It’s not necessary to know a great deal about the cause of a yeast infection to be able to cure it easily and quickly. However, those of you who are of a scientific mindset may be interested to know more about the biological mechanisms behind yeast infections.
As you may already know, Candida albicans is a species of fungus which is normally present in many parts of the body in comparatively small numbers. It’s held in check by the activity of what we have come to term “probiotic bacteria”.
This natural balance can be disturbed in a number of ways, allowing the Candida fungus to multiply much more rapidly than normal and cause a full-blown yeast infection with all the attendant symptoms.
Any change in the bodily environment can potentially cause of the overgrowth of Candida. Let’s start by looking at what can cause overgrowth in the case of a vaginal infection or genital infection in men.
Causes Of Vaginal Yeast Infections
The most common changes in the vaginal environment are due to
- some kind of injury
- transmission of yeast by sexual intercourse
- an increase or decrease in the pH of the vagina
- an increase in the warmth and dampness of the crotch area
- some kind of allergic reaction
- increased levels of sugar in the blood stream
- changes in hormone levels
- and reduction in probiotic bacteria due to the activity of antibiotics.
Antibiotics probably do rate as the most common cause of vaginal yeast infection.
It’s an irony that something which has proved to be so useful in curing bacterial infection can cause another problem which in its own way is just as uncomfortable.
Because antibiotics are indiscriminate in the bacteria which they target, they kill off the good bacteria, the probiotics, just as they do all the others, after which Candida is free to flourish unrestricted.
Clothing is another common problem; any tight clothes that trap heat or moisture certainly can provide an environment in which Candida is predisposed to reproduce rapidly.
You can probably understand why chemicals such as vaginal douches can upset the balance in the vagina and trigger an allergic reaction.
In either case, the good bacteria are definitely disrupted in a way that allows Candida to flourish.
It’s certainly been reported by many women that scented or dyed toilet paper contains some ingredient which is responsible for killing off good bacteria and leaving you susceptible to yeast infections.
The same is true of compounds contained in bubble baths, bath salts, scented tampons and some sanitary towels.
Condoms have been blamed for causing yeast infections, although actually it’s the spermicidal lubricant known as nonoxynol 9 which is responsible for yeast infections.
Additionally, any allergy to latex can be responsible for causing a yeast infection.
Popular mythology has it that diet can be responsible for the generation of yeast infections, and therefore by cutting down on foods such as bread or beer which contain yeast, you will experience fewer infections from Candida.
This seems rather unlikely to me because the yeast in bread and beer making is a completely different species to Candida albicans; nonetheless, there’s a good deal of anecdotal evidence which suggests that this can be a factor.
We’re on much firmer ground with the role of sugar in causing yeast infections; we know that diabetics, whose urine sugar levels are often elevated, experience many more yeast infections than non-diabetics.
It’s also a common observation that hormonal fluctuations can influence the susceptibility of women to yeast infections. Apparently pregnant women and those taking contraceptive pills tend to experience more yeast infections as their hormone levels fluctuate.
The author of this site relates an anecdote about how she was on the pill for a while, and developed a yeast infection every single month right before her period.
She also makes the observation that the pH of menstrual blood can generate a hostile environment for yeast infections, so women may notice a yeast infection tends to disappear during the period.
Unfortunately, the infection tends to come back after it.
And as you may also know, vigorous sex without enough lubrication can cause a yeast infection. This seems to be because small tears or damage to the membranes of the vulva or vagina.
The Science Behind It All
But of course that’s all very well in broad terms, but these explanations do not give us any understanding as to the mechanism that causes Candida to explode in what we’ve termed an “overgrowth”.
Work by Flavia de Bernadis, Fritz A. Muhlschelegel and others has demonstrated that infection may occur in response to environmental signals given off by the host organism.
One of these signals as the acidity or alkalinity of the environment in the body of the person concerned.
These researchers tested two genes, one of which (PHR1) appears to be activated when the pH is 5.5 or higher (slightly acidic), and one of which (PHR2) appears to be activated a pH below 5.5 (less acidic to alkaline).
The acidity of the vagina is usually around pH 4.5, so changes in this pH could easily cause either of the two genes responsible for Candida growth.
As the researchers say, a lot of scientific research has been directed at understanding what makes Candida grow in its virulent form, but comparatively little data has been obtained on the matter. However, this research produced clear proof that pH is a trigger.
These researchers located a gene they called PHR1 which encoded a putative cell surface glycoprotein anchored to the membrane by glycosylphosphatidylinositol.
This gene was active when the pH was above 5.5, but inactive below this pH. PHR2, a functional homolog, was expressed in the opposite way: it was active at high levels below pH 5, but not at a pH above 6.
Finding these genes allowed the researchers to investigate the influence of pH as a trigger in Candida overgrowth.
