Vaginal smear. Light micrograph of cells obtained by carrying out a vaginal smear test. This test is used to diagnose bacterial infections such as vaginitis and vulvitis. Bacteria (blue) are seen here. A healthy vagina also contains bacteria, such as Lactobacillus acidophilus. This bacterium form the predominant fauna in the vagina, where it forms an acidic environment that they produce that inhibits the growth of many other bacterial forms. This helps protects the vagina from infection.