The sexually transmitted disease gonorrhea is becoming increasingly resistant to yet another drug, which now leaves just one medication that can be used as a first-line treatment for the disease, according to a new report from the Centers for Disease Control and Prevention.

Over the last several decades, the bacteria that cause gonorrhea have developed resistance to many antibiotics used to treat the condition, including penicillin, tetracycline and fluoroquinolones. That left just one class of drugs, called cephalosporins — which include the drugs cefixime and ceftriaxone — to be used as treatment.

But today, the CDC announced it no longer recommends cefixime, an oral medication, as a first-line treatment for gonorrhea, citing data over the last several years that show cefixime has become less effective at treating the infection.

That leaves ceftriaxone — an antibiotic delivered by injection — as the most effective therapy for the condition, health officials say.

"Treatment of patients with gonorrhea with the most effective therapy will limit the transmission of gonorrhea, prevent complications, and likely will slow emergence of resistance," the CDC report says.

But because health officials expect that gonorrhea will eventually become resistant to ceftriaxone, new treatment options are urgently needed, the CDC says.

Gonorrhea is caused by the bacterium Neisseria gonorrhea and is spread through sexual activity. People with gonorrhea often show no symptoms, but the disease can lead to serious complications, including infertility and chronic pelvic pain in women, and in men, epididymitis, a painful inflammation of the ducts attached to the testicles that may cause infertility if left untreated, according to the CDC. If the bacteria spread to the blood or joints, the condition can be life-threatening, the CDC says.

There were more than 300,000 cases of gonorrhea reported to the CDC in 2011.

Between 2006 and 2011, the dosage of cefixime needed to prevent growth of gonorrhea strains circulating in the United States increased, suggesting that the drug's effectiveness was waning. And there were reports from other countries that the recommended dose of cefixime did not cure the condition in some patients.

This recent lab data, and gonorrhea's history of developing resistance to other antibiotics, prompted the CDC to change its treatment recommendations, the report said.

Now, to treat uncomplicated gonorrhea cases, the CDC recommends ceftriaxone along with another antibiotic, such as azithromycin or doxycycline, for seven days. However, cefixime can still be used in some cases.

Patients that are not cured by treatment should be tested to see if they are infected with a resistant strain, the CDC says.

The CDC hopes the new recommendations to limit cefixime use will help preserve ceftriaxone as a treatment option for a little longer.

The new recommendations will be published tomorrow (August 10) in the CDC's Morbidity and Mortality Weekly Report.

Editor's Note: This article has been changed to reflect the fact that gonorrhea is not totally resistant to cefixime.

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