3). There was no association between H. pylori infection and consumption of alcohol or NSAID use or with smoking. Having pets was associated with a lower frequency of H. pylori infection in both blacks and whites, although the association was significant only among blacks (P < 0.05) and was very highly associated with higher socioeconomic status for both races (P < 0.01). Discussion H. pylori is the most common cause of type B gastritis; current evidence suggests that the presence of antibody against H. pylori predicts the presence of gastritis. Similarly, the presence of gastritis can be used as an index of the frequency of H. pylori infection (10,17-22). Studies in Finland suggested that the rate of acquisition of type B gastritis is approximately 1% per year (21). In Western countries, the frequency of H. pylori infection is low in children and increases with age at approximately the same rate as it does in gastritis, i.e., 1%2%/yr (4,5,12,22). Our data are consistent with that observation; i.e., extrapolation of our data to the population of metropolitan Houston (65% white, 35% black) yields an increase of 1%/yr. H. pylori infections are present worldwide. Knowledge of epidemiology of H. pylori infection is rudimentary; many early reports emphasized H. pylori infection in patients presenting for endoscopy and thus provide little information about the frequency in the general population (5,7,12,13,23-26). Others have not been formal epidemiological studies but have relied on serum sample collections obtained from uncharacterized populations and have unknown selection biases (2,4,5,8,10,11,13,26). Data obtained from blood donors are particularly difficult to interpret, because the pattern and reasons for giving blood vary widely from country to country; also, these difficulties are compounded by the problem of acquired immunodeficiency syndrome (AIDS), which has led to marked restrictions on who can, and who will, donate blood. Recent U.S. epidemiology studies have contained only a very small number of H. pyloriinfected individuals, making it difficult to evaluate possible associations (927-29). The purpose of our present study was to begin to define the epidemiology of H. pylori infection in the United States and to identify parameters that affect its
1498
GRAHAM
GASTROENTEROLOGY
ET AL.
Vol. 100, No. 6
Table 2. Results of Logistic Regression Analysis Total population P
F
P
P
F
P
0.446 -0.015
45.8 0.00
0.001 0.951
0.397 -0.020
19.6 0.00
0.001 0.952
-1.650
40.7
0.001
-0.360 -0.008 0.158 0.156 -0.618
10.6 0.82 1.27 0.78 6.86
0.001 0.366 0.260 0.378 0.009
-0.346 -0.153 0.213 0.156 -0.683
4.27 1.12 1.17 0.34 4.07
0.039 0.291 0.279 0.558 0.044
0.413
1.29
0.256
0.094
0.03
0.857
Factor Age Gender 1 = male 2 = female Race I = black 2 = white Education Income Smoking Alcohol use Having pets 1 = yes 2 = no Taking pain or arthritis tion B, population
regression
White
Black
F
P
0.526 0.001
27.9 0.00
0.000 0.996
-0.383 -0.312 0.067 0.179 -0.547
5.73 4.80 0.10 0.52 2.45
0.016 0.028 0.749 0.472 0.117
0.621
1.57
0.210
P
medica-
coefficient.
prevalence. The large body of information concerning gastritis was a considerable help in recognizing factors that might influence the epidemiology of H. pylori infections. Consistent with previous studies, we observed that the prevalence of H. pylori infection increased with age. The prevalence of the infection was twice as great in blacks than in whites, and the racial difference remained after adjustment for age and socioeconomic
factors. The striking difference in the prevalence of H. infection was surprising. The mechanism for this difference is unknown, but we were able to confirm the observation and the lack of association with socioeconomic factors in a recent study in children in Little Rock, AR (30). In most instances the difference in prevalence between ethnic group or race represents a surrogate marker for differences in exposure(s), such as differences in standards of living or sanitation practices. Whether this apparent increase
pylori
(14). /\
(40)
‘e-e
‘C
2
80
(34) /
2
:
(32)
(;)&cks
.
60
(W
(37)
*
I
KU\ /
.-‘,
I
(31) ,.
01
0
0
1020304050607080
Income
be Figure 1. The prevalence of H. pykwi infection in the study population is shown according to race. The age ranges plotted are: 15-19,20-29,30-39,40-49,50-59,60-69, and > 70 years.
1020304050607080 (in 1000s)
Figure 2. The relationship between income and the prevalence of pylori infection is shown. H. pylori infection was inversely related to income in whites (A-A) but not in blacks (O-O).
H.
