Medical Hypotheses I Mdical Hyporhcrrs (1991) 36. 126-130 (D Langnan UK Lid 1991
Gmup
The Ecologically Wrong Vaginal Lactobacilli C. PAHLSON* and P.G. LARSSON+ *Department of Clinical Immunology and Transfusion Medicine, University Hospital Uppsala, 757 85 Uppsala, Sweden, ‘Department of Obstetrics and Gynecology, Wmsjukhuset, 541 86 Skiivde, Sweden
Abstract - Morphologically different Lactobacilli can be observed in wet smear preparations from the lower female genital tract; this morphological difference seems to correlate with the ability of the bacterium to produce hydrogen peroxide. This discussion will examine the role of the normal bacterial flora in protection of the host against recurrent infections. Further, we will propose a model as to how the potential role of immunological tolerance or ‘immunological preference for’ the maternal bacterial flora, can give individual differences in disposition for infections.
Introduction
In the first microbiological study of the human vagina, Doderlein in 1892 described long straight Gram positive bacteria, later found out to be Lactobacilli, as the normally predominating species (1). This was an observation so generally accepted that the bacteria are still called ‘Doderlein’s bacilli’. A simple way to discriminate between different bacterial species is microscopic examination of the morphology and size of the bacterium. By this method most vcnercologists and gynaccologists examine different bacteria, and this could explain why authors who publish photographs of the normal wet smear are giving a uniform picture, with all lactobacilli of a similar size (Fig. 1). However, it is known that within the genus Laclobacillus the morphology can vary from long slender rods to coryneform coccobacilli, and that some of the species are uniform in size, while others can vary as much as from 0.5-6.0 urn (2). The genus Lactobacilli consist of a conglomerate of at least 44 different species. Microbiological studies have shown
that the lactobacilli occurring in the vagina can be divided into a great variety of species and strains, where the most frequent occurring species is L. acidophiluf (3, 4). The
colonization of vagina takes place in the birth canal during delivery, and the flora that is established in the newborn girl must therefore consist of the same strains as in the mother. The reason why lactobacilli colonize newborn girls is probably the high content of glycogen in the epithelial cells, which creates a good environment for lactobacilli. The newborn girl has the mature woman’s levels of oestrogen, a hormone that among other things stimulates the anabolism of glycogen in the epithelial cells. During the first month after birth the level of the hormone, and thereby the glycogen content of the epithelial cells, decreases to the level of the prepubertal girl. The number of lactobacilli in the vagina will also decrease and the flora will be dominated by normal skin and emetic bacteria. At menarche, lactobacilli once again become predominating when the glycogen level increases, stimulated by endogenously produced oestrogen. In the
Datereceived
2 May 1990 Date accepted 21 June 1990
126
127
THE I?COLOGIC!ALLY WRONG VAGINAL IACI-OBACILLI
Figs. l-9 Different morphological types of Lactobacilli. 1. long straight type ‘DCderleins bacii’. 2. Wet smear of patient with Bacterial vaginosis. 3. Wet smear from healthy women with straight lactobacilli of variable size. 4. Gram stained bacteria fran single colony of isolated pure cultured strain from patient in Figure 3. 5. Wet smear from a patient with cytolysis and long straight Lactcbacilh. 6. Wet smear from patient with cytolysis and short straight Lactobacilli. 7. Wet smear fran a patient with straight lactobacilli dominated by the shorter variant (similar to Fig. 3). 8. Wet smear fran women with long fusiform Lactobacilli. 9. Curved Lactobacilli in wet smeer of healthy women.
child-bearing age of life, women furthermore have a temporal variability in the numerical relation between different species of bacteria, connected to the menstrual cycle. In spite of these and individual differences, changes from the normal flora can be seen as pathological. In 1984, the syndrome Bacterial vaginosis, BY previously non-specific vaginitis (NSV), or Gardnerella vaginalis vaginitis, was defined (5). The BV syndrome is defined when at least three of the following four criteria are fulfilled: 1)
typical homogeneous discharge;
2) 3) 4)
pH > 4.5; positive amindor sniff test and; presence of ‘clue cells’.
