Staphylococcus aureus, commonly referred to as Staph, is a bacterium frequently found on the skin and in the nasal passages of healthy people. While often harmless, Staph can cause serious infections if it enters the body through a cut, scrape, or wound. The ability of this microorganism to persist outside a host, specifically on inanimate surfaces, makes environmental contamination a significant public health consideration. Understanding how long Staph can remain viable on everyday objects is important for controlling its spread, particularly concerning Methicillin-resistant Staphylococcus aureus (MRSA) strains.
How Long Staph Survives on Inanimate Surfaces
Staphylococcus aureus is recognized as a hardy bacterium that can survive on dry, non-porous surfaces for extended periods. Studies show that Staph, including MRSA, can remain infectious on environmental surfaces for days, weeks, and sometimes months.
The duration of viability depends on the specific surface material and environmental conditions. On hard, non-porous surfaces like plastic, stainless steel, or glass, Staph has been shown to survive for up to 300 days or more in laboratory settings. Research examples include the detection of viable MRSA on dust for as long as seven months.
Porous materials, such as cotton towels, blankets, or mop heads, also support the long-term survival of the bacteria. MRSA strains have been documented to remain viable on cotton for up to nine weeks and on mop heads for approximately eight weeks. The bacteria’s robust cell structure and tolerance for dry conditions contribute significantly to this prolonged survival.
Environmental Factors Influencing Survival Time
The wide range of reported survival times is directly linked to fluctuating environmental factors. Surface material is a primary determinant; non-porous surfaces offer a stable, nutrient-poor environment that supports long-term persistence. Surfaces like wood, which may have natural antimicrobial properties, generally show shorter survival times for Staph.
Temperature also plays a substantial role in bacterial longevity, with lower temperatures promoting longer survival. Staph survival rates decrease sharply as temperatures increase. Cooler environments offer a more stable condition for the bacteria to remain viable, explaining why objects in controlled settings may harbor the bacteria for maximum reported durations.
The presence of organic matter, such as blood, pus, or other bodily fluids, can significantly extend survival time by providing a protective layer and nutrients. While Staph is highly tolerant of dry conditions, the influence of humidity is complex and varies depending on the strain and the surface type. Staph is more resistant to desiccation than many other types of bacteria.
The ability to form a protective layer known as a biofilm also increases longevity. Biofilms are structured communities of bacteria encased in a self-produced matrix, which enhances their resistance to environmental stress and disinfection efforts. This protective layer allows staphylococci to persist in aquatic systems and on various materials.
Surface-to-Person Transmission Risk
The extended survival of Staph on inanimate objects means that these items, known as fomites, can act as intermediaries in the chain of infection. Transmission occurs when a person touches a contaminated surface, transferring the bacteria to their hands. The bacteria can then be introduced into the body if the contaminated hand touches a vulnerable area.
Common high-touch objects frequently implicated in this transfer include door handles, shared athletic equipment, computer keyboards, and towels. This process is concerning because the bacteria can easily be transferred to a portal of entry, such as a hangnail, a small cut, or the nasal passages. Hand contact is responsible for a high percentage of pathogen transmission, underscoring the importance of surface hygiene.
Contaminated items in community settings, such as gym equipment or shared linens, pose a risk, as do surfaces in healthcare environments. While direct skin-to-skin contact is the most frequent way Staph spreads, viable bacteria on surrounding surfaces provide a constant source for recontamination. The risk is elevated when there is poor hand hygiene or when an individual has broken skin.
Disinfecting Surfaces and Reducing Risk
To reduce the risk of Staph transmission from surfaces, a two-step approach is recommended: cleaning followed by disinfection. Cleaning first removes organic material and soil, which can interfere with the disinfectant’s effectiveness. Disinfection then targets the remaining microorganisms to eliminate them from the surface.
When selecting a disinfectant, choose one that is registered with the Environmental Protection Agency (EPA) and specifically lists Staphylococcus aureus or MRSA on its label. Effective disinfectants include diluted bleach solutions, quaternary ammonium compounds, and certain alcohol-based products. Following the label directions precisely is essential for achieving the intended result.
A crucial component of successful disinfection is the contact time, which is the duration the surface must remain visibly wet with the disinfectant solution to kill the bacteria. Contact times vary by product, ranging from 30 seconds to 10 minutes. Failure to meet this requirement can allow Staph to survive the cleaning process, so users must reapply the solution if the surface dries before the stated contact time is met.
Beyond chemical disinfection, non-chemical methods limit the spread of Staph from fomites. Frequent hand hygiene using soap and water for at least 20 seconds, or an alcohol-based hand sanitizer, significantly reduces bacteria on hands. Shared items like towels and bedding should be laundered in hot water and dried thoroughly in a high-temperature setting to eliminate residual bacteria.