The Puzzle of Coccoid Forms of Helicobacter pylori: Beyond Basic Science

Abstract

Helicobacter pylori (H. pylori) may enter a non-replicative, non-culturable, low metabolically active state, the so-called coccoid form, to survive in extreme environmental conditions. Since coccoid forms are not susceptible to antibiotics, they could represent a cause of therapy failure even in the absence of antibiotic resistance, i.e., relapse within one year. Furthermore, coccoid forms may colonize and infect the gastric mucosa in animal models and induce specific antibodies in animals and humans. Their detection is hard, since they are not culturable. Techniques, such as electron microscopy, polymerase chain reaction, loop-mediated isothermal amplification, flow cytometry and metagenomics, are promising even if current evidence is limited. Among the options for the treatment, some strategies have been suggested, such as a very high proton pump inhibitor dose, high-dose dual therapy, N-acetycysteine, linolenic acid and vonoprazan. These clinical, diagnostic and therapeutic uncertainties will represent fascinating challenges in the future.

Keywords: Helicobacter pylori; antibiotic resistance; coccoid form; real time polymerase chain reaction; therapy; viable non culturable.

Figure 1

Transition from spiral-shaped viable form of H. pylori to viable but non culturable (VBNC) coccoid forms (scanning electron microscope) and factors affecting this process.