The STI Clinic News > Gardnerella May Inhibit Absroption of Tenofovir Gel
# Saturday, July 8, 2017
Posted: Saturday, July 8, 2017 | Categories: Women's Sexual Health

If you’re a woman, you may be familiar with Gardnerella vaginalis, a type of bacteria that can invade the vaginal tract, altering the pH balance and causing unpleasant odours and discharge. Usually this condition is known as bacterial vaginosis, but it’s also sometimes referred to as gardnerella (after the bacteria that is commonly responsible).

Typically, bacterial vaginosis is associated with foul, fishy smelling vaginal discharge – but it’s not a serious condition in any sense, and is not usually accompanied by any other symptoms. What is known, however, is that conditions that change the vaginal microflora can have implications for the transmission of sexually transmitted infections. Recently, we reported that, because gardnerella can disrupt the "good" bacteria in the vagina, this can lead to inflammation, which can in turn make HIV transmission easier. In the same article, we also noted that women with bacterial vaginosis may also be harder to treat with the anti-HIV pre-exposure treatment tenofovir. Now, further studies have come to light seeming to confirm this worrying research.

The Research

As reported here, Dr Sharon Hillier from the University of Pittsburgh School of Medicine has been looking into the HIV/gardnerella question for some time. In a recent study she looked at 41 HIV-negative women who were administered tenofovir vaginal gel or film for six days. Before the trial, vaginal swabs were collected to ascertain levels of bacterial vaginosis, and at the end, further tests were carried out to measure levels of tenofovir in the women’s systems.

Hillier and her team found that, overall, concentrations of tenofovir were lower in women with high levels of gardnerella bacteria. In simple terms, that means that gardnerella reduces the amount of tenofovir that can enter the genital tissues and blood.

This is significant because it could change the way that doctors administer pre-exposure prophylaxis, such as tenofovir, to HIV-negative women. Before PrEP of this kind can be administered, it may be that women will have to undergo a gardnerella test and, if their levels of these bacteria are too high, take a course of antibiotics.

Until more is known about the efficacy of PrEP treatments, people at risk of HIV transmission are advised to take certain precautions, which can be found below.

Preventing HIV Transmission

The best way to avoid contracting HIV is to practise safe sex. That means that you should always use condoms when you aren’t certain that your sexual partner is free from infection. You should never share needles or other injecting equipment, as HIV is carried in blood as well as seminal, anal and vaginal fluids.

During sex, using lubricants can help prevent condoms from breaking, and dental dams can be used for oral stimulation (HIV can be passed on through oral sex, although the risk is far greater with penetrative vaginal or anal sex).

If you already know that your sexual partner has HIV, there are some other things to be aware of; if your partner is being treated for their HIV and they have what is known as an undetectable viral load, for instance, it is extremely unlikely that they can pass on the infection during sex.

However, if you have had unprotected sex with an HIV-positive partner and you think you may have been exposed, you should seek out post-exposure prophylaxis. This is an emergency anti-HIV treatment that must be commenced within 72 hours of unprotected sex. It lasts for a month and is often accompanied with serious side effects; however, it’s the best option for people who have been exposed.

Unfortunately, pre-exposure prophylaxis such as tenofovir vaginal gel is not currently available on the NHS. However, it is going to be trialled in the UK over the next three years.

The last thing to bear in mind is that HIV is best managed when it is diagnosed early. If you think you might be at risk of HIV you should get regular tests.

Gardnerella Tests

Until pre-exposure prophylaxis such as tenofovir becomes available on the NHS, concerns over gardnerella and bacterial vaginosis needn’t be a priority. However, if you would like to get tested for gardnerella, you can do so easily at your local NHS centre or through The STI Clinic. We can safely supply a simple home test kit and a course of prescription antibiotics.


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