By microscopy the BV syndrome is characterized by a fundamentally different bacterial composition, almost exclusively consisting of an enormous amount of coccoid bacteria (Fig. 2). In BV the most common bacterial species found are Gardnerella vaginalis, Bacteroides sp. and cat&se positive coryneforms (6). This is a situation completely different, compared to the corresponding normal flora which is a monoculture of lactobacilli.
MEDICAL HYFQTHESES
128 BV is a very common syndrome, and can be diagnosed in approximately lO-30% of the female population attending for gynaecological examination at an STD clinic (7). Clinically the acute BV is easily cured by the antibiotic metronidazole. However, this treatment gives a high rate of relapse, or re-infection - up to 50% (8) - on a 2-year basis. Another common inflammatory problem of the female genital tract is ‘Candida vaginitis’ which starts by overgrowth by the yeast Candida albicans. However, about l/3 of all women are colonized by Candida, and there is a discussion if Candida should be considered as a pathogen or as a member of the normal flora. Often Candida vaginitis starts in connection with penicillin therapy, for example given against an upper respiratory tract infection. The penicillin will inhibit the normally occurring lactobacilli but not the infecting fungi. These types of vaginitis are easily treated with antimycotic drugs. In some women, however, Candida vaginitis can be a rather severe handicap as the infection often recurs after therapy. As the antimycotic drugs are very effective, and exterminate all living fungi, it seems that these women are specially sensitive to re-infection. Another common mild form of vaginitis is cytolysis, or cytolytic fluor, a syndrome characterized by an massive growth of lactobacilli. This condition is by most authors considered harmless or even as a sign of health. This condition can also be seen in very young women before they start to ovulate and is in these cases thought to be caused by an increased level of oestrogen. We have indications that cases of cytolysis occurring in the child-bearing period of life could be caused not by the increased oestrogen level itself, but by characteristics of the lactobacillus strain. It is known that lactobacilli have an ability to produce a variety of different bactericidal substances like inhibitory proteins (9), lactic acids (lo), ‘lactocidines’ (11) or hydrogen peroxide Hz02 (12). Eschenbach has shown that lactobacilli occurring in patients with BV differ in their ability to produce H202, compared to lactobacilli isolated from healthy women (13). Hydrogen peroxide is an extremely toxic substance which can kill both pro- and eucaryotic cells, it is regularly produced in the respiratory chain, where it normally is converted to water by a reaction catalysed by one of the most efficient enzymes known, catalase. Lactobacilli, however, neither have cytochromes nor menaquiones, and they utilize oxygen only via flavin-containing oxidases and pcroxidases. None of the lactobacilli species produce catalase, a fact that
makes bacteriologists use the lack of this enzyme as a biochemical criterion to discriminate between different species. The lack of cytochromes might suggest that lactobacilli do not produce Hz@ for energy production but as a bactericidal substance to compete with other bacteria. Observations
In studies of BV therapy (8), we have observed that the microscopic picture of the lactobacilli after treatment varies between different individuals. The main differences are in shape and number of the lactobacilli seen or isolated. We have also seen that the different morphological types can be divided into different biochemical types by their ability to produce H202. The most common morphological type of lactobacilli which, in a wet smear does not appear as a monoculture, but occurs in both long and short forms shows, however, in pure culture the same impression of bacteria of different sizes. Figure 3 shows the wet smear from a healthy patient and Figure 4 shows the gram stained bacteria from a single colony from the same patient. This is the most common type found in healthy patients and the type that almost exclusively gives Hz02 production. If the woman is colonized with a strain of homogeneous long bacteria, and if the bacteria occur in high numbers, the patient suffers from cytolysis syndrome (Fig. 5). In cases of cytolysis the patient may also be colonized by a short homegeneous strain of lactobacilli (Fig. 6): none of the strains isolated from patients with cytolysis seem to produce Hz& and we believe that these patients are a risk group for re-infection with Candida or BV. A variant of lactobacilli occurring in healthy patients is one with a morphology that in the microscope shows a curved form (Fig. 9). This form may be misunderstood for curved rods or Mobiiuncus in smears. This form seems too be less common, but must be classified as a member of the normal flora, since it in the few cases where we have had the opportunity to test it always has shown Hz@ production. The Table shows the approximate number of the different morphological types in a consecutive series of patients attending for first trimester therapeutic abortion during one year. Cytolysis will mostly occur after treatment with different antimicrobial agents. This could then be due to the fact that the lactobacilli which have recolonized the women belong to a strain that has so little of the antibacterial substances that it will grow without restriction.
