Hand hygiene is a foundational practice for preventing the spread of infectious disease, and hand sanitizers are a common and convenient tool when soap and water are unavailable. This widespread use leads to questions about their specific effectiveness against various pathogens. This article focuses on the interaction between alcohol-based hand sanitizers and the bacterium Staphylococcus aureus.
Understanding Staphylococcus aureus
Staphylococcus aureus, often called “Staph,” is a common bacteria found on the skin and in the nasal passages of healthy individuals. While colonization typically causes no symptoms, Staph can become an opportunistic pathogen if it enters the bloodstream or internal tissues through a break in the skin. Infections range from minor skin conditions, such as boils and impetigo, to severe, life-threatening illnesses like pneumonia or sepsis. A primary concern is the emergence of drug-resistant strains, such as Methicillin-Resistant S. aureus (MRSA), which complicates antibiotic treatment.
How Alcohol-Based Sanitizers Function
Alcohol-based hand sanitizers (ABHS) rely on a rapid chemical process to destroy microbes. The active ingredients are typically alcohols like ethanol, isopropanol, or n-propanol, which act as broad-spectrum antiseptics. These alcohols work primarily by denaturing proteins within the bacterial cell, effectively scrambling their structure. The alcohol also dissolves the cell’s lipid membranes, causing the contents to leak out and leading to quick death. For optimal activity, the alcohol concentration must be between 60% and 95%.
Efficacy of Hand Sanitizers Against Staph
Alcohol-based hand sanitizers are highly effective at inactivating Staphylococcus aureus. Studies show that sanitizers containing at least 60% alcohol produce a substantial reduction in the bacterial load on hands within 15 to 30 seconds of application. The rapid, physical-chemical destruction of the cell structure by alcohol means that Staph is highly susceptible to this method of hygiene.
The efficacy extends even to Methicillin-Resistant S. aureus (MRSA). MRSA is resistant only to certain antibiotics, not to alcohol’s cellular destruction mechanism. Because alcohol does not rely on biological pathways like antibiotics, it remains an effective agent against multidrug-resistant organisms.
For the sanitizer to be successful, the application must be thorough, covering all surfaces of the hands, and a sufficient volume of product must be used. Hands must remain wet for the recommended contact time (20 to 30 seconds) to allow the alcohol to complete the microbe-killing process. While a single application of alcohol gel significantly reduces the burden of MRSA, incomplete removal is more common when the starting level of bacteria is very high.
When Handwashing is Superior
Despite alcohol’s effectiveness against Staph, hand sanitizers have limitations that make traditional handwashing the preferred method in certain situations. Sanitizers are ineffective at physically removing soil, dirt, grease, or grime. When hands are visibly soiled, the physical debris can shield microorganisms, including Staphylococcus aureus, from the alcohol, preventing full contact and reducing efficacy.
Soap and water are also superior for eliminating specific types of pathogens that are inherently resistant to alcohol. These include non-enveloped viruses, such as Norovirus, and bacterial spores like those produced by Clostridioides difficile (C. difficile). Alcohol-based products cannot inactivate these resistant forms; handwashing mechanically removes them from the skin through friction and rinsing.
The mechanical action of soap and running water ensures that both physical contaminants and alcohol-resistant microbes are washed down the drain. Hand sanitizer is a convenient and effective alternative when hands are not visibly dirty and soap is unavailable. Handwashing is recommended after using the restroom, before eating, and whenever hands are soiled.