Microbiology Case Study Questions

Block 2: ID Board Review: Q & A

1. A 15-year-old girl comes to your office with the complaint of a vaginal discharge. She states that she is sexually active with a new partner and has noted a cream-colored, thin discharge. She also has had some burning with urination and vaginal itching. On pelvic examination, you note reddened labia majora and minora; a frothy, foul-smelling discharge in the vagina; and a cervix that has small erosions and petechiae. Her pregnancy test results are negative, and microscopic evaluation of vaginal secretions shows motile organisms.

Of the following, the MOST appropriate treatment is

A. azithromycin 1 g orally in a single dose

B. boric acid 600 mg capsule BID intravaginally for 14 days

C. clindamycin 300 mg BID orally for 7 days

D. fluconazole 150 mg orally in a single dose

E. metronidazole 2 g orally in a single dose

Preferred Response: E

Sexually active 15- to 19-year-olds have the highest rates of many sexually transmitted infections (STIs). Many STIs manifest as abnormal vaginal discharge in females. Trichomoniasis, caused by the protozoan Trichomonas vaginalis, is characterized by a diffuse, malodorous, frothy, yellow-green discharge. There also can be vulvar irritation. However, some young women have minimal or no symptoms.

Trichomoniasis is diagnosed most commonly by microscopic evaluation of vaginal secretions. As demonstrated for the young woman described in the vignette, trichomonads are seen on microscopy as motile bodies that have three to five anterior flagella and one posterior flagellum. When the wet preparation slide is evaluated immediately, microscopic sensitivity is approximately 60% to 70%. Other United States Food and Drug Administration approved tests for trichomoniasis in women include immunochromatographic capillary flow dipstick technology and a nucleic acid probe, which have greater than 83% sensitivity and greater than 97% specificity. Culture is the most sensitive and specific method...