A handful of bacteria are the signature of chronic pain

We know the gut microbiota contributes to visceral hypersensitivity through the production of bacterial metabolites. But what about other organs and microbiota? Do urinary or vaginal microbiota contribute to bladder or vaginal pain sensitivity? To find out more, researchers studied 30 patients suffering from chronic pelvic pain (sidenote: Chronic pelvic pain Persistent, noncyclic pain perceived to be in structures related to the pelvis and lasting more than six months. Often no specific etiology can be identified, and it can be conceptualized as a chronic regional pain syndrome or functional somatic pain syndrome. It is typically associated with other functional somatic pain syndromes (e.g., irritable bowel syndrome, nonspecific chronic fatigue syndrome) and mental health disorders (e.g., posttraumatic stress disorder, depression). Explore Speer LM, Mushkbar S, Erbele T. Chronic Pelvic Pain in Women. Am Fam Physician… ) (CPP), half of whom also suffered from hypersensitivity (sidenote: Pelvic hypersensitivity Decreased cortical nociceptive thresholds leading to discomfort or pain from stimuli that are not usually painful, such as bladder filling; exaggerated perception of digestive system function; vulvar burning on contact; and abnormally intense pain from stimuli that are usually painful. Explore CHU Dijon ) in a pelvic organ.

Impaired microbiota in cases of hypersensitivity

Pain pressure thresholds were found to be much lower in women with CPP and hypersensitivity in the vagina, rectum, bladder, and perineum than in women suffering from CPP with no associated hypersensitivity. After stimulation, these women experience not only more intense pain but also longer-lasting pain in the perineal muscles and bladder.
 

In terms of microbiota, hypersensitive women show signs of dysbiosis, including a decline in beneficial lactobacilli. The digestive microbiota is depleted in Lactobacillus; the vaginal microbiota is more diverse (whereas optimal vaginal flora is typically not very diverse), considerably enriched in Streptococcus and Prevotella, and depleted in Lactobacillus jensenii and Gardnerella vaginalis; while the urinary microbiota is also more diverse and enriched in Clostridium sensu stricto 1.

Dysbiosis linked to clinical characteristics

Above all, the relative abundance of certain bacteria in hypersensitive individuals is associated with clinical characteristics and increased organ sensitivity:

• A low intestinal abundance of Akkermansia, Desulfovibrio, Faecalibacterium, and CAG-352 is associated with increased rectal pain intensity;
• in the vagina, a lack of Lactobacillus jensenii is associated with more dysmenorrhea and a loss of bladder capacity, while an increased abundance of two Prevotella species is associated with the occurrence of dysmenorrhea;
• in the urinary microbiota, a lower abundance of Lactobacillus is correlated with reduced bladder capacity and poorer quality of life.

A signature of sensitivity

Lastly, the researchers identified gut, vaginal, and urinary bacterial signatures that serve as biomarkers for pelvic hypersensitivity in women suffering from chronic pelvic pain.

Are these bacteria the cause of the disease? Preclinical animal models will be required to validate any causal relationship. Nevertheless, this work paves the way for nutritional and therapeutic approaches where prebiotics, probiotics, and synbiotics targeting various urogenital microbiota have the potential to improve sensitization in women with CPP.