Researchers have long been worried about the growing antibiotic resistance to treat sexually transmitted diseases (STDs), especially gonorrhea.

The multidrug-resistant strains of gonorrhea have threatened the efficacy of the current treatment regimen – a shot of ceftriaxone (Rocephin) with or without an oral dose of azithromycin (Zithromax).

New antibiotics for gonorrhea are undergoing clinical trials but since gonorrhea has been quickly developing resistance to all the antibiotics, it is unclear how long a new antibiotic would remain effective.

This dilemma has led Dr. Jeffrey Klausner of the University of California, Los Angeles (UCLA), and other researchers across the nation to examine a different treatment strategy for gonorrhea, the third most common STD in the United States.

The new strategy involves targeting patients whose gonorrhea infections are still susceptible to antibiotics that were previously advised.

The researchers published the results of the new study last week in Clinical Infectious Diseases, explaining that the new strategy could be highly effective.

Dr. Klausner and colleagues used a genotypic polymerase chain reaction (PCR) test to screen gonorrhea-infected patients for the presence of a genetic mutation in the gyrase subunit A (gyrA) enzyme.

The genetic mutation renders ciprofloxacin (Cipro), the antibiotic recommended for the treatment of gonorrhea until 2007, ineffective.

The experts explained that if the gonorrhea bacterial samples from the patients did not contain the single point mutation in the gyrA gene, “that would be an indication that their infection could be treated with ciprofloxacin.”

Dr. Klausner said, “We know that 70 to 80 percent of gonococcal infections in the United States are actually susceptible to Cipro, but we never had a test that could tell in that individual patient if their infection is amenable to ciprofloxacin treatment.”

“Based on that discovery of the association with this molecular marker, or altered gene, I thought we could develop a test that would then be able to predict resistance in Neisseria gonorrhoeae based on the alteration of this gene,” he added.

Using the new strategy, the researchers found that 106 patients out of 117 gonorrhea-infected patients susceptible to ciprofloxacin were cured with a single dose of the antibiotic. Only two patients, who were accidentally included, failed the therapy.

The authors wrote, “Our results provide very strong evidence that the gyrA serine 91 N gonorrhea genotype reliably predicts clinical outcome in patients treated with ciprofloxacin.”

“We thought this was the case, but we never had the clinical outcome study to really prove it, and that’s why this study is so important,” Dr. Klausner explained. “This is one of the few studies that actually takes a new test and demonstrates, in a clinical study, that on the basis of the test, people can have a 100-percent cure.”

Dr. Klausner said he hopes that the CDC might include screening for ciprofloxacin resistance in the next STD treatment guidance, which is expected in the coming months.

It would take 30 minutes to get the results from the genotypic test. The test has already been in use in Europe and Australia. Dr. Klausner hopes that the inclusion of the test in the CDC’s new STD guidelines will encourage diagnostics and clinicians. He said, “I’m hoping that clinicians are going to recognize the value of treating someone with a pill versus a shot.”