THE ECOLOGICALLY WRONG VAGINAL LACTOBACILLI
Table Number of patients with different morphological wet smear preparation, 981 patients examined. Wet smear
No. of parienls
Total no. of patients Bacterial vaginas Nr patients wilh iacobaciili Variable,slraighl Long, straight ‘cyfolysis’ Shor,f, straight %ytolysir’ Shor,f, straight irormal amount’ Very long ‘*(form’ Curved Mixed
(%I
types in
Representative morphology figure
1293
348
26.9*
2
945 438
loo*’ 46.3
3
163
17.3
5
132
14.0
6
80
8.5
7
70 39 23
7.4 4.1 2.4
8 9
*The. parcentage of patients with Bacterial vaginosis in the total material of 1293 patients, no Lactobacilli could here be determined by microscopy. * l The percentage of patients with Lacobacilli in wet smear.
Our hypothesis Our hypothesis postulates that within the genus lactobacilli there are a number of species/strains that can produce various amounts of different bactericidal substances that can inhibit growth of other bacteria, fungi or protozoa and furthermore self-restrict its own growth and thereby protect the women differently against infection or re-infections after antimicrobial treatment, and that it is possible to identify these species/strains by microscopy. If this hypothesis is correct it will mean that: 1. Bacterial vaginosis is a congenital disease. If the particular strain the girl was first colonized with is protected from the local immune defence of the host by immunological tolerance, developed by growth of a particular strain of lactobacilli during the neonatal period. Hence, the lactobacillus strain that the girl has received from her mother will be the strain that follows her through life. This is similar to with what we know from studies of E. cofi in the gut (14). 2. The attempts that have been made to explain the recurrence of BV have mostly dealt with the type and duration of the antibiotic regimen used. The recurrences of Candida infections have always been hard to
129
understand, as the antifugal substances available are very effective. This can be due to the ability of different lactobacilli to protect the host against infections; according to our hypothesis, a low number of Cundidu albicans, together with lactobacilli with a high production of H207, will be a stable ecosystem. This could explain why many women harbour the yeast cells without symptoms and that Cundidu could be considered as a commensal. If the lactobacilli, on the contrary, have a low or absent production of Hz% there will be no restriction in the growth of the yeast cells which will create a Candida vaginitis with symptoms. 3. An even more interesting subject is the connection between different lactobacilli and premature birth (~37 weeks of gestation) or PROM (premature rnpture of the membranes). These are conditions representing a high rate of mortality and morbidity all over the world. The cause is still unknown but many studies have suggested that an infection could be the cause (15). An indication of this is that culture from transabdominal puncture, of the supposed sterile amnion liquid, seems to yield a variety of bacteria among which also lactobacilli spp could be isolated (16). According to our hypothesis, women colonized by low protecting lactobacilli could more easily be colonized by a higher number of opportunistic bacteria that can cause a chorioamnionitis, a plausible theory since culture from the cervix will yield mostly normal vaginal flora including lactobacilli. 4. Nearly 30% of pregnant women ha&our group B streptococci, GBS, but only a few will suffer from any complication connected to the infection. This may be due to the amount of GBS harboured, a quantitative difference that could be explained by the protective capacity of the lactobacilli strain. As our culture is only qualitative, obstetricians normally do not use cervical cultures to identify the risk group of GBS infections. Instead, the use of urine sampling has become widespread. If the pregnant woman still has GBS in her urine culture after treatment, she will be at risk. As urine culturing is quantitative the women must be colonized with high numbers of GBS in the vagina if it easily could re-infect the urine. With an ecologically correct lactobacilli strain only a small number of GBS can develop and the GBS in the vagina will be harmless. But with the ecologically wrong lactobacilli the number of GBS can rise to a number so high that when the child is passing through the birth canal it will be infected with so many GBS that it can produce the typical neonatal early onset GBS, which has a high mortality rate.
