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Exposure to e-cigarette vapor increases MRSA virulence
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Exposure to electronic cigarette vapor increases the virulence of MRSA, researchers reported at the 2014 American Thoracic Society International Conference in San Diego.
MRSA frequently colonizes the nasopharynx, which is exposed to e-cigarette vapors and cigarette smoke, according to Laura E. Crotty Alexander, assistant professor of medicine in pulmonary and critical care at the University of California, San Diego, and colleagues.
In the study, the researchers grew the USA300 strain of MRSA in culture that was exposed to e-cigarette vapors. The exposure was similar to concentrations delivered by inhalers on the market today.
They assessed virulence by measuring the bacteria’s growth rate and changes in pH, sensitivity to reactive oxygen species, surface charge, hydrophobicity, and the formation of biofilm.
The researchers found that e-cigarette vapors prompted MRSA to defensively secrete acids within 3 hours of exposure. Although the effects of e-cigarette vapor exposure on MRSA growth were modest, the vapor triggered significant changes in pH levels, from 7.4 to 8.4, creating a highly alkalotic environment. According to Crotty Alexander, alkalosis can stress bacterial cells and trigger the activation of defense mechanisms. This may have caused the bacteria to have a more positively charged surface, helping it to avoid binding to lethal antimicrobial peptides. E-cigarette vapor-exposed MRSA was able to avoid being killed by both macrophages and neutrophils in cellular killing tests.
E-cigarette vapor exposure also promoted biofilm formation, which is consistent with increased virulence.
Although e-cigarette vapors boosted drug resistance in MRSA, cigarette smoke induces even greater virulence in bacteria, according to Crotty Alexander.
Crotty Alexander said these findings challenge the notion that e-cigarettes are a safe alternative to smoking.
“As health care professionals, we are always being asked by patients, ‘Would this be better for me?’ In the case of smoking e-cigarettes, I hated not having an answer,” she said in a press release. “While the answer isn’t black and white, our study suggests a response: Even if e-cigarettes may not be as bad as tobacco, they still have measurable detrimental effects on health.”
For more information:
Crotty Alexander LE. Abstract 57341. Presented at: The American Thoracic Society International Conference; May 16-21, 2014; San Diego.
Disclosure: The researchers report no relevant financial disclosures.