Melbourne scientists say they have made a major breakthrough in the search for an alternative to antibiotics.

Researchers from Monash University in Melbourne, along with The Rockfeller University and the University of Maryland in the United States, have spent the past six years studying the structure of a viral protein called PlyC.

They say they have discovered the way it kills the bacteria that causes a range of infections including sore throats, pneumonia and streptococcal toxic shock syndrome.

They have described the protein as a powerful anti-bacterial killing machine and say that discovering what it looks like and how it attacks bacteria is a major step forward in developing alternatives to antibiotics.

They say scientists have been trying to decipher the structure of PlyC for more than 40 years.

Monash University's Dr Sheena McGowan says identifying the atomic structure of PlyC is crucial to understanding how it can be used to fight bacteria.

"Over the last few years or few decades, there has been a lot of instances of resistance to antibiotics of bacteria," she said.

"I'm sure you've all heard... of multi-resistant bacteria and drug resistant bacteria. What we're looking at over the next coming decades is a time when antibiotics may not be as effective as they are now.

"So by doing research early, we can start to look for alternatives."