130 5. There exists a vaccine against BV and Trichomoniasis (17). This vaccine consists of whole lactobacilli, isolated from women with trichomonas infection. The vaccine effect was first proposed to be caused by antibodies cross-reacting with Trichomonas (18). However, this has later been shown to be wrong (19). The efect of the vaccine can with our hypothesis be explained, if the vaccine breaks the tolerance of the host and makes it possible for the immune defence to attack the wrong, non-HZOZ-producing lactobacilli and create an environment for the H202--producing strain of lactobacilli to become dominant. 6. Ecological treatment of BV has been reported as inactive (20), but these studies have to be repeated with different types of lactobacilli since we do not know if the L. acidophilus strain used was a Hz%producing variant or not. Conclusion As has been discussed here, the microbial flora of the human vagina seems to be an extraordinary stable ecosystem, except when infected by the recognized pathogenic microorganisms. We propose that it is possible by microscopy to determine the normal flora’s ability to protect the host from infection or re-infection after therapy. Further studies will find out if it is possible to change the normal flora from one type of lactobacilli to another, and if these types can be designated to different taxonomic species of the genus Lactobacilli. A further challenge is to find out how this kind of flora exchange should be practically performed. References Doderlein A. Das scheidensekret und seine bedeutung fiir das puerperalfieber. 0. Durr, Leipzig, 1892. Krieg NR, Halt JG (eds). Bergerys manual of systematic bacteriology. Volume 1. Williams and Wilkins Baltimore/London, 1984. Rogosa M. Shape ME. Species differentiation of human vaginal lactobacilli. J Gen Microbial 23:197. 1960. Wylie G, Henderson A. Identity and glycogen-fementing ability of lactobacilli isolated from the vagina in pregnant women.
MEDICAL HYPOTHESFiS
J Med Microbial 21:363, 1969. D. (eds): Bacterial Vaginosis. 5. MPrdh P-A, Taylor-Robinson Stand J Ural Nepbrol Suppl 86, 1985. 6. Taylor E, Barlow D, Blackwell A, Pbillps I. Gardnerella vaginalis, anaerobes and vaginal discharge. Lancet 1, 1376-1379, 1982. I. Hallen A, Pahlsar C, Forsum U. Bacterial vaginosis in women attending a STD clinic: diagnostic criteria and prevalence of Mobiluncus spp. Genitourin Med 63:386, 1987. 8. Larsson PG, Bergman B, Forsum U, Piihlson C. Treatment of BV in women with vaginal bleeding complicatiars or discharge and ha&outing Mobiluncus. Gynaecol Obstet Invest. In press. 9. Mehta AM, Pate1 KA, Dave PJ. Isolation and purification of an inhibitory protein from Lactobacillus acidophilus ACl. Microbios 37~37. 1983. acidophilus. 10. Tramer J. Inhibitory effect of Lactobacillus 211:204, 1966. 11. Vincent JG. Veomett RC. Riley RF. Antibacterial activity associated with Lactobacillus acidophilus. J Bacterial 78:477. 1959. 12. Wether DM, Ilirsch A, Mattrick ATR. Possible identity of ‘lactobacillin’ with hydrogen peroxide produced by lactobacilli. Nature 170:623. 1952. 13. Eschenbach D, Davick PR, Williams BL, Klebanoff SJ. Young-Smith K, Critchlow CM, Holmes KK. Prevalence of hydrogen peroxide-producing Lactobacillus species in normal women and warren with bacterial vaginosis. J Clin Microbial 27~251, 1989. 14. van der Waaij D. Evidence of Immunoregulation of the composition of intestinal microflora and its practical consequences. Eur J Microbial Infect Dis 7:103, 1988. 15. McGregor JA. Prevention of preterm birth: New initiatives based on microbial-host interactions. Obstet Gynecol Surv 43:2. 1988. 16. Cox SM, Phillips LE. Mercer LJ. Stager CE. Waller S, Faro S. Lactobacillemia of amnioc fluid origin. Obstet Gynecol 68:134. 1986. 17. Milovanovic R, Grcic R, Stojkovic L. Changes in the vaginal flora of trichomoniasis patients after vaccination with SolcoTrichovac. In Gyniikol Rundsch (Riittgers H, ed.) Base1 Kager 23:50, 1983. 18. Pavic R, Stojkovic L. Vaccination with Solco-Trichovac. Immunological aspects of a new approach for therapy and prophylaxis of trichomoniasis in women. Gynekologishe Rundschrift 23:suppl 2:27. 1983. 19. Alderete JF. Does IactobacilIus vaccine for trichmariasis, Solco-Trichovac, induce antibody reactive with Trichomonas vaginalis? Genitourin Med 64:118. 1988. 20. Fredriksson B, Englund K, Weintraub L, Glund A, Nordh CE. Ecological treatment of Bacterial vaginosis. Lancet II:276, 1987.
