Impact of Helicobacter pylori Biofilm Formation on Clarithromycin Susceptibility and Generation of Resistance Mutations

Abstract

The human gastric pathogen Helicobacter pylori forms biofilms in vitro and in vivo. The purpose of this study was to evaluate the effects of H. pylori biofilm formation in vitro on clarithromycin (CLR) susceptibility. CLR susceptibility of H. pylori intermediate (2-day) and mature (3-day) biofilms on glass coverslips was determined at concentrations from 0.03 to 0.5 µg/ml. H. pylori biofilm biomass was increased after treatment with CLR at minimum inhibitory concentration levels by up to 4-fold (2-day biofilm) and 16-fold (3-day biofilm). Minimum bactericidal concentrations of CLR against cells in a biofilm were higher (1.0 µg/ml) than that for planktonic cells (0.25 µg/ml). It was shown that the expression of efflux pump genes was significantly increased in biofilm cells. In addition, exposure of biofilms to CLR resulted in high level resistance generation compared to planktonic cells with increased resistance associated with the presence of a point mutation at either position 2142 or 2143 in the domain V loop of the 23S rRNA gene. These results demonstrate that H. pylori biofilm formation decreases the susceptibility to CLR and that H. pylori CLR resistance mutations are more frequently generated in biofilms than in planktonic cells.

Helicobacter pylori biofilm cells are metabolically distinct, express flagella, and antibiotic tolerant

“…However, the impact of biofilm mode of growth on susceptibility to antimicrobial agents in H. pylori has not been well documented. Previous studies have shown that H. pylori clinical strains TK1402 and TK1049 increased levels of tolerance and resistance to clarithromycin of up to 8 to 16-fold times the minimum inhibitory concentration (MIC) as compared to planktonic grown cells (Yonezawa, Osaki et al 2013, Yonezawa, Osaki et al 2019. We thus decided to investigate this phenomenon in the strong-biofilm forming strain G27 and determine biofilm and planktonic cells susceptibility to three clinically relevant antibiotics: the macrolide clarithromycin, the b-lactam amoxicillin, and tetracycline.…”

Characterization of Key Helicobacter pylori Regulators Identifies a Role for ArsRS in Biofilm Formation

“…Biofilm formation by H. pylori has been demonstrated both in vitro (30)(31)(32) and in vivo (33)(34)(35)(36)(37). While it is unclear exactly what drives biofilm formation in H. pylori, protection from antibiotics and host defenses during infection (35,38,39) and/or protection in putative environmental reservoir (40-43) have been proposed. Basic characterization has shown that in vitro biofilm formation is varied across strains (32) and appears to be induced under conditions, such as serum/nutrient starvation (44,45).…”

A proposed role for diffusible signal factors in the biofilm formation and morphological transformation of Helicobacter pylori

“…These results correlate with the findings from other studies in which the H. pylori biofilm was treated with MIC of clarithromycin. A 4-fold and 16-fold increase in biofilm biomass was observed in 2-day and 3-day culture, respectively (21). For the three antibiotics most commonly used for eradication of this pathogen, i.e.…”