June 1991
EPIDEMIOLOGY
OF
HELZCOBAC7ERPYLORI INFECTION
100
(3
m
-0
EY
4
1499
Black
White
(n-07)
80
2
(n-26)
(n-W
.
t_
(n-51)
60
.L
-w
c 0
;
40
.e 3
Figure 3. An inverse correlation existed between educational level (reflected as years of school cornpleted) and H. pylori infection; those with the highest education showed the lowest rate of infection. This association was significant among both blacks (P < 0.04) and whites (P < 0.02).
n-96)
-cI &
20
2 a,
a
0 Primary
in susceptibility to H. pylori infection relates to subtle differences in exposure or to genetic factors remains unknown. The prevalence of H. pylori infection was inversely related to socioeconomic status defined either by level of education completed or by income. This is consistent with previous studies demonstrating that gastritis is more frequent in those who come from large families, are of low socioeconomic class, and live in crowded conditions and also demonstrating that gastritis varied with the ethnic population studied (3 1,32). The evolving epidemiology of H. pylon’ infection is very reminiscent of the epidemiology of poliomyelitis or hepatitis A, in which differences in prevalence were not based on geography but were related to standards and practices of hygiene and socioeconomic conditions (3 3-35). We found that ethanol, nicotine, and NSAID use
Table 3. Relationship of Helicobacter Different Parameters
pylori
Infection With
Black Parameter Alcohol use Do not use (1) Not weekly (2) Weekly (3) Smoking Never smoked (1) Ex-smokers (21 Smoker (3) Owned pets Do not own (1) Own f2)
No.
White
Positive
(%)
No.
Positive
122 88 32
70 66 78
110 36
37 27 47
122 41 a2
61 a5 73
122 50 65
25 48 40
158 86
74 60
116 116
42 23
90
(%)
12 yr
14yr
)16 yr
were not important factors, thus confirming previous studies on chronic gastritis (28,31,32). The isolation of H. pylori and the subsequent proof that it is the major cause of type B gastritis resulted in a reappraisal of many concepts in gastroenterology. Many disparate facts can now be linked through the common mechanism of a bacterial infection. Current data suggest that, once acquired, H. pylori infection is life-long. H. pylori has a predilection for the surface cells of the gastric mucosa (36); this seemingly rigid requirement for gastric mucosa suggests that the transmission is oral. Clustering of H. pylori occurs (37-40). The mode(s) of transmission is unknown. The disease is apparently spread by human association Available data suggest that direct contact and contamination of the immediate environment are both important. The geographic and social patterns of H. pylori infection are consistent with fecal-oral transmission as one important pathway; this is consistent with recent data from Lima, Peru, demonstrating a direct association between the prevalence of H. pylori infection and source of drinking water (41). One particularly striking recent finding is that motile spiral forms of H. pylori can survive for at least a week in river water (42). Coccoid forms of H. pylori can also survive in river water for a year or more, but the clinical relevance of that observation remains unclear (43). H. pylori has not yet been isolated from the environment, but the technology that can address this question is now available (e.g., complementary DNA probes). Iatrogenic transmission of H. pylori infection has been documented (44,45), and the high prevalence of H. pylori infection among endoscopists, particularly those who did not always use gloves,
1500
GRAHAM
ET AL.
suggests that H. pylon’ infection may also be spread from instruments contaminated with gastric secretions [gastric secretion/oral spread) (43,46). Finally, H. pylori has been recovered from dental plaque (47), and although this appears to be a rare phenomenon, it emphasizes that there may be many potential pathways for transmission. Humans and primates appear to be the primary hosts for H. pylori. Owning pets was associated with a lower frequency of H. pylori infection, but the association was thought to be secondary to owning pets, being a surrogate for higher socioeconomic status. A previous association of a higher rate of H. pylori infection among abattoir workers compared with office workers suggested that H. pylori might be a zoonosis but did not take the possible differences in socioeconomic factors into account (48). In approximately 8% of cases, the results of ELISA were positive and the UBT results were negative. Both tests were repeated after several months in 12 volunteers; in 8 the results did not change, in 2 the ELISA value decreased to negative (,v1oridis”)-clinical correlations
organism (“Campylobacter and distribution in the nor-
mal population. J Med Microbial 1986;22:57-62. 23. Gnarpe H, Unge P. Blomqvist C, Makitalo S. Compylobacter patients referred for gastroscopy. APMIS p_vh-i in Swedish 1988;96:128-132. 24. Hirsch1 A, Potzi R, Stanek G, Wende L, Rotter M, Gang1 A,
40.
41.
in patients Holzner JH. Occurrence of Compylobocterpyloridis from Vienna with gastritis and peptic ulcers. Infection 1986;14: 275-278. 25. Czunn SJ, Dahms BB, Jacobs GH, Kaplan B. Rothstein FH. Compylobacfer-like organisms in association with symptomatic gastritis in children. J Pediatr 1986;109:80-83. organ26. Jones DM, Lessells AM, Eldridge J. Compylobacter-like isms on the gastric mucosa: culture, histological, and serological studies. JClin Path01 1984;37:1002-1006. 27. Barthel JS, Westblom TU, Havey AD, Gonzalez Gastritis and Campylobacter pylori in healthy, volunteers. Arch Intern Med 1988;148:1149-1151.
F, Everett ED. asymptomatic
28. Dooley CP, Cohen H, Fitzgibbons PL, Bauer M, Appleman MD, Perez-Perez GI, Blaser MJ. Prevalence of Helicobocter pylori infection and histologic gastritis Engl J Med 1989;321:1562-1566.
in asymptomatic
persons.
