Introduction

Bacterial vaginosis and thrush are both common vaginal infections. Although typically harmless, the symptoms of both conditions may bring discomfort and affect sexual health. Both can present with very similar symptoms, but it is important to seek medical advice from a doctor or sexual health clinical as the pathology of each condition is very different. Bacterial vaginosis and thrush are caused by different microorganisms, and therefore treatment varies significantly. There are a lot of misconceptions about both conditions, so it is important to understand the difference between the two and seek out the correct diagnosis for treatment and prevention.¹

Bacterial vaginosis

Definition and cause

Bacterial vaginosis (BV) is a common vaginal condition caused by changes to normal vaginal flora.² Vaginal flora refers to the microorganisms that live in the vagina and an abundance of the bacteria Lactobacillus sp. shows a healthy vaginal flora. Under BV, there is a reduction in Lactobacilli, leading to an overgrowth of anaerobic bacteria, which causes the symptoms of BV.³ BV can occur at any age but is most common in women of childbearing age (aged 15-44).

Symptoms

The main symptom of BV typically includes watery, white/grey vaginal discharge that produces a strong and unpleasant odour. Other symptoms include itchiness and irritation around the vulva. It is also important to know that some cases of BV may be asymptomatic, 50% of women do not experience any symptoms at all.

Risk factors

Sexual activity can increase the risk of BV.² While BV itself is not a sexually transmitted infection (STI), it significantly increases the risk of future STI development as it makes the vaginal tract vulnerable to other vaginal pathogens. 

Improper hygiene practices can increase the risk of BV. In a particular study, patients who did not wash their vaginal region were found 13.7% more likely to have BV compared to those that did. This should not be confused with vaginal douching, which actually increases the risk of BV. 

Similarly, patients who did not change their underwear frequently had a higher chance of getting BV. Not to be confused with vaginal douching, which actually increases the risk of BV. 

The overuse of antibiotics could cause harmful bacteria to become resistant to antibiotics and over-populate, rendering BV treatment ineffective. 

Smoking and IUD contraceptives also increase the risk of getting BV.⁴

Diagnosis 

Seek out a medical professional for clinical evaluation and testing. A clinical diagnosis is made by carrying out vaginal swab tests and having at least 3/4 of the Amsel criteria present, this includes:⁵

• The presence of watery, white discharge
• A pH paper test, whereby a positive diagnosis is made when the pH of the sample is above 4.5 
• The presence of clue cells under a microscope
• The whiff test, whereby a fishy odour is produced when the sample is mixed with potassium hydroxide

Treatment 

Since BV is a bacterial infection, treatment revolves around taking antibiotics like clindamycin or metronidazole, but this is only recommended if you have symptomatic BV.⁶ Medication can be administered orally, topically by creams or gels, or inserted into the vagina. Despite established treatment plans, 80% of BV cases reoccur after treatment, so a second course of antibiotics is then prescribed. 30% of BV cases resolve themselves without any treatment. 

Prevention strategy 

To prevent BV or to manage its symptoms:

• Avoid smoking
• Avoid using vaginal douches
• Keep the vaginal area clean by rinsing the outer genital area with water and by changing underwear frequently
• Avoid contact with perfumed soaps, strong detergents 
• Avoid sex until you have finished your course of antibiotics

Thrush

Definition and cause

Thrush is a common term used for yeast infections and the medical term for thrush is candidiasis. Thrush can be found on many parts of the body, including the vagina, mouth, and skin. It has been reported that around 70% of women have experienced thrush at least once in their lifetime, with 8% of women suffering from recurrent thrush. 

Vaginal candidiasis is a fungal infection caused by Candida albicans. This fungus causes inflammation in the vagina and vulva, which subsequently leads to the clinical symptoms of thrush. Candida is a part of healthy vaginal flora, however, thrush occurs when there is an overgrowth of the fungus, and causes associated symptoms.⁷

Symptoms 

The clinical symptoms of thrush include thick, white, odourless vaginal discharge, itching and swelling, and pain during sex or urination. 10% of cases are asymptomatic.⁸

Diagnosis 

Diagnosis of thrush is based on pelvic examination and positive indications for clinical symptoms.⁹ Thick, white, odourless discharge and swelling are observed. As many vaginal disorders present with similar symptoms, diagnostic tests like microscopy, pH tests, and whiff tests may be conducted to rule out other disorders. 

