Cigarette smoke may make MRSA even more resistant to antibiotics, scientists now fear.
Researchers found some strains of the superbug became stronger after they were exposed to smoke.
Methicillin-resistant Staphylococcus aureus (MRSA) is already resistant to several widely-used antibiotics.
Experts at the University of Bath called for further trials, saying they are currently unsure if the finding could affect humans.
They believe the chemicals in smoke trigger an emergency response in the bacteria, which makes them mutate quicker.
Researchers found some strains of the superbug became stronger after they were exposed to cigarette smoke
The researchers exposed six different strains of MRSA – as well as other strains of S aureus – in the laboratory to tobacco smoke.
The smoke came from lighting just one cigarette – but they were exposed for up to six hours, the scientists warned.
The half-dozen strains of MRSA are known to cause conditions including pneumonia and endocarditis, both of which can kill.
Three of the strains, which were community-acquired – those that infect healthy people, were better able to survive in cigarette smoke.
Other strains of the superbug also showed more resistance to rifampicin, a crucial antibiotic dished out to MRSA patients.
Health officials in the UK tell doctors they should not dish out rifampicin alone when dealing with an MRSA patient because ‘resistance may develop rapidly’.
Methicillin-resistant Staphylococcus aureus (MRSA) is already resistant to several widely-used antibiotics
The team, who published their findings in the journal Scientific Reports, warned smoke could also cause resistance to other antibiotics.
Other tests revealed some strains of S aureus, estimated to be carried by up to 60 per cent of people, became more invasive and persistent.
It is believed this is because the smoke causes a ‘hardy’ sub-population in the bugs to emerge, called small colony variants.
Lead author Dr Maisem Laabei said: ‘We expected some effects but we didn’t anticipate smoke would affect drug-resistance to this degree.
‘It seems reasonable to hypothesise, based on our research and others’, that stressful conditions imposed by smoking induce responses in microbial cells.’
This then leads to ‘adaptation to harsh conditions, with the net effect of increasing virulence and/or potential for infection’, Dr Laabei added.
He said the team recognises exposure to smoke in a laboratory is ‘different’ to inhaling smoke over a long time.
However, Dr Laabei and colleagues hope the results ‘provide another reason for people not to smoke and for current smokers to quit’.
The scientists are now keen to discover if pollution, especially from diesel exhaust fumes, may have a similar effect on bacteria.
The team worked with experts at Imperial College London and Oxford University, as well as academics based at institutions in Spain.
Antibiotic resistance has been listed as one of the top 10 threats to human health by the World Health Organization, alongside cancer, global warming and Ebola.
It happens when a bacteria evolves to become strong enough to survive antibiotic treatment, and is caused by exposure to low amounts of the drugs over long periods of time.
Some strains of the STI gonorrhoea are already showing signs of responding to first line drugs, and there are fears once easy-to-treat illnesses will become deadly.
Figures estimate that superbugs will kill ten million people each year by 2050, with patients succumbing to once harmless bugs.
Around 700,000 people already die yearly due to drug-resistant infections including tuberculosis (TB), HIV and malaria across the world.
Concerns have repeatedly been raised that medicine will be taken back to the ‘dark ages’ if antibiotics are rendered ineffective in the coming years.