N
29. Graham DY, Klein PD, Opekun AR, Boutton TW, Evans DG Jr, Evans DG, Albert LC, Michaletz PM, Yoshimura HH, Adam E. Epidemiology of Campylobacterpylori infection: ethnic considerations. Stand J Gastroenterol 1988;23(Suppl 142):9-13. CL, Casteel HB, 30 Fiedorek SC, Malaty HM, Evans DG, Pumphrey Evans DJ Jr, Graham DY. Factors influencing the epidemiology in children. Pediatrics (in of Helicobacter p_vlori infection press). 31 Edwards FC. Goghill NF. Aetiological factors in chronic atrophic gastritis. Br Med J 1966;2:1409-1415. 32
Massarrat S, Paidlik A, Pittner P, Schmitz-Moorman P, Wurbs M. The role of certain habits and various diseases in the occurrence of gastritis (abstr). Hepatogastroenterology 1983:30:
249. 33. Paul JR. Historical ogy of poliomyelitis. 34. Paul JR. Serological versus epidemicity.
and geographical aspects of the epidemiolYale J Biol Med 1954;27:101-113. surveys and antibody patterns. Endemicity In: A history of poliomyelitis. New Haven,
CT: Yale, 1971:357-368. 35. Dienstag JL, Szmuness W, Stevens CE, Purcell RH. Hepatitis A virus infection: new insights from seroepidemiologic studies. J Infect Dis 1978;137:328-340. curved bacilli on gastric epithelium in 36. Warren JR. Unidentified active chronic gastritis [letter]. Lancet 1983;2:1273-1275. study of the 37. Reiff A, Jacobs E, Kist M. Seroepidemiological immune response to Campylobocter pylori in potential risk groups. Eur J Clin Microbial Infect Dis 1989;8:592-596. GI, Blaser MJ, Sherman PM. Intrafamil38. Drumm B, Perez-Perez ial clustering of Helicobocter pylori infection. N Engl J Med 1990:322:359-363, to Campyloboc39. Jones DM, Eldridge J, Whorwell PJ. Antibodies
42.
43.
44.
45.
46.
47
48.
OF HELICOBACTER PZOZU INFECTION
1501
terpyloridis in household contacts of infected patients. Br Med J 1987;294:615. Mitchell HM, Bohane TD, Berkowitz J, Hazel1 SL, Lee A. Antibody to Campylobacterp_vlori in families of index children with gastrointestinal illness due to C. pylori. Lancet 1987;2:681682. Klein PD, The Gastrointestinal Physiology Working Group of Cayetano Heredia and The Johns Hopkins Universities, Graham DY, Opekun AR, Skeley S. Evans DC, Evans DJ Jr. High prevalence of Campylobocter pylori (CP) infection in poor and rich Peruvian children determined by “C urea breath test (“C-UBT) (abstr). Gastroenterology 1989;96:A260. Shahamat M, Vives-Rego J, Paszko-Kolva C, Pearson AD, Colwell RR. Survival of Campvlobacter pylori in river water: ‘H-thymidine uptake and viability under stimulated environmental conditions. Klin Wochenschr 1989;67:63. Shahamat M. Paszko-Kolva C, Yamamoto H, Mai U, Pearson AD, Colwell RR. Ecological studies of Camp,vlobocter p_vlori. Klin Wochenschr 1989;67:62-63. Graham DY, Alpert LC, Smith JL, Yoshimura HH. Iatrogenic Compylobacterpylori infection is a c:ause of epidemic achlorhydria. Am J Gastroenterol 1988;83:974-980. Langenberg W, Rauws EA. Oudbier JH. Tytgat GNJ. Patient-topatient transmission of Camp.vlobacter pylori infection by fiberoptic gastroduodenoscopy and biopsy. J Infect Dis 1990; 161:507-511. Mitchell HM, Lee A, Carrick J. Increased incidence of Campylobatter pylori infection in gastroenterologists: further evidence to support person-to-person transmission of C. {qdori. Stand J Gastroenterol 1989;24:396-400. Krajden S, Fuksa M, Anderson J. Kempston J. Boccia A, Petrea C, Babida C, Karmali M, Penner JL. Examination of human stomach biopsies, saliva, and dental plaque for Compylobacter p.vlori. J Clin Microbial 1989;27:1397-1398. Vira D, D’Anastasio CD, Holton J, Dowsett JF, Londei M, Bertoni F, Beltrandi E, Grauenfels P, Salmon PR, Gandolfi L. Compylobacter pylori in abattoir workers: is it a zoonosis. Lancet 1988;2:725-726.
Received July 19, 1990. Accepted October 28, 1990. Address requests for reprints to: David Y. Graham, M.D., Veterans Administration Medical Center (lllD), 2002 Holcombe Boulevard, Houston, Texas 77030. This work was supported by the Department of Veterans Affairs; grant DK 39919 from the National Institute of Diabetes and Digestive and Kidney Diseases; U.S. Department of Agriculture/ Agricultural Research Service Children’s Nutrition Research Center: Baylor College of Medicine General Clinical Research Center at The Methodist Hospital under grant RR-00350 from the Division of Research Services, National Institutes of Health; and the generous support of Hilda Schwartz. The investigators also acknowledge the help of Kathleen Smith, Marion Brown, Antone Opekun, Gloria Thompson, Valeria TapScott. and Sara Sekely.
