Molecular Patterns of Resistance Among Strains in South-Western Poland.

Treatment failure of infection is caused mainly by progressive antibiotic resistance among strains. In Poland, the prevalence of strains resistant to metronidazole is higher than in other developed countries, reaching almost 50%, and resistance to clarithromycin is as high as 30% and is still increasing, contributing to the failure of first-line therapy in approximately 70% of patients. Moreover, the introduction of levofloxacin to eradication therapy of infection quickly led to the emergence of resistant strains. Therefore, a necessary approach in microbiological diagnostics of infection should be determination of susceptibility of strains before the eradication treatment. In this study was to evaluate the molecular mechanisms of resistance among 170 strains to clarithromycin, involving mutations in the 23S rRNA gene (A2143G, A2142G, A2143G) and to levofloxacin, involving mutations of and . Analysis was performed by using polymerase chain reaction and classical sequencing of DNA fragments. Among examined strains, 26% were fully sensitive and 74% were resistant to at least one of the tested antibiotics. The overall resistance rate to metronidazole was as high as 56%, whereas to clarithromycin 46%, respectively. Resistance to LEV occurred among 6% of strains. All tested strains were susceptible to AMC and TET. The A2143G point mutation was found in 72% of clarithromycin-resistant strains. The most common mutation, present in 40% of strains resistant to levofloxacin, was a change at position 91 of . The increasing number of point mutations in the 23S rRNA gene leads to an increase in the rates of antimicrobial resistance. Presence of the GCG allele at position 122 of the gene may cause an eightfold increase in risk of development of resistance to levofloxacin.