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Self-Study STD Module - PID

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.

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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.

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Pathway of Ascendant Infection

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.

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Normal Human Fallopian Tube Tissue

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C. trachomatis Infection (PID)

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Page last modified: June 3, 2009
Page last reviewed: June 3, 2009

Content Source: Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention


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