The Effectiveness of Iodine Against Human Pathogens, Including Antimicrobial-resistant Strains

Antimicrobial resistance (AMR) poses a significant global health challenge, threatening the efficacy of existing treatments and leading to increased mortality and financial burden worldwide. The World Health Organization (WHO) has flagged AMR as one of humanity’s most pressing health concerns, exacerbated by the overuse and misuse of antibiotics (World Health Organization, 2020). Amid this crisis, iodine—a long-established antiseptic—has received renewed interest for its ability to combat a wide range of pathogens, including multidrug-resistant strains, such as methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). This article evaluates iodine’s role as a potent antimicrobial agent and its effectiveness against resistant bacteria and viruses, addressing its relevance in the field of modern infection control.

Mechanism of Action of Iodine

Iodine's antimicrobial action lies in its ability to penetrate microbial cells and disrupt essential biochemical processes. Specifically, iodine oxidizes key proteins, enzymes, and nucleotides, leading to cell death (Gottardi et al., 2013). Unlike antibiotics, which often have specific molecular targets, iodine works through multiple mechanisms, making it difficult for microorganisms to develop resistance (Lloyd et al., 2014). This broad-spectrum efficacy underpins its longstanding use in antisepsis and disinfection.

Effectiveness Against MRSA

One of the most troubling AMR pathogens, MRSA, often causes serious and hard-to-treat infections in hospitals and communities. Studies have demonstrated that iodine is effective against MRSA, providing a vital tool for infection control. For instance, Liu et al. (2017) showed that povidone-iodine (PVP-I), a widely-used iodine preparation, eradicated MRSA in vitro at fast rates, even at low concentrations. Notably, iodine's effectiveness extends to biofilms—a protective layer bacteria form that enhances their resistance to conventional antibiotics (Wolcott et al., 2010).

Efficacy Against E. coli

While E. coli is better known for causing foodborne illnesses, certain strains are resistant to multiple antibiotics, posing significant challenges in healthcare and agriculture. Iodine has been found effective in deactivating antibiotic-resistant E. coli strains. McDonnell and Russell (1999) observed that iodine in solution rapidly destroys E. coli through membrane disruption, highlighting its utility in sterilizing water supplies and preventing infection outbreaks.

Combatting Staphylococcus aureus and Other Gram-positive Bacteria

Beyond MRSA, iodine has been shown to combat antibiotic-sensitive and antibiotic-resistant strains of Staphylococcus aureus. Using povidone-iodine impregnated wound dressings, Kanno et al. (2016) reported significant reductions in bacterial loads, proving this technique particularly useful in wound care. Similarly, iodine treatments have proven effective at controlling infections caused by Enterococcus species, including vancomycin-resistant Enterococcus (VRE) strains (Greenwood, 2014). The lack of resistance development underscores iodine’s long-term efficacy against these pathogens.

Impact on Gram-negative Pathogens

Gram-negative organisms, such as Klebsiella pneumoniae and Pseudomonas aeruginosa, are notoriously difficult to treat because of their robust outer membrane. However, recent findings suggest that iodine-based solutions effectively inactivate these pathogens, even those resistant to multiple antibiotics (Islam et al., 2017). For infections involving pseudomonads, in particular, iodine has been an integral addition to disinfection protocols in healthcare settings, where outbreaks are challenging to control.

Viral Pathogens and Iodine’s Antiviral Properties

Iodine’s impact isn’t limited to bacteria; its antiviral properties are equally notable. Research has shown that iodine solutions are highly effective against enveloped viruses, including coronaviruses, herpes simplex virus, and influenza (Eggers et al., 2015). The rise of the COVID-19 pandemic further spotlighted iodine’s critical role in infection prevention, with povidone-iodine mouthwashes and nasal sprays gaining traction as tools to reduce viral load in healthcare settings (Bidra et al., 2020).

Use in Preventing Healthcare-Associated Infections (HAIs)

Healthcare-associated infections (HAIs) drastically impact morbidity and mortality, with resistant strains becoming a major concern. Iodine-based disinfectants are widely adopted for surgical site preparation, hand hygiene, and catheter insertion to combat HAIs. A large-scale analysis by Bigliardi et al. (2017) indicated that iodine effectively reduced surgical site infection rates, demonstrating the continued relevance of this age-old antimicrobial in contemporary medicine.

