No one wants to be told that they have super gonorrhea. Alas, that is actually a diagnosis now. Everyone would also really prefer that if they did catch the abnormally drug-resistant infection, doctors didn’t tell them that treatment might actually spread the antibiotic resistance even faster. New research suggests, however, that this is unfortunately true as well.

Neisseria gonorrhoeae is a sexually transmitted bacteria that has recently developed a broad resistance to antibiotics. Current public health efforts to reduce the burden of the infection include increased screening and treatment of sexually active individuals. The approach could have unintended negative consequences thought Swiss researchers Stephanie Fingerhuth and Christian Althaus, both from ETH Zurich. Together with colleagues, they developed a mathematical model to understand and study the spread of bacterial resistance.

Using international data from two separate surveillance programs, the researchers began working on an estimate of how quickly resistant strains could spread in different host populations, namely men who have sex with men and heterosexual men. They analyzed the sexual behavior of both groups and obtained data on the prevalence, or overall number of cases, and incidence, the number of new cases every year, of gonorrhea. The team used all of the information to calibrate a mathematical model capable of predicting the spread of N. gonorrhoeae.

The results showed that the infection spread much faster in men who have sex with men, with an estimated doubling time of 6 months, compared to 16 months in heterosexual men. On average, those in the former group had more sexual partners than the heterosexual men, but the argument that logically followed — that a higher number of sexual partners leads to a faster spread of resistance — didn’t hold true.

Instead it was the more frequent antibiotic treatment for N. gonorrhoeae among men who have sex with men that was responsible for the faster spread of resistance. The researchers hypothesized that the higher level of treatment was because those men more frequently developed symptoms or sought out screening for STIs.

The study authors said that this was the first research, to their knowledge, that analyzed and interpreted the spread of antibiotic resistance in super gonorrhea in a quantitative manner. The study had limitations, including the fact that it relied on simplified assumptions, but it still strongly suggests that treatment rate is the main force behind the spread of resistance.

“Estimating rates of resistance spread is useful for projecting future resistance levels and the expected time it will take until a certain threshold in the proportion of antibiotic-resistant N. gonorrhoeae is reached,” the researchers wrote in the study. “Future treatment recommendations for N. gonorrhoeae should carefully balance prevention of N. gonorrhoeae infection and avoidance of the spread of resistance.”

Source: Fingerhuth S, Bonhoeffer S, Low N, Althaus C. Antibiotic-resistant Neisseria gonorrhoeae Spread Faster with More Treatment, Not More Sexual Partners. PLOS Pathogens. 2016.