STD Awareness: Fully Antibiotic-Resistant Gonorrhea Is on the Horizon

shot-in-armWe’ve been anticipating its arrival for years now, but earlier this fall, the Centers for Disease Control and Prevention (CDC) finally made an announcement: Cases of gonorrhea resistant to the last drugs we use to cure it are emerging.

Over the years, gonorrhea has evolved resistance to every drug we’ve thrown at it — sulfonamides, penicillins, tetracyclines, macrolides, fluoroquinolones, and narrow-spectrum cephalosporins. The last line of defense we have is a one-two punch of a pair of antibiotics: azithromycin and ceftriaxone. By using two drugs, we can delay the inevitable evolution of antibiotic resistance by attacking the bacteria in two vulnerable locations, rather than just one, making it more difficult for the bug to mount a defense and pass on its superior survival skills to subsequent generations.


Prevention is paramount: Stop the spread of antibiotic resistance by practicing safer sex!


Unfortunately, we could only stave off the inevitable for so long. At their conference in September, the CDC announced a cluster of gonorrhea infections that are highly resistant to azithromycin, and that fall prey only to high doses of ceftriaxone. As gonorrhea’s tolerance to ceftriaxone increases, the infection will get more and more difficult to cure.

This cluster of drug-resistant cases was identified in Honolulu in April and May of this year, with five infections showing “dramatic” resistance to azithromycin, as well as reduced vulnerability to ceftriaxone. The good news is that these cases were cured with higher-than-usual doses of antibiotics, but the bad news is that dosages can only climb so high before a drug is no longer considered to be an effective treatment. Continue reading

STD Awareness: Gonorrhea’s Ever-Growing Resistance to Antibiotics

gonococci

Gonococci, the bacteria that cause gonorrhea.

Ever since the advent of effective antibacterial therapies less than a century ago, humans with access to these drugs can easily cure gonorrhea. 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 — sulfa drugs and antibiotics not only erased these infections from our bodies, they also erased memories of gonorrhea’s dangers from our collective consciousness.


There are two drugs remaining to treat gonorrhea, and resistance to them is climbing higher as the years march on.


Unfortunately, thanks to their talent for genetic gymnastics, gonococci, the bacteria that cause gonorrhea, have been evolving resistance to every drug we’ve thrown at them — to tetracycline, to penicillin, and more recently to fluoroquinolones. One class of antibiotics remains to treat gonorrhea: cephalosporins. In 2013, Centers for Disease Control and Prevention (CDC) Director Tom Frieden warned that we could find ourselves in a “post-antibiotic era” – unless we take precautions. And, just two weeks ago, the latest study from the CDC’s Gonococcal Isolate Surveillance Project sounded the alarm that the post-antibiotic era is drawing ever closer, especially when it comes to gonorrhea.

Azithromycin and ceftriaxone, the two drugs that are used in combination to deliver a one-two punch to invading gonococci, are the best antibiotics remaining in our arsenal. Azithromycin is taken by mouth, while ceftriaxone is administered by a shot, and when taken together they team up to target different weak points in gonococci’s armor. Azithromycin interferes with the bacteria’s ability to make proteins, shutting the cells down, while ceftriaxone causes the cell wall to fall apart. However, the gonococci can acquire resistance. For example, in the case of azithromycin, a resistant bacterium can spit out the drug before it has a chance to kill it, or it can change the shape of its protein-making apparatus such that the drug can’t attach to it.  Continue reading

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: Ceftriaxone-Resistant Gonorrhea

syringeNestled in the throat of a Japanese woman was a collection of clones that scientists abducted from their temporary habitat and christened H041 — a humdrum moniker for a strain of bacteria that would burn headlines in medical journals. Though the bacteria never caused symptoms in their host, they lingered in her throat from at least January until April of 2009, when a swab finally tested negative. Rather than succumbing to repeated bombardment by an antibiotic called ceftriaxone, the infection probably just went away on its own — as oral gonorrhea infections tend to do.


Resistance to ceftriaxone, our last good gonorrhea drug, has been reported in Japan, Australia, Sweden, France, and Spain.


