Pullularia, scientifically known as Aureobasidium pullulans, is a widespread fungus. It often appears as a black mold, though its early growth stages can be creamy, yellowish, or light pink before turning dark. This organism is found globally across diverse environments.
Characteristics and Common Habitats
Aureobasidium pullulans is highly adaptable. Its black color comes from melanin, which protects it from environmental stressors. This fungus thrives in high humidity and organic matter, making it widespread.
Naturally, A. pullulans is commonly found on plant surfaces, particularly leaves, where it can survive with minimal nutrients and water. It also lives in soil, fresh and saltwater, and decaying wood. It also frequently occurs in human-made spaces like bathrooms, kitchens, and basements due to consistent dampness.
It is also found on building materials like painted surfaces, window sills, frames, tile grout, and textiles. It withstands extreme conditions, including very cold temperatures and high salt concentrations.
Impact on Human Health and Property
Aureobasidium pullulans is a recognized airborne allergen, and exposure to its spores can lead to various allergic reactions. Individuals may experience respiratory symptoms such as sneezing, nasal congestion, coughing, and wheezing. It can also trigger or worsen asthma symptoms in sensitive individuals.
Skin irritation, rashes, and itchy eyes are other common allergic responses. In rare instances, particularly with chronic exposure through sources like humidifiers or air conditioners, A. pullulans has been linked to hypersensitivity pneumonitis, an inflammatory lung condition. While generally not considered a primary human pathogen, it has been associated with opportunistic infections like phaeohyphomycosis, keratomycosis, and skin infections, predominantly in immunocompromised individuals.
Beyond health concerns, A. pullulans causes aesthetic damage to property. Its growth results in black staining on various surfaces, including shower curtains, caulk, painted walls, and wood. This mold contributes to the degradation of building materials and can spoil certain food products, especially fruits and vegetables with high moisture content, due to its metabolic activities.
Management and Prevention
Controlling and preventing Aureobasidium pullulans growth primarily involves managing moisture and humidity levels. Using dehumidifiers in damp areas like basements and bathrooms can help maintain humidity below 60%. Promptly fixing any leaks or plumbing issues is also important to prevent water accumulation that encourages mold growth.
Effective cleaning methods are necessary to remove existing growth. Surfaces can be cleaned with household cleaners, dilute bleach solutions (approximately 10% bleach with a small amount of non-ammoniated detergent), or commercial mold removers. It is helpful to allow the cleaning solution to remain on the affected area for about 15 minutes before rinsing and drying thoroughly.
Preventive measures include regular cleaning of surfaces prone to moisture, such as sinks, countertops, and windowsills, ensuring they remain dry. Improving air circulation through better ventilation or using fans can also inhibit future growth. Additionally, removing organic debris like leaves or wood chips from around the property minimizes potential food sources for the mold.