Medicine
Emerging Antimicrobial Resistance in Neisseria gonorrhoeae
Quick fact
Neisseria gonorrhoeae has developed resistance to every class of antibiotic previously recommended for treatment, including sulfonamides, penicillins, tetracyclines, fluoroquinolones, and most recently, the last-line oral antibiotic cefixime.
Why this is interesting
The bacterium that causes gonorrhea has defeated almost every antibiotic we have ever thrown at it. Why does it keep winning?
Read the full explanation
Understanding Emerging Antimicrobial Resistance in Neisseria gonorrhoeae
Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. For decades, antibiotics have been able to cure it, but the bacterium adapts quickly. Resistance emerges when a bacterium changes so that an antibiotic can no longer stop it, allowing the bacterium to survive and multiply. In N. gonorrhoeae, this can happen through spontaneous mutations in its own genes, or by picking up new genes from other bacteria. Once a resistant strain appears, it can spread through sexual contact, making the infection harder to treat. The rise of multidrug-resistant gonorrhea threatens to make the infection untreatable, which could lead to severe complications such as infertility and increased risk of HIV transmission.
A deeper explanation
N. gonorrhoeae is a naturally transformable bacterium, meaning it can take up free DNA from its environment. When an individual is infected with multiple strains, or when the gonococcus lives in the throat alongside other bacterial species, it can incorporate DNA fragments that contain resistance genes. For example, resistance to penicillin arose partly through acquisition of beta-lactamase plasmids, while resistance to ciprofloxacin came from point mutations in the gyrA gene. More recently, resistance to extended-spectrum cephalosporins (like cefixime) has been linked to mutations in the penA gene that alter the penicillin-binding protein, reducing drug binding. Additionally, some strains overexpress efflux pumps that actively expel drugs, contributing to multidrug resistance. These mechanisms can accumulate, leading to strains resistant to multiple antibiotic classes simultaneously. The global spread of such strains is a major public health threat, as treatment options become limited to injectable ceftriaxone, and even that is showing rising minimum inhibitory concentrations in some regions. The WHO has identified antimicrobial resistance in gonorrhea as a high-priority threat, highlighting the urgent need for new antibiotics and a vaccine.