Some doctors see their rise as heralding the end of the age of antibiotics.
BBC News Online's health team presents an overview of the past, present and future of the 20th century's greatest medical breakthrough. The emerging superbug Visa is resistant to just about every antibiotic known to medicine and has been discovered in hospitals from Japan to Scotland - find out where it comes from and why it has got doctors worried. A brief history of antibiotics Antibiotics have revolutionised medical care in the 20th century, but in recent years bugs have been winning the battle against the medical profession. A bug's life Meet the most successful organism on earth, and find out why it poses a threat to humans. BBC News Online finds out.