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Abstract
Background: Helicobacter pylori resistance to antibiotics is the main cause for eradication failures. Methods: Antibiotic resistance in 299 H. pylori strains from 233 untreated adults, 26 treated adults, and 40 untreated children was assessed by E tests and, for metronidazole, by breakpoint susceptibility testing and two breakpoint systems. Results: Using EUCAST breakpoints (EBPs) and previous breakpoints (PBPs), overall resistance rates were: amoxicillin 4.0 and 0.6%, metronidazole 33.8 and 33.8%, clarithromycin 28.1 and 27.4%, levofloxacin 19.4 and 19.4%, tetracycline 3.7 and 1.5%, respectively, and rifampin 8.3% (EBP). Multidrug resistance was detected in treated and untreated adults and an untreated child and included 17 (EBPs) and 15 strains (PBPs). Differences between susceptibility categories were found for amoxicillin (3.5% of strains), clarithromycin (0.7%), and tetracycline (2.2%). Using PBPs, from 2005–2007 to 2010–2015, overall primary clarithromycin resistance continued to increase (17.9–25.6%) as noted in our previous study. However, in 2010–2015, overall primary metronidazole (24.0–31.5%) and fluoroquinolone (7.6–18.3%) resistance rates also increased. Primary resistance rates in children and adults were comparable. Conclusions: Briefly, differences in resistance rates by the two breakpoint systems affected the results for three antibiotics. National antibiotic consumption was linked to macrolide resistance in adults. Current primary H. pylori resistance to three antibiotics increased in all untreated patients and in the untreated adults, with the sharpest rise for the fluoroquinolones. The presence of fivefold H. pylori resistance to metronidazole, clarithromycin, tetracycline, levofloxacin, and amoxicillin according to EBPs is alarming.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the writing and content of the paper. This research was funded by the Grant/Contract B02/17 (12.12.2014) from the National Science Fund at the Ministry of Education and Science of Bulgaria, Project Ref. B02/2 (14.07.2014) entitled ‘Complex study of Helicobacter pylori virulence and resistance factors and epidemiology of the infection.’