Gmup
The Ecologically Wrong Vaginal Lactobacilli C. PAHLSON* and P.G. LARSSON+ *Department of Clinical Immunology and Transfusion Medicine, University Hospital Uppsala, 757 85 Uppsala, Sweden, ‘Department of Obstetrics and Gynecology, Wmsjukhuset, 541 86 Skiivde, Sweden
Abstract - Morphologically different Lactobacilli can be observed in wet smear preparations from the lower female genital tract; this morphological difference seems to correlate with the ability of the bacterium to produce hydrogen peroxide. This discussion will examine the role of the normal bacterial flora in protection of the host against recurrent infections. Further, we will propose a model as to how the potential role of immunological tolerance or ‘immunological preference for’ the maternal bacterial flora, can give individual differences in disposition for infections.
Introduction
In the first microbiological study of the human vagina, Doderlein in 1892 described long straight Gram positive bacteria, later found out to be Lactobacilli, as the normally predominating species (1). This was an observation so generally accepted that the bacteria are still called ‘Doderlein’s bacilli’. A simple way to discriminate between different bacterial species is microscopic examination of the morphology and size of the bacterium. By this method most vcnercologists and gynaccologists examine different bacteria, and this could explain why authors who publish photographs of the normal wet smear are giving a uniform picture, with all lactobacilli of a similar size (Fig. 1). However, it is known that within the genus Laclobacillus the morphology can vary from long slender rods to coryneform coccobacilli, and that some of the species are uniform in size, while others can vary as much as from 0.5-6.0 urn (2). The genus Lactobacilli consist of a conglomerate of at least 44 different species. Microbiological studies have shown
that the lactobacilli occurring in the vagina can be divided into a great variety of species and strains, where the most frequent occurring species is L. acidophiluf (3, 4). The
colonization of vagina takes place in the birth canal during delivery, and the flora that is established in the newborn girl must therefore consist of the same strains as in the mother. The reason why lactobacilli colonize newborn girls is probably the high content of glycogen in the epithelial cells, which creates a good environment for lactobacilli. The newborn girl has the mature woman’s levels of oestrogen, a hormone that among other things stimulates the anabolism of glycogen in the epithelial cells. During the first month after birth the level of the hormone, and thereby the glycogen content of the epithelial cells, decreases to the level of the prepubertal girl. The number of lactobacilli in the vagina will also decrease and the flora will be dominated by normal skin and emetic bacteria. At menarche, lactobacilli once again become predominating when the glycogen level increases, stimulated by endogenously produced oestrogen. In the
Datereceived
2 May 1990 Date accepted 21 June 1990
126
127
THE I?COLOGIC!ALLY WRONG VAGINAL IACI-OBACILLI
Figs. l-9 Different morphological types of Lactobacilli. 1. long straight type ‘DCderleins bacii’. 2. Wet smear of patient with Bacterial vaginosis. 3. Wet smear from healthy women with straight lactobacilli of variable size. 4. Gram stained bacteria fran single colony of isolated pure cultured strain from patient in Figure 3. 5. Wet smear from a patient with cytolysis and long straight Lactcbacilh. 6. Wet smear from patient with cytolysis and short straight Lactobacilli. 7. Wet smear fran a patient with straight lactobacilli dominated by the shorter variant (similar to Fig. 3). 8. Wet smear fran women with long fusiform Lactobacilli. 9. Curved Lactobacilli in wet smeer of healthy women.
