You might be wondering: why can syphilis be cultured? If that’s the case, here’s your complete guide. Click here for more!


Syphilis is estimated to affect around 0.5% of the global population. That’s 385 million people who have to deal with the devastating and sometimes deadly symptoms of this sexually transmitted infection (STI). Worse, these numbers are rising.

The good news is that syphilis is curable upon diagnosis. Despite this fact, researchers have long struggled to culture the bacterium that causes syphilis for studying in a lab. 

That is, until now. 

In 2018, researchers successfully cultured the very first model of Treponema pallidum— the bacteria that causes syphilis in humans. 

Curious to find out how it’s possible to culture this infectious bacteria and why it matters? Then check out this article for a full guide to T.pallidum, how it’s cultured, and what that could mean for your or a loved one who is diagnosed with syphilis. 

What is Treponema pallidum?

T.pallidum is a pathogen, meaning it’s a germ that causes infectious disease. For a long time, researchers couldn’t study this bacterium in petri dish because it only survives inside human hosts. 

Instead, all of our knowledge about syphilis and the bacteria that cause it came from animals. Researchers would infect animals with syphilis and study the course of the infection. Still, they couldn’t investigate the bacterium itself. 

Prior to the successful cultivation of T.pallidum, there were four known strains or types of this bacterium:

  • The Nichols strain
  • The SS14 strain
  • The Chicago strain
  • The DAL-1 strain

Each of these types of T.pallidum is known to cause syphilis in humans. 

Other Treponemes

In addition to the aforementioned T.pallidum strains, genetically related agents known as treponemes have the potential to cause syphilis. Samoa D, CDC-2, Gauthier, and T.paraluiscuniculi are closely genetically related to syphilis-causing strains. 

What does that mean? If only a few genes mutate, these treponemes may also cause syphilis in humans. 

Already, these treponemes cause another disorder called Yaws. Yaws is a bacterial infection of the skin and bones, known for affecting people in tropical locales. 

The possibility that Samoa D, CDC-2, Gauthier, or T.paraluiscuniculi could mutate into syphilis-causing bacteria spurred researchers to find a better way to study them.

What T.pallidum Cultures Mean for People with Syphilis

For over 115 years, scientists have been trying to successfully culture syphilis-causing T.pallidum. Why? Because culturing allows scientists to grow large, long-lasting amounts of bacteria in a petri dish.

Bacterial cultures give rise to more bacteria, allowing researchers to look out for potentially harmful genetic mutations. This saves hundreds of animal models and thousands of dollars each year. 

Not to mention, culturing T.pallidum bacteria may offer more convenient new ways to cure and diagnose syphilis. Or, it may allow scientists to uncover a way to eradicate syphilis in humans for good. 

By now, you may be wondering: if T.pallidum thrives in humans, how did researchers cultivate it in a lab? We’re talking about that next, so keep reading.

How Researchers Cultured T.pallidum 

Here’s the problem with T.pallidum— it will grow in a petri dish, but not for long. For years, researchers had successfully cultured this bacterium only for the culture to die off after eighteen days. 

Here are some of the methods scientists tried to keep their cultures alive:

  • Improving growth conditions
  • Creating subcultures
  • Switching out the medium

All attempts to expand the lifespan of the cultures failed. Until a lab at UTHealth’s McGovern Medical School in Houston, Texas managed to keep a T.pallidum culture alive for a whopping eight months. 

Here’s how they did it.

The Ultimate Growth Conditions

Since T.pallidum only thrives in humans, the researchers knew they’d have to mimic a tissue-like environment. That’s why they created what’s known as a co-incubation system. 

The researchers took elephant skin cells and incubated them with the bacterial cells. Ever so often, they’d add nutrients commonly found in the human body to nourish the cultures. 

Yet, even with tissue-like conditions, researchers had to recreate one of the hallmarks of the human system: homeostasis.

Advances to the Medium

Homeostasis is the human body’s way of keeping things consistent. When you move into a cold room from the hot temperatures outside, your internal body temperature flexes to maintain balance.

Inspired by the previously successful attempt to keep T.pallidum alive for eighteen days, the researchers decided to make changes to the growing medium. More specifically, they transferred the culture to a new medium every week.

Though a complex system, this allowed the bacterial culture to remain as close to homeostasis as possible. Clearly, it worked. 

What We Know About Syphilis-Causing T.pallidum Now

Despite successfully keeping T.pallidum alive in their Houston lab, the UTHealth researchers realized something. This syphilis-causing agent doesn’t grow like other bacteria. 

Unfortunately, that means researchers will likely never be able to culture large amounts of T.pallidum. Still, we’ve come a long way from not knowing what does syphilis look like to cultivating a culture of it for nearly a year. 

Soon, the scientific world hopes to uncover the secrets of syphilis-causing bacteria. That way, we can eventually prevent people from spreading this devastating STI altogether.

Diagnosing Syphilis with T.pallidum Antigens

For now, the only way to eradicate the spread of syphilis is with prompt diagnosis and treatment. Once a person is screened positive for this STI, they only need a few rounds of penicillin treatment to return to optimal health.

Are you searching for T.pallidum antigens for diagnosing syphilis? White Antibodies is the largest manufacturer of Treponema pallidum antigens in the UK. Get in touch with us today to make an inquiry.