SCIENTISTS at Monash University have made a breakthrough in the hunt for an alternative to antibiotics - at a time when the World Health Organisation is predicting a bleak future in which current bug-killing drugs are so ineffective ''a child's scratched knee or a strep throat could kill again''.

The researchers, in collaboration with Rockefeller University and the University of Maryland, have published a paper revealing the structure and workings of PlyC, a protein that kills bacteria that cause infections from sore throats to pneumonia and streptococcal toxic shock syndrome.

PlyC is a viral protein - known as a bacteriophage lysin - that infects and kills bacteria.

Professor James Whisstock, Associate Professor Ashley Buckle and Dr Sheena McGowan of the Monash School of Biomedical Sciences, have spent the past six years deciphering PlyC's atomic structure - a key step in developing the protein into a drug therapy.

Professor Buckle said PlyC, in its purified form, seemed to be 100 times more efficient at killing certain bacteria than any other lysin to date. ''Even faster than household bleach,'' he said.

While developing a drug and delivery system - such as a pill or nasal spray - is at least a decade away and subject to serious challenges, Rockefeller University scientists have already been successful in treating strep infections in mice with a nasal spray.

After World War I, bacteriophage therapies were investigated as a means of containing bacteria-based disease, but research was largely abandoned in the 1940s, when antibiotics came into wide use.

However, Dr McGowan said it was still common for people in east European countries who could not afford antibiotics to drink whole bacteriophage cultures as a cure for infections.

Fears have been around for years that the world could return to a pre-antibiotic era because of bacteria becoming increasingly resistant to the drugs.