Cladosporium cladosporioides, although generally nonpathogenic, can cause illness. This species, along with Exserohilum rostratum and Aspergillus fumigatus, was one of the pathogens isolated during a multistate outbreak of fungal meningitis due to contaminated sterile medication manufactured by the New England Compounding Center.^2,5,9

Colony Appearance: 

The colonies on malt extract agar are olivaceous-green or grayish-green. They begin as velvety but become powdery due to abundant conidia. The reverse side is greenish-black.¹¹

Microscopic Characteristics:

Conidiophores arise from hyphae, bearing conidial chains laterally and terminally. Conidia are ellipsoidal to lemon-shaped, smooth-walled, olivaceous and easily liberated.⁷

Conditions for Growth: 

Grows optimally within a temperature range of 18-28 °C.  C. cladosporioides is considered to be xerophilic and xerotolerant, meaning it is capable of growth at or below a water activity (a_w) of 0.85. It is also psychrophylic as demonstrated by its ability to grow at freezing temperatures. It can grow at a slower pace at temperatures between -10°C and -3°C on Potato Dextrose Agar and Malt Extract Agar.¹⁰

Top 3 mold species found in Miami on July 17, 2017; Source: AAAAI

Habitat:

C. cladosporioides is widely prevalent in outdoor air and on decaying organic material. These fungi are frequently found as contaminants on food.¹⁰   It can also be found on in areas where moisture is present. In field studies this genus was found within 70% of examined dwellings in the U.S.A.¹⁰

The American Academy of Allergy Asthma & Immunology (AAAAI) occasionally lists types of mold, including Cladosporimum, found in a city on a specific day. For example, the top three species of molds seen in Miami on July 17, 2017, were Cladosporimum, Smuts/Myxomycetes and Curvularia.¹

Pathogenicity:

C. cladosporioides is a common air-borne saprobe that has been associated with indoor allergies.³  Cladosporium species is a rare cause of human illness, but it has been known to cause several different types of infections including skin, eye, sinus and brain infections.⁴  Rarely, it can cause onychomycosis (nail infection).⁸

Environmental Risk:

C. cladosporioides favors moist areas for growth such as:

• Buildings where the indoor humidity is higher than 50 percent
• Damp areas such as basements and carpet pads
• Buildings that have been exposed to excess moisture
• Buildings with poor ventilation³

The species thrives on cellulose based material such as wood and paper.² Cladosporium species is more likely to be found in a support area than an aseptic processing area of a pharmaceutical facility. Over an eight year period at one sterile product manufacturing plant, 28% of the fungal species isolated in the class D area were Cladosporium spp.⁶ 

Taxonomy¹⁰

References: 

¹ AAAAI. NAB Station: Florida Center For Allergy & Asthma Care. 7/17/2017 http://pollen.aaaai.org/nab/index.cfm?p=allergenreport&stationid=222&datecount=07%2F17%2F2017

² Abraham, Z. (2013) Understanding, Preventing, and Remediating Mold in Cleanrooms IVT Network. http://www.ivtnetwork.com/article/understanding-preventing-and-remediating-mold-cleanrooms

³ CDC. (2017) Mold Allergy. http://www.mayoclinic.org/diseases-conditions/mold-allergy/symptoms-causes/dxc-20200846

⁴ CDC. (2017) Cladosporium https://www.cdc.gov/fungal/diseases/other/cladosporium.html

⁵ CDC. (2017) Multistate Outbreak of Fungal Meningitis and Other Infections. https://www.cdc.gov/hai/outbreaks/meningitis.html

⁶ Cundell, Tony. (July 30, 2016) Mold Monitoring and Control in Pharmaceutical Manufacturing Areas. American Pharmaceutical Review. http://www.americanpharmaceuticalreview.com/Featured-Articles/190686-Mold-Monitoring-and-Control-in-Pharmaceutical-Manufacturing-Areas/

⁷ de Hoog, G.S., Guarro, J., Gené, J., Figueras, M.J. (2000)  Atlas of Clinical Fungi 2^nd Edition.

⁸ Dongmei Shi et al. Open Journal of Clinical and Medical Case Reports. (2016) Volume 2. Issue 2. ISSN 2379-1039. http://jclinmedcasereports.com/articles/OJCMCR-1072

⁹ FDA. U.S. Food and Drug Administration 2012) Multistate state outbreak of fungal meningitis and other infections

¹⁰ INSPQ. Centre d’expertise et de référence en santé publique. Institut national de santé publique Quebéc. https://www.inspq.qc.ca/node/488

¹¹ Samson, R., Hoekstra, E., Frisvad, J., Filtenborg, O. (2002) Introduction to Food and Airborne Fungi, 6^th Edition.