Scientists were able to kill bacteria in test-tubes
It could be the secret weapon scientists have been seeking for decades because of the growth of antibiotic-resistant infections.
Research published in the journal Science suggest the enzyme, which comes from bacteriophage, or phage viruses which attack and kill bacteria, could be used to prevent infection.
The scientists, from Rockefeller University, New York, said the enzyme might also improve treatment if used in combination with antibiotics.
It may even be possible to tailor a treatment for a particular bacteria.
Researcher Dr Vincent Fischetti of Rockefeller University, said: "A nasal spray containing this enzyme would prevent infection before the start. We would no longer have to wait for an infection to arise in order to treat it."
'Resistance a concern'
Tests in mice have shown the enzymes wiped out the streptococcus pneumonia, naturally present on mucous membranes in the nose and throat.
They were also shown to kill penicillin-resistant strains of the bacterium, a major cause of infections, in test-tubes.
'Phage' is found anywhere bacteria are found, including sewage and soil. They infect, replicate and burst out of bacteria before infecting their next host.
Special phage enzymes punch a hole in the bacteria wall, allowing the phage to escape.
The Rockefeller team's key finding was that the enzymes also work from the outside of bacteria - and millions of bacteria can be killed with just a few drops of the enzyme in seconds.
Dr Fischetti said: "Resistance to antibiotics is rapidly becoming a serious public health concern. These enzymes offer an alternative method for combating resistant pathogens [disease-causing micro-organism]."
Researcher, Dr Julia Loeffler, said "This enzyme will kill pneumococci on mucous membranes within seconds.
"By treating individuals carrying this bacterium with the enzyme, you could significantly reduce the reservoir of these bugs in the population and consequently reduce infection rates."
'No side effects'
The researchers from the Laboratory of Bacterial Pathogenesis at Rockefeller University say that an added benefit of the enzyme is that resistance will not easily develop against the enzyme treatment because phage and bacteria have developed together over millions of years.
Phage enzymes are also unlikely to have side effects because they could be targeted against particular bacteria.
Antibiotics are known to kill may different kinds of bacteria leading to complications such as intestinal problems.
Unlike antibiotics, which mainly attack bacteria which live inside cells, the phage, enzymes only kill disease bacteria which lie on the surface of cells.
But scientists say that together, they could be a "powerful weapon" against infections.