Viable, Multi-Drug-Resistant Bacteria Recovered from E-Liquids Used with Commercial Electronic Cigarettes

Area of Science:

• Microbiology
• Public Health
• Toxicology

Background:

• Electronic cigarette use is rising, with menthol and mint flavors being popular.
• Research on bacterial contaminants and antibacterial properties in e-liquids is limited.
• Understanding microbial presence and activity in e-liquids is crucial for assessing health risks.

Purpose of the Study:

• To investigate the presence of viable bacteria in e-liquids.
• To characterize the antimicrobial susceptibility of these bacteria.
• To evaluate the antibacterial activity of e-liquids themselves.

Main Methods:

• Culture-based methods and Sanger sequencing were used to identify bacteria in e-liquids.
• Antimicrobial susceptibility testing and e-liquid antibacterial activity assays were performed using the Kirby Bauer disc diffusion method.
• Two flavors (menthol, non-menthol) and three nicotine concentrations (0, 6, 12 mg/mL) were analyzed.

Main Results:

• Pseudomonas aeruginosa and Bacillus spp. were the predominant bacteria found.
• Multidrug resistance was observed in P. aeruginosa and P. fluorescens isolates.
• E-liquids inhibited bacterial growth, with higher nicotine concentrations showing greater antibacterial activity, particularly in menthol flavors.

Conclusions:

• E-liquids can harbor viable, multidrug-resistant bacteria.
• E-liquids exhibit antibacterial properties, influenced by nicotine concentration and flavor.
• Findings indicate potential public health concerns regarding microbial safety in electronic cigarettes, necessitating ongoing surveillance.