The pink or reddish slime found in bathrooms and other damp areas is a common household nuisance. Often mistaken for mold, this discoloration is caused by the bacterium Serratia marcescens. This article provides practical guidance on identifying, removing, and preventing its growth.
What is Pink Slime?
The pink or reddish discoloration in moist areas is most often Serratia marcescens. This bacterium thrives in damp environments such as shower stalls, toilet bowls, sinks, and pet water dishes, where it can feed on fatty substances like soap residues. The distinctive pink, orange, or deep red color comes from a pigment it produces called prodigiosin.
Prodigiosin production is temperature-dependent, with optimal synthesis occurring between 20°C and 30°C (68-86°F), which aligns with common indoor temperatures. This airborne bacterium is widespread in the environment, settling in wet areas and forming visible colonies. Once established, these colonies create a slimy biofilm, which provides protection and allows them to persist on surfaces.
Potential Health Concerns
For most healthy individuals, household exposure to Serratia marcescens poses a minimal health risk. However, it is an opportunistic pathogen, meaning it can cause infections under certain conditions, particularly in vulnerable populations.
Individuals who are immunocompromised, such as infants, the elderly, or those with underlying health conditions, are more susceptible to infections from this bacterium. Serratia marcescens has been identified as a cause of various infections, including urinary tract infections, respiratory infections like pneumonia, and wound infections, especially in healthcare settings. Regular cleaning is important, particularly in homes where vulnerable residents may be present, to minimize potential exposure.
Eradicating the Growth
Effectively removing Serratia marcescens involves thorough cleaning, focusing on physical removal and disinfection. Prepare a cleaning solution, such as a paste of four parts baking soda to one part liquid dish soap, or equal parts white vinegar and water. Apply this mixture to affected areas using a scrub brush, allowing it to sit for at least 10 minutes to loosen the biofilm.
After scrubbing, rinse surfaces thoroughly with warm water. For disinfection, a solution of 1 part chlorine bleach to 10 parts water is effective. Alternatively, hydrogen peroxide can be sprayed directly onto the area and left for at least 10 minutes, as it also works as an effective disinfectant. Always ensure good ventilation by opening windows or using exhaust fans, and wear protective gear, such as rubber gloves and eye protection, when handling cleaning agents.
Preventing Recurrence
Preventing the return of Serratia marcescens involves consistently reducing moisture and eliminating potential nutrient sources. Utilizing exhaust fans during and after showers for at least 30 minutes significantly lowers humidity, which is conducive to bacterial growth. Opening windows also helps improve air circulation and reduce dampness.
Regularly wiping down shower walls, sinks, and other damp surfaces after each use with a squeegee or towel removes standing water and soap scum, a food source for the bacteria. Establishing a routine cleaning schedule for bathrooms and other susceptible areas, ideally weekly, helps prevent biofilm formation and organic matter accumulation. Addressing any plumbing issues that contribute to constant moisture, such as leaky faucets or pipes, removes persistent dampness that allows the bacteria to thrive.