The normal microbial flora of the human vagina comprises lactic acid producing bacteria, which by tradition have been designated as Döderlein's bacilli.
Such lactic acid producing bacteria relate to non-spore-forming, Gram-positive bacteria producing lactic acid by fermentation of various sugars, such as glycogen and/or glucose.
Lactic acid producing bacteria comprise bacteria of, for instance, the genera Lactobacillus, Leuconostoc, Pediococcus, Streptococcus, Lactococcus, and Enterococcus. 
Lactic acid producing bacteria may be divided into homofermentative and heterofermentative bacteria depending on their metabolic pathways. Homofermentative bacteria (e g Lactobacillus acidophilus) produce merely lactic acid, whereas heterofermentative bacteria also produce, for instance, carbon oxide, ethanol or acetic acid.
The genus Lactobacillus is a phenotypically heterogenous group of facultatively anaerobic, catalase-negative, rod-shaped lactic acid producing bacteria. Over 50 different species are recognised, and these species generally possess DNA with a low content of guanine (G) and cytosine (C), approximately 33-53%. The GC-content is constant within a species. Several species of Lactobacillus are found in humans, e g in the oral cavity, intestinal tract, and vagina. Species of Lactobacillus that are present in the vagina are, for instance, Lactobacillus acidophilus, Lactobacillus fermentum, Lactobacillus gasseri, Lactobacillus crispatus, Lactobacillus casei (sub-species rhamnosus), and Lactobacillus jensenii. 
The genus Pediococcus is phenotypically a group of Gram-positive, catalase-negative, facultatively anaerobic, oxygen-tolerant, round-shaped (diameter about 0.6-1.0 μm), non-pathogenic, lactic acid producing bacteria.
Healthy, fertile women (about 15-60 years of age) present a pH of about 3.8-4.2 in the vagina between menses, primarily as a result of said lactic acid production. An acidic environment prevents vaginal establishment of, for instance, bacteria that are present in the colon, such as Gardnerella vaginalis, Mobiluncus, Bacteroides, Prevotella and Eschericha coli. 
The skin of the urogenital tract and the urogenital mucus membranes of a healthy woman host a specific flora of beneficial and/or commensal microorganisms, such as various species of Lactobacillus. However, the urogenital tract can also be colonised by disease-causing microorganisms. The colonisation of unwanted microorgansims can be a result of sexual transmission, it can occur spontaneously or it can be the result of a disturbed normal microbial flora. The latter is, for instance, known to happen after certain antibiotic therapies.
Thus, the microbial flora of the female urogenital tract, such as in the vagina, may be disturbed and altered by a microbial infection, such as yeast (Candida albinancs), Trichomonas vaginalis, Neisseria gonorrhoeae, and Chlamydia trachomatis, and bacterial vaginosis (caracterized by increased prevalence of Gardnerella vaginalis and Mobiluncus), an antibiotic treatment or other often complex causes.
During menstruation and sexual intercourse, the pH in the vagina is increased by the addition of blood and sperm, respectively. These fluids contain a lot of proteins, which may be digested by bacteria (e g Gardnerella vagnalis and Mobiluncus), which, as previously disclosed, might be established in the vagina under conditions of increased pH. Degradation products, such as amines (e g putrescine and cadacerine) are then produced. At increased pH, these amines become volatile and present a “fishy” odour. Additionally, these women often have complaints of increased vaginal discharge and irritation. This condition is called bacterial vaginosis (BV), and is the most common condition associated with irritation and increased amount of odorous vaginal discharge (see Morris, M; Nicoll, A; Simms, I; Wilson, J; Catchpole, M, Bacterial vaginosis: A public health review, British Journal of Obstetrics and Gynaecology, 108(5): 439-450, May 2001).
Bacterial vaginosis is believed to be the result of displaced vaginal lactic acid producing bacteria which are replaced by a range of unwanted species such as Gardnerella vaginalis, Bacterioides, Mobiluncus, Prevotella bivia, and Mycoplasma hominis. 
