[Microbiologic diagnosis of Helicobacter pylori and its resistance to antibiotics]

From March 1995 to February 1996 a total of 386 gastroduodenal biopsies were processed for microbiological diagnosis of Helicobacter pylori which included culture, Gram staining and urease test. For susceptibility studies to five antimicrobial agents, 35 additional gastroduodenal biopsies (n = 421) were added. There were 272 (70.4%) positive cultures, 220 (56.9%) samples with positive urase test and 244 (63.2%) with positive result in Gram-staining; both tests were statistically significant compared with culture (p < 0.05). Considering culture as the reference method, sensitivity and specificity values for the urease test were 77.0% and 92.1% and for Gram staining 86.7% and 92.9%, respectively. A total of 11 isolates were recovered from the 35 biopsies processed only for culture. Susceptibility testing of 283 isolates (272 + 11) was performed to the following antimicrobials: amoxicillin, metronidazole, clarithromycin, azythromycin and tetracycline. Resistance to metronidazole was 25.4% and the corresponding values for clarithromycin and azithromycin 9.5%. No resistance to amoxicillin or tetracycline was observed. Urease test and Gram staining are two easy-to-perform tests and when taken together allow the microbiological diagnosis of Helicobacter pylori infection. Culture should be performed to know the evolution of resistance to antimicrobials used for treatment of this infection.