The microbiome of pseudomyxoma peritonei: a scoping review

There is growing interest in the role of the microbiome in carcinogenesis, but few studies examine the microbiome of pseudomyxoma peritonei (PMP). This scoping review summarises the microorganisms identified in PMP samples and examines the evidence of their role in disease outcomes. The methodology was developed in accordance with the PRISMA-ScR framework and checklist. Nine relevant studies were included. Microbiological testing was performed on PMP samples from 85 patients. At the phylum level, Proteobacteria was detected in greatest relative abundance in tumour tissue, cellular and acellular mucin. The relative proportion of different phyla more closely resembled the gut microbiome in inflammatory bowel disease than in a healthy gut. High-grade specimens showed significantly higher bacterial density than low-grade specimens and non-neoplastic non-perforated appendix specimens. Survival data of 58 patients were published, correlating outcomes to pre-operative antibiotic administration. Observed differences were not statistically significant. There is evidence of an altered bacterial profile in PMP samples compared to a healthy gut microbiome, the significance of which is unclear. Significant methodological challenges remain in this field of study. This scoping review supports the need for further analysis of the PMP bacterial profile, using methodologies that incorporate controls and deliver taxonomic resolution at species level.