@David Drake: In fact, as luck would have it, I can:
One of hundreds of papers on FMT, showing feasibility of alteration of gut micro biome through rectal delivery (I won't go into any vivid detail but suffice to say, surface contact in that area, due to micro-abrasions and capillary effects, are sufficient for transmission without actual insertion):
Fecal microbiota transplantation and emerging applications. (2012). 9(2), 88–96. doi:10.1038/nrgastro.2011.244
Again, one of numerous papers on the emerging evidence that gut microbiome controls numerous physiological aspects, including central nervous system:
The microbiome-gut-brain axis: from bowel to behavior. (2011). 23(3), 187–192. doi:10.1111/j.1365-2982.2010.01664.x
And finally, one of millions of papers on plant pathogens, this one in particular which is known to pathogenic to humans:
Pantoea agglomerans, a plant pathogen causing human disease. (2007). 45(6), 1989–1992. doi:10.1128/JCM.00632-07
Similar to how there are unlikely to be any papers showing that using a dirty needle found on the street is a bad idea, there are unlikely many biological / biomedical studies done on this exact topic. However, all of the components of such a study have been performed in one way or another with fairly conclusive evidence.
All that said, I understand that everyone likes to think their way is the best way, and I'm not trying to change anyones behaviors or style. I'm simply trying to give a perspective on the matter that some may have not otherwise considered.