Cigarette smoke has been found to make MRSA bacteria more resistant to antibiotics.

The MRSA bacteria, s. aureus, can cause severe infections in humans. These are difficult to treat as MRSA is resistant to most commonly used antibiotics. MRSA poses a major problem in hospitals due to the high numbers of patients with open wounds and compromised immune systems, which enable the infection to spread easier.

Previous research has identified that smoking makes patients more susceptible to MRSA infection. However, this is the first study that demonstrates this may be due to genetic changes taking place in the MRSA bacteria.

Six different strains of MRSA were exposed to cigarette smoke. Although each strain responded differently to the smoke, after exposure all strains were both more resistant to the antibiotic rifampicin and more invasive. The researchers speculate that the bacteria increased the mutation rate in their microbial DNA to deal with the toxic chemicals in the cigarette smoke.

Researchers also observed the emergence of Small Colony Variants (SCVs), small subsets of the bacteria population with genetic variations that make them more resistant to antibiotics. SCVs are characterised by their high adhesiveness and invasiveness, which can cause long-term chronic infections.  

Researchers stress that exposing MRSA to cigarette smoke does not accurately represent the effects of regular smoke inhalation experienced by a regular smoker. However, they express that the results do demonstrate that smoking does increase the potential of MRSA infection.

Further research will investigate the how air pollution, including exhaust fumes, may also impact MRSA resistance.