It's strange how the reputation of some medicines has changed over the last few years. Take antibiotics as an example. Ten years ago they were looked on as life-savers. Now the impression is that they are losing their effect because the germs they used to kill are resistant to them. News stories about 'flesh-eating bugs' and 'killer' hospital infections haven't helped.

The backlash from these stories, in the experience of many GPs like myself, is that many people are frightened of antibiotics - and this even spreads into a fear about new medicines in general. So it's good to put a few misconceptions right. Because in the vast majority of infections needing antibiotics, they still work very well, and will do so for the foreseeable future. Bugs that are resistant to them will remain in the minority, usually in hospitals, and will need special attention, but the prescriptions we give out in general practice are still extremely useful.

The first antibiotics, such as penicillin and streptomycin, were natural substances. They started with Alexander Fleming and the mould spore that drifted in through his laboratory window. It settled on a germ culture plate, and killed off the bacteria that he had been growing on it. Moulds like the penicillin fungus feed on bacteria - that's why they produce substances to kill them. All Fleming and the scientists who followed him had to do was to find ways to produce these substances in the laboratory in big enough quantities to be useful for killing germs in humans - without killing the humans themselves.

Penicillin set off the hunt for more mould-produced bacteria-killers, and the name 'antibiotic' was born. For more than 30 years after the end of the war, researchers found new antibiotics in bizarre places - near sewage outlets in the sea, in infected skin ulcers, and in soil samples. Japanese scientists found frogs that lived happily in filthy puddles teeming in bacteria - and found that their skin was producing antibiotics so that they could survive. Called magainins, they have become the basis of a series of new antibiotics - although to start with a lot of frogs had to be killed to develop them.

As in any branch of nature, however, evolution provided bacteria with ways of fighting back against mould and fungal attack. Many can change their surfaces in subtle ways so that the antibiotics no longer work - and they become antibiotic resistant. Only in the last 20 years, as we learned much more about the chemistry between germs and our own tissues, have we learned how to prevent resistance.

One way is to produce synthetic antibiotics. The scientists have moved on from searching nature for new germ-killers to designing chemicals specifically to attack weak spots in the bacteria - spots at which they can't mount a change towards resistance. The days when one person can discover a new substance are long gone - it needs teams of microbiologists, geneticists, chemists, and molecular biologists working together with doctors who can point them at the target 'bugs'.

The biggest story of the beginning of the 21st century will be antivirals. The same research disciplines used to beat the bacteria are now being used to vanquish the viruses. Good news hardly ever hits the headlines - but there is plenty of it about. The new 'cocktails' of drugs against HIV (the AIDS virus) is keeping thousands of sufferers alive and well when they would otherwise have died. There are promising leads for all the forms of viral hepatitis (infections in the liver).

Most encouraging are recent discoveries linking viruses to diseases not previously thought to be infections. Cervical cancer in women may well be prevented in future by antiviral drugs aimed at the 'human papilloma virus' thought to start it off. Already there is evidence that interferon - a drug initially developed as a virus killer - may help some people with multiple sclerosis.

Despite the bad publicity, we humans are still winning the war against the bacteria, and have won the first few battles in the long war recently declared on viruses. Deaths from infections in countries with developed health services are still falling. Hospitals everywhere are now well aware of the problems of resistant infections, and have hard-working committees to keep them at the minimum. We have more reason to be confident in the future than to fear it.

Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.