ALIMENTARY
1991;100:1495-1501
TRACT
Epidemiology of Helicobacter PyIori in an Asymptomatic Population in the United States Effect of Age, Race, and Socioeconomic
Status
DAVID Y. GRAHAM, HODA M. MALATY, DOLORES G. EVANS, DOYLE J. EVANS, Jr., PETER D. KLEIN, and ERVIN ADAM Departments of Medicine and Pediatrics and Division of Molecular Virology, United States Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine: and Veterans Affairs Medical Center, Houston, Texas
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, hut 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 [‘“Cl 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 l%lyr for the overall population. The frequency of H. pylori infection was higher in blacks (70%) than whites (34%) (P < 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 hut 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 Socioeconomic factors seem to determine acquisition.
H
pathway. the age of
elicobacter
pylori is now accepted as the major cause of type B gastritis, and H. pylori gastritis is strongly associated with duodenal ulcer and gastric ulcer disease (1). There is a considerable body of information concerning gastritis, and studies specifically linking epidemiological data on H. pylori with older observations on gastritis are beginning to appear. These preliminary studies have reported that the prevalence of H. pylori infection increases with age (2-13), 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. Most studies reported to date have involved small numbers of subjects or have surveyed poorly characterized populations. As a result, specific correlations of H. pylori infection with epidemiological factors such as race or socioeconomic class have not been possible. The present study was designed to study [a) the prevalence of H. pylori infection in a defined asymptomatic population, (b) the age-distribution pattern of H. pylori infection, and (c) the possible relationships between H. pylori infection and factors such as race, gender, socioeconomic status, alcohol consumption,
Abbreviations usedin thispaper: ELISA, enzyme-linked immunosorbent assay; HM-CAP, high-molecular-weight, cell associated proteins; UBT, urea breath test. o 1991 by the American Gastroenterological Association 0016-5085/91/$3.00
GASTROENTEROLOGYVol. lOO,No.6
1496 GRAHAM ETAL.
of nonsteroidal antiinflammatory smoking, and ownership of pets.
use
drugs (NSAIDs),
Subjects and Methods Study Population Volunteers between the ages of 15 and 80 years were eligible for enrollment. Entry criteria were: both subjects and their parents were born in the United States: the enrollees planned to reside in the Houston metropolitan area for the next 4 years; and they considered themselves to be in good health and denied symptoms referable to the upper gastrointestinal tract. Each potential volunteer completed a self-administered screening questionnaire, and the results were reviewed by a trained interviewer. In addition to demographic information, the instrument asked the volunteers: (a) did they consider themselves to be in good health; (b) had they had any serious illness or surgery in the past 2 months; (c) had they ever had gastric surgery or a peptic ulcer, or had anyone in their immediate family had a peptic ulcer; and (d) did they have arthritis and if yes, what medication were they taking and for how long? Each individual was questioned about the presence and the frequency of symptoms referable to the upper gastrointestinal tract, including indigestion, heartburn, sour stomach, nausea/vomiting, and burning pain in the stomach area and/or in the chest. In addition, enrollees were questioned about the use of any medications during the preceding 2 months, specifically antibiotics, bismuth-containing compounds, or NSAIDs. All enrollees were also questioned about smoking and alcohol use and whether they kept pets at home. Subjects were excluded if they had a history of peptic ulcer, frequent (defined as occurring more than once a month) symptoms referable to the upper gastrointestinal tract, or if they used antacids or antibiotics regularly. Demographic information was obtained directly from each participant through the self-administered questionnaire and included race, age, gender, weight, height, marital status, highest educational level, place of birth, occupation, and family income.
Methods of Enrollment The primary method of recruitment was by advertisement in local and public newspapers and by flyers placed in the various facilities in the Texas Medical Center Houston, TX. Teenagers aged 15-18 years were recruited from schools through contacts with the school’s principal and nurse. Short explanatory talks were given to the children, and letters were sent to the parents explaining the aims of the project, the breath test procedure, and the procedure of blood drawing. Many elderly subjects were recruited from senior citizens’ homes and churches. Elderly subjects were required to maintain an active lifestyle. No more than eight individuals were accepted from any one school, senior citizens’ home, or church. The study was approved by the Institutional Review Board for the VA Medical Center, Baylor College of Medicine, The Methodist Hospital, and the Clinical Research Center. A consent form was signed by each individual
before participating in the study. Both the subjects under 18 years of age and their parents certified their assent by their signatures before participating in the study. A serum sample was obtained from each subject for evaluation of immunoglobulin G (IgG) antibody to the high-molecular-weight, cell-associated proteins (HM-CAP) of H. pylori (14); the sera were stored at -70” C. A ‘C-urea breath test (UBT) was also done to assess whether urease activity was present in the stomach (15,161.
