The effect of cigarette smoke condensate (CSC) on Pseudomonas aeruginosa virulence and antibiotic sensitivity.

Abstract

Despite a decline in tobacco smoking in the developed world, the developing world has witnessed an increase in such activity over recent years. An increase in antibiotic resistance has accompanied this increase in tobacco use, and we suggest that the two may be linked. This study aims to investigate the effect of cigarette smoke exposure on bacterial virulence and susceptibility to antibiotics. Pseudomonas aeruginosa passaged in the presence of Cigarette Smoke Condensate (CSC) exhibited reduced susceptibility towards Amikacin (p=0.02), Tobramycin (p=0.03) and Aztreonam (p=0.007) and was accompanied by changes in growth dynamics as exposure to CSC increased. These observed changes persisted after passaging bacteria in CSC-free medium for 10 days. The genotoxicity of CSC on P. aeruginosa was evaluated by the standard Comet assay, which demonstrated DNA damage in the P. aeruginosa genome in Passage 15 compared to the CSC-unexposed cells. Gene expression analysis on selected virulence and quorum sensing genes showed that both flagellar (fliC and fleR) and quorum sensing (lasI/R and rhII) genes were significantly up-regulated in Passage 15. Results confirm the genotoxic effect of cigarette smoke manifested in an increased antibiotic resistance, coupled with increased bacterial virulence SIGNIFICANCE AND IMPACT OF STUDY: This study is the first to elucidate a clear link between tobacco smoke residues and both increases in antibiotic resistance and the up-regulation of bacterial virulence markers.