(HealthDay News) — Antibiotic-resistant cases of gonorrhea have more than quadrupled in the United States, according to research published in the US Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.

This new data should serve as a warning that “the future of current treatment options may be in jeopardy,” the CDC said in a news release issued Thursday.

For now, the multidrug therapy that the CDC recommends for gonorrhea still works, the agency said, and there’s not yet been a US case where treatment completely failed. However, agency researchers report that the number of US cases of gonorrhea where strains showed decreased susceptibility to azithromycin jumped from 0.6% in 2013 to 2.5% a year later. This suggests that azithromycin “will be next in the long line of antibiotics to which gonorrhea bacteria have become resistant — a list that includes penicillin, tetracycline, and fluoroquinolones,” the CDC said.

“It is unclear whether these increases mark the beginning of trends, but emergence of cephalosporin and azithromycin resistance would complicate gonorrhea treatment substantially,” the authors write.