ACTA FAC. MED. NAISS. 2003; 20 (1): 22 - 28

Pregledni rad
 

MICROBIOLOGICAL DIAGNOSIS OF HELICOBACTER PYLORI INFECTION

Marica Otašević, Marina Dinić, Biljana Miljković-Selimović, Ljiljana Otašević, Predrag Stojanović
Medical Faculty Niš
 

SUMMARY

Methods for H. pylori infection diagnosis are classified in two groups: invasive and noninvasive ones. Microbiological and histological methods, as well as urease test performed on biopsy are invasive because of preceding gastroscopy, but 13C and 14C-urea test breathing and serology are noninvasive methods. Any of these methods solely possess some advantages and disadvantages too, and choose of the most convenient one, depend on team that conduct investigation in specialized laboratories. Many conditions must be fulfilled for successfully performing of microbiological diagnosis in H. pylori infection: sampling, transport medium quality, velocity of collected material transport to laboratory, correct and urgent samples processing, selection of nutritive media and microaerophilic conditions and optimal temperature providing for growth and multiplying of H. pylori. Microbiological diagnosis is preformed by direct microscopy, culturing and by serological methods. H.pylori is slim, S shaped, sometimes spiral Gram-negative rod. Its length varies from 2,5 to 5 µm and wide from 0,5 to 1 µm. It possesses 4 - 6 monopolar flagella. Immediately after patient material arrival in laboratory, performing of smears and staining according to Gram should be done. Microscopically investigation of preparation stained according to Gram is based on recognition of typical S shaped Gram-negative rods placed singular or in groups. Smear staining is considered to be successful method for H. pylori detection in gastric tissue, but this method is never recommended as the only one. Culturing of gastric tissue bioptates is the most reliable method in establishing of H. pylori infection diagnosis. For successfully diagnosis of H. pylori, variety of basic agar media supplemnted with 5-10% sheep or horse blood are in use. Selective use of antibacterial and antifungal agents is recommended for primary isolation of H. pylori in order to inhibit growth of contaminants. Colonies of H. pylori primoculture are convex, smooth, shiny and translucent, with entire margin, 0,5 - 1 mm in diameter. In order to identify suspected colonies in primary nutrient media microscopical preparations are maid and stained according to Gram. Microscopically, curved, Gram-negative rods, S and U shaped are seen. Verification of microorganisms microscopically, directs to further investigation of biochemical properties necessary for finally identification of spiral, gastric microorganisms. Microorganisms are identified as H. pylori if urease, oxidase and catalase tests are positive. Noninvasive, serological methods can be used for diagnosis of H. pylori infection by detection of anti H. pylori antibodies presence in patients' sera. Serological diagnosis of H. pylori infection by ELISA method based on detection of specific anti H.pylori IgA and IgG antibodies. ELISA test is convenient, noninvasive method for therapy efficiency following because of the fact that an eradication of H. pylori has been followed by gradual decrease of antibody level.

Key words: H. pylori, microbiological diagnosis, culturing, serological diagnosis