This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of the female genital tract, Subject name: Gynaecology & Obstetrics
The organism contributing to vaginal defence mechanism is _________ 
Select and explain. 
A. Doderlein's bacillus, B. Staphylococcus, C. Streptococcus, D. Treponema pallidum
A: Doderlein's bacillus
Answer: A: Doderlein's bacillus 
Explanation: The organism contributing to vaginal defence mechanism is Doderlein&;s bacillus. Doderlein&;s bacillus is a gram positive rod shaped bacillus which grows anaerobically in acidic media. It appears in vagina 3-4 days after bih and disappears after 10-14 days. It appears again at pubey and disappears after menopause. Its presence is dependent on estrogen Its function is to conve glycogen to lactic acid and maintains acidic pH in vagina thus preventing growth of pathogenic bacteria. Ref: Shaw&;s textbook of Gynaecology 17th edition Pgno: 16