Serratia marcescens is a rod-shaped, Gram-negative bacterium widely present in the environment that can become an opportunistic human pathogen. The bacterium is often recognized by the reddish-pink pigment it produces, called prodigiosin, which can sometimes be mistaken for blood or mold growth. While generally harmless to healthy individuals, S. marcescens causes serious infections, particularly in healthcare settings. Because of its ability to survive in diverse environments and its increasing resistance to antibiotics, a proactive approach to prevention is necessary.
Identifying High-Risk Environments and Vulnerable Populations
Serratia marcescens is found ubiquitously in soil, water, and on plant surfaces, but it poses the greatest risk when it colonizes moist indoor environments. The bacterium thrives in areas where moisture and organic material accumulate, such as in sinks, drains, shower corners, and toilet water lines, where it forms protective biofilms. In a household setting, this colonization is often visible as the characteristic pink or reddish slime frequently seen in bathrooms.
The bacterium is a significant cause of hospital-acquired infections because it contaminates medical equipment and can persist on surfaces in intensive care units. Contaminated respiratory equipment, intravenous catheters, and urinary catheters have all been identified as sources of outbreaks in clinical environments. Sinks and their drains are particularly problematic reservoirs for S. marcescens within hospitals due to the constant presence of water and the formation of bacterial biofilms.
Infection primarily threatens individuals who are immunocompromised, elderly, or neonates. People undergoing prolonged hospitalization, especially those in intensive care units, are at increased risk due to their exposure to the contaminated environment and medical procedures. Those with underlying chronic conditions like diabetes or chronic pulmonary disease, or patients with indwelling medical devices such as breathing tubes or catheters, are also highly susceptible to developing severe infections.
Essential Personal and Patient Care Hygiene
The single most effective measure for preventing the transmission of Serratia marcescens is rigorous hand hygiene, especially in clinical settings. Healthcare workers and caregivers must wash their hands thoroughly with soap and water for at least 20 seconds before and after every patient contact and after touching any potentially contaminated surfaces. If soap and water are not immediately available, an alcohol-based hand sanitizer may be used, though proper technique is still required.
Preventing the bacterium from entering the body often relies on strict management of invasive medical devices. Protocols for insertion and maintenance of devices like urinary catheters, central lines, and ventilators must be meticulous and follow sterile technique to avoid introducing the organism. It is important to remove these indwelling devices as soon as they are no longer necessary, as the presence of a foreign body provides a surface for the bacteria to colonize.
Proper wound care is also necessary to prevent skin and soft tissue infections, as the organism can enter through broken skin. Wounds must be kept clean and dry, and dressings should be changed using sterile or clean techniques as directed by a healthcare professional. Any breach in the skin barrier, even minor trauma, can provide an entry point for the opportunistic bacterium, particularly in high-risk individuals.
In community and clinical settings, basic respiratory hygiene helps reduce the spread of pathogens that can colonize the respiratory tract. Individuals should cover their mouth and nose with a tissue when coughing or sneezing, and then immediately dispose of the tissue and perform hand hygiene. This practice minimizes the dispersal of droplets that could contaminate surfaces or other people.
Strategies for Environmental Disinfection and Surface Management
Controlling the environment eliminates the reservoirs where S. marcescens persists. High-touch surfaces, such as doorknobs, bed rails, countertops, and shared medical equipment, require frequent cleaning and disinfection. The bacterium has shown resistance to certain disinfectants, so it is important to ensure the use of effective germicides, such as a 10% bleach solution or hospital-grade products known to be effective against Gram-negative bacteria.
When using chemical disinfectants, the manufacturer’s instructions for concentration and contact time must be strictly followed to achieve inactivation. Contact time, the period the disinfectant must remain wet on the surface, is a factor often overlooked in cleaning procedures. In the household, surfaces prone to the pink buildup should be scrubbed and then treated with a bleach-based cleaner, followed by rinsing and drying to remove the biofilm and its food source.
Controlling moisture is important, especially in areas like sinks and drains where the organism forms resilient biofilms. In healthcare settings, this may involve specialized cleaning of sink drains or the use of self-disinfecting drain systems. For home environments, regularly flushing drains with very hot water or a bleach solution and ensuring proper ventilation in bathrooms reduces the moist habitat the bacterium requires.
All non-disposable medical equipment, particularly those that involve water or the respiratory tract like nebulizers and humidifiers, must be cleaned and sterilized according to established protocols. This includes dismantling the equipment, cleaning all components, and using high-level disinfection or sterilization methods to prevent the formation of biofilms inside the devices. Consistent environmental surveillance and adherence to these protocols are necessary to prevent outbreaks and limit the spread of this opportunistic pathogen.