New ‘superbug’ strain of gonorrhea resistant to all available antibiotics; researchers fear global outbreak
Japanese and European researchers have identified a new strain of Neisseria gonorroeae that is exceptionally resistant to cephalosporins, the last remaining family of antibiotics available to treat the sexually transmitted disease. Although physicians have identified only a handful of infections by the new strain of gonorrhea, called H041, they fear that its ability to grow even in the presence of the cephalosporins may allow it to spread rapidly throughout the world. “This is a large public health problem and the era of untreatable gonorrhea may now have been initiated,” the team wrote in their abstract for the report presented Sunday at a Quebec City meeting of the International Society for Sexually Transmitted Disease Research. The report comes only days after the U.S. Centers for Disease Control and Prevention reported a growing incidence of gonorrhea infections that require unusually high doses of cephalosporins to cure them.
Gonorrhea, known to generations of Americans as “clap,” is one of the most common sexually transmitted diseases in the world. In the United States alone, an estimated 700,000 new cases are diagnosed each year, according to the CDC, affecting men and women. The disease exhibits no symptoms in about half of women and in about 2% to 5% of men. When symptoms appear, they typically include a burning sensation when urinating and discharge of pus from the genitals. In women, it can cause chronic pelvic pain, ectopic pregnancies and loss of fertility. In men, it can also lead to loss of fertility. In both sexes, it increases the risk of transmitting or contracting HIV. Untreated, it can prove fatal.
The development of sulfonamides in the 1940s provided the first breakthrough in the treatment of gonorrhea, but the bug soon became resistant and physicians switched to penicillin. Since the 1970s, the pathogen has become resistant to penicillin, then to tetracycline, and then to fluoroquinolines such as Cipro. The current standard of treatment is with cephalosporins: cefixime, which is given orally, and ceftriaxone, an injectible drug. Experts say that if gonorrhea becomes resistant to the cephalosporins as well, there are no other new antibiotics available or on the horizon to treat it.
According to Maryn McKenna, author of “Superbug,” Japanese scientists warned in 2007 that they had seen four cases of gonorrhea that did not respond to cefixime, but were treatable with ceftriaxone. In 2010, Norwegian researchers reported that they had observed two such cases. Then, in January of this year, Japanese researchers reported that they had isolated a strain of gonorrhea from the throat of a sex worker that was highly resistant to both drugs. The new report Sunday revealed further details about the strain.
A team headed by Dr. Magnus Unemo of the Swedish Reference Laboratory for Pathogenic Neisseria sequenced the genome of the new strain and found four never-before seen mutations that were responsible for the resistance to the cephalosporins. Perhaps more frightening, when they grew the bacterium in culture with other strains of gonorrhea, the new strain was quickly able to pass its resistance along to the other strains, increasing their resistance to the drugs 500-fold. That, said the researchers, suggests that the new strain could spread resistance rapidly through the population.
The CDC report issued last Thursday examined more than 6,000 gonorrhea samples obtained in the U.S. since 2000. The study found that the number of samples with at least some resistance to cephalosporins grew slowly during the first part of the decade, but has been increasing recently. From 2000 to 2006, only 0.02% of the sample showed resistance to cefixime, but by 2009 the proportion had grown to 0.11% Most of the samples with increased drug resistance were obtained from men who have sex with men. The largest growth in incidence during the period was observed in Hawaii (from 0% to 7.7%) and California (from 0% to 4.5%). All of the cases were eventually cured by used higher-than-normal doses of the cephalosporins, but such high doses can have adverse side effects.
The CDC report urged that physicians treat new cases of gonorrhea with cephalosporins and the antibiotic azithromycin in an effort to curb resistance. The agency said it is also working with the National Institutes of Health to identify existing drugs that might be effective against the strains and to develop new antibiotics.