Try out PMC Labs and tell us what you think. Learn More. Bacterial vaginosis BV is the most common cause of vaginal discharge. Secondary objectives were to correlate low versus high Nugent scores with vaginal symptoms among women with BV and to correlate BV diagnosis with sexual practices. Among women with BV reporting symptoms, there was no ificant difference in the proportion of women with low-positive versus high-positive Nugent scores.
Bryan Larsen, Gilles R. The microbiological flora of the lower female genital tract provides a dynamic, complex example of microbial colonization, the regulation of which is not fully understood. When an exogenous bacterial species, with its array of virulence factors, is introduced into the host, disease does not always occur.
Conversely, under selected conditions, commensal endogenous bacteria—for example, Gardnerella vaginalis and group B streptococci—can participate in disease processes. Disease caused by both exogenous and endogenous bacteria correlates positively with a markedly increased level of bacterial replication.
The key question is what determines the quantity of a given bacterium at any given time.
For disease to occur, exogenous or endogenous bacteria that possess pathogenic prerequisites must attain replicative dominance. Their ability to do so is potentially governed by inhibitory or synergistic interrelationships with other microbes. The microbiological flora of the lower female genital tract is a dynamic, complex example of microbial colonization, the regulation of which is not fully understood. Much of what we know about the bacterial composition of the female genital tract is derived from qualitative, descriptive studies [ 1—10 ].
The fund of information that such studies have provided with regard to the microbial flora of the lower female genital tract is weakened by the intrinsic technical limitations that are inherent in the studies. Often, even the usefulness of qualitative data is negatively affected by inappropriate or suboptimal methods of data collection, failure to use appropriate transport systems or enriched media, or a lack of stringent anaerobic technique in the processing and culture of specimens. The importance of using specialized media is illustrated in a study of Clostridium difficile by Bramley et al.
These investigators evaluated cultures of vaginal specimens obtained from women who made a total of visits to a family planning clinic, and they found this organism in only 1 patient.
Unprotected sex may disrupt the microbiome in vagina
However, when a specialized medium that contained 0. One can only speculate as to how many more microbial species would have been recovered if truly optimal media and methods had been used for all studies reported in the literature prior to the s. Isolation techniques used prior to the s resulted in a gross underestimation of the importance of anaerobic bacteria as major constituents of the normal flora of the female genital tract.
Failure to use appropriate transport systems as well as failure to use optimal media and anaerobic culture techniques have compromised the of many studies with regard to the delineation of the bacterial constituents present. Although anaerobic bacteria had been identified ly, it was not until publication of the work of Gorbach et al. Gorbach et al.
This ratio clearly reflects a dynamic colonization process. For example, although adolescent subjects appeared to have a greater prevalence of anaerobic bacteria, aerobic bacteria appeared to become more abundant with advancing age, onset of sexual activity, and parity. A study of postmenopausal women who were either receiving or not receiving estrogen replacement therapy found that such therapy had no effect on facultative organisms; however, anaerobic isolates tended to be less prevalent among women who received such therapy.
A notable exception, however, were anaerobic lactobacilli, which appeared to be more prevalent in the tissue of women receiving estrogen therapy [ 12 ]. Combined qualitative and quantitative studies require a quantum increase in technical effort and, as a consequence, tend to be limited in scope despite yielding richer information [ 13—18 ].
Recent studies have begun to focus more on the fact that the density of microbial colonization appears to be relevant not only to the condition of asymptomatic individuals but, also, to the initiation of disease states, in which it is a critical factor [ 131819 ]. The microbial load for a given organism appears to influence the relative risk of symptomatic infection; however, in the absence of quantitative data, data that have been extrapolated from qualitative studies e. The concept exploited is that organisms of which there are a great are readily found in cultures, whereas those species that are fewer in may not be noticed during primary isolation.
Quantitative studies of upper and lower female genital tract disease due to exogenous bacterial species e. The studies that have been published to date, although technically imperfect, do provide some information regarding the dynamics of the bacterial flora of the female genital tract.
