Infections occur when an organism has the opportunity to overgrow and cause negative signs or symptoms. We have billions of bacteria all over us constantly, yet hardly ever get any infections – this is because usually all the microbes live in harmony with one another.

When it comes to pelvic infections (that is, any infection that occurs in your reproductive tract), there are a few nasties we need to be on the lookout for, since they can cause some miserable problems. Some infections you don’t know about and so can’t protect yourself against (for example yeast infections after antibiotics often come as a surprise) but some we do know about and have strategies in place to deal with before they happen – like those microbes that get passed on during sex.

     How do we tell if a microbe is a pathogen or commensal (healthy or neutral)?

Microbes come in many shapes and sizes, and some can be both pathogens, or normally found in the reproductive tract and considered ‘normal flora’. That is, commensal flora. You have bacteria that is ‘native’ to various parts of your body, like the mouth, vagina, bowel, and skin. When you get a swab or other test done, like for sexually transmitted infections, there are some bacteria that are marked as ‘commensal’.

Commensal comes from the French word commensalism, which means ‘eating at the same table’. 

Commensal bacteria are those organisms that promote human health, as opposed to take from it. In the vagina, this would include our lactobacilli species, which provide some very key services to our vaginas and urinary tracts. Lactobacilli in the gut, however, are not useful in the same way – the gut has other prized organisms that help break down our food, keep our intestinal walls healthy, and provide us with vitamin B12, for example.

Some commensal bacteria can change forms and, if given the opportunity, may become pathogenic. This depends on how the bacteria works and what genetic tactics it has up its sleeve for survival.

Pathogens are those microbes or organisms that use our bodies to survive (just like commensal organisms do), but they alter it in a negative way. In the vagina, this includes bacteria that change the pH, cause bad smells, itching, and pain, like those involved in bacterial vaginosis or aerobic vaginosis.

Microbes have very different skills that they use to survive, and one such skill is being adaptable. This is a huge issue when it comes to antibiotic resistance, since many bacteria that used to be easy to kill are now very difficult to get rid of, because they have altered their genetics to prevent death by antibiotic.

Some infections don’t cause symptoms, or they may cause symptoms in one part of the body or one type of person, but not another. For example a man may not notice he has chlamydia, whereas a woman might, or the other way around. Some infections are untreatable directly, for example the viral infections of HIV, herpes and HPV. We manage symptoms and the immune system response to these viruses, but we cannot kill the virus outright.

     How we catch infections

Just because a microbe or organism isn’t classified as a sexually transmitted infection doesn’t mean it can’t be transmitted sexually. As you will have experienced, catching a cold isn’t that hard if you are in the wrong place at the wrong time, including kissing or having sex with someone who has a cold. People catch germs off each other all the time, and just touching someone results in the exchange of bacteria.

If you test the bacteria on two strangers’ hands, then get them to shake hands, then test the bacterial colonies afterwards, you’ll find they have exchanged microbes. The new microbes don’t last long on us, because we have our own communities of microbes that don’t like newcomers, so the incoming microbes typically fade away quickly.

But, sometimes they don’t. This may be true if you have sex with someone who has chlamydia. If you don’t have strong enough colonies of good bacteria that can fight off chlamydia, or there is so much of the bacteria introduced that your vagina can’t defend itself, you will catch chlamydia. You may or may not get symptoms, but the bacteria can cause damage to your system if it’s left untreated for a long time. This is why it’s important to get regular STI checks if you are having sex.

Some infections can be life-threatening. Just think back to the HIV and AIDS epidemic of the 80s where many men in our communities died. Now, nobody in developed countries dies from AIDS, and HIV is not a life sentence, but our societies suffered huge blows due to (at that time) an uncontrolled, mysterious sexually transmitted infection.

New viruses and infections crop up every so often, as we’ve seen with the Zika virus, bird flu, mad cow disease, and swine flu. The mode of transmission differs per organism, but typically contact is to blame for most genital and reproductive infections. That might be body fluids, faeces spread by mistake, or skin-to-skin contact.

     Treating infections

Proper testing is required to establish what sort of organism is causing the symptoms. Treatments vary widely depending on the organisms, which is why good testing is paramount to ridding yourself effectively of bacteria.

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