Antibiotic Treatment Speeds up Spread of Resistant Gonorrhea

A new study suggests that screening and treatment of patients infected with Neisseria gonorrhoeae might actually spread antibiotic resistance of the sexually transmitted bacterium.

Researchers at ETH Zurich (Switzerland) and the University of Bern (Switzerland) conducted a mathematical modeling study to understand what drives the spread of Gonorrhea resistance. To do so, they used data from two different surveillance programs for N. gonorrhoeae in order to estimate how fast resistant strains spread in two different host populations, homosexual and heterosexual men. They found that resistant strains spread much faster in homosexual men, with an estimated doubling time of 6 months, compared with 16 months in heterosexual men.

The researchers also obtained data on the prevalence and incidence of N. gonorrhoeae infection, and on sexual behavior among homosexual men and heterosexual men and women. They then used all of the data to calibrate a mathematical model that could predict the spread of antibiotic-resistant N. gonorrhoeae in the different populations. The model predicted a much faster spread of resistant strains in homosexual men, due to the fact that on average, they have more sexual partners.

They also found, however, that the intuitive argument that a faster spread of an infection, due to a higher number of sexual partners, would result in a faster spread of resistance did not hold true. In fact, it was the higher level of antibiotic treatment among homosexuals--presumably because they more frequently develop symptoms or seek out screening--that was responsible for the faster spread of resistance. The study was published on May 19, 2016, in PLOS Pathogens.

“We could attribute the faster spread of resistant pathogens to higher treatment rates. This finding implies that promoting screening to control antibiotic-resistant N. gonorrhoeae could in fact accelerate their spread,” concluded lead author Stephanie Fingerhuth, MSc, of the ETH institute of integrative biology, and colleagues. “As higher treatment rates result in faster spread of antibiotic resistance, treatment recommendations for N. gonorrhoeae should carefully balance prevention of infection and avoidance of resistance spread.”

Gonorrhea (colloquially known as the clap) is a common human sexually transmitted infection (STI). The usual symptoms in men are burning with urination and penile discharge. Women, on the other hand, are asymptomatic half the time or have vaginal discharge and pelvic pain. Although cephalosporins are the cornerstone of treatment of N. gonorrhoeae infections, cefixime is the only oral antimicrobial option. Increased minimum inhibitory concentrations (MICs) to cefixime have been identified worldwide and have been associated with reports of clinical failure.

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ETH Zurich
University of Bern