The occurrence of clarithromycin resistance among Helicobacter pylori strains is a major cause of the treatment failure. Resistance to this drug is conferred by point mutations in 23S rRNA gene and the most prevalent mutations are A2143G and A2142G. The aim of the study was to evaluate the occurrence of A2143G and A2142G mutations in a group of H. pylori strains resistant to clarithromycin. The study included 21 clarithromycin-resistant H. pylori strains collected between 2006 and 2009 in southern Poland. Resistance to clarithromycin was quantitatively tested with the E-test to determine the minimal inhibitory concentration (MIC value). The point mutations of H. pylori isolates were detected by PCR followed by RFLP analysis. The MIC values for clarithromycin for the analyzed strains ranged from 1.5 mg/L to 64 mg/L. Nine H. pylori strains exhibited A2143G mutation and A2142G mutation was found in 9 isolates as well. The results of RFLP analysis of 3 clarithromycin-resistant strains were negative for both mutations. The average MIC values for A2143G and A2142G mutants were 6 and 30 mg/L, respectively. Frequencies of A2143G and A2142G mutations were the same in all isolates tested. Strains with A2143G mutation exhibited lower MIC values than A2142G mutants. Application of PCR-RFLP method for detection of clarithromycin resistance allows for better and more efficient management of H. pylori infections.

The aim of this study was to assess the primary and secondary resistance of H. pylori strains cultured from adult patients of the Małopolska region of Poland, mainly of Kraków and the surrounding areas, to antibacterial agents (amoxicillin, clarithromycin, metronidazole and levofloxacin). In total, 115 H. pylori strains were isolated, of which 90 strains originated from patients who had never been treated for H. pylori infection, while the remaining 25 were isolated from patients in whom eradication of the infection failed after treatment. All tested H. pylori strains were susceptible to amoxicillin. Forty-four percent of strains isolated were resistant to metronidazole. The primary and secondary resistance to this antimicrobial chemotherapeutic reached 37% and 72% (p = 0.002), respectively. In total, 34% of strains were resistant to clarithromycin, and the ratio of strains with secondary resistance was significantly greater than that of the strains with primary resistance (80% vs. 21%, p < 0.001). The double resistance to both metronidazole and clarithromycin was confirmed in 23% of H. pylori strains. Five percent of H. pylori strains were resistant to levofloxacin, while primary and secondary resistance to this drug accounted for 2% and 16% (p = 0.006), respectively. In total, 4% of H. pylori strains were simultaneously resistant to metronidazole, clarithromycin and levofloxacin. Thus, the high resistance to metronidazole and clarithromycin excludes the possibility of using these drugs for treatment of H. pylori infection without earlier antibiogramming. Levofloxacin, as a drug of high efficacy against H. pylori, should be reserved for an "emergency" therapy and used in a limited capacity in order to preserve its potent antimicrobial activity. The Polish Society of Gastroenterology recommends levofloxacin as a third-line therapy.

Background. An increasing resistance of Helicobacter pylori strains to antimicrobial agents is the serious therapeutic problem. The aim of this study was to compare the primary and secondary resistance of H. pylori strains isolated between 2006–2008 (data published) and 2009–2011 to clarithromycin and levofloxacin. Material and Methods. 220 dyspeptic patients (153 before treatment, 67 after), were enrolled in the study. 51 H. pylori strains were isolated. MIC values of clarithromycin and levofloxacin were determined by the E-test method. The statistical analysis was conducted with the χ 2 test with Yates correction at the 0.05 significance level (P ≤ 0.05). Results. Between 2006 and 2008, 34% (39/115) of H. pylori strains were resistant to clarithromycin (primary 21% (19/90), secondary 80% (20/25)). 5% (6/115) of strains were resistant to levofloxacin (primary 2% (2/90), secondary 16% ((4/25); data published) Between 2009–2011, 22% (11/51) of H. pylori strains were resistant to clarithromycin (primary 19% (8/43), secondary 38% (3/8)). 16% (8/51) of strains were resistant to levofloxacin (primary 12% (5/43), secondary 38% (3/8)). Conclusion. The present study has shown the increasing amount of resistant H. pylori strains isolated from patients in Southern Poland to levofloxacin and decreasing number of resistant strains to clarithromycin.