This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Normal vaginal anaerobe is: 
Select and explain. 
A. Lactobacillus, B. Corynebacterium, C. Gardenella, D. E. coli
A: Lactobacillus
Answer: A: Lactobacillus 
Explanation: Lactobacillus are gram positive bacilli, nonspore forming anaerobes. Normally they are present in mouth, intestines and vagina. They rarely cause disease, though L.catenaforme is associated with bronchopulmonary infections. Most of them are vancomycin resistant. Lactobacillus forms the predominat bacterial flora of vagina. They ferment glycogen deposited in the vaginal epithelium and forms lactic acid which helps to maintain a acidic pH. Good to know: Albe Dorderlein in 1891 described the cultural and physiological characters of organism,"Lactobacilus acidophillus", which has since born its name as "Dorderlein bacillus" . Ref: Jawetz, 'Medical microbiology', 23rd Edition, Page 244 ; A textbook of microbiology, By P.Chakraboy, 2nd Edition, Page 309.