3-D illustration of Neisseria gonorrhoeae diplococci bacteria, which is responsible for the sexually transmitted infection gonorrhea.

Gonorrhea cases have continued to climb as STD rates have recently spiked across the nation. But doctors have had one less drug in their toolkit over the last decade, since the bacteria started to develop resistance to a key antibiotic.

But by skipping over the drug, Ciprofloxacin, they risk the bacteria also becoming resistant to the new standard treatment, ceftriaxone.

Now, UCLA researchers have developed a test that determines whether the first antibiotic, ciprofloxacin, could be used in the some 80 percent of the gonorrhea infections in the U.S. where it would be useful, as they describe in the journal Clinical Infectious Diseases.

The breakthrough could mean using ceftriaxone less – and thereby preventing the bacteria from developing resistance to that vital treatment, as well, they explain.

“These findings are important because there are a limited number of medication to treat gonorrhea,” they write. “Reusing previously effective antibiotics and decreasing the use of ceftriaxone may slow down the continued emergence of antibiotic resistance.”

Ciprofloxacin became used less after the Centers for Diseases Control and Prevention recommended against using it to treat gonorrhea in 2007.

But the problem is that four in five of the cases in the U.S. could still be treated with that drug. So instead doctors went right to ceftriaxone for initial treatments – which means that gonorrhea has started to slowly build up a resistance to that antibiotic as well (although that resistance is still less than one percent).

The UCLA doctors developed a DNA test for the bacteria to flag the resistance genes. They used the laboratory diagnostic to evaluate all gonorrhea cases at UCLA Health’s hospital, emergency departments, and primary-care clinics.

The physicians, armed with the knowledge of the gonorrhea infection’s virulence, were able to tailor their treatments effectively, according to the records.

The use of ciprofloxacin increased from zero percent to 40 percent of gonorrhea cases, while ceftriaxone dropped from 100 percent of cases to 60 percent of cases, they report.

“Scientists have been trying to determine how to better identify cases for targeted use of ciprofloxacin therapy, reducing the need to use the antibiotic ceftriaxone and risking increased resistance to that drug,” the scientists conclude.

Gonorrhea is one of the many STDs that have been spreading at record-setting rates over several years. A CDC surveillance report released last October counted 400,000 cases of gonorrhea in 2015 – an increase of 13 percent over the prior year. That figure was part of a total caseload of 2 million infections of gonorrhea, syphilis, and chlamydia – which was a new U.S. record.