child-bearing age of life, women furthermore have a temporal variability in the numerical relation between different species of bacteria, connected to the menstrual cycle. In spite of these and individual differences, changes from the normal flora can be seen as pathological. In 1984, the syndrome Bacterial vaginosis, BY previously non-specific vaginitis (NSV), or Gardnerella vaginalis vaginitis, was defined (5). The BV syndrome is defined when at least three of the following four criteria are fulfilled: 1)
typical homogeneous discharge;
2) 3) 4)
pH > 4.5; positive amindor sniff test and; presence of ‘clue cells’.
By microscopy the BV syndrome is characterized by a fundamentally different bacterial composition, almost exclusively consisting of an enormous amount of coccoid bacteria (Fig. 2). In BV the most common bacterial species found are Gardnerella vaginalis, Bacteroides sp. and cat&se positive coryneforms (6). This is a situation completely different, compared to the corresponding normal flora which is a monoculture of lactobacilli.
MEDICAL HYFQTHESES
128 BV is a very common syndrome, and can be diagnosed in approximately lO-30% of the female population attending for gynaecological examination at an STD clinic (7). Clinically the acute BV is easily cured by the antibiotic metronidazole. However, this treatment gives a high rate of relapse, or re-infection - up to 50% (8) - on a 2-year basis. Another common inflammatory problem of the female genital tract is ‘Candida vaginitis’ which starts by overgrowth by the yeast Candida albicans. However, about l/3 of all women are colonized by Candida, and there is a discussion if Candida should be considered as a pathogen or as a member of the normal flora. Often Candida vaginitis starts in connection with penicillin therapy, for example given against an upper respiratory tract infection. The penicillin will inhibit the normally occurring lactobacilli but not the infecting fungi. These types of vaginitis are easily treated with antimycotic drugs. In some women, however, Candida vaginitis can be a rather severe handicap as the infection often recurs after therapy. As the antimycotic drugs are very effective, and exterminate all living fungi, it seems that these women are specially sensitive to re-infection. Another common mild form of vaginitis is cytolysis, or cytolytic fluor, a syndrome characterized by an massive growth of lactobacilli. This condition is by most authors considered harmless or even as a sign of health. This condition can also be seen in very young women before they start to ovulate and is in these cases thought to be caused by an increased level of oestrogen. We have indications that cases of cytolysis occurring in the child-bearing period of life could be caused not by the increased oestrogen level itself, but by characteristics of the lactobacillus strain. It is known that lactobacilli have an ability to produce a variety of different bactericidal substances like inhibitory proteins (9), lactic acids (lo), ‘lactocidines’ (11) or hydrogen peroxide Hz02 (12). Eschenbach has shown that lactobacilli occurring in patients with BV differ in their ability to produce H202, compared to lactobacilli isolated from healthy women (13). Hydrogen peroxide is an extremely toxic substance which can kill both pro- and eucaryotic cells, it is regularly produced in the respiratory chain, where it normally is converted to water by a reaction catalysed by one of the most efficient enzymes known, catalase. Lactobacilli, however, neither have cytochromes nor menaquiones, and they utilize oxygen only via flavin-containing oxidases and pcroxidases. None of the lactobacilli species produce catalase, a fact that