Enzyme-finked
Anti-Helicobacter
lmmunosorbent Assay for pylori Zmmunoglobulin G
Specific details of the procedure are published elsewhere (14); the high-molecular-weight, cell-associated antigen preparation contains at least two proteins in the molecular-weight range of 400,000-700,000. The enzymelinked immunosorbent assay (ELISA) was done in 96-well Microtiter plates (Linbro, Scientific Co., Hamden, CT] coated with HM-CAP diluted with phosphate-buffered saline (PBS) to approximately 7 t.&mL. Sera diluted 1:50 and 1:lOO were added, and alkaline phosphatase-conjugated anti-human IgG (Southern Biotechnology, Birmingham, AL) was used as the detector. Each plate included HM-CAP ELISA-positive and -negative control sera. The test was scored positive for OD value ~0.20.The specificity and positive predictive value of the HM-CAP ELISA were each previously shown to be 100%; the sensitivity is 98.70/o, and the negative predictive value 98.6% (16). There is no cross-reactivity with Campylobacter jejuni.
Urea Breath Test The [“Cl-UBT exploits the existence of a target bond linking the [‘C]-labeled portion to the rest of the molecule. Scission of this bond by a specific enzyme results in the rapid formation of ‘“CO, and can be detected in respiratory CO,. In this instance, the high local concentration of H. pylori urease in the stomach acting on the [‘Qurea results in readily measurable increases in respiratory [‘“C] within 20 minutes of substrate administration. This action can be distinguished from that of colonic bacteria by the rapidity and extent of urea hydrolysis in H. pylori-infected individuals. The urea breath test result was positive if the urease activity was 2 0.500kmol kg-’ h-‘; the test duration was 1 hour.
Analyses H. pylori infection was defined as a positive ELISA test result. The data were analyzed by logistic regression and x2 using the SAS program (SAS Institute, Cary, NC]. We categorized subjects into seven age groups. The MantelHaenszel x2 analysis was used to examine relationships between H. pylori infection and age, gender, race, socioeconomic level, educational level, smoking, alcohol consumption, keeping pets, and use of NSAIDs. Logistic regression was used to evaluate the association of each independent variable of the study on the frequency of H. pylori infection with adjustment for the other variables. The analyses were done on the whole population and for each race separately.
June
1991
EPIDEMIOLOGY
Results
We enrolled 490 healthy asymptomatic volunteers residing in the Houston metropolitan area. In 441 of the enrollees, the results of both the ELISA and the UBT were concordant; in 44 the results of ELISA were positive and the UBT results negative. Five individuals had a positive UBT and a negative ELISA result and were excluded. The discordant findings were randomly spread, and inclusion or exclusion of those with discordant findings would not change any of the results obtained. H. pylori infection was present in 253 subjects or 52% of the population studied (Table 1). The subjects ranged in age from 15 to 80 years. The black population represented 35% of the total population in the geographic area. To compare the frequency of H. pylori infection between races, a similar number of persons from each of the two racial groups were enrolled. The male-female ratio was similar (1:0.84 and 1:0.99 for whites and blacks, respectively). Table 2 presents the results of logistic regression analysis with H. pylori infection as the dependent variable. The overall frequency of H. pylori infection was higher in blacks (70%) than whites (34%) (P < 0.001; Figure 1). The frequency of H. pylori infection among blacks remained greater than among whites after adjustment for all parameters evaluated (e.g., age, gender, educational level, and income). The frequency of H. pylori infection in men and women was similar when controlled for race and age (Table 1; P > 0.5). Thus, the data are presented (except where noted) according to race, with gender merged. Associations Between Study Variables and Helicobacter pylori Infection
There was a significant inverse correlation between age-adjusted frequency of H. pylori infection and income in the white population (P < 0.001) but not in the black population (Table 2 and Figure 2). A similar inverse correlation existed between educa-
Table 1. Study Population Black Age group
White
Men
Women
Men
Women 13
15-19
17
31
14
20-29
19
19
21
18
30-39
23
17
16
22
40-49
19
15
23
15
50-59
7
7
18
13
60-69
14
21
16
18
> 70
13
24
11
21
112
134
119
120
72
67
35
33
Total Infected
(%)
OF HELZCOBACTER I’Y’LOHI INFECTION
1497
tional level and H. pylori infection; those with the highest education showed the lowest rate of infection (P < 0.05; Figure 3). This association was significant among both blacks (P < 0.04) and whites (P < 0.02). The possible associations of alcohol consumption, NSAID or tobacco use, and pet ownership on the frequency of H. p_vlori infection was analyzed (Tables 2 and 3). There was no association between H. pylori infection and consumption of alcohol or NSAID use or with smoking. Having pets was associated with a lower frequency of H. pylori infection in both blacks and whites, although the association was significant only among blacks (P < 0.05) and was very highly associated with higher socioeconomic status for both races (P < 0.01). Discussion H. pylori is the most common cause of type B gastritis; current evidence suggests that the presence of antibody against H. pylori predicts the presence of gastritis. Similarly, the presence