By experimenting in animals whose vaginal environment was naturally acidic or alkaline, and by using different genetic strains of Candida which contained one or other gene, the researchers were able to demonstrate that the pH of the vagina was indeed an important trigger for the overgrowth of Candida.
We must therefore assume that probiotic bacteria maintain a certain pH, and the absence due to the activity of antibiotics allows Candida to flourish. Hormonal changes, too, will cause the pH to change and give the Candida optimum conditions to grow.
(Contradictory evidence that suggests there is no relationship between contraceptive pills and genital thrush was collected by F Davidson and J K Oates, consultants in genitourinary medicine, and reported here.
Studies of 1360 new patients attending three different clinics reveal the genital Candidosis was present in just under 30% of patients was not associated with oral contraceptive usage.
The conclusion made was that vaginal thrush was more likely to be associated with non-specific infection, viral infection and other genital disorders. And, as these researchers say, there is much work still to be done on the epidemiology of Candidosis.)
Causes Of Thrush
In essence, the conditions in the mouth which can lead to an overgrowth of Candida causing oral thrush are essentially the same as those on of the mucous membranes such as the vagina.
Those conditions which allow the balance between the bacteria and fungus to tilt in favor of Candida include an impaired immune system (which is often the reason why infants and older adults develop oral thrush).
Quite simply, their immune system is weaker than a healthy adult’s. People whose immune system is weakened because of HIV (human immunodeficiency virus) are also very likely to get thrush.
The same is true of those who have diabetes because high blood sugar levels promote overgrowth of Candida.
Sjogens syndrome can cause thrush indirectly, due to the dry mouth that it produces (known as xerostomia). Similarly, poor oral hygiene can allow bacteria to develop which produced an environment favorable for Candida.
So can taking antibiotics or inhaled corticosteroid medication, once again because both of these medications may upset the balance of good and bad bacteria in the mouth.
Thrush spreads in a number of ways: the most interesting of these is that it can be passed from mother to her newborn baby if she has vaginal yeast infection.
Thrush is common during the first few months of life anyway, but in otherwise healthy toddlers and older children it’s not usually infectious. It can however be passed from child to child if one individual has a weak immune system.
Older people are at risk of thrush if they have dentures, because contamination with bacteria is common when poor oral hygiene is a feature of dental care.
The Overgrowth Of Candida
It may be helpful to clarify the two different forms of Candida albicans. In its normal form it is a unicellular, oval-shaped diploid fungus and its normal habitat is the mucous membranes of the body.
However it is dimorphic, and it can change from one form to the other in certain environmental conditions. In this respect it distinguishes itself from other yeast, because it can produce myceli. Most yeasts do not produce filamentous forms; nor does Candida albicans – at least, most of the time.
Under certain conditions of temperature and pH, it changes from multiplication by budding and develops polarized cell division which form a mycelium.
Chlamydospores can be formed on the pseudomycelium, which look like round, refractile spores. An overgrowth of the multicellular filamentous pseudohyphae is responsible for what we call the fungal infection candidiasis or thrush.
The transition from commensal to pathogenic form is dependent on particular types of environmental conditions within the host. What complicates this further is the fact that Candida albicans is in reality a polymorphic organism.
Certain strains of Candida albicans can spontaneously generate different cellular morphologies: a worrying trend of antifungal resistance is emerging due in part to the organism’s ability to change form so readily.
The factors that make it damaging to the host include the fact that it bonds to the host using Adhesin proteins, which make it resistant to the cavity of the immune system of the host.
If it penetrates the surface of the mucous membranes on which it’s living, after its morphogenesis has produced invasive filaments, the polymorphic growth pattern produces various enzymes such as proteases and phospholipases which degrade the host tissue.
Its ability to switch between polymorphic forms also allows it to escape the activity of the host immune system and medication which would normally destroy it.
Candida albicans is part of the normal human flora, but only becomes a problem when the environment in the host allows it to turn into the filamentous form.
Healthy eating, and all the other lifestyle factors which maintain good immune system activity are essential for keeping vaginitis at bay.
And it isn’t just antibiotics that cause a loss of bacteria that keep Candida albicans growth in check; for example, stomach ulcer drugs have been implicated in its proliferation.
It’s a pathogen which can affect the mouth, vagina or skin, but it’s also possible for it to affect the penis, although this is less common, and such infection is generally as a result of sexual intercourse with an infected woman.
Candida is known as thrush when it infects the mouth, when it tends to manifest as white patches visible to the naked eye on the tongue and sides of the mouth.
Often the tongue is a deeper red than normal, and there may be a loss of taste sensitivity.
A case of thrush – oral yeast infection
It’s also possible for Candida albicans to cause candidal onchomychosis on the nails.