A hefty sneeze can fling bacteria up to 4 metres, where it remains alive for up to 45 minutes.

QUT and UQ scientists have developed a new technique to study how some common disease-causing bacteria spreads.

The research is among the first to study the longevity of airborne pseudomonas aeruginosa bacteria, a multi-drug resistant germ associated with hospital-acquired infections, when they are expelled by human coughs and sneezes.

“We developed a novel technique to target the short-term and long-term ageing of bio-aerosols from people, without contamination from the ambient air,” said lead researcher Professor Lidia Morawska.

“To demonstrate the technique, airborne cough droplets were sampled from two patients with cystic fibrosis and chronic pseudomonas aeruginosa infection.”

Professor Morawska said the team found that the bacteria in the cough droplets from the patients decayed in two different time spans.

“As soon as cough droplets hit the air they rapidly dry out, cool and become light enough to stay airborne. They also partly degrade through contact with oxygen in the air, with larger droplets taking much longer to evaporate,” she said.

“We found that the concentration of active bacteria in the dried droplets showed rapid decay with a 10-second half-life for most of the bacteria but a subset of bacteria had a half-life of more than 10 minutes,” she said.

“This suggests some of the pseudomonas aeruginosa bacteria are resistant to rapid biological decay and thus remain viable in room air long enough to form an airborne infection risk, especially to people with respiratory problems such as patients with cystic fibrosis.

“We think this could be because droplets are produced in different parts of the respiratory tract and carry different ‘loads’ of bacteria.

“The larger droplets carrying bacteria take longer to evaporate which makes them more resistant to decay and able to maintain bacteria viability for extended periods.”

Professor Morawska said the findings had implications for infection control, particularly in hospitals and with the treatment of people with cystic fibrosis.

The study is accessible here.