The impact of antibiotics on the presence of the protozoan anaerobe Blastocystis and the surrounding microbiome: a case study

Background: Blastocystis, the most prevalent eukaryotic gut microbe in humans, has a global distribution. Studies have linked its presence with distinct gut microbiome and metabolome profiles compared to those where the organism is absent. However, the in vivo effect of antibiotics on Blastocystis and the surrounding gut microbiome remains understudied. This case study aimed to explore how antibiotic consumption influences the presence of Blastocystis and the subsequent changes in the gut microbiome and metabolome of an individual with irritable bowel syndrome (IBS). Methods: Stool samples from an IBS patient, collected at various time points, were tested for Blastocystis presence using RT-PCR targeting the SSUrRNA gene, followed by sequencing of positive samples. Illumina sequencing determined the gut microbiome composition, while one-dimensional proton NMR spectroscopy analysed the metabolome composition. Statistical analyses were conducted to identify relationships between antibiotic consumption, bacterial diversity, metabolome composition, and Blastocystis presence. Results: Antibiotics significantly impacted the gut microbiome, with diversity declining early in the antibiotic course, then recovering later and post-course. Blastocystis was detected early, late, and post-course but not mid-course, coinciding with the decline in bacterial diversity. No significant differences were observed between Blastocystis-positive and Blastocystis-negative samples. However, bacterial composition significantly differed between samples collected before, early, and after the antibiotic course compared to those collected mid-course. Metabolite groups, including short-chain fatty acids, amino acids, and succinate, exhibited changes throughout the antibiotic course, indicating that gut metabolite composition is affected by antibiotic consumption. Discussion/Conclusion: While antibiotics did not significantly impact Blastocystis colonisation, they did cause a mid-course decline in microbial diversity and Blastocystis presence. The study also revealed significant alterations in important metabolites such as SCFAs and amino acids throughout the antibiotic course, with an altered metabolome observed post-course. This case study underscores the complex interactions between antibiotics, gut microbiota, and metabolites, highlighting the resilience of Blastocystis in the gut ecosystem.