Hanafiah A, et al. - Primary and secondary resistances in H. pylori in Malaysia were determined and characterized. From 288 patients who underwent endoscopy at Universiti Kebangsaan Malaysia Medical Center (UKMMC), Kuala Lumpur, Malaysia, researchers obtained gastric biopsies from antrum (n = 288) and corpus (n = 283). Using the E-test, they identified overall resistance rates of 59.3% (35/59) to metronidazole, 35.6% (21/59) to clarithromycin and 25.4% (15/59) to levofloxacin. Secondary isolates vs the primary isolates exhibited significantly higher resistance rates to clarithromycin. In 16.2% (6/37) of cases, they identified mixed infection with susceptible and resistant isolates; of these, 83.3% (n = 5) had infection with the same strain. Resistance to more than one class of antibiotics was identified in 41% (18/44) of isolates; of these, 50% (9/18) were multidrug-resistant, two being primary and seven being secondary isolates. Resistance to metronidazole, clarithromycin, and levofloxacin, was observed in correlation with mutations in rdxA, 23S rRNA and gyrA genes, respectively. Given the detection of the high level of resistance to antibiotics in H. pylori isolates, they support performing continuous surveillance and practicing caution in using antibiotics which are generally used as first-line therapy in H. pylori eradication regimen.