Impetigo is a highly contagious, superficial skin infection caused by bacteria, frequently affecting children. The infection often spreads through contact with contaminated non-living objects, known as fomites. Understanding how long these bacteria remain viable on surfaces is important for effective hygiene and preventing indirect transmission.
The Causative Bacteria and Their Resilience
The primary bacterial agents responsible for impetigo are Staphylococcus aureus and, less commonly, Streptococcus pyogenes. Both organisms are classified as gram-positive bacteria, a structural feature that contributes significantly to their hardiness. Gram-positive bacteria possess a thick peptidoglycan cell wall, which provides a robust defense against drying and environmental stressors.
This structure allows them to tolerate desiccation, or extreme dryness, better than many other types of bacteria. Strains of S. aureus, particularly methicillin-resistant S. aureus (MRSA), are resilient, enabling them to persist on inanimate surfaces for extended periods and remain a source of potential transmission.
Survival Duration on Non-Living Surfaces
The time the impetigo-causing bacteria can survive on surfaces varies considerably, but they demonstrate remarkable persistence. Staphylococcus aureus, including the MRSA strains, can remain viable and transmissible on dry, non-porous surfaces for weeks to months. Studies have shown that MRSA can be transferred from non-porous items like plastic or vinyl for more than eight weeks following contamination.
Streptococcus pyogenes is generally considered less environmentally stable than S. aureus, but it can still survive for a significant duration. Viability of S. pyogenes on dry fomites, such as clothing or bedding, can last up to a month, and possibly longer if the bacteria are embedded in organic matter like dust or secretions. The presence of biofilms can also significantly enhance the survival of S. pyogenes.
Environmental conditions play a strong role in determining the exact survival time. Lower temperatures and higher humidity levels are associated with prolonged persistence for both species. The material itself matters, as porous surfaces like towels or fabric tend to show a more rapid decrease in bacterial transmissibility compared to non-porous surfaces like plastic toys or countertops.
Practical Steps for Decontamination and Reducing Fomite Spread
Given the long survival times of the bacteria, protocols are necessary to prevent indirect spread through contaminated objects. Proper laundry procedures are fundamental, beginning with isolating items used by an infected person, such as towels, bed linens, and clothing. Washing these items in a hot water cycle at a temperature of at least 140°F (60°C) for a minimum of 10 to 25 minutes is effective for decontamination.
If a washing machine cannot reach this temperature, the use of an oxygenated laundry compound or household bleach is recommended to ensure bacterial elimination. Clothes should be machine-dried completely on a hot setting, as the heat and lack of moisture help destroy any remaining microorganisms. Infected individuals should not share towels, washcloths, or bedding with others in the household.
For hard, non-porous surfaces, disinfection should follow an initial cleaning to remove organic material. Effective surface disinfectants include a 1:100 dilution of household chlorine bleach, which provides 500 to 615 parts per million of available chlorine. Alcohol-based solutions are also effective, with concentrations between 60% and 95% rapidly killing both S. aureus and S. pyogenes. High-touch surfaces, including doorknobs, light switches, faucet handles, and frequently handled toys, require frequent and thorough cleaning to break the chain of fomite transmission.