In a study published this week in Nature Communications, researchers characterized the population structure of Helicobacter pylori in individual patients, demonstrating an important role of antibiotics in its within-patient evolution.
H. pylori, a global gastric bacterium, is responsible for one of the most prevalent chronic infections found in humans. This infection provokes no definable symptoms but can result in a range of gastrointestinal tract pathologies, ranging from inflammation of the lining of the stomach to gastric and duodenal tumors.
The stomach is conventionally divided into three main anatomical regions, which are differentiated by their physiology and function, providing ecological niches for different subpopulations of H. pylori. “Using samples obtained from different regions of the stomach, we asked how strongly the H. pylori strains differed within each patient,” says senior author Sebastian Suerbaum of LMU in Munich. “To do so, we isolated at least 20 strains of bacteria from each patient and analyzed their genomes by a variety of sequencing methods.”
The results showed that H. pylori is indeed capable of adapting to the specific conditions that prevail in each of the anatomically defined regions of the stomach. This adaptability can be found, for example, in gene families that code for the organism’s outer membrane proteins, which serve to attach it to the gastric epithelium in its human hosts.
Additionally, the use of antibiotics has a significant impact on the genetic diversity of H. pylori. In one particular patient, the H. pylori population in the initial sample was highly diverse and showed no signs of antibiotic resistance. However, in a sample collected 2 years later, the level of diversity within the population was extremely low, and the bacteria were completely resistant to a frontline antibiotic.
The researchers found that exposure to antibiotics had a profound impact on all the H. pylori populations they studied. “As a rule, application of the most appropriate combination of antibiotics is essential to completely eradicate H. pylori from the stomach and prevent the emergence of resistance,” Suerbaum concludes. “However, it is now becoming apparent that antibiotics have had a huge impact on the evolutionary dynamics of the species as a whole in recent decades, as antibiotics have become readily available, and are increasingly employed, all over the world.”