Bacteriology
Enzyme immunoassay and immunoblotting analysis of Helicobacter pylori infection in Turkish asymptomatic subjects

https://doi.org/10.1016/j.diagmicrobio.2004.07.005Get rights and content

Abstract

Approximately half of the world population is infected with Helicobacter pylori, particularly in developing countries. The aims of the study were to detect H. pylori infection in asymptomatic Turkish subjects, correlate the infection with the associated risk factors, and to evaluate the cytotoxin-associated gene (CagA) status and other H. pylori antigens. Three hundred nine asymptomatic subjects (124 female) 1–82 years of age (average: 31 years) were serologically tested by enzyme immunoassay and immunoblotting. The enzyme immunoassay detected IgG anti–H. pylori antibodies in sera of 216 (70%) out of 309 subjects, 132 (61%) male. Infection rates of 42% in subjects <10 years of age, 55% in 10–19 years, 66% in 20–29 years, 78% in 30–39 years, 79% in 40–49 years, 91% in 50–59 years, 100% in 60–69 years, and 80% in those >70 years of age were detected. Subjects >45 years of age had significantly higher antibody responses, odds ratio = 0.16 (95% confidence interval: 0.07–0.37), than those <45 years. H. pylori infection was significantly higher in married subjects, odds ratio = 0.38 (95% confidence interval: 0.20–0.73), and those with low socioeconomic status. No correlation between gender, education, smoking, and nonsteroidal anti-inflammatory drug intake and infection was detected. Immunoblots revealed antibodies to CagA in 58 (83%) of 70 samples tested. H. pylori infection is prevalent in the asymptomatic Turkish subjects. Marital and socioeconomic status was significantly associated with the acquisition of H. pylori. Antibodies to CagA antigen were highly prevalent in these subjects.

Introduction

Infection with Helicobacter pylori is prevalent worldwide. Reports from developing countries indicate higher infection rates than those from developed countries. The pattern of infection in developing countries is an early childhood infection that reaches over 90% during adulthood (Megraud, 1992, Bardhan, 1997), whereas infection in developed countries is less common in young children and reaches 60% in higher age groups (Axon, 1996, Go, 2002, Frenck and Clemens, 2003), suggesting rapidly improving socioeconomic conditions. Recently, Frenck and Clemens (2003) reported a 20% infection rate among adolescents in the United States in comparison to rates exceeding 90% by 5 years of age in parts of the developing world. Although the World Health Organization estimates indicate that approximately 50% of the world populations are infected with H. pylori, the majority of infected subjects develop no clinical symptoms or peptic ulceration and continue their life with superficial chronic gastritis (Hunt, 1996, Blaser, 1997, Rothenbacher and Brenner, 2003). Several factors are involved in the pathogenesis of peptic ulcer diseases; among these are the expression of the putative virulence markers, the cytotoxin-associated gene (cagA), and the vacuolating cytotoxin gene (vacA), which are shown to have a significant association with the disease (Ching et al., 1996).

The detection of H. pylori infection has been performed using either biopsy-based tests (Campylobacter-like organisms, culture, histology) and/or non–biopsy-based tests (serology, urea breath test) (Hunt, 1996). Among several serological tests, the ELISA test is widely used for the detection of H. pylori antibodies in epidemiological and post-treatment studies (Megraud, 1996, The EUROGAST Study Group, 1993, Laheij et al., 1998). Immunoblotting is another sensitive serologic test that enables the detection of antibodies against specified H. pylori antigens, such as CagA and VacA antigens (Nilsson et al., 1997, Rocha et al., 2000).

In Turkey, no detailed study is being reported. In one earlier report, it was shown that 53% of the subjects tested were seropositive for H. pylori, and more than 30% acquired the infection before age 13 (Us and Hascelik, 1998).

Because of limited data on the epidemiology of H. pylori and its associated risk factors in Turkey, our objectives were to serologically analyze H. pylori infection in asymptomatic Turkish subjects by the ELISA test, correlate infection with age, gender, education, socioeconomic and marital status, smoking, and nonsteroidal anti-inflammatory drug intake, and to evaluate the CagA status and other H. pylori antigens by immunoblotting.

Section snippets

Subjects

Three hundred nine apparently healthy asymptomatic Turkish subjects with no complaints of upper abdominal pain and no medication for the last three months were enrolled. They were a group of university students and staff members, blood donors, businessmen, nursery homers, housewives, nurses, laborers, school children, preschoolers, and infants. The age range of the subjects was 1–82 years (average: 31 years); the subjects were grouped into eight different age groups, as depicted in Fig. 1. One

Results

The IgG anti–H. pylori antibodies were detected by the ELISA test in 216 (70%) of the total of 309 asymptomatic subjects tested. Of these, 132 (61%) were male, and 84 (39%) were female. The H. pylori infection rates in these subjects were shown according to their age group (Table 1).

Subjects over 45 years of age had significantly higher antibody response to H. pylori (odds ratio = 0.16 [95% confidence interval: 0.07–0.37]) than those less than 45 years of age (p < 0.05) (Table 2). Anti–H.

Discussion

The overall H. pylori infection rate of 70% detected in our subjects appeared to be similar to our findings (76%) in a study conducted previously on Libyan asymptomatic subjects (Bakka and Salih, 2002) and to reports from Saudi Arabia and India (70%, 79%), respectively (Al-Moagel et al., 1990, Graham et al., 1991). Acquisition of infection appears obviously as an early infection during childhood with transmission modes of oral–oral and fecal–oral routes being described (Rothenbacher et al., 1999

Acknowledgements

The authors would like to thank Ms. Serap Findik and Ms. Rahsan Sahin for their technical assistance.

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