**Question:** Most common cause of pelvic inflammatory disease is -

A. Chlamydia trachomatis
B. Neisseria gonorrhoeae
C. Trichomonas vaginalis
D. Candida albicans

**Core Concept:**
Pelvic Inflammatory Disease (PID) is a condition characterized by inflammation of the upper female genital tract, including the uterus, cervix, fallopian tubes, and ovaries. It is often caused by ascending infection from the lower genital tract, such as the vagina and cervix.

**Why the Correct Answer is Right:**
The most common causes of PID are sexually transmitted infections (STIs) that affect the lower genital tract. Among the options provided, Chlamydia trachomatis (A) and Neisseria gonorrhoeae (B) are the most common STIs causing PID. Chlamydia is the leading cause of PID worldwide, and gonorrhea is a common co-infection with chlamydia.

**Why Each Wrong Option is Incorrect:**
C. Trichomonas vaginalis (C) is less common than chlamydia and gonorrhea and is typically associated with a different clinical presentation (e.g., urethritis in males).
D. Candida albicans (D) is a common cause of vaginal infections like vaginitis but is not a common cause of PID, as it primarily affects the vagina and cervix rather than the upper female genital tract.

**Clinical Pearl:**
It's essential for healthcare providers to screen and treat STIs like Chlamydia and Gonorrhea in at-risk patients to prevent progression to PID, ectopic pregnancy, and other complications. Early diagnosis and treatment can significantly reduce the risk of long-term sequelae.

**Correct Answer:** Chlamydia trachomatis (A) and Neisseria gonorrhoeae (B) are the most common causes of Pelvic Inflammatory Disease (PID). These sexually transmitted infections can ascend from the lower genital tract to cause PID.