of gastritis can be used as an index of the frequency of H. pylori infection (10,17-22). Studies in Finland suggested that the rate of acquisition of type B gastritis is approximately 1% per year (21). In Western countries, the frequency of H. pylori infection is low in children and increases with age at approximately the same rate as it does in gastritis, i.e., 1%2%/yr (4,5,12,22). Our data are consistent with that observation; i.e., extrapolation of our data to the population of metropolitan Houston (65% white, 35% black) yields an increase of 1%/yr. H. pylori infections are present worldwide. Knowledge of epidemiology of H. pylori infection is rudimentary; many early reports emphasized H. pylori infection in patients presenting for endoscopy and thus provide little information about the frequency in the general population (5,7,12,13,23-26). Others have not been formal epidemiological studies but have relied on serum sample collections obtained from uncharacterized populations and have unknown selection biases (2,4,5,8,10,11,13,26). Data obtained from blood donors are particularly difficult to interpret, because the pattern and reasons for giving blood vary widely from country to country; also, these difficulties are compounded by the problem of acquired immunodeficiency syndrome (AIDS), which has led to marked restrictions on who can, and who will, donate blood. Recent U.S. epidemiology studies have contained only a very small number of H. pyloriinfected individuals, making it difficult to evaluate possible associations (927-29). The purpose of our present study was to begin to define the epidemiology of H. pylori infection in the United States and to identify parameters that affect its
1498
GRAHAM
GASTROENTEROLOGY
ET AL.
Vol. 100, No. 6
Table 2. Results of Logistic Regression Analysis Total population P
F
P
P
F
P
0.446 -0.015
45.8 0.00
0.001 0.951
0.397 -0.020
19.6 0.00
0.001 0.952
-1.650
40.7
0.001
-0.360 -0.008 0.158 0.156 -0.618
10.6 0.82 1.27 0.78 6.86
0.001 0.366 0.260 0.378 0.009
-0.346 -0.153 0.213 0.156 -0.683
4.27 1.12 1.17 0.34 4.07
0.039 0.291 0.279 0.558 0.044
0.413
1.29
0.256
0.094
0.03
0.857
Factor Age Gender 1 = male 2 = female Race I = black 2 = white Education Income Smoking Alcohol use Having pets 1 = yes 2 = no Taking pain or arthritis tion B, population
regression
White
Black
F
P
0.526 0.001
27.9 0.00
0.000 0.996
-0.383 -0.312 0.067 0.179 -0.547
5.73 4.80 0.10 0.52 2.45
0.016 0.028 0.749 0.472 0.117
0.621
1.57
0.210
P
medica-
coefficient.
prevalence. The large body of information concerning gastritis was a considerable help in recognizing factors that might influence the epidemiology of H. pylori infections. Consistent with previous studies, we observed that the prevalence of H. pylori infection increased with age. The prevalence of the infection was twice as great in blacks than in whites, and the racial difference remained after adjustment for age and socioeconomic
factors. The striking difference in the prevalence of H. infection was surprising. The mechanism for this difference is unknown, but we were able to confirm the observation and the lack of association with socioeconomic factors in a recent study in children in Little Rock, AR (30). In most instances the difference in prevalence between ethnic group or race represents a surrogate marker for differences in exposure(s), such as differences in standards of living or sanitation practices. Whether this apparent increase
pylori
(14). /\
(40)
‘e-e
‘C
2
80
(34) /
2
:
(32)
(;)&cks
.
60
(W
(37)
*
I
KU\ /
.-‘,
I
(31) ,.
01
0
0
1020304050607080
Income
be Figure 1. The prevalence of H. pykwi infection in the study population is shown according to race. The age ranges plotted are: 15-19,20-29,30-39,40-49,50-59,60-69, and > 70 years.
1020304050607080 (in 1000s)
Figure 2. The relationship between income and the prevalence of pylori infection is shown. H. pylori infection was inversely related to income in whites (A-A) but not in blacks (O-O).
H.
June 1991
EPIDEMIOLOGY
OF
HELZCOBAC7ERPYLORI INFECTION
100
(3
m
-0
EY
4
1499
Black
White
(n-07)
80
2
(n-26)
(n-W
.
t_
(n-51)
60
.L
-w
c 0
;
40
.e 3
Figure 3. An inverse correlation existed between educational level (reflected as years of school cornpleted) and H. pylori infection; those with the highest education showed the lowest rate of infection. This association was significant among both blacks (P < 0.04) and whites (P < 0.02).
n-96)
-cI &
20
2 a,
a
0 Primary
in susceptibility to H. pylori infection relates to subtle differences in exposure or to genetic factors remains unknown. The prevalence of H. pylori infection was inversely related to socioeconomic status defined either by level of education completed or by income. This is consistent with previous studies demonstrating that gastritis is more frequent in those who come from large families, are of low socioeconomic class, and live in crowded conditions and also demonstrating that gastritis varied with the ethnic population studied (3 1,32). The evolving epidemiology of H. pylon’ infection is very reminiscent of the epidemiology of poliomyelitis or hepatitis A, in which differences in prevalence were not based on geography but were related to standards and practices of hygiene and socioeconomic conditions (3 3-35). We found that ethanol, nicotine, and NSAID use
Table 3. Relationship of Helicobacter Different Parameters
pylori
Infection With
Black Parameter Alcohol use Do not use (1) Not weekly (2) Weekly (3) Smoking Never smoked (1) Ex-smokers (21 Smoker (3) Owned pets Do not own (1) Own f2)
No.
