Pseudomonas fluorescens-like bacteria from the stomach: a microbiological and molecular study

Area of Science:

• Microbiology
• Molecular Biology
• Gastroenterology

Background:

• Acid peptic diseases are often associated with Helicobacter pylori infection.
• The stomach's antrum is a common site for bacterial colonization.
• Understanding diverse bacterial populations in the stomach is crucial for disease pathogenesis.

Purpose of the Study:

• To characterize oxidase- and urease-producing bacteria isolated from antral biopsies of patients with acid peptic diseases.
• To identify bacterial species capable of aerobic growth in the stomach environment.
• To assess the acid tolerance of these isolates.

Main Methods:

• Isolation and culture of bacteria from 258 antral biopsy specimens.
• Tests for oxidase, urease production, acid tolerance, and aerobic growth.
• Molecular characterization using 16S rRNA and HSP60 gene sequencing.
• Phylogenetic analysis using UPGMA and bootstrap testing.
• Assessment of acid tolerance using hydrochloric acid solutions.

Main Results:

• Pseudomonas fluorescens was identified as the predominant aerobic isolate, showing 99% similarity to Pseudomonas species via 16S rRNA sequencing.
• HSP60 gene sequencing provided higher discriminatory power, confirming isolates as P. fluorescens.
• Isolates demonstrated significant acid tolerance, surviving for hours at low pH.
• A high percentage of biopsy specimens (96.9%) and isolates (93%) were positive for P. fluorescens-specific genes.

Conclusions:

• Aerobically grown bacterial isolates from antral biopsies are primarily P. fluorescens.
• Acid-tolerant bacteria, such as P. fluorescens, can colonize the stomach independently of H. pylori.
• These P. fluorescens isolates may play a role in the pathogenesis or protection associated with acid peptic diseases.