Depending of the definition of ‘resistance’ used, between 1% and 10% of people with gonorrhoea in the UK have a strain which is resistant to the antibiotic that is most frequently used to treat the infection. Releasing the data today, the Health Protection Agency drew attention to the risk of treatments becoming ineffective but did state that actual cases of treatment failure remain rare.
The public health body also released figures showing that just under half a million new diagnoses of sexually transmitted infections were made in 2009, continuing the upward trend seen over the last decade. The largest number of diagnoses are in young people under the age of 25.
Drug-resistant gonorrhoea
Recommended antibiotic treatments for gonorrhoea have changed frequently, as bacterial strains have developed resistance to existing treatments. In the late 1990s, resistance to drugs in the quinolone class (e.g. ciprofloxacin) led to the drugs being abandoned as first-choice treatment, to be replaced by drugs in the cephalosporin class (e.g. cefixime, ceftriaxone).
But while ciprofloxacin is no longer widely used in the UK, a third of new gonorrhoea infections are of strains that are resistant to it. Similarly a fifth have a strain that is resistant to penicillin and two-thirds have a strain resistant to tetracycline. With so many treatment options already exhausted, it would be of concern if currently used treatments become ineffective in the next few years.
The Health Protection Agency’s Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) has monitored the issue since the year 2000. The programme conducts antimicrobial susceptibility testing on isolates of N. gonorrhoeae collected at 26 sexual health clinics in England and Wales. In 2009, 1395 samples were tested.
Reflecting the wider epidemiology of gonorrhoea, a large number of samples came from men who have sex with men (38%), and a third of this group also had HIV. Among women (28%) and heterosexual men (34%), significant proportions came from young people under 25 and from people of black Caribbean ethnicity.
Cefixime is the most commonly used antibiotic to treat gonorrhoea. There is some uncertainty about which cut-off point to use to define decreased susceptibility, or resistance, to the antibiotic. The HPA provide data for two different cut-off points: the most widely accepted definition (a Minimal Inhibitory Concentration of greater than 0.25mg/L) and an alternative, lower one (a Minimal Inhibitory Concentration of greater than 0.125mg/L).
Using the standard definition, 1.2% of cases in 2009 were resistant. However, using the lower cut-off point 10.6% of cases were resistant, a jump from 0.1% in 2005 and 2.8% in 2008.
These strains were found in people from all demographic groups, but were more predominant in gay and bisexual men. These men tended to be white and to report at least two UK sexual partners in the three months before diagnosis.
Although gonorrhoea treatment guidelines recommend that that local patterns of drug sensitivity should be considered when providing treatment, the Health Protection Agency (HPA) report does not contain data on regional variations.
Less than 1% of strains were resistant to the second most commonly used treatment, ceftriaxone. However strains which were resistant to one drug were very frequently resistant to a number of other drugs.
The HPA is investigating combination therapies to treat the bacteria and is encouraging pharmaceutical companies to develop new drugs.
The HPA recommends that clinicians should be vigilant to the possibility of treatment failures among their patients. Moreover, they should consider performing tests of cure, particularly if symptoms persist or following a throat infection.
Professor Cathy Ison of the HPA commented: “At the moment the drugs we use in the UK are still effective for treating gonorrhoea. But our lab tests show that the bacteria are becoming less sensitive to these drugs and the worry is that we could see gonorrhoea become a very difficult infection to treat within the next five years, as elsewhere in the world.”
She added that this could mean that changing sexual behaviour would become the only way to control the infection.
New diagnoses of sexually transmitted infections
The HPA also released data today on the 482,696 new diagnoses of sexually transmitted infections made in 2009. The data shows that in the general population, the peak age for woman acquiring an STI is 19 to 20, and for men it is between 20 and 23.
Among women, two-thirds of new diagnoses were in those under the age of 25. Among men, around half are in this age group.
New diagnoses of chlamydia, gonorrhoea and genital herpes increased between 2008 and 2009, each by between 5-7%. Some of this is likely to be driven by increased rates of testing, including through the National Chlamydia Screening Programme.
On the other hand diagnoses of syphilis and genital warts have stabilised, with decreases of 1% and 0.3% respectively.
Sir Nick Partridge, chief executive of the Terrence Higgins Trust, called it "staggering" that infections had risen to almost half a million a year. "Until we improve sex education and give extra support to young people, they will continue to take avoidable risks with their sex lives," he said.