A sexually active 25-year-old man develops epididymitis and orchitis. Needle biopsy demonstrates a prominent leukocytic infiltrate with numerous neutrophils. Which of the following organisms is the most likely cause of this man’s infection?
**Core Concept**
The patient's symptoms of epididymitis and orchitis, accompanied by a prominent leukocytic infiltrate with numerous neutrophils, suggest a bacterial infection. The epididymis and testes are susceptible to infection due to their rich blood supply and proximity to the urethra, which can serve as a conduit for pathogens.
**Why the Correct Answer is Right**
The most common cause of bacterial epididymitis and orchitis in sexually active young men is **Chlamydia trachomatis**. This bacterium is a sexually transmitted pathogen that can ascend from the urethra to the epididymis and testes, leading to inflammation and infection. Chlamydia trachomatis infects host cells by utilizing the host's energy-producing mechanisms, which helps the bacterium to replicate and evade the host's immune response.
**Why Each Wrong Option is Incorrect**
**Option A:** *Escherichia coli* is a common cause of urinary tract infections (UTIs) in women, but it is less likely to be the cause of epididymitis and orchitis in a sexually active young man. While E. coli can ascend from the urethra to the epididymis, Chlamydia trachomatis is more commonly associated with this condition.
**Option B:** *Staphylococcus aureus* can cause a variety of infections, including skin and soft tissue infections, but it is not typically associated with epididymitis and orchitis.
**Option C:** *Neisseria gonorrhoeae* is another sexually transmitted pathogen, but it is less commonly associated with epididymitis and orchitis compared to Chlamydia trachomatis.
**Option D:** *Mycoplasma genitalium* is a sexually transmitted pathogen that can cause urethritis, but it is not typically associated with epididymitis and orchitis.
**Clinical Pearl / High-Yield Fact**
In sexually active young men with epididymitis and orchitis, Chlamydia trachomatis should be considered a primary cause, and empirical treatment with antibiotics should include coverage for this pathogen.
**Correct Answer:** C. *Neisseria gonorrhoeae*