The Protective Lactobacillus System
Role of lactobacilli
The human vagina possesses a bio-system which under normal conditions provides a balance between physiologic lactobacilli and pathogenic bacterial flora, and so ensures a good protection against the spreading of pathogens, including their ascension to the uterine cavity. The importance of lactobacilli for the normal vaginal milieu was first described by Döderlein [1892].
In an article of particular interest to us, Gregor Reid [2001] describes the role of lactobacilli in urogenital tract infections.
The following main functions of lactobacilli are known (Fig. 1):
1. They produce acids, mainly lactic acid.
2. They produce hydrogene peroxide (H2O2), which releases oxygen and has a disinfecting effect. These factors, combined with
3. Bacteriocines inhibit the growth of pathogens which are always present in the vagina.
4. They produce biosurfactants, which cover the surface of the vaginal wall, thereby inhibiting the adhesion of pathogens
5. They produce coaggregation molecules which block the spread of pathogens.
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Fig 1: Protective vaginal bio-system
Please click on the miniature picture
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Not every lactobacillus strain produces all the factors mentioned above. That’s the reason why some strains are more effective against specific infections than others. For instance, women with H2O2-producing lactobacilli have a lower risk of suffering from Bacterial Vaginosis, than women whose lactobacilli don’t produce H2O2 [Hillier et. al 1992a]. Unfortunately, there are also some microorganisms, the growth of which is not or only marginally inhibited by lactobacilli (e.g. Streptococci and Candida).
However, we can assume that lactobacilli are the main regulating factor of the vaginal milieu. Vaginal pH measurement gives us insight – like peering through a keyhole – into this protective bio-system. Vaginal pH measurement was already used by Döderlein, in order to distinguish pathological from normal vaginal fluid [Döderlein 1892].
Importance of pH measurement
The importance of Lactobacilli and measurement of vaginal pH is illustrated for instance by the following facts:
Ernest et al. [1989] found out, that the risk of premature rupture of the membranes before 37+0 gestational weeks (gw) is three times higher when the vaginal pH is repeatedly above 4.5, compared to pregnant patients with pH  4.5.
From a retrospective evaluation carried out by one of our co-workers it reveals that: The earlier in pregnancy the examined children were born, the more frequently the mothers had an increased vaginal pH, when admitted to hospital. All 15 mothers (100%) of children with a gestational age lower than 32+0 gw had increased pH values, as far as prematures between 32+0 gw and 36+6 gw were concerned, the rate was still about 60%; when born mature only 43.5 % were affected [Schumacher 1999]. It follows, that ascending infections very frequently play a role concerning very early prematurity, and that in many of these cases threatening prematurity can be detected by measurement of increased pH values.
In a prospective study, Hengst et. al [1992] was able to show the practical importance of measuring the vaginal pH, which we recommend in routine prenatal care for the prevention of prematurity. In a cohort of pregnant women with so far normal course of pregnancy, who had an increased pH values of > 4.5 and who had received no therapy for acidification, the number of prematures amounted to 15.1%. On the other hand, the number was only 2.0% when an acidifying therapy with L. acidophilus preparations had been applied.
In another earlier evaluation, we also found results concerning how many pregnant patients had normal vaginal pH values and how many had pathological ( 4.7). In 67% of all the 695 evaluated cases, normal pH values were present; in 33%, the values were increased twice or more, and 7% of these were permanently increased [Saling et al. 1995].
It is of particular interest to examine the success rate in normalizing the pH, in cases with increased vaginal pH values, by using L. acidophilus therapy. Success was achieved in 83% of 75 such patients, and this is really an unexpectedly good result. The therapy was carried out for 5 ± 3 days to achieve this success [Saling et al. 1995].
Normal flora – disturbed milieu – infection
According to some published data, we assume that the main reason for the good results of our Prematurity-Prevention-Program is not the early detection of existing infections, but the early detection of their precursors, namely disturbances of the vaginal milieu:
Hillier et al. [1992b] diagnosed an intermediate pattern between normal flora and Bacterial Vaginosis – see also Schröder [1921] – in 16% of the pregnant women examined, while 22% of the women suffered from Bacterial Vaginosis, and 61% had a normal flora. Of the women with such a transitional stage in the 2nd trimester, in the 3rd trimester in about 1/3 the findings were the same, in about 1/3 the findings were normal, and about 1/3 developed a Bacterial Vaginosis.
Hay et al. [1994] found in a study an increased risk for loss of pregnancy, when just an intermediate pattern was present.
Viehweg et al. [1997] reported, that an increasing pH value during the course of pregnancy leads to an increased risk of prematurity, even when the pH value stays within the normal range.
In the literature, there are controversial results concerning the success of treatment of Bacterial Vaginosis, and its effects on pregnancy outcome. However, there may have been little success, when screening, diagnose, and treatment took place rather late in the course of pregnancy, or when the diagnosis was incorrect, and there was probably a so-called ”Aerobic Vaginitis” (which is associated with aerobic microorganisms, mainly group B streptococci and E. coli) rather than a Bacterial Vaginosis [Donders et al. 2002].
We assume, that the main reason for those different results is the following:
Up to now no studies have been published, where vaginal acidity was checked by pH-measurement so early in pregnancy, and at such short intervals (allowing early treatment), like is the case for the pregnant women, who participate in our Self-Care-Program.
We have first results which indicate, that already disturbances of the vaginal milieu can be detected by pH-measurement at regular intervals, before Bacterial Vaginosis develops [Saling/Schreiber 2005]. In 24 pregnant patients, who visited their doctor because they had themselves measured an increased vaginal pH value, 33 diagnoses were made:
46% of the patients were told, that they only had a disturbance of the vaginal milieu, and not yet a Bacterial Vaginosis.
A Bacterial Vaginosis was diagnosed only in 4%.
Candida were diagnosed in 33%, Chlamydia in 8%, and other bacteria in 8%, too.
Although we received these data from the patients, and not directly from their physicians – and thus they should be interpreted with caution – there is no reason to question the results on principle.
Further information:
Prematurity-Prevention-Program
Self-Care-Program for pregnant women to prevent prematurity
Early Total Cervix Occlusion
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