makes bacteriologists use the lack of this enzyme as a biochemical criterion to discriminate between different species. The lack of cytochromes might suggest that lactobacilli do not produce Hz@ for energy production but as a bactericidal substance to compete with other bacteria. Observations
In studies of BV therapy (8), we have observed that the microscopic picture of the lactobacilli after treatment varies between different individuals. The main differences are in shape and number of the lactobacilli seen or isolated. We have also seen that the different morphological types can be divided into different biochemical types by their ability to produce H202. The most common morphological type of lactobacilli which, in a wet smear does not appear as a monoculture, but occurs in both long and short forms shows, however, in pure culture the same impression of bacteria of different sizes. Figure 3 shows the wet smear from a healthy patient and Figure 4 shows the gram stained bacteria from a single colony from the same patient. This is the most common type found in healthy patients and the type that almost exclusively gives Hz02 production. If the woman is colonized with a strain of homogeneous long bacteria, and if the bacteria occur in high numbers, the patient suffers from cytolysis syndrome (Fig. 5). In cases of cytolysis the patient may also be colonized by a short homegeneous strain of lactobacilli (Fig. 6): none of the strains isolated from patients with cytolysis seem to produce Hz& and we believe that these patients are a risk group for re-infection with Candida or BV. A variant of lactobacilli occurring in healthy patients is one with a morphology that in the microscope shows a curved form (Fig. 9). This form may be misunderstood for curved rods or Mobiiuncus in smears. This form seems too be less common, but must be classified as a member of the normal flora, since it in the few cases where we have had the opportunity to test it always has shown Hz@ production. The Table shows the approximate number of the different morphological types in a consecutive series of patients attending for first trimester therapeutic abortion during one year. Cytolysis will mostly occur after treatment with different antimicrobial agents. This could then be due to the fact that the lactobacilli which have recolonized the women belong to a strain that has so little of the antibacterial substances that it will grow without restriction.
THE ECOLOGICALLY WRONG VAGINAL LACTOBACILLI
Table Number of patients with different morphological wet smear preparation, 981 patients examined. Wet smear
No. of parienls
Total no. of patients Bacterial vaginas Nr patients wilh iacobaciili Variable,slraighl Long, straight ‘cyfolysis’ Shor,f, straight %ytolysir’ Shor,f, straight irormal amount’ Very long ‘*(form’ Curved Mixed
(%I
types in
Representative morphology figure
1293
348
26.9*
2
945 438
loo*’ 46.3
3
163
17.3
5
132
14.0
6
80
8.5
7
70 39 23
7.4 4.1 2.4
8 9
*The. parcentage of patients with Bacterial vaginosis in the total material of 1293 patients, no Lactobacilli could here be determined by microscopy. * l The percentage of patients with Lacobacilli in wet smear.
