The antibiotics used to treat gonorrhea, a common sexually transmitted disease, have become less effective as the bacteria evolved to be resistant, according to a study.

Jim Collins, a veterinary sciences and microbiology professor, explained that gonorrhea’s bacterium strain, called neisseria, has genetically mutated and several types of antibiotics that were once effective in curing this type of infection no longer work. The common antibiotics include penicillin, tetracycline, fluoroquinolones and cephalosporin, he said.

“Bacteria has a way to genetically change in which change makes it resistant to the antibiotics,” Collins said. “It can grow in the presence of that antibiotic, which gives an advantage for the bacterium.”

According to Richard Herrier, a pharmacy professor, bacteria can become resistant to antibiotics when one’s body is exposed to many different kinds, or if the same antibiotic dose is continuously taken over time. Resistance can also occur through horizontal gene transfer, which is when bacterium acquires genetic material from other bacteria, causing it to come together and transfer genetic materials. This can become a problem for treatment — if one strain of bacterium is resistant to a certain antibiotic, the resistance can transfer to other species, Herrier added.

“It used to be you just took penicillin and the bacteria dropped, but over time they (bacteria) have developed over multiple different mechanisms and now we have chunks of them that are resistant to drugs,” he said.

Undetected and untreated STDs can increase a person’s risk for HIV and cause other serious health problems, according to the Centers for Disease Control and Prevention. In 2010, 309,341 cases of gonorrhea were reported in the United States, which is a 2.8 percent increase from 2009, according to the center.

At the UA, Campus Health Service provides confidential tests for both chlamydia and gonorrhea. Although some men and women infected with gonorrhea experience symptoms like painful or burning sensations upon urination, these symptoms don’t affect everyone, said Lee Ann Hamilton, assistant director of Health Promotion and Preventative Services at Campus Health.

Currently, there are no new antibiotics to help cure the disease, Herrier said. But not every strain of neisseria gonorrhea is resistant to antibiotic.

The CDCP is monitoring trends in antibiotics and is closely reviewing treatment recommendations to test new drug combinations, according to their website.