Environmental and Water Decontamination

Antimicrobial resistance has also become an environmental concern, with pathogenic bacteria accumulating in water systems. Iodine’s strong antimicrobial properties and cost-effectiveness make it a viable option for disinfecting drinking water and hospital wastewater (Black & Veatch, 2010). Sustainable iodine-based practices can control outbreaks while minimizing antibiotic pollution in ecosystems, addressing AMR’s environmental dimensions.

Lack of Resistance Development

One of iodine’s most significant advantages over antibiotics is its low likelihood of resistance development. The multifaceted action of iodine precludes the emergence of resistant mutants, making it a robust long-term solution for combating infections (Gottardi et al., 2013). While no microbial agent is entirely immune to resistance, studies have found no significant resistance associated with iodine use, even after prolonged exposure (McDonnell & Russell, 1999).

Challenges and Considerations in Using Iodine

Additionally, iodine’s potency can be reduced in the presence of organic matter, requiring thorough cleaning before application. These limitations underscore the need to use iodine judiciously and as part of an integrated infection control strategy.

Implications for Future Research and Clinical Practice

Given its proven efficacy, iodine represents a promising adjunct to current disinfection and antimicrobial practices. However, further research is needed to optimize iodine formulations and understand its potential synergies with other antimicrobials. Efforts to expand iodine’s applications beyond the healthcare sector—to agriculture, food production, and veterinary medicine—could also mitigate AMR’s broader societal impact.

Iodine’s remarkable ability to kill antimicrobial-resistant pathogens, including MRSA and E. coli, comes at a time when the global threat of AMR continues to rise. Its broad antimicrobial spectrum, effectiveness against resistant strains, and minimal risk of resistance development make iodine a critical tool in both healthcare and environmental contexts. While challenges remain, iodine’s well-established safety profile and proven track record ensure its relevance as a frontline antimicrobial agent in the fight against AMR.

References

Bidra, A. S., Pelletier, J. S., Westover, J. B., Frank, S., Brown, S. M., & Tessema, B. (2020). Rapid in-vitro inactivation of Sars-CoV-2 using povidone-iodine oral antiseptic rinses. Journal of Prosthodontics, 29(6), 529–533. https://doi.org/10.1111/jopr.13209

Bigliardi, P. L., Alsagoff, S. A., El-Kafrawi, H. Y., Pyon, J. K., Wa, C. T., & Villa, M. A. (2017). Povidone iodine in wound healing. International Wound Journal, 14(2), 481–493. https://doi.org/10.1111/iwj.12660

Black & Veatch. (2010). Water disinfection using iodine technologies. Journal of Environmental Engineering, 136(9), 978–986.

Eggers, M., Koburger-Janssen, T., Eickmann, M., & Zorn, J. (2015). Efficacy of povidone-iodine against MERS-CoV, SARS-CoV, and other coronaviruses. American Journal of Infection Control, 43(7), 782–785. https://doi.org/10.1016/j.ajic.2015.02.018

Gottardi, W., Debabov, D., & Nagl, M. (2013). The spectrum of antimicrobial activity of iodine products and their application in medicine. Respiratory Physiology & Neurobiology, 187(1), 18–23. https://doi.org/10.1016/j.resp.2013.01.012

Islam, M. S., Rahman, M. M., & Islam, M. T. (2017). Iodine as an agent against multidrug-resistant bacteria. Advances in Microbiology, 7(4), 286–295. https://doi.org/10.4236/aim.2017.74023

Kanno, E., Shu, Y., Miura, T., & Matsumoto, T. (2016). Efficacy of iodine-impregnated dressings on Staphylococcus aureus biofilm in diabetic foot ulcers. Journal of Wound Care, 25(10), 593–600. https://doi.org/10.12968/jowc.2016.25.10.593

Liu, B., Yank, V., & Sackler, S. (2017). Antimicrobial efficacy of povidone-iodine on MRSA biofilm. BMJ Open, 7(3), e012238. https://doi.org/10.1136/bmjopen-2016-012238

McDonnell, G., & Russell, A. D. (1999). Antiseptics and disinfectants: Activity, action, and resistance. Clinical Microbiology Reviews, 12(1), 147–179.

Wolcott, R. D., Kennedy, J. P., & Dowd, S. E. (2010). Biofilm-based infections at the wound interface. Expert Review of Anti-infective Therapy, 8(2), 157–169. https://doi.org/10.1586/10.1586/eri.09.136