MICROBIOLOGICAL DIAGNOSIS OF HELICOBACTER-PYLORI AND ANTIMICROBIAL RESISTANCE

From March 1995 to February 1996 a total of 386 gastroduodenal biopsie s were processed for microbiological diagnosis of Helicobacter pylori which included culture, Gram staining and urease test. For susceptibil ity 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 po sitive result in Gram-staining; both tests were statistically signific ant compared with culture (p < 0.05). Considering culture as the refer ence method, sensitivity and specificity values for the urease test we re 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) w as performed to the following antimicrobials: amoxicillin, metronidazo le, clarithromycin, azythromycin and tetracycline. Resistance to metro nidazole was 25.4% and the corresponding values for clarithromycin and azithromycin 9.5%. No resistance to amoxicillin or tetracycline was o bserved. Urease test and Gram staining are two easy-to-perform tests a nd when taken together allow the mirobiological diagnosis of Helicobac ter pylori infection. Culture should be performed to know the evolutio n of resistance to antimicrobials used for treatment of this infection .