A method to diagnose bacterial vaginosis (BV) is described by Amsel Criteria. First, the pH of vaginal discharge is measured. The pH is elevated above 4.5 in about 90% of women with BV. Second, if 10% KOH is added to the vaginal discharge, a “fishy” odour will be released in about 70% of women with BV. Third, often the presence on wet mount of squamous epithelial cells covered with small coccobacilli (“clue cells”) is observed. Another reliable test for BV is direct Gram stain of vaginal fluid. A standardised method for interpretation of Gram stains for BV was presented by Nugent et al. (See Example 1.)
It is known that lactic acid producing bacteria have an ability to inhibit the growth and/or reduce the pathogenicity of many of the pathogens associated with urogenital infections (see e g Redondo-Lopez, V; Cook, R L; Sobel, J D, Emerging role of lactobacillus in the control and maintenance of the vaginal bacterial microflora, Reviews of infectious diseases, vol 12, no 5, September-October 1990, and Boris, S; Barbes, C, Role played by lactobacilli in controlling the population of vaginal pathogens, Microbes and infection, vol 2, pp 543-546, 2000).
It is also known that the antagonistic properties of lactic acid producing bacteria against said pathogens are at least partially denoted by their ability of producing different antagonistic substances, such as lactic acid, hydrogen peroxide, bacteriocins, etc.
A healthy vagina is estimated to host between 108-109 cfu (=colony-forming units) lactic acid producing bacteria. The composition of this flora is a result of which specific strains the woman has inherited from her mother and/or which strains have migrated from her digestive tract to the urogenital tract.
Prior art describes formulations, such as suspensions, suppositories and gelatine capsules, comprising viable lactic acid producing bacteria. Such formulations are for instance disclosed in U.S. Pat. No. 5,466,463 and WO 9 309 793.
Furthermore, it is known how to impregnate absorbent articles, such as tampons and sanitary napkins, with lactic acid producing bacteria for the purpose of preserving a normal microbial flora in the urogenital tract of women, and thereby preventing urogenital infections, or regenerating a normal microbial flora in the urogenital tract of women. Such a product is disclosed in EP 0 594 628 and the Swedish patent application 0003544-4.
However, to obtain the above disclosed effect it is crucial that the uropathogen-inhibiting, lactic acid producing bacteria really colonise and establish in vivo, and actually remain in the vagina over more than one menstruation cycle upon vaginal administration.
Whether a bacterial strain will colonise the vagina or not is dependent on the adhesive properties of the specific bacterial strain as well as the hormonal, nutritional and acidity status of the vagina. Ongoing genital infection or treatment with antibiotics will also influence the ability of an introduced strain to colonise the vagina.
The menstrual cycle also affects the adherence, and maximum adherence occurs prior to ovulation and prior to menstrual discharge (U.S. Pat. No. 6,180,100 and Chan et al, Journal of Urology, March 1984). Thus, the most difficult time for administered lactic acid producing bacteria to colonise and establish in the vagina is during menstrual discharge.
With regard to colonisation and establishment of lactic acid producing bacteria in vivo, there might be a considerable disparity between clinical results and supposed bacterial behaviour from interpretation of in vitro analysis results. It is common that interactions between different bacterial species occur in the vagina, and this interaction pattern is difficult to recreate in the laboratory. Thus, even if a bacterial species display promising in vitro results, it might not establish in vivo and provide the desired therapeutic effect, i e to prevent, alleviate the effects of, and/or treat a microbial infection of the urogenital tract.
Furthermore, it is of great importance that the bacteria display stability of its genetic profile both upon repeated cultivation in large-scale production and for longer periods in vivo.
Another criterion that has to be fulfilled to produce an acceptable consumption product that provide the desired therapeutic effect, is the preservation of bacterial viability upon lyophilisation of the bacteria and upon storage of the lyophilised bacteria (i e, shelf life).