* Cases soar by 25 percent in England over past year
* Overuse of antibiotics fuels drug resistance
* Gonorrhoea among most common sexually transmitted diseases
* Totally antibiotic-resistant strain found in Japan in 2008
LONDON, Feb 27 (Reuters) - Gonorrhoea cases have soared by 25 percent in the past year in England as superbug or drug-resistant strains of the sexually transmitted infection (STI) take hold worldwide, British health officials said on Wednesday.
Nearly 21,000 new cases had been diagnosed in 2011, with more than a third of cases in gay men and more than a third in people who have had gonorrhoea before, the UK Health Protection Agency (HPA) said in a statement.
Effective treatment with antibiotics has been compromised by growing resistance, it said, noting "a drift towards decreased susceptibility" of gonorrhoea infections to drugs called cephalosporins which are normally recommended as treatment.
"We are seriously concerned about continuing high levels of gonorrhoea transmission and repeat infection," said Gwenda Hughes, the HPA's head of STI surveillance.
A strain of gonorrhoea that was resistant to all recommended antibiotics was found in Japan in 2008, scientists said in 2011. They warned then it could transform a once easily treatable infection into a global health threat.
Last year the World Health Organisation said cases of drug-resistant gonorrhoea had spread across the world.
Gonorrhoea is a bacterial STI which, if left untreated, can lead to pelvic inflammatory disease, ectopic pregnancy, stillbirths and infertility in both men and women.
It is one of the most common sexually transmitted diseases in the world and is most prevalent in south and southeast Asia and sub-Saharan Africa. In the United States alone, according to the Centers for Disease Control and Prevention, the number of cases is estimated at about 700,000 a year.
The emergence of superbugs has been driven by the overuse and misuse of antibiotics, which help fuel genetic mutations within the bacteria. (Reporting by Kate Kelland; Editing by Louise Ireland)