Microflora, commensal

P. acnes is an anaerobic diphteroid that populates the androgen-stimulated sebaceous follicles and is a normal constituent of the cutaneous microflora even if acne is not infectious, the commensal P. acnes acts in acne pathogenesis. Three pieces of evidence support the role of P. acnes in acne 1) higher counts of P. acnes in individuals with acne than in those without acne 2) correlation between the reduction of P. acnes counts and the clinical improvement of the disease and 3) correlation between development of acne and presence of antibiotic-resistant P. acnes organisms. P. acnes products mediate the formation of comedones and contribute to their rupture, leading to extrusion of... 

Sartor RB Enteric microflora in IBD Pathogens or commensal Inflamm Bowel Dis 1997 3 230-235. 

Rakoff-Nahoum S, Paglino J, Eslami-Varzaneh F, Edberg S, Medzhitov R Recognition of commensal microflora 60... 

Bashir ME, Louie S, Shi HN, Nagler- 34 Anderson C Toll-like receptor-4 signaling by intestinal microbes influences susceptibility to food allergy. J Immunol 2004 172 6978-6987. Rakoff-Nahoum S, Paglino J, Eslami-Varzaneh F, Edberg S, Medzhitov R Recognition of commensal microflora by toll-like receptors is required for intestinal homeostasis. Cell 2004 118 229-241. 

In general, probiotic bacteria do not colonize the human intestinal tract permanently, but specific strains are able to transiently colonize or persist for some time in the intestine and may modulate the indigenous microflora. The rationale for modulating the gut microflora by means of probiotics derives from the demonstration that this microflora is important to the health of the host. Specific probiotics have been shown to colonize temporarily the human intestinal tract, thereby modulating the intestinal microflora both locally and at the commensal level. Such modification has not been reported to be permanent rather it is related to a balancing of aberrant or disturbed microflora to assist it to return to normal metabolic and physiological activities. Such modulation and restoration of the normal state of the microflora activity is a key target for probiotic action. However, the state of the microflora should be well characterized to enable the selection of specific probiotics to counteract the aberration or disturbance in question. 

---