Patients with thrush will have:⁹

• A vaginal pH below 5 
• A negative result for a whiff test
• The presence of the Lactobacillus bacteria, inflammatory cells, and budding yeast on the wet mount

Risk factors

Risk factors for thrush include:⁹ 

• Elevated oestrogen levels (contraceptives, pregnancy, obesity)
• Diabetes 
• A weakened immune system (chemotherapy, immunodeficiency disorders) 
• Overuse of antibiotics 

Antibiotics cannot distinguish between good and bad bacteria, therefore overdose can kill the bacteria in vaginal flora that keep fungus under control.⁹

Treatment

Thrush is typically treated with antifungal agents, like clotrimazole and fluconazole.⁹ Medication can be taken orally, applied topically, and inserted into the vagina. In cases of recurrent thrush, doctors may put you on extended treatment regimes, with a higher dosage of medication over a longer period. Some patients may also benefit from suppressive therapy in combination with medication. 

Prevention strategy 

To prevent thrush or to manage its symptoms:

• Keep your genital regions dry after washing
• Avoid using harsh soaps and detergents
• Avoid sex until clear of thrush
• Avoid douching 
• Avoid tight trousers and underwear

Similarities between bacterial vaginosis and thrush 

Both BV and thrush are caused by an overgrowth of microorganisms in the vagina, which disturb the normal vaginal flora. At first glance, BV and thrush have very similar symptoms. Both present clinically with vaginal discharge and irritation in the genital area. The tests used to confirm the diagnosis are similar: microscopy, pH testing and the whiff test. Both BV and thrush have similar risk factors and prevention methods. The overuse of antibiotics increases the chances of BV and thrush, as well as douching and unhygienic practices. 

Both conditions are common and harmless, but they can affect sexual health. For both conditions, it is important to seek medical advice as they have the tendency to come back after treatment, Although uncommon, it is also possible to have both BV and thrush at the same time. If this happens, you would need to be treated for both. 

Differences between bacterial vaginosis and thrush

The biggest difference between BV and thrush is the microorganism involved. BV is caused by an overgrowth of bacteria, whereas thrush is due to a fungus, so the treatment varies significantly. BV is primarily treated by antibiotics, whereas thrush is treated by antifungal medication. Knowing this difference is vital as if you are being mistreated for thrush and prescribed antibiotics, it can exacerbate your symptoms and condition. 

The biggest symptomatic difference, and the one most used for diagnosis with tests, is the presence or absence of odorous vaginal discharge. BV is typically accompanied by a discharge that is strong and unpleasant in odour, whereas thrush has an odourless discharge. Whilst both have the primary symptom of vaginal discharge, BV causes thin/watery discharge that has a strong odorous smell, whereas thrush causes discharge that is thick and odourless. The same diagnostic test is used to test for both, however differing results will determine the diagnosis. 

Other diagnostic tests show more symptomatic differences between thrush and BV. BV vaginal pH is greater than 4.5 whereas thrush is below 5. Thrush produces a negative result for a whiff test, whereas BV produces a positive result, indicated by a fishy odour. When a swab sample is viewed on a wet mount under a microscope, clue cells will be present in BV culture, whereas Lactobacillus bacteria, inflammatory cells, and budding yeasts will be present in the thrush culture. 

Summary 

Bacterial vaginosis and thrush are common and harmless vaginal infections. They are often mistaken for one another as they present with similar symptoms; excess vaginal discharge. However, they have completely different causes, BV is due to an overgrowth of bacteria, whereas thrush is due to an overgrowth of the Candida fungus. Because of this, there is significant emphasis on the importance of accurate diagnosis and appropriate treatment. 

If you are unsure about whether you have BV or thrush, contact a doctor or a local sex clinic. You could have either BV or thrush, both at the same time, or neither (another vaginal disease e.g. vaginitis). The correct diagnosis is extremely important as treatment methods are vastly different. If you are incorrectly diagnosed, you could make your condition even worse.

Vaginal and sexual health is extremely important. Topics surrounding vaginal infections and conditions need to be de-stigmatised, and open communication with healthcare providers should be encouraged.