Bacterial vaginosis is not considered an STD because it's not something that's contracted; it merely is the result of floral imbalance secondary to one or more of a variety of factors. Trichomonas, in contrast, is considered an STD.
Yeah, but it's largely just transient. Its presence vaginally is analogous to that of Propionibacterium acnes on the skin: it's almost always present in some number, but only under particular conditions is proliferation increased.
Lactobacillus is most common in reproductive-age women, but Staph, and even some Strep species, can exceed Lactobacillus in pre-pubescent and post-menopausal women (I had encountered this in a practice question a long time ago).
It increases susceptibility to STD but is part of the normal vaginal flora. Also bacterial vaginosis is often seen overgrowth of G. vaginalis in combination with Mobiluncus...
Posting this before the knowledge falls out of my brain since we took the micro shelf today haha