Just add water...
Mold grows in hospitals and other healthcare facilities for the same reason it grows in old buildings. Mold spores are everywhere, and all it takes is a bit of moisture to activate them. However, while common molds in a residential or office building may cause allergy symptoms in those with mold sensitivities, even relatively harmless molds can be deadly to immunocompromised individuals. In this post, we’ll look at four common types of molds that post the greatest risk of causing nosocomial infections, also commonly referred to as hospital-acquired infections or healthcare-associated infections.
#1 Aspergillus
Aspergillus is a common genus of mold found both indoors and out. There are several hundred species of Aspergillus, but only a few are known to cause human illnesses. The most notorious species is A. fumigatus. Aspergillus typically appears as a powdery growth of spores and can present in various colors, including green, white, yellow, and black. In an indoor environment, Aspergillus spores can be found in the air, on surfaces among dust, and within HVAC systems – anywhere excess moisture or decaying organic matter can be found.
While Aspergillus can cause illness in sensitive people who are otherwise healthy, this mold is considered particularly dangerous in a healthcare setting because of its potential to cause aspergillosis, an infection that can severely impact immunocompromised patients. The most severe form, invasive aspergillosis, occurs when the infection spreads to the blood vessels and beyond. Mortality rates for invasive aspergillosis can be high, between 30% to 95%, depending on the patient population and specificities of the infection, such as which organs are affected.
#2 Mucormycetes
Mucormycetes are a group of molds responsible for the infection known as mucormycosis. These molds belong to the order Mucorales and are commonly found in soil, decaying organic matter, and compost piles. Mucormycetes, in general, prefer wet, moist environments and grow rapidly, producing thick, filamentous structures and spores-producing structures called sporangiophores. Several genera, such as Rhizopus, Lichtheimia, and Mucor, in the Mucorales include infectious species.
Rhizopus is the largest genus and includes several infectious species. The most common species of Rhizopus causing infections among humans and animals is Rhizopus oryzae. On the other hand, the most common Rhizopus species, R. stolonifer, does not cause human infections because it does not grow at human body temperatures. Therefore, it is important to identify causative fungi to species. Other species, such as Lichtheimia corymbifera, Mucor racemosus, M. hiemalis, and Rhizomucor pusillus, have gained notoriety due to increases of immunocompromised patients, organ transplant patients, and diabetic patients.
In healthcare settings, mucormycosis represents a serious risk due to its aggressive nature. The infection typically affects the sinuses, brain, or lungs, though it can also manifest as a cutaneous infection at the site of an injury or other disruption of the skin barrier. The infection can invade blood vessels, resulting in thrombosis and tissue necrosis. People with weakened immune systems, such as those with uncontrolled diabetes, cancer patients, organ transplant recipients using immunosuppressive drugs, and patients with severe burns or other trauma are at the highest risk. Mortality rates for mucormycosis can range from 40% to 80%, depending on the body part affected and the timeliness of diagnosis and treatment.
#3 Cladosporium
Cladosporium is a very common mold found on plants, textiles, wood, in soil, and anywhere damp, organic material is abundant. Its spores are the most common airborne fungal spores on the earth. Typically, this mold has a dark green to black or brown velvety appearance. Indoors, Cladosporium may flourish on cold-condensing surfaces or areas, such as wallpaper, carpet, insulation, and in HVAC systems and other areas prone to moisture accumulation.
Despite being less notorious than molds like Aspergillus, Cladosporium can cause respiratory problems, and has been linked to skin and nail infections, sinusitis, and in very rare cases, more serious lung infections. Immunocompromised individuals, including patients undergoing chemotherapy, organ transplant recipients, and those with chronic respiratory conditions or weakened immune systems, may be at a higher risk of developing severe complications from exposure to Cladosporium. Although mortality rates directly attributable to Cladosporium infections are not as high as those associated with other molds, it can exacerbate existing conditions or cause healthcare-associated infections.
#4 Penicillium
Penicillium is one of the common fungal types found in the indoor and outdoor environments, and recognizable by its dense brush-like spore structures and often has a blue or green fuzzy appearance when growing on food, walls, insulation, carpet, and other surfaces. Renowned for being the mold from which the first antibiotic was discovered, certain species of Penicillium can be harmful to human health, producing allergens, irritants, and in some circumstances, mycotoxins that can lead to health issues when inhaled or ingested. On the other hand, a few Penicillium species are well known in the ripening and developing of flavors of several blue cheeses.
In the healthcare setting, Penicillium becomes dangerous due to its potential to cause respiratory issues in individuals with compromised immune systems. While not as directly lethal as some other fungi, the rare infections caused by Penicillium can complicate existing health conditions, leading to increased morbidity and a higher rate of hospital stays. Mortality rates attributed to Penicillium are not well-documented; however, the risk is considered non-negligible, especially in sensitive patient groups.
Addressing Medically Relevant Molds
Nationwide, routine testing for mold is not strictly required, although many hospitals and healthcare facilities voluntarily monitor for mold to ensure patient safety and limit liabilities. In addition, mold testing may be required by local regulations and guidelines. One such regulation is the USP <797> standard, which calls for compounding pharmacies to test for microorganisms, including molds, to ensure the safety and efficacy of compounded sterile preparations. Many state pharmaceutical boards follow USP <797> closely when creating state regulations.
Industry best practices and guidance for controlling mold growth in healthcare environments emphasize the importance of maintaining indoor air quality and managing humidity levels. Guidelines from organizations such as the CDC, the World Health Organization (WHO), and the Environmental Protection Agency (EPA) recommend routine inspections for mold, immediate remediation of detected mold growth, and the use of HEPA filtration systems during renovation or construction activities to prevent mold spores from spreading through the air.
Sampling and analyzing molds can be done using various techniques, which I touched on in a recent post: 3 Ways to Analyze Mold Samples. Healthcare settings typically call for a combination of spore trapping and fungal culturing since even hidden molds can cause infections and proper species identification are critical in infection prevention and control. Swab testing is also performed, especially when required by standards such as USP <797>. Sample culturing is typically done to identify the genus of mold as some species are more likely to be life-threatening in a healthcare setting.
For more information on Pace® mold testing services, download our Information Sheet. I’m also happy to answer individual questions about mold analysis. You can send me your questions through our website.