National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention
Division of Sexually Transmitted Diseases
Program and Training Branch
Pathogenesis and Microbiology
Most cases of PID are polymicrobial. The most common pathogens associated with PID are N. gonorrhoeae and C. trachomatis. N. gonorrhoeae and C. trachomatis are present in combination in approximately 25%-75% of patients with PID. The relative prevalence of these and other organisms depends on prevalence in the population studied.
Other microbes associated with PID include aerobic
Gram-negative rods (e.g., E. coli),
anaerobes (Bacteroides spp., Prevotella spp., Peptostreptococcus spp.), especially
those associated with bacterial vaginosis (BV), and
Gram-positive organisms
(streptococcus spp). Mycoplasma genitalium and Ureaplasma urealyticum have also been isolated from the endometrium and fallopian tubes of women with PID.
Pathway of Ascendant Infection
There are indications that an intermittent ascent of microorganisms into the endometrial
cavity and fallopian tubes may be a physiological phenomenon. The fate of such ascended
organisms depends on their viability, number, pathogenicity, and local defense mechanisms of
the host.
In the case of PID, the response to the ascending organisms is an inflammatory
one in the endometrium, fallopian tubes, or peritoneum. The resulting scarring of the tubes
may lead to infertility, ectopic pregnancy, or chronic pelvic
pain even in women who do not report a history of PID
symptoms.
(Click on image for larger view)
The normal fallopian tube tissue has millions of tiny
hair-like cilia that beat in waves that assist in the
transportation of the egg through the tube to the uterine
cavity. As a result of inflammation by C. trachomatis, the
fallopian tube may have a loss of cilia.