Our hypothesis Our hypothesis postulates that within the genus lactobacilli there are a number of species/strains that can produce various amounts of different bactericidal substances that can inhibit growth of other bacteria, fungi or protozoa and furthermore self-restrict its own growth and thereby protect the women differently against infection or re-infections after antimicrobial treatment, and that it is possible to identify these species/strains by microscopy. If this hypothesis is correct it will mean that: 1. Bacterial vaginosis is a congenital disease. If the particular strain the girl was first colonized with is protected from the local immune defence of the host by immunological tolerance, developed by growth of a particular strain of lactobacilli during the neonatal period. Hence, the lactobacillus strain that the girl has received from her mother will be the strain that follows her through life. This is similar to with what we know from studies of E. cofi in the gut (14). 2. The attempts that have been made to explain the recurrence of BV have mostly dealt with the type and duration of the antibiotic regimen used. The recurrences of Candida infections have always been hard to
129
understand, as the antifugal substances available are very effective. This can be due to the ability of different lactobacilli to protect the host against infections; according to our hypothesis, a low number of Cundidu albicans, together with lactobacilli with a high production of H207, will be a stable ecosystem. This could explain why many women harbour the yeast cells without symptoms and that Cundidu could be considered as a commensal. If the lactobacilli, on the contrary, have a low or absent production of Hz% there will be no restriction in the growth of the yeast cells which will create a Candida vaginitis with symptoms. 3. An even more interesting subject is the connection between different lactobacilli and premature birth (~37 weeks of gestation) or PROM (premature rnpture of the membranes). These are conditions representing a high rate of mortality and morbidity all over the world. The cause is still unknown but many studies have suggested that an infection could be the cause (15). An indication of this is that culture from transabdominal puncture, of the supposed sterile amnion liquid, seems to yield a variety of bacteria among which also lactobacilli spp could be isolated (16). According to our hypothesis, women colonized by low protecting lactobacilli could more easily be colonized by a higher number of opportunistic bacteria that can cause a chorioamnionitis, a plausible theory since culture from the cervix will yield mostly normal vaginal flora including lactobacilli. 4. Nearly 30% of pregnant women ha&our group B streptococci, GBS, but only a few will suffer from any complication connected to the infection. This may be due to the amount of GBS harboured, a quantitative difference that could be explained by the protective capacity of the lactobacilli strain. As our culture is only qualitative, obstetricians normally do not use cervical cultures to identify the risk group of GBS infections. Instead, the use of urine sampling has become widespread. If the pregnant woman still has GBS in her urine culture after treatment, she will be at risk. As urine culturing is quantitative the women must be colonized with high numbers of GBS in the vagina if it easily could re-infect the urine. With an ecologically correct lactobacilli strain only a small number of GBS can develop and the GBS in the vagina will be harmless. But with the ecologically wrong lactobacilli the number of GBS can rise to a number so high that when the child is passing through the birth canal it will be infected with so many GBS that it can produce the typical neonatal early onset GBS, which has a high mortality rate.
130 5. There exists a vaccine against BV and Trichomoniasis (17). This vaccine consists of whole lactobacilli, isolated from women with trichomonas infection. The vaccine effect was first proposed to be caused by antibodies cross-reacting with Trichomonas (18). However, this has later been shown to be wrong (19). The efect of the vaccine can with our hypothesis be explained, if the vaccine breaks the tolerance of the host and makes it possible for the immune defence to attack the wrong, non-HZOZ-producing lactobacilli and create an environment for the H202--producing strain of lactobacilli to become dominant. 6. Ecological treatment of BV has been reported as inactive (20), but these studies have to be repeated with different types of lactobacilli since we do not know if the L. acidophilus strain used was a Hz%producing variant or not. Conclusion As has been discussed here, the microbial flora of the human vagina seems to be an extraordinary stable ecosystem, except when infected by the recognized pathogenic microorganisms. We propose that it is possible by microscopy to determine the normal flora’s ability to protect the host from infection or re-infection after therapy. Further studies will find out if it is possible to change the normal flora from one type of lactobacilli to another, and if these types can be designated to different taxonomic species of the genus Lactobacilli. A further challenge is to find out how this kind of flora exchange should be practically performed. References Doderlein A. Das scheidensekret und seine bedeutung fiir das puerperalfieber. 0. Durr, Leipzig, 1892. Krieg NR, Halt JG (eds). Bergerys manual of systematic bacteriology. Volume 1. Williams and Wilkins Baltimore/London, 1984. Rogosa M. Shape ME. Species differentiation of human vaginal lactobacilli. J Gen Microbial 23:197. 1960. Wylie G, Henderson A. Identity and glycogen-fementing ability of lactobacilli isolated from the vagina in pregnant women.
MEDICAL HYPOTHESFiS
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