White
Positive
(%)
No.
Positive
122 88 32
70 66 78
110 36
37 27 47
122 41 a2
61 a5 73
122 50 65
25 48 40
158 86
74 60
116 116
42 23
90
(%)
12 yr
14yr
)16 yr
were not important factors, thus confirming previous studies on chronic gastritis (28,31,32). The isolation of H. pylori and the subsequent proof that it is the major cause of type B gastritis resulted in a reappraisal of many concepts in gastroenterology. Many disparate facts can now be linked through the common mechanism of a bacterial infection. Current data suggest that, once acquired, H. pylori infection is life-long. H. pylori has a predilection for the surface cells of the gastric mucosa (36); this seemingly rigid requirement for gastric mucosa suggests that the transmission is oral. Clustering of H. pylori occurs (37-40). The mode(s) of transmission is unknown. The disease is apparently spread by human association Available data suggest that direct contact and contamination of the immediate environment are both important. The geographic and social patterns of H. pylori infection are consistent with fecal-oral transmission as one important pathway; this is consistent with recent data from Lima, Peru, demonstrating a direct association between the prevalence of H. pylori infection and source of drinking water (41). One particularly striking recent finding is that motile spiral forms of H. pylori can survive for at least a week in river water (42). Coccoid forms of H. pylori can also survive in river water for a year or more, but the clinical relevance of that observation remains unclear (43). H. pylori has not yet been isolated from the environment, but the technology that can address this question is now available (e.g., complementary DNA probes). Iatrogenic transmission of H. pylori infection has been documented (44,45), and the high prevalence of H. pylori infection among endoscopists, particularly those who did not always use gloves,
1500
GRAHAM
ET AL.
suggests that H. pylon’ infection may also be spread from instruments contaminated with gastric secretions [gastric secretion/oral spread) (43,46). Finally, H. pylori has been recovered from dental plaque (47), and although this appears to be a rare phenomenon, it emphasizes that there may be many potential pathways for transmission. Humans and primates appear to be the primary hosts for H. pylori. Owning pets was associated with a lower frequency of H. pylori infection, but the association was thought to be secondary to owning pets, being a surrogate for higher socioeconomic status. A previous association of a higher rate of H. pylori infection among abattoir workers compared with office workers suggested that H. pylori might be a zoonosis but did not take the possible differences in socioeconomic factors into account (48). In approximately 8% of cases, the results of ELISA were positive and the UBT results were negative. Both tests were repeated after several months in 12 volunteers; in 8 the results did not change, in 2 the ELISA value decreased to negative (,v1oridis”)-clinical correlations
organism (“Campylobacter and distribution in the nor-
mal population. J Med Microbial 1986;22:57-62. 23. Gnarpe H, Unge P. Blomqvist C, Makitalo S. Compylobacter patients referred for gastroscopy. APMIS p_vh-i in Swedish 1988;96:128-132. 24. Hirsch1 A, Potzi R, Stanek G, Wende L, Rotter M, Gang1 A,
40.
41.
in patients Holzner JH. Occurrence of Compylobocterpyloridis from Vienna with gastritis and peptic ulcers. Infection 1986;14: 275-278. 25. Czunn SJ, Dahms BB, Jacobs GH, Kaplan B. Rothstein FH. Compylobacfer-like organisms in association with symptomatic gastritis in children. J Pediatr 1986;109:80-83. organ26. Jones DM, Lessells AM, Eldridge J. Compylobacter-like isms on the gastric mucosa: culture, histological, and serological studies. JClin Path01 1984;37:1002-1006. 27. Barthel JS, Westblom TU, Havey AD, Gonzalez Gastritis and Campylobacter pylori in healthy, volunteers. Arch Intern Med 1988;148:1149-1151.
F, Everett ED. asymptomatic
28. Dooley CP, Cohen H, Fitzgibbons PL, Bauer M, Appleman MD, Perez-Perez GI, Blaser MJ. Prevalence of Helicobocter pylori infection and histologic gastritis Engl J Med 1989;321:1562-1566.
in asymptomatic
persons.