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.” 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. Resistance to cefixime was first documented in 1999, leaving ceftriaxone as our best remaining option, and the CDC’s first choice for treating gonorrhea. There are no good alternatives to ceftriaxone remaining, which is why reports of ceftriaxone-resistant gonorrhea are so deeply troubling.

What made H041 special was that it was the first extensively drug-resistant strain of Neisseria gonorrhoeae, the bacteria that cause gonorrhea. With an unusually high level of resistance to ceftriaxone — four to eight times higher than the previous record holder — the strain was also resistant to a slew of other antibiotics: penicillin and its relatives, fluoroquinolones, macrolides, tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, nitrofurantoin, cefpodoxime, cefixime, ciprofloxacin, and levofloxacin — and had reduced susceptibility to azithromycin to boot.

Another thing that made H041 special — as special as clones can be, anyway — is that it never reappeared. After its discovery, researchers in Kyoto and Osaka intensified their surveillance, trying to uncover it again and track its spread through the population. However, their search for H041 turned up empty handed. But other ceftriaxone-resistant strains have been documented around the world. 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: Three Sexually Transmitted Bugs That Will Fascinate and Intrigue You

From creepy crawly pubic lice, which can be seen with a magnifying glass, to minuscule human papillomaviruses, which can be seen with some of the most expensive microscopes in the world, there are many tiny pathogens that we can acquire through sexual contact. And, despite their diminutive sizes, some of them work in complicated ways, or tell stories about our origins that would blow you away. Let’s learn some amazing facts about three sexually transmitted bugs!

Phthirus pubis, the louse that causes scabies. Image from the Public Health Image Library.

Image: Public Health Image Library

Pubic lice: tiny insects that live in pubic hair

Fans of Charles Darwin might like learning about pubic lice, which offer clues about human evolution. While other apes’ bodies are habitat to only one species of louse, human bodies can host three different types of louse: head lice and the closely related body lice, as well as the distantly related pubic lice.

It is thought that when early humans lost their body hair, human lice followed this receding hairline and migrated to their heads to become head lice. At a later date, the gorilla louse colonized early humans’ pubic regions. Since pubic lice can be transmitted by infested bedding, one idea is that an early human caught pubic lice by sleeping in a burrow that had been recently vacated by a lice-ridden gorilla — no sexual contact required.

By examining the number of differences in the genetic codes of the modern gorilla louse and the human pubic louse, we can place their divergence into two separate species at about 3 million years ago, suggesting that our human ancestors lost their body hair at around that time.

A quite frankly weird fact about pubic lice involves the method their young use to hatch from their eggs — by releasing so much gas that the increase in air pressure causes them to burst from their shell. So there’s that. Continue reading

STD Awareness: The Herpes Virus and Herpes Medications

herpes medicationOne of the most common sexually transmitted diseases (STDs) is herpes, which affects an estimated 1 out of 6 Americans between the ages of 14 and 49. Herpes is caused by a virus, and one reason that it’s so widespread is that the herpesvirus is ancient. Prehistoric, even — dinosaurs are thought to have been infected by herpesviruses! The Herpesviridae family is huge, with at least 100 members infecting mammals, birds, reptiles, bony fish, amphibians, and oysters.


Herpes drugs from the acyclovir family physically block herpes DNA from replicating — which is pretty amazing!


Humans can suffer from both oral herpes and genital herpes, which are caused by two types of the herpes simplex virus (HSV-1 and HSV-2). Recent genetic analysis reveals that the virus that causes cold sores, HSV-1, has been evolving with us since before we were Homo sapiens, diverging from the viruses that infected our common ancestors 6 million years ago. Interestingly, we didn’t acquire HSV-2 — which mostly causes genital herpes — until our Homo erectus ancestors caught it from early chimpanzees 1.6 million years ago, well before the emergence of modern Homo sapiens around 200,000 years ago.

Most people know what the virus doesgenital herpes can involve blisters, pain, and itching — but most people don’t know how the virus works. Luckily, scientists have uncovered a lot of the virus’ secrets — which has allowed them to develop some pretty effective drugs that we can use to foil herpes’ plans. Continue reading