Helicobacter species

Test codes:
B0020 - Qualitative detection of Helicobacter pylori by polymerase chain reaction
B0022 - Qualitative detection of Helicobacter heilmannii by polymerase chain reaction
P0010 - Ultrasensitive Helicobacter species screen by nested polymerase chain reaction (detects H. pylori, H. heilmannii, H. bilis, H. hepaticus and other Helicobacter species)
P0011 - Ultrasensitive Helicobacter species identification by nested polymerase chain reaction and restriction fragment length polymorphism (detects and differentiates H. pylori, H. heilmannii, H. bilis, H. hepaticus and other Helicobacter species)

Many species of the genus Helicobacter have been identified in mammals and their pathogenicity varies. Some species can induce significant disease while others appear to merely colonize the gastrointestinal tract.

Helicobacter pylori is a gram-negative spiral bacterium found in gastric mucosa and associated with active and chronic gastritis. H. pylori can establish a chronic, persistent infection, which may lead to gastric or duodenual ulcers, gastric cancer and gastric lymphomas. Studies have revealed that approximately 50% of the world’s human population is infected with H. pylori.

Biochemically, the bacterium produces catalase, oxidase and urease enzymes. The urease enzyme permits the bacterium to metabolize urea present in the gastric mucosa and establish a microenvironment favorable to the organism. H. pylori is a highly motile organism with multiple unipolar flagella. Both the urease enzyme and the flagella are considered to be important virulence factors.

Diagnosis of Helicobacter pylori infection in humans relies on upper endoscopy or the 13C-urea breath test (see review by Nakamura, 2001). Although the endoscopy procedure permits culture of the bacterium from biopsy specimens (the gold standard for diagnosis), demonstration of urease activity and histological detection of the germ, the procedure is expensive and invasive. The 13C-urea breath test is a well-established, relatively sensitive, specific and noninvasive method. Molecular tests, such as PCR, can also offer precise diagnosis of H. pylori infections. In fact, molecular testing by PCR can complement other diagnostic tests because it can be applied to archival fixed tissue, environmental samples, gastric fluid, oral secretions, and stool samples, in which traditional diagnostic tests do not have sensitivity and perform poorly. Studies have shown than PCR detection of H. pylori in gastric fluid specimens can reach a sensitivity of 96% and a specificity of 100% (Westblom et al., 1993; Yoshida et al., 1999). This capability is especially useful in monitoring active H. pylori infection in rodents and other animals, as the breath test is difficult to conduct for these animals.

Helicobacter heilmannii (previously known as Gastrospirillum hominis) is a 4-10 µm long, spiral-shaped, motile bacterium with three to eight coils, a wavelength of about 1 µm, up to 14 uni- or bipolar flagella, and no periplasmic filaments. In humans, gastric infection with H. heilmannii is associated with the development of chronic gastritis (found in the stomachs of 0.2 to 4% of patients with gastritis) and low-grade mucosa-associated lymphoid tissue lymphoma in humans. Eradication of H. heilmannii by antibiotic treatment of patients can result in complete remission of MALT lymphoma, indicating a causal relationship between H. heilmannii infection and MALT lymphoma. Unlike H. pylori infections, gastric infections with H. heilmannii or Gastrospirillum-like organisms are not restricted to humans. A broad range of animals including dogs, cats, pigs, and cattle are naturally infected, with frequencies ranging from 80% to 100%. It has been suggested that H. heilmannii infection in humans may be a zoonosis and that animals may serve as a reservoir for transmission to humans.

Definitive culture of H. heilmannii has not been achieved to date (Anderson et al., 1996) and diagnosis of H. heilmannii infection is usually made on the basis of its distinct spiral morphology, compared with H. pylori, on silver- stained tissue sections. However, there are a number of large, gastric, spiral organisms such as H. felis, H. salomonis, and H. bizzozeronii which are indistinguishable from H. heilmannii on routine light microscopy, and H. pylori grown in a broth culture can also adopt a morphology identical to that of H. heilmannii (Fawcett et al., 1999). Molecular detection methods, such as PCR, are always required for more definitive identification (Trebesius et al., 2001).

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of Helicobacter infection.
• Ensure that horse populations are free of Helicobacter species
• Early prevention of spread of these bacteria
• Minimize personnel exposure to these bacteria
• Safety monitoring of biological products that derive from horses

Specimen requirements: 1 ml gastric lavage or feces or tissue shipped overnight at room temperature; or tissue shipped frozen.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days (3 business days for P0011)

Methodologies:
B0020 - Qualitative PCR
B0022 - Qualitative PCR
P0010 - Qualitative nested PCR
P0011 - Qualitative nested PCR and RFLP

Normal range: Nondetected