N
29. Graham DY, Klein PD, Opekun AR, Boutton TW, Evans DG Jr, Evans DG, Albert LC, Michaletz PM, Yoshimura HH, Adam E. Epidemiology of Campylobacterpylori infection: ethnic considerations. Stand J Gastroenterol 1988;23(Suppl 142):9-13. CL, Casteel HB, 30 Fiedorek SC, Malaty HM, Evans DG, Pumphrey Evans DJ Jr, Graham DY. Factors influencing the epidemiology in children. Pediatrics (in of Helicobacter p_vlori infection press). 31 Edwards FC. Goghill NF. Aetiological factors in chronic atrophic gastritis. Br Med J 1966;2:1409-1415. 32
Massarrat S, Paidlik A, Pittner P, Schmitz-Moorman P, Wurbs M. The role of certain habits and various diseases in the occurrence of gastritis (abstr). Hepatogastroenterology 1983:30:
249. 33. Paul JR. Historical ogy of poliomyelitis. 34. Paul JR. Serological versus epidemicity.
and geographical aspects of the epidemiolYale J Biol Med 1954;27:101-113. surveys and antibody patterns. Endemicity In: A history of poliomyelitis. New Haven,
CT: Yale, 1971:357-368. 35. Dienstag JL, Szmuness W, Stevens CE, Purcell RH. Hepatitis A virus infection: new insights from seroepidemiologic studies. J Infect Dis 1978;137:328-340. curved bacilli on gastric epithelium in 36. Warren JR. Unidentified active chronic gastritis [letter]. Lancet 1983;2:1273-1275. study of the 37. Reiff A, Jacobs E, Kist M. Seroepidemiological immune response to Campylobocter pylori in potential risk groups. Eur J Clin Microbial Infect Dis 1989;8:592-596. GI, Blaser MJ, Sherman PM. Intrafamil38. Drumm B, Perez-Perez ial clustering of Helicobocter pylori infection. N Engl J Med 1990:322:359-363, to Campyloboc39. Jones DM, Eldridge J, Whorwell PJ. Antibodies
42.
43.
44.
45.
46.
47
48.
OF HELICOBACTER PZOZU INFECTION
1501
terpyloridis in household contacts of infected patients. Br Med J 1987;294:615. Mitchell HM, Bohane TD, Berkowitz J, Hazel1 SL, Lee A. Antibody to Campylobacterp_vlori in families of index children with gastrointestinal illness due to C. pylori. Lancet 1987;2:681682. Klein PD, The Gastrointestinal Physiology Working Group of Cayetano Heredia and The Johns Hopkins Universities, Graham DY, Opekun AR, Skeley S. Evans DC, Evans DJ Jr. High prevalence of Campylobocter pylori (CP) infection in poor and rich Peruvian children determined by “C urea breath test (“C-UBT) (abstr). Gastroenterology 1989;96:A260. Shahamat M, Vives-Rego J, Paszko-Kolva C, Pearson AD, Colwell RR. Survival of Campvlobacter pylori in river water: ‘H-thymidine uptake and viability under stimulated environmental conditions. Klin Wochenschr 1989;67:63. Shahamat M. Paszko-Kolva C, Yamamoto H, Mai U, Pearson AD, Colwell RR. Ecological studies of Camp,vlobocter p_vlori. Klin Wochenschr 1989;67:62-63. Graham DY, Alpert LC, Smith JL, Yoshimura HH. Iatrogenic Compylobacterpylori infection is a c:ause of epidemic achlorhydria. Am J Gastroenterol 1988;83:974-980. Langenberg W, Rauws EA. Oudbier JH. Tytgat GNJ. Patient-topatient transmission of Camp.vlobacter pylori infection by fiberoptic gastroduodenoscopy and biopsy. J Infect Dis 1990; 161:507-511. Mitchell HM, Lee A, Carrick J. Increased incidence of Campylobatter pylori infection in gastroenterologists: further evidence to support person-to-person transmission of C. {qdori. Stand J Gastroenterol 1989;24:396-400. Krajden S, Fuksa M, Anderson J. Kempston J. Boccia A, Petrea C, Babida C, Karmali M, Penner JL. Examination of human stomach biopsies, saliva, and dental plaque for Compylobacter p.vlori. J Clin Microbial 1989;27:1397-1398. Vira D, D’Anastasio CD, Holton J, Dowsett JF, Londei M, Bertoni F, Beltrandi E, Grauenfels P, Salmon PR, Gandolfi L. Compylobacter pylori in abattoir workers: is it a zoonosis. Lancet 1988;2:725-726.
Received July 19, 1990. Accepted October 28, 1990. Address requests for reprints to: David Y. Graham, M.D., Veterans Administration Medical Center (lllD), 2002 Holcombe Boulevard, Houston, Texas 77030. This work was supported by the Department of Veterans Affairs; grant DK 39919 from the National Institute of Diabetes and Digestive and Kidney Diseases; U.S. Department of Agriculture/ Agricultural Research Service Children’s Nutrition Research Center: Baylor College of Medicine General Clinical Research Center at The Methodist Hospital under grant RR-00350 from the Division of Research Services, National Institutes of Health; and the generous support of Hilda Schwartz. The investigators also acknowledge the help of Kathleen Smith, Marion Brown, Antone Opekun, Gloria Thompson, Valeria TapScott. and Sara Sekely.