Studies of the normal bacterial flora of the female genital tract are primarily limited to characterization of the types of bacteria present in women who do not have identifiable disease. Studies by Bartlett et al. In terms of planning empirical therapy, it may be just as important to know which organisms are not isolated with high frequency as it is to know which organisms are commonly isolated. Prevalence of aerobic facultative isolates Wives looking real sex Flora in vaginal flora studies published in the literature.
Prevalence of anaerobic microorganisms present in cultures of cervical and vaginal specimens obtained from asymptomatic women according to the of selected reports. Within colonized tissues, such as those of the female genital tract, what constitutes a pathogen is dependent not only on the type of offending microorganism and its intrinsic virulence but, also, on the species complexity of the flora—that is, the relative dominance, in s, of the various bacteria that can be recovered—in individual asymptomatic patients.
Comparisons of vaginal flora patterns among sexual behaviour groups of women: implications for the pathogenesis of bacterial vaginosis
According to traditional thinking, a pathogen was a microbe that was genetically endowed with a factor that, when expressed, caused disease. This postulate became central to the concept of the monomicrobial etiology of infectious diseases, which was derived from correlation of the disease back to the etiological agent. Examples that fit this concept well are diseases caused by N.
However, the mere presence of an unknown, exogenous, potentially pathogenic species does not necessarily constitute disease when disease is defined in terms of symptoms. Understanding how specific bacteria produce disease has been tied to knowledge of virulence properties, which allow the bacteria to function as monoetiological agents.
Such microorganisms as Neisseria gonorrhoeae, Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, Listeria monocytogenesand Trichomonas vaginalis are not ordinarily part of the flora of the female genital tract. Once the normal bacterial constituents of the female genital tract are defined, one is confronted with having to explain why apparently commensal bacteria e.
In the middle of the 19th century, Pasteur provided evidence that the presence of an organism, such as the anthrax bacillus, in a host is associated with disease; however, there frequently Wives looking real sex Flora been a tendency to think that the mere presence of certain organisms is synonymous with disease.
It was not until the early part of the 20th century that Theobald Smith introduced the idea that disease was the result of the interplay between microbial virulence, dominance of the organism in terms of s, and the innate defenses of the host [ 25 ]. Because Koch's postulates stated that monoetiological disease could be demonstrated through production of infections in animals, many studies were done in which animals could be successfully infected with microbial pathogens.
Often, however, these infections eventuated only when a change in the microenvironment was created as part of the experimental model of infection. For example, peritonitis might be more efficiently induced when blood is added Wives looking real sex Flora the inoculum.
Gangrene has been known to develop when calcium chloride is implanted into muscle along with the Clostridium species. In rodents, vaginal infection with Candida albicans requires estrogen replacement therapy for the animal host. Bacteria that are normal constituents of the vaginal flora of the host have the potential to cause symptoms of disease, but they apparently require some alteration in the microenvironment to do so.
These seeming inconsistencies focus on a critical question regarding the pathogenesis of infectious diseases: what enables a given organism to produce disease? For endogenous bacteria of the female genital tract, the microbiological environment may supersede selected inherent virulence factors in terms of importance; at the very least, the microbiological environment may affect the bacterial expression of virulence factors [ 26 ].
Theoretically, if a virulence factor is constitutive, the of organisms present will determine the amount of the virulence factor available to promote infection. The of organisms may be controlled by means of the antagonistic or synergetic interaction between the different microbial species present. Three relatively common conditions that involve the female genital tract—namely, vaginal candidiasis, bacterial vaginosis, and infection with GBS—show evidence of regulation.
During the past several decades, the many published surveys of vaginal flora specimens obtained from asymptomatic women have clearly shown that C. In a study by Glover and Larsen [ 27 ], the of successive cultures of vaginal flora specimens obtained from women who were followed throughout pregnancy indicated that Candida species may be present in stable association with the genital epithelium.
Moreover, the majority of women who have vaginal yeast also carry the organism in the gut. The typical rate of yeast carriage varies among populations and increases both after puberty and during pregnancy, which suggests an important role for host physiology in cases of vaginal candidiasis.
