Disinfectants and Their Role in Rising Antimicrobial Resistance

During the COVID-19 pandemic, disinfectants became a vital part of daily life. Items such as hand sanitizers, disinfectant wipes, and antimicrobial sprays helped many feel safer in a world gripped by uncertainty. Today, these products remain ubiquitous in homes, hospitals, and public spaces. However, their widespread use carries a hidden cost: they may contribute to the growing issue of antimicrobial resistance.

Understanding the Chemicals at Play

The most common active ingredients in disinfectants are quaternary ammonium compounds, known as QACs. These chemicals are not only present in cleaning products but also in everyday items like fabric softeners and personal care products. According to the U.S. Environmental Protection Agency (EPA), nearly half of the disinfectants listed as effective against SARS-CoV-2 contain QACs.

Due to their extensive use, QACs enter wastewater treatment facilities in significant amounts. Although over 90 percent of these compounds are typically removed during treatment, small quantities remain in effluents that eventually reach rivers and lakes. Once in the environment, QACs interact with microbial communities that are essential for nutrient recycling and water purification. This interaction can have profound effects on these communities, as some microorganisms die while others adapt and develop resistance.

The Paradox of Disinfection

QACs attack microbes in various ways, damaging cell walls, proteins, and lipids. This broad-spectrum action makes them effective disinfectants. However, microbes exhibit remarkable adaptability. Some may fortify their cell membranes, expel toxins, or form biofilms to survive exposure to QACs.

Evidence suggests that these adaptations not only help microbes withstand QACs but also increase their resistance to antibiotics. Resistance genes associated with QACs are often found on mobile DNA, which can be transferred between different bacteria. This co-resistance allows both QAC and antibiotic resistance genes to spread through bacterial populations. The increasing use of QACs amplifies these mechanisms, creating a concerning pathway for antimicrobial resistance to reach human pathogens.

According to a recent report by the World Health Organization (WHO), antimicrobial resistance is “critically high and rising” worldwide. In 2023, one in six laboratory-confirmed bacterial infections was resistant to commonly used antibiotics. Between 2018 and 2023, resistance increased in over 40 percent of monitored pathogen-antibiotic combinations, with an annual rise of 5 to 15 percent. In 2019 alone, antimicrobial resistance was responsible for approximately 1.27 million deaths globally.

The implications of these findings link everyday cleaning habits to a significant public health issue. Antimicrobial resistance is often perceived as a clinical problem stemming from antibiotic misuse, but it begins much earlier in the chain, starting in households, wastewater systems, rivers, and soils. These environments serve as battlegrounds where microbes share resistance traits, adapting to human-made chemical pressures.

Reevaluating Disinfection Practices

While this information does not advocate for abandoning disinfectants altogether, it underscores the need for responsible use. Disinfectants play a crucial role in infection control, particularly in hospitals and high-risk environments where their benefits outweigh potential risks. The challenge lies in their overuse in everyday cleaning practices, where the desire for cleanliness often translates to an assumption that “clean” equates to “microbe-free,” regardless of necessity or consequence.

It is essential to recognize that cleaning is not merely about achieving a hygienic appearance. Some disinfectants remain active long after their application, continuing to influence microbial communities. QACs, for instance, persist in the environment, exposing microbes to low, chronic selective pressures that can foster resistance. Other disinfectants, such as alcohol and bleach, may pose different environmental risks, highlighting the importance of conducting comprehensive risk assessments that consider long-term ecological consequences.

Ultimately, the issue of disinfectants and antimicrobial resistance serves as a reminder that managing microbial populations involves both ecological and chemical considerations. To clean responsibly, it is crucial to think beyond immediate disinfection and consider how our choices will shape the microbial landscape of the future.

Milena Esser is a postdoctoral researcher in the department of biology at McMaster University. This article was originally published by The Conversation Canada.