Extra Credit, H. Pylori

Topics: Immune system, Helicobacter pylori, Gastritis Pages: 9 (2647 words) Published: December 3, 2006
Gastroenteritis and Transmission of Helicobacter pylori Infection in households

Sharon Perry, Maria de la Luz Sanchez, Shufang Yang, Thomas D. Haggerty, Phillip Hurst, Guillermo Perez-Perez, and Julie Parsonnet Stanford University School of Medicine, Stanford, California, USA; Santa Clara County Health and Hospital Systems, San Jose, California, USA; and New York University of Medicine, New York, New York, USA

The mode of transmission of Helicobacter pylori infection is not yet defined. In Northern California, 2,752 people-household members were tested for H. pylori infection in serum or stool. They were tested at a baseline visit and again three months later at a follow-up visit. At baseline visit 1,752 persons were diagnosed negative; at the follow-up visit, there were 30 new incidences of infection. Children age two and above accounted for 21% of these incidences. Exposure to an infected household member was associated with a 4.8-fold increased risk for definite or probable new infection. It was noted that if the infected household member had vomiting as a symptom the incidence of exposure increased as compared to members who have diarrhea only.

Helicobacter pylori infects at least 50% of the world's population. Infection occurs early in life. However, the precise age of inoculation is unknown. It often goes undetected. In industrialized countries, infection rates are declining rapidly, but high rates of infection persist among disadvantaged and immigrant populations.

The mechanisms of transmission of H. pylori are still not defined. The most common theory is person-to-person transmission by fecal/oral, oral/oral, or gastric/oral pathways. Infection is associated with crowding, poor hygiene, and intrafamilial clustering. This organism is reliably collected from vomit and stools during rapid gastrointestinal transit. These findings lead to the hypothesis that gastroenteritis episodes provide the opportunity for H. pylori transmission.

Household transmission of gastroenteritis is common in the United States, especially in households with small children. It is suspected that rates of new infection will be elevated after exposure to persons with H. pylori-infected cases of gastroenteritits. To determine if diarrhea or vomiting contribute to H. pylori transmission, households in California experiencing gastroenteritis were monitored and evaluated for infection of H. pylori. Symptoms of new infection were also monitored and noted.

The study population consisted of households that were participation in the Stanford Infection and Family Transmission study, initiated in1999 to prospectively evaluate the association of H. pylori infection and household gastroenteritis. Demographically, Hispanic immigrant families residing in South San Francisco Bay, has a high seroprevalence of H. pylori infection. Volunteers were selected from near-by community clinics, who complained of diarrhea, vomiting or both. Visits were made to the volunteers homes, they were interviewed regarding symptoms, onset, and duration of gastroenteritis within the previous 21 days. Both stool and blood samples were taken to test for H. pylori.

Stool samples were collected from children and others who refused to have their blood drawn. Approximately three weeks later the same people were re-visited, re-interviewed and another sample taken for testing. Volunteers were given a gift for their participation.

Laboratory Methods

H. pylori Serologic Testing

Anti-H. pylori immunoglobulin G (IgG) was quantified by using an in-house ELISA. Optical density (OD) results were categorized as negative, borderline, or positive. This test is 91% sensitive and 98% specific for infection in adults. Serologic testing in children was considered unreliable for this study.

Each sample was tested three times on two separate occasions; first soon after the sample was received and later, when it was paired with the second visit...
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