International Journal of Environmental Research and Public Health | An Interview with One of the Authors—Dr. Suhana Chattopadhyay

Name: Dr. Suhana Chattopadhyay
Affiliation: Department of Global, Environmental, and Occupational Health, University of Maryland School of Public Health, College Park, MD 20742, USA

“Viable, Multi-Drug-Resistant Bacteria Recovered from E-Liquids Used with Commercial Electronic Cigarettes”
by Suhana Chattopadhyay, Leena Malayil and Amy R. Sapkota
Int. J. Environ. Res. Public Health 2025, 22(11), 1725; https://doi.org/10.3390/ijerph22111725
Available online: https://www.mdpi.com/1660-4601/22/11/1725

We had the pleasure of speaking with Dr. Suhana Chattopadhyay, who recently published an article in the International Journal of Environmental Research and Public Health (IJERPH, ISSN: 1660-4601). Here, she shares insights into her academic journey, research focus, and the motivation behind her recent work.

1. Congratulations on your recent publication! Could you briefly introduce yourself and your current research focus?

Thank you so much for this wonderful opportunity to share more about my work and the recent publication. I’m Dr. Suhana Chattopadhyay. I’m an assistant research professor at the Department of Global, Environmental, and Occupational Health at the University of Maryland School of Public Health, and I also serve as the Program Manager of the Global Future Alliance, an interdisciplinary and international initiative led by Dr. Amy R. Sapkota. This alliance focuses on developing holistic system-based solutions at the food, energy, and water nexus to strengthen our climate resilience and protect global public health.

My research focus broadly examines how environmental exposures influence human health, with a particular emphasis on microbial and chemical risks in everyday environments. This recent study reflects this focus by investigating viable multidrug-resistant bacteria in electronic liquids, highlighting that consumer products have potentially under-recognized bacterial contaminants that are relevant to public health. In parallel, I’m also leading projects on recreational water quality in Maryland and working on initiatives to protect drinking water in underserved communities in Maryland. So altogether, our research efforts focus on understanding these environmental reservoirs of risks and translating this knowledge into strategies that promote the environment and healthier communities.

2. What inspired your team to investigate viable bacteria in e-liquids, and why is this an important public health issue?

I’m so glad you asked this question. We were motivated by the rapid increase in electronic cigarette use in America and around the globe. We found there was a major gap in the knowledge about whether electronic liquids could harbor living bacteria. Most of the prior research on tobacco products has focused on chemical constituents and their toxic capabilities, but very little attention has been given to the microbiological quality of these products. At the same time, over the past decade, studies from our team and others on traditional tobacco products have shown that they can contain diverse and sometimes harmful bacteria, which raises the question of whether similar risks might exist in electronic cigarette liquids.

This is an important public health issue because electronic cigarette users inhale aerosol products produced from these liquids, and, potentially, any of the viable bacteria that might be present in this liquid may be delivered directly into the respiratory tract of the user. Such exposure could affect the oral and the lung microbiomes, increase susceptibility to infections, and potentially contribute to the spread of antibiotic-resistant bacteria. Understanding these risks is essential for informing product safety standards and protecting electronic cigarette users in America.

3. Your study found multidrug-resistant bacteria like Pseudomonas aeruginosa in e-liquids. Could you explain what makes this finding particularly concerning?

Our study reported the presence of multiple viable multidrug-resistant bacteria, including Pseudomonas aeruginosa, in commercial electronic liquids that are used with these electronic cigarettes. This finding is particularly concerning for several reasons rooted in microbiology and public health. First, I want to point out the pathogenic potential of this bacteria, Pseudomonas aeruginosa. It is a very well-known opportunistic pathogen capable of causing respiratory and systemic infections, especially in individuals with compromised immunity or underlying lung conditions. This bacterial species is well-known in clinical settings for causing difficult-to-treat infections. Isolates recovered from the tested electronic liquids in our study showed multidrug resistance, meaning their growth was resistant to multiple antibiotics, namely penicillin, tetracyclines, and phenicols. This multidrug resistance potentially means that standard antimicrobial therapies may not be effective should exposure lead to colonization or infection.

We also found exposure risks via inhalation. Electronic liquids are aerosolized and inhaled directly into the respiratory tract, so the detection of Pseudomonas aeruginosa in these products particularly raises concern that users could be exposed to viable multidrug-resistant bacteria through vaping. And bypassing many of the body’s usual first-line defenses, as I mentioned, has direct public health implications. The combination of viability, multidrug-resistance capability, and direct inhalation exposure increases the likelihood that such bacteria could contribute to colonization or infection. These could complicate disease management and potentially contribute to the broader issue of antimicrobial resistance in the community. So, continued surveillance of microbial contaminants in electronic cigarette products is most crucial in this case.

4. What is the most important takeaway for the general public regarding the safety of e-cigarettes from a microbiological perspective?

