Overview
Pelvic inflammatory disease (PID) is an ascending infection of the female upper reproductive tract — uterus, fallopian tubes, and ovaries. Traditionally attributed to Neisseria gonorrhoeae and Chlamydia trachomatis, PID is now recognized as predominantly polymicrobial, with bacterial vaginosis-associated organisms playing a central role in many cases.
Microbiome Associations
Culture-independent studies have revealed that PID-associated microbiomes are enriched in BV-associated organisms including gardnerella-vaginalis, atopobium vaginae, Prevotella bivia, and Sneathia species. These organisms ascend from the vaginal tract when the protective Lactobacillus-dominant community is disrupted. The gut vagina axis may contribute to vaginal dysbiosis that precedes PID.
Metal Associations
Iron availability in the upper reproductive tract increases during menstruation and inflammation, potentially facilitating pathogen expansion. Organisms implicated in PID — particularly Prevotella and Gardnerella — possess iron acquisition systems that exploit this iron-rich environment. Zinc deficiency has been associated with increased PID susceptibility through impaired local immune function.
Associated Conditions
PID shares microbial overlap with bacterial vaginosis (which often precedes it), endometriosis (shared inflammatory and microbial patterns in the peritoneal cavity), and tubal factor infertility (scarring sequela). Recurrent PID episodes progressively increase infertility risk, highlighting the importance of addressing the underlying microbial ecology rather than relying solely on antibiotic courses.
Open Questions
Whether gut microbiome restoration could reduce PID recurrence — by improving vaginal Lactobacillus colonization through the gut-vagina axis — remains untested in clinical trials.
Cross-References
- atopobium vaginae — BV biomarker ascending in PID
- bacterial vaginosis — predisposing condition
- gut vagina axis — cross-compartment microbial source
- endometriosis — shared pelvic inflammatory ecology