a SIMPLE blood test may pick up the early signs of Australia's second most deadly cancer, saving thousands of lives.

St Vincent’s Hospital microbiology registrar Dr Sanchia Warren has found certain bacterial blood infections could be one of the first signs of bowel cancer.

More than 12,000 Australians are diagnosed with bowel cancer each year, and 4000 die from the disease, making it the biggest killer after lung cancer.

Dr Warren said many die because the disease is diagnosed too late, but if patients with symptoms of a blood infection were screened for the cancer, lives could be saved.

Analysing a database of more than 1.2 million people, Dr Warren found those treated for some bloodstream infections were more likely to be diagnosed with cancer over the next 12 months.

The infections included a range of bacteria, but the highest risk was clostridium, which made people 115 times more likely than the normal population to develop bowel cancer.

"a bloodstream infection caused by particular bacterium like certain clostridium species … may provide the earliest possible indicators that the patient may have bowel cancer," Dr Warren said.

The findings, presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in the US, showed those with the bloodstream infections might benefit from targeted cancer screening programs, she said.