Clostridioides difficile, commonly known as C. diff, is a bacterium that causes severe diarrhea and inflammation of the colon (colitis). It is a significant public health concern, particularly within healthcare settings like hospitals and long-term care facilities. Infection often follows the use of broad-spectrum antibiotics, which disrupt the gut microbiome, allowing C. diff to proliferate and release toxins. While C. diff is highly infectious and can contaminate the air, its primary method of spread is not through the sustained aerosol transmission seen with viruses, leading many to ask if it is airborne.
Why C. diff Is Not Considered Airborne
C. diff is fundamentally different from truly airborne pathogens, such as the microbes that cause measles or tuberculosis. Those pathogens are transmitted via tiny, lightweight aerosols that can remain suspended in the air for extended periods, traveling long distances on air currents. In contrast, C. diff forms metabolically dormant and highly resilient spores when outside the human gut. These spores are too heavy to float indefinitely as true aerosols.
When C. diff spores are briefly found in the air, it is due to “aerial dissemination” rather than true airborne transmission. Activities like changing soiled linens, making a patient’s bed, or vigorous cleaning can disturb spores that have settled on surfaces. This disturbance kicks up the heavier spores, which quickly settle back down onto nearby surfaces and equipment.
Evidence suggests that these short-lived, transient clouds of spores can contaminate a wider range of surfaces. However, this process is still one of surface contamination, not respiratory infection via fine aerosol inhalation. The infectious cycle relies on contact with contaminated surfaces, which must then be ingested to cause disease. Therefore, the mechanism of spread is described as contact-based, involving environmental contamination.
How C. diff Spreads
The main route of C. diff transmission is the fecal-oral pathway, which means spores from infected feces must be ingested by a new host. Infected individuals shed massive numbers of spores into the environment, contaminating everything they touch. These spores are incredibly resistant to common cleaning agents, heat, and stomach acid, allowing them to survive on inanimate objects, known as fomites, for months.
Contaminated surfaces are the major reservoirs for spread in healthcare facilities. These surfaces include:
- Toilets
- Bed rails
- Call buttons
- Medical equipment
Healthcare personnel can inadvertently transfer spores from a contaminated patient or surface to an uninfected patient on their hands or gloves. This indirect contact is a primary reason C. diff is so prevalent in hospitals, where the spore load is high.
Infection occurs when a person touches a contaminated surface and then transfers the spores to their mouth, ingesting them. Once swallowed, the resilient spores survive the acidic stomach environment and travel to the intestine. In the gut, particularly in individuals whose natural gut flora has been altered by antibiotics, the spores sense specific bile salts and germinate, transforming into toxin-producing vegetative cells that cause the symptoms of C. diff infection.
Preventing C. diff Transmission
Effective prevention strategies must target the spore’s unique resilience and the contact-based spread mechanism. Hand hygiene is the single most important action, but it requires specific methods. Alcohol-based hand sanitizers are generally ineffective because C. diff spores are resistant to alcohol.
Thorough hand washing with soap and water is mandatory for removing the spores from the skin. The physical action of rubbing and rinsing with water is what removes the spores, which are then washed down the drain. This mechanical removal is superior to the chemical action of alcohol in this specific context.
Environmental cleaning also requires specialized products, as standard household cleaners are insufficient to destroy the hardy spores. Healthcare settings must use spore-killing disinfectants, such as those containing a dilute bleach solution, to effectively eliminate the environmental reservoir. In a hospital setting, patients with a suspected or confirmed infection are typically placed in isolation with contact precautions to contain the shedding of spores.
Antibiotic stewardship involves using antibiotics only when necessary and for the shortest effective duration. Since antibiotic use is the strongest risk factor for C. diff infection, limiting their use helps preserve the gut microbiome. This prevents ingested spores from germinating and causing disease.