Oral sex linked to vaginal condition bacterial vaginosis
A relationship between estrogen levels and bacterial colonization has been recognized almost since the inception of studies of normal vaginal flora; this relationship holds true for Candida species as well. For example, rats are resistant to colonization by Candida species, unless the animals have an amount of estrogen sufficient enough to cause vaginal cornification [ 28 ]. Growth of bacteria in the flora of the genital tract is stimulated by estrogen [ 2829 ].
Prevalence of Lactobacillus species and prevalence of yeast in different populations tend to show that the times when prevalence of Lactobacillus species is highest during the reproductive years and, especially, during pregnancy are also the times when the prevalence of Candida species is highest. Hydrogen peroxide-producing Lactobacillus species may co-colonize with Candida species [ 28 ]. Although Candida species are less susceptible to the microbicidal effects of hydrogen peroxide than are non-catalase producers, such as N.
This is presumably due to the fact that hydrogen peroxide Wives looking real sex Flora cellular membranes unimpeded by the intracellular catalase [ 32 ]. Classically, vulvovaginal candidiasis occurs in association with a ificant increase in the of colony-forming units of Candida species that are present in the tissue-invasive form.
Any microbiological influence that allows the yeast concentration to increase may result in the development of symptoms, and any microbiological effect that suppresses the of yeast could ensure that it remains as a commensal organism [ 3334 ]. Both studies of animal models and observation of humans suggest that there is an inverse relationship between bacterial and yeast floras with respect to prevalence and numerical abundance.
Savage [ 35 ], in a classic study of the gastric flora of mice, found that 2 distinct tissue areas exist, and these are normally colonized by a nearly pure culture of Lactobacillus species and a nearly pure culture of yeast, respectively. When Lactobacillus species were eliminated by means of antibiotic treatment, the yeast took over the microbiological void.
This observation suggested control of yeast through an antagonistic effect of the Lactobacillus species.
Conversely, Candida species may exert their own antagonistic effects on populations of bacteria. Monif and Carson [ 36 ] compared the patterns of isolates from women with and without co-isolation of C. In the presence of C. Hipp et al. Later, Shah and Larsen [ 3839 ] showed that Candida species can produce gliotoxin, which, along with other inhibitory compounds in appropriate concentrations, is antagonistic toward various bacteria. The relationship of G. McCormack et al.
Role of oral lactobacilli on vaginal flora of pregnant women
Again, the difference between colonization and disease appears to be partially a function of the magnitude of replication of bacteria. Quantitative bacteriological studies have shown that symptoms that involve G. For disease to occur, not only must there be an environment that will sustain G. For metronidazole to function effectively, an organism must have a functional nitroreductase system. This observation has led investigators to speculate that the mechanism by which metronidazole has its effect involves its impact on the concomitantly flourishing anaerobic bacteria population, which sustains dominance in conjunction with Gardnerella species [ 43 ].
The complexity of interspecies interactions has not been completely unraveled with regard to BV. Among the prevailing conditions in the patient who has BV are an elevated pH level range, 5—5. It is not clear what precipitates the condition, and several causes could be suggested.
A decrease in the of lactobacilli could result in decreased production of hydrogen peroxide and acid, thereby allowing for unrestricted growth of other constituents of the flora. A shift in the redox potential favoring anaerobic bacterial may in turn contribute to proteolysis, thereby leading to a more alkaline environment [ 46 ].
Sexually transmitted bacteria
The proteins and amino acids that are released may be metabolized by anaerobic bacteria as a result of the production of amines, which contribute to both the alkalinization of the vaginal environment and the odor problem, and which may also contribute to vaginal irritation [ 47 ]. Some anaerobic bacteria produce succinic acid, which is known to diminish the efficacy of neutrophilic phagocyte activity; this may allow for some species to proliferate [ 48 ].
Increased growth of Gardnerella species can augment production of hemolysin, which may further blunt any phagocytic protection that might otherwise occur in the vaginal milieu [ 49 ].