So here you could maybe make a case for the propionibacterium species being the most abundant commensal that might dominate everywhere but the stool.
So obviously fecal counts or transplants wouldnt reflect its status.
Propionibacterium acnes: Disease-Causing Agent or Common Contaminant? Detection in Diverse Patient Samples by Next-Generation Sequencing
https://jcm.asm.org/content/54/4/980
Propionibacterium acnes is a facultative anaerobic Gram-positive bacterium present on human skin as part of the normal flora, as well as in the oral cavity, large intestine, conjunctiva, and external ear canal (1). P. acnes is the most prevalent bacterium in sebaceous areas of the skin (2, 3) but is also abundant in dry areas (3). P. acnes predominates in the pilosebaceous follicles of the skin (4).
P. acnes is proposed to play a role in the development of acne vulgaris (5) and is considered an opportunistic pathogen causing postoperative infections (6). It has been isolated from patients with endocarditis (7), synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome (8), and sarcoidosis (9), among other syndromes. Some studies also identify P. acnes to be a contaminant of blood products, tissue cultures, and surgical wounds (10–13), and the significance of this widely abundant skin commensal is consequently debated.
The postulated role of P. acnes in various conditions is often highly speculative and based on the mere detection of the bacterium (8, 9, 14–19). To expand the knowledge of the abundance of P. acnes, we investigated the proportions of P. acnes sequences in samples of a wide variety of cancer types, as well as blood samples. Next-generation sequencing was performed on DNA extracted either after enrichment for intact microbes or directly from the samples. This study is the first large-scale analysis investigating the abundance of P. acnes DNA in such diverse tissue types by next-generation sequencing, and we show that P. acnes can be readily detected in literally all sample types investigated, particularly when samples are subjected to microbial enrichment.