I’d say the key takeaway for the general public regarding microbiological safety would relate to the liquid that is used with electronic cigarettes. It can contain, as we show, viable bacteria, including strains that are multidrug resistant. And our findings do indicate that users could potentially be exposed to these living viable bacteria that have antibiotic resistance, which represents a microbiological safety concern beyond the chemical and the toxicological risks typically discussed in research on these products.

Although the electronic liquids do show some antimicrobial activity themselves in the laboratory tests that we performed, the mere presence of these viable and resistant bacteria underscores the need for improved quality control, surveillance, and regulation of these electronic cigarette products to protect public health. I would also like to add, in this context, from a microbiological standpoint, this research does suggest that electronic cigarette safety is not solely about inhaled chemicals or toxins but also includes biological contamination. This poses an infection risk, especially to individuals with weakened immunity or respiratory conditions, and it does reinforce the importance of strict manufacturing standards and proper handling of e-liquid products to minimize microbial contamination of these products.

5. What was the most challenging aspect of this study, and how did your team overcome it?

The most challenging aspect of our study was detecting and characterizing these viable bacterial contaminants in our tested commercially available electronic liquids, given that there is limited precedent and methodological constraints in this area of research. Prior to our work, to our knowledge, there was no published data on the presence of viable bacteria in electronic liquids or their antimicrobial properties.

Existing microbiological methods have not been optimized for this specific product. This posed two interrelated challenges. One was recovering a representative diversity of bacteria from these complex and low-biomass products. Electronic liquids are formulated with solvents such as propylene glycol and glycerin, both of which are known to inhibit microbial growth, and they typically contain very low microbial load in these electronic liquids. So the use of non-selective culture media, which we used under aerobic conditions, while necessary for baseline viability assessment, inherently limited the range of bacteria that could be recovered, and so that may have underestimated the total microbial diversity that we report in our study.

Challenge number two was distinguishing between the viable multidrug-resistant bacteria and artifacts of the culture. Confirming that these cultured isolates were both viable and clinically relevant required careful application of these culture-based methods, the gold standard plating method, the Kirby–Bauer susceptibility testing method, and molecular confirmation methods like Sanger sequencing. These techniques have been adapted to ensure reliable identification and resistance profiling despite the low biomass and potential interference by the electronic liquid constituents. To overcome the methodological challenge, we employed rigorous culture methods that are designed to maximize the recovery of viable bacteria from the electronic liquid samples.

Recognizing that standard environmental microbiology approaches might not translate directly to this product, we also used well-validated antimicrobial susceptibility assays to help confirm the multidrug-resistant phenotypes from the recovered isolates. Furthermore, I want to add that we explicitly acknowledged the methodological constraints in the publication, such as reliance on a single culture medium, testing only one brand of electronic liquids, and the low culturability of environmental bacteria. We also outlined concrete strategies for overcoming these in future work if somebody were to replicate the study or test out other electronic liquids on the market.

6. For young researchers interested in environmental microbiology or global health, what advice would you give?

My advice is to focus on research questions that sit at real-world human–environment interfaces. Our work shows that microbes and antimicrobial resistance can exist in everyday products and environments, so not just in hospitals. Asking questions with direct exposure and public health relevance is critical. Secondly, build strong interdisciplinary skills. Environmental microbiology today combines classical culture methods with molecular tools like sequencing and data analysis. Being comfortable across these approaches makes someone more versatile and better prepared to study these complex environmental systems. Thirdly, I would say to adopt the One Health approach or perspective. Human health, environmental reservoirs, and microbial evolution are tightly interconnected. So, especially for antimicrobial resistance, which is a growing public health concern, and these emerging pathogens, research that integrates these dimensions tends to have a broader impact on communities, overall health, human health, and the Earth’s health.

So finally, translationally and collaboratively, consider how your findings could inform surveillance, regulations, or interventions, and seek collaborations across disciplines and sectors. Environmental and global health problems are systems problems, so they do require team-based solutions. If you work in silos, you’re never going to solve a particular problem. So, working across teams and disciplines and trying to develop that at a young age helps you be a better researcher.

7. What led you to choose our journal for publishing this particular study, and how was your experience with the publication process with IJERPH?

We chose IJERPH because the journal has a strong track record of publishing interdisciplinary studies at the intersection of environmental exposure, public health, and microbial risk, which closely aligns with the objectives of our work. Our study does address the emerging exposure pathway with implications for antimicrobial resistance and consumer safety, so we felt that IJERPH’s broad public health focus was well-suited to disseminate these findings to researchers, practitioners, or even policymakers.

Our experience with the publication process was very positive. The reviewer feedback was very constructive and helped us strengthen both the methodological clarity and the public health framing of the manuscript. The editorial process was very efficient, transparent, and well-coordinated, which we greatly appreciated for our work with policy implications. Overall, the process was very professional and supportive of rigorous interdisciplinary research. I’m very appreciative of the staff who worked with us on our group’s two recent publications in the journal.