Helicobacter Pylori Seroprevalence in Low Income Women and Children in El Paso

 

 

Flor Puentes

 

Supervised and directed by

Thomas Redlinger, PhD

 

Bridges to the Future

University of Texas at El Paso

 

18 December 1998

 

Introduction

            The objective of the research study was to determine Helicobacter pylori seroprevalence in low socioeconomic status women and their children in El Paso, Texas.  The manner in which H pylori is transmitted is poorly understood and is currently being investigated in both this country and around the world.  In the United States, H. pylori has been found to be more prevalent among lower socioeconomic groups (CDC).  It has also been shown that H. pylori is acquired early in life (Fricker).  Helicobacter pylori has been widely accepted as the cause of many gastric problems, such as gastritis, peptic ulcers and duodenal ulcers (Blaser; CDC).  It is estimated that one third to one half of the world's population harbors H. pylori (Blaser).

 

            The Australian pathologists Robin Warren and Barry Marshall discovered H. pylori, a gram-negative, spiral-shaped, and flagellated bacteria in 1979 (Micromedex).  H. pylori is able to survive in the high acidity of the stomach because it places itself between the gastric epithelial cells and their mucus coating (Blaser).  This bacteria produces a microenvironment around itself by secreting the enzyme urease that breaks down urea to CO2 and ammonia.  Ammonia then acts as a base to neutralize some of the stomach acid in their locale (Blaser). 

 

Materials and Methods

The study was conducted at two sites: (a) one at a Women Infant and Children (WIC) clinic in the lower valley of El Paso, Texas; and (2) one at the Instituto Mexicano del Seguro Social (IMSS) located in Cd. Juarez, Chih.  The (WIC) clinic offers services to predominantly low-income women and their children; the IMSS hospital provides free medical services to employees and their families who are employed.  Participants in the study included pregnant women in their third trimester and their children under 5 years of age.  H. pylori seroprevalence was determined by analyzing blood serum samples, obtained from participants at the clinic/hospital during the time period 5/98-12/98.  Blood was drawn by the finger stick method. 

            Blood was processed by centrifugation at 5,000rpm for 3 min and the clear supernatant removed to a clean tube.  All tubes were labeled and serum samples were refrigerated or frozen until analyzed for antibodies to H pylori.  The serum was transported and tested in a research laboratory at UTEP.  H. pylori total antibodies were determined in the samples using the EIA (Enzyme Immunoassay) produced by Enteric Products, New York.  The assay consists of pipeting 5ul of serum into a precoated microtiter plate containing the H pylori antigen and incubating for 20 min at 20C.  The microtiter wells are washed 3 times with wash buffer (0.1% ProClin300,).  The antibody/antigen reaction is determined using a conjugated second antibody containing the reporter enzyme peroxidase.  A total of 100ul of conjugate is added to each well and incubated for 20 min at 20C.  After washing again 3 times, the substrate is added and allowed to incubate for 10 min at 20C.  The reaction is terminated by adding 100ul 1N H2SO4 to each well and color intensity is measured by a plate reader at 450nm.

 

            Calculations of results of EIA are determined using cutoff values based on standard calibrator values of standards.  Absorbance readings are converted into ELISA values using a best-fit linear regression program.  ELISA values >2.2 were considered H. pylori positive and <1.8 negative.  Those values between 2.2 and 1.8 are indeterminate and for purposes of this study are considered negative. 

 

Results and Discussion

            A total of 617 subjects participated in the study, 306 from El Paso and 311 from Juarez.  Study participants were grouped into categories according to whether they were mothers or children.  A total of 91children in El Paso and 67 in Juarez plus 214 mothers in El Paso and 235 in Juarez were enrolled in the study.  Refusal rate for participation was 19%.

 

            Results of the EIA (Table 1) revealed that children in Juarez had a higher H pylori seropositivity (11.9%) compared to those in El Paso (8.8%).  This indicated that Juarez children were exposed to H. pylori at a younger age than children in El Paso were.  This result is not statistically significant due to the small number of children tested.  In addition, EIA results for mothers indicated that women in Juarez were significantly more likely to be seropositive than women in El Paso (74.5% and 50%, respectively).  This result was statistically significant. 


Table 1.  Percent of children and mothers with antibodies to H. pylori by place of residence. 

 

 

El Paso (%)

Cd. Juarez (%)

Relative Risk

p-value

 

Children

8.8         

11.9

1.36

0.520

 

Mothers

50.0

74.5

1.49

<0.001

 

Figures 1 and 2 show graphically the number of study participants who were H pylori negative and positive by children and mother categories.  In general, the number of children who participated in the study was low, especially in Juarez.  This situation, however, is not final as we

Figure 1.  Number of children and mothers with antibodies to H. pylori in El Paso, Texas.  Category 1 is positive and negative children; category 2 is positive and negative mothers.

 

 

We are continuing to analyze samples from both El Paso and Juarez.  On the other hand, in El Paso, mothers bring their children to register them in the WIC program when they come for certification.

Figure 2.  Number of children and mothers with antibodies to H. pylori in Cd. Juarez, Chih. Category 1 is positive and negative children; category 2 is positive and negative mothers.

   

Figure 3.  Comparison of H. pylori seroprevalence for mothers between study areas and the national US average for ages 20-40 years.

 

             H. pylori seroprevalence in El Paso was greater than the US average (50% and 22%, respectively); however, rates were much higher for Mexican nationals with 75% of childbearing aged women H. pylori positive.

 

References

 

Blaser, M. "The bacteria behind ulcers." Scientific American.  Feb (1996): 104-107.

 

CDC.  "H pylori."  CDC, 1998.

 

Fricker, J. "Helicobacter infection in common in US children." Lancet 348.9037 (1996): 1301-2.

 

Micromedex.  "Disease and trauma monographs for acute care."  vol. 97, Micromedex Inc, 1998, 1998.

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