STD Awareness: Which STDs Are Resistant to Antibiotics?

pillsYou’ve probably heard of MRSA, which is pronounced “mersa” and stands for methicillin-resistant Staphylococcus aureus — a strain of bacteria that is resistant to methicillin, as well as pretty much every other antibiotic out there. MRSA is an example of evolution by natural selection — what didn’t kill its ancestors made them stronger, spawning a drug-resistant strain.


There are drug-resistant strains of gonorrhea, trichomoniasis, and syphilis.


Evolution is the force behind life’s diversity. Normally, diversity is a good thing — but when it comes to microbes that cause diseases like gonorrhea, trichomoniasis, and syphilis, these organisms’ ability to evolve new defenses against our antimicrobial drugs isn’t good for us.

STDs have plagued us for millennia, but it wasn’t until the 20th century that we finally developed antibiotics, which gave us a powerful tool against many of our most formidable sexually transmitted foes. Suddenly, scourges like gonorrhea and syphilis could be quickly and easily treated with a dose of penicillin.

Problem solved, right? Nope. Enter evolution by natural selection. Continue reading

STD Awareness: Genetics and the Gonococcus

Illustration: CDC

Illustration: CDC

Ever since the discovery of effective antibacterial therapies less than a century ago, humans have been able to easily cure gonorrhea, the sexually transmitted scourge that laid waste to fallopian tubes and robbed newborns of vision. Most of us in the developed world have forgotten that this disease was once a leading cause of infertility in women and blindness in babies — and still is in much of the developing world.

Unfortunately, gonococci — the species of bacteria that cause gonorrhea — have been evolving resistance to every antibiotic we’ve thrown at them, including sulfonamides, penicillins, tetracyclines, macrolides, fluoroquinolones, and narrow-spectrum cephalosporins. We have one remaining first-line gonorrhea treatment left: extended-spectrum cephalosporins, which include cefixime, which is taken orally, and ceftriaxone, which is administered as a shot — and resistance is emerging to those drugs, as well.


Gonococci don’t swap potato salad recipes at family reunions — they swap genetic material!


The emergence of antibiotic-resistant gonorrhea is considered one of the most pressing problems in infectious disease — just two years ago, the Centers for Disease Control and Prevention named it an “urgent threat,” and indeed, gonorrhea seems to be evolving resistance to drugs at quite a rapid clip. Gonococci can acquire resistance to antibiotics in three ways.

First, a genetic mutation can endow bacteria with special antibiotic-fighting powers, making it harder for a drug like penicillin to attach to their cells and destroy them. Such a mutant is more likely to gain evolutionary traction if it finds itself in an antibiotic-drenched environment in which resistance to that drug allows it to “outcompete” other bacteria. Indeed, antibiotic resistance was first documented in the 1940s, just years after sulfonamides and penicillin were introduced as the first effective cures for gonorrhea. Continue reading

STD Awareness: Antibiotic-Resistant Syphilis

Treponema pallidum under a microscope. Image: Dr. Edwin P. Ewing, Jr., CDC

The image to your right, with lively yellow splotches against a pale green background, is not a long-lost Jackson Pollack piece, and the dark squiggly lines aren’t strands of paint haphazardly splattered onto a canvas. In fact, those squiggly lines are magnified images of the spiral-shaped bacteria species Treponema pallidum. You might not have heard of T. pallidum, but you’ve probably heard of syphilis, the sexually transmitted disease (STD) that these bacteria cause. While syphilis isn’t as common as other STDs, like chlamydia and HPV, it’s still out there, and occasionally communities experience outbreaks. It’s always best for sexually active people to be screened for STDs and practice safer sex.


The evolution of syphilis strains that are resistant to certain antibiotics underscores the need to use antibiotics properly.


Syphilis can inflict serious long-term damage — in fact, before the introduction of antibiotics, syphilis was the worst STD out there! Known as the Great Pox when it descended upon Europe 500 years ago, it could cause large and painful boils. Eventually, natural selection led to T. pallidum’s evolution into a form with milder symptoms, which benefited the bacteria by enabling its less boil-ridden (and presumably more attractive) human hosts to spread it farther and wider. Nevertheless, the symptoms of syphilis, if present, still include infectious sores, and when the disease goes untreated, it can cause severe, possibly fatal, damage to the nervous system.

Back in the day, there were myriad inadequate “treatments” for syphilis, ranging from straight-up quackery to the use of partially effective but toxic chemicals such as mercury. But a century ago, in 1912, a new arsenic-based chemical called Neosalvarsan was hailed as a “magic bullet.” Unfortunately, this treatment took weeks or even more than a year to administer — and had dangerous side effects. Quack treatments continued to flourish, and it wasn’t until the widespread adoption of penicillin in the 1940s that an effective cure with few side effects was available.

But natural selection endures; in fact, by flooding T. pallidum’s habitat with certain antibiotics, we’ve created an environment that favors the organism’s evolution against us. While not as immediately threatening as antibiotic-resistant gonorrhea, syphilis has been quietly evolving resistance to some of the antibiotics we use to treat it. This underscores the importance of using antibiotics correctly and emphasizing safer-sex practices, such as using latex condoms during vaginal or anal intercourse and during oral contact with a penis. Continue reading

Get Smart About Antibiotics!

This week we celebrate Get Smart About Antibiotics Week. Antibiotics, or antimicrobials as they are also called, cure bacterial infections by killing bacteria or reducing their ability to reproduce so your own body’s immune system can overcome an infection. Penicillin was the first antibiotic, and was discovered in 1924 by Alexander Fleming. Since its widespread use, beginning in the 1940s, countless lives have been saved from devastating bacterial infections. Talk about a wonder drug!


Improper use of antibiotics can have dangerous consequences.


Since then, different types of antibiotics have been developed to combat many different types of infectious bacteria. Classes of antibiotics include penicillins, cephalosporins, macrolides, fluoroquinolones, aminoglycosides, and others. In each of these classes there are lots of different individual medications. (For example, cephalosporins include the drugs cephalexin, ceftriaxone, cefaclor, and others.) Some antibiotics are broad spectrum, which means they work on many different bacteria. Some are more narrow spectrum, used for specific bacteria.

Antibiotics only work for bacterial infections … not viral infections. They are ineffective at killing viruses. Viral infections include colds, flu, runny noses, most coughs and bronchitis, and sore throats unless they are caused by strep. Sexually transmitted viruses include human papillomavirus (HPV), herpes simplex virus, and HIV. Continue reading