Changes in salivary microbiota due to gastric cancer resection and its relation to gastric fluid microbiotaOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This study characterized how the salivary microbiota changes after gastric cancer resection and how it relates to the gastric fluid microbiota. Saliva and gastric fluid were collected from the same patients before and after gastrectomy. Microbial composition was compared using 16S rRNA metagenomic analysis of the V1-V2 region. Analyses included alpha and beta diversity, PERMANOVA on UniFrac distances, and LEfSe to find genera that differed before and after surgery.
Who was studied?
The cohort was 63 patients with primary gastric cancer treated in Japan. All underwent distal gastrectomy with reconstruction between January 2019 and February 2021. Saliva and gastric fluid were sampled from each patient at two time points: before surgery and six months after gastrectomy. Patients on immunosuppressants, corticosteroids, acid-suppressing drugs, or recent antibiotics were excluded. Specialized dentists confirmed that oral status did not change significantly between the two time points.
What were the most important findings?
Salivary species richness fell after surgery, with the observed OTU index decreasing significantly (p = 0.018), though evenness (Shannon) did not change. Gastric fluid lost both richness and evenness. Salivary community structure shifted after gastrectomy (PERMANOVA, unweighted UniFrac, p = 0.003). The number of species shared between a patient's saliva and gastric fluid dropped by about 9.7 percent after surgery (p < 0.001). At the phylum level, Firmicutes and Bacteroidota predominated. LEfSe found several genera that changed in the same direction in both saliva and gastric fluid, one rising and three falling.
What are the greatest implications of this study?
The results suggest that changes in the gastric environment after cancer surgery reach the oral microbiota, underscoring a close link between the mouth and stomach. Parallel shifts in both sites point to bacterial exchange along the digestive tract. This supports focusing on oral hygiene during the perioperative period for gastric cancer patients. The study is observational, so causation is unknown and confounders such as reflux and smoking could contribute. Sequencing did not distinguish live from dead bacteria.