People seeking treatment for symptoms of sexually transmitted diseases are often given antibiotics although tests later show they didn’t need the medication.

Three-quarters of people given antibiotics in the emergency department after showing symptoms for certain sexually transmitted infections actually don’t have those conditions, according to new research.

Researchers from St. John Hospital & Medical Center in Detroit say the vast majority of people suspected to have gonorrhea and/or chlamydia received antibiotics when cultures would later show bacteria weren’t responsible for their infection.

But what harm can prescribing these unneeded antibiotics do? Quite a bit actually.

Overprescribing antibiotics, namely using them for when they can’t do any good, is dangerous, even for people who don’t even swallow the pills.

Antibiotics are the kind of medicine where use in one person affects others, especially if they’re used unnecessarily.

The new research findings come at a crucial time when the world is battling bacteria that have developed defenses to the strongest of available antibiotics.

Last month, officials with the U.S. Centers for Disease Control and Prevention (CDC) announced a woman with a urinary tract infection in Pennsylvania carried a type of E. coli that had a gene making it resistant to the strongest antibiotics available.

The CDC estimates these drug-resistant “superbugs” are responsible for 2 million infections annually that result in 23,000 deaths.

As gonorrhea is the second most commonly reported communicable disease, effective treatments are crucial from preventing it from spreading further. In recent years, the incidence of drug-resistant gonorrhea has been on the rise, according to the CDC.

Of all antibiotics prescribed to humans, a third are unnecessary, meaning they’re for conditions caused by viruses, not bacteria, according to the CDC.

“Antibiotics are lifesaving drugs, and if we continue down the road of inappropriate use we’ll lose the most powerful tool we have to fight life-threatening infections,” Dr. Tom Frieden, director of the CDC, said at a press conference last month. “Losing these antibiotics would undermine our ability to treat patients with deadly infections, cancer, provide organ transplants, and save victims of burns and trauma.”

Read More: ‘Nightmare Bacteria’ May Signal ‘End of the Road’ for Antibiotics

The St. John researchers examined records of 1,103 patients who underwent STD testing in the emergency department during a two-month period.

These patients complained about a variety of symptoms, including penile discharge or pain.

Genital cultures are commonly collected from patients with signs and symptoms of STDs to determine which kind of organism — bacteria, fungus, or virus — is causing the infection.

The problem is the results from the culture testing are not immediately available. They typically take 48 hours or less, but few people call back to hear the results of the culture.

“The turnaround time is not fantastic,” Karen Jones, M.P.H., B.S.N., R.N., infection preventionist at St. John, told Healthline. “People want to be in and out with a prescription.”

Those prescriptions, at least in 40 percent of the people’s records studied, were antibiotics for gonorrhea and/or chlamydia. Of those given antibiotics, 76 percent eventually tested negative for having either of the STDs.

Only 7 percent of the 60 percent who didn’t receive antibiotics ultimately tested positive for either or both STDs.

Read More: Where Will the New Antibiotics Come From?

The study, presented this week at the 43rd Annual Conference of the Association for Professionals in Infection Control and Epidemiology (APIC), also examined what physical symptoms were associated with positive STD cultures.

A quarter of women who had inflammation of the cervix or cervical motion tenderness tested positive for gonorrhea and/or chlamydia.

In men, who comprised a smaller portion of patients studied, 60 percent with penile discharge and 57 percent with inflammation of the urethra tested positive for gonorrhea and/or chlamydia.

Thirty-five percent of all patients who disclosed they had more than one sex partner also tested positive for either STD.

This, Jones says, highlights the importance of clinicians taking a complete sexual history of their patients before prescribing antibiotics.

Another issue at stake is the high volume of patients who are using the emergency department for STD concerns, which may be better addressed at outpatient facilities or public health clinics.

Even there, Jones says, there’s little focus on antibiotic resistance. In working with the Detroit Public Health Department and previously with one in Chicago, she says the focus isn’t on the judicious use of antibiotics to prevent antibiotic resistance.

“They really want patients to be treated so the disease doesn’t spread,” she said. “This is another area where antibiotic stewardship can be improved.”