Mold Bacteria Consulting Services

Serving Ontario and British Columbia

You are here: Home / Archives for Fungi

Cladosporium: A Common Allergenic Indoor Mould

Cladosporium is a leaf mould and one of the most common in outdoor and indoor air worldwide. It is a very common household mould in bathrooms, around tubs, shower stalls, or window frames and even bathroom walls and ceilings.  Like every other mould, it requires free water for growth.  Around the edge of the tub there is water from splashing or water running down the wall from the shower.  The water just sits around the edge of the tub and may evaporate very slowly.  On walls and ceilings  the steamy air results in condensate, especially on colder, outer walls.  The spores are ubiquitous and will germinate in this available water and  very quickly little dark brown colonies start to grow.  Eventually there will be an olive-brown to blackish brown growth of Cladosporium around the tub.

Some species of Cladosporium cause serious diseases to plants. The mold is commonly isolated from air, soil, foodstuffs, stored fruits, cereal grains, groundnuts, paint, and textiles. Cladosporium is a well known allergenic mould. The most common Cladosporium species in outdoor air are Cladosporium cladosporioides and Cladosporium herbarum. During summer there can be very high concentrations of airborne spores of Cladosporium cladosporioides and Cladosporium herbarum, and both contain allergenic proteins in their spores. Cladosporium cladosporioides and Cladosporium hebarum may be found colonizing painted metal surfaces of covering panels and vents of heating, air conditioning and ventilation systems.Cladosporium sp.

Cladosporium sphaerospermum is the most predominant species growing in buildings. Studies have shown it can outgrow Penicillium chrysogenum because of its ability to re-initiate growth from the hyphal tips much faster than Penicillium species. Cladosporium sphaerospermum and occasionally Cladosporium herbarum is frequently isolated from indoor surfaces such as in bathrooms, windowsills and damp painted surfaces. It is also commonly found colonizing wood.

Species of Cladosporium are not known to produce any serious mycotoxins.

Do you have a mould question? Send it to My Question.

Water Damaged Homes: The Primary, Secondary and Tertiary Colonizers.

If a water problem in a building is not repaired and the water dried out within 48 hours, growth of mould and other microorganisms would naturally occur. The types of moulds predominant at anyone time would be determined by the level of moisture in the building material. This level of moisture is usually referred to as the water activity and it determines the order in which different categories of moulds appear. The first group of moulds to appear (at water activities less than 0.85) is referred to as the primary colonizers, the second group (at water activities of 0.85-0.90) is secondary colonizers and the third group (at water activities greater than 0.90) is the tertiary colonizers.

Primary colonizers
The primary colonizers are capable of growing at water activities below 0.85. This group may include Alternaria citri, Eurotium amstelodami, Aspergillus candidus, Aspergillus glaucus, Aspergillus niger, Aspergillus penicillioides, Aspergillus repens, Aspergillus restrictus, Aspergillus versicolor, Paecilomyces variotii, Penicillium aurantiogriseum, Penicillium brevicompactum, Penicillium chrysogenum, Penicillium commune, Penicillium expansum, Penicillium griseofulvum, and Wallemia sebi.

Secondary colonizers
Secondary colonizers grow best at water activities of 0.85 to 0.90. Secondary colonizers may include Aspergillus flavus, Cladosporium cladosporioides, Cladosporium herbarum, Cladosporium sphaerospermum, Mucor circinelloides, and Rhizopus oryzae.

Tertiary colonizers
At water activities greater than 0.90, tertiary colonizers appear. These may include Alternaria alternata, Aspergillus fumigatus, Epicoccum spp., Exophiala spp., Fusarium moniliforme, Mucor plumbeus, Phoma herbarum, Phialophora spp., Rhizopus spp., Stachybotrys chartarum, Trichoderma spp., Ulocladium spp., Rhodotorula spp., Sporobolomyces spp., and Actinomycetes.

Do you have a mould question? Send to My Question.

The Mould Stachybotrys chartarum: Why Is It So Feared?

The health effects due to the mould Stachybotrys chartarum are controversial. Stachybotrys chartarum, also known by an old name as Stachybotrys atra, is a cellulose degrading fungus commonly found in soil and on materials rich in cellulose such as hay, straw, cereal grains, plant debris, wood pulp, paper, and cotton. Although Stachybotrys chartarum mainly survives as a saprophyte (i.e., by feeding on dead organic material), it has also been reported to cause root lesions on soybean.

Why is Stachybotrys chartarum so feared?
The first reports associating Stachybotrys chartarum with ill-health dates back to the 1930s. Horses and other animals fed with straw and grains in Ukraine and other parts of eastern Europe were found to develop disease symptoms such as irritation of the mouth, throat, and nose; shock; dermal necrosis; a decrease in leukocytes; hemorrhage; nervous disorder; and death. Russian scientists, in 1938 conducted intensive studies and demonstrated that these symptoms were due to mycotoxins produced by Stachybotrys chartarum that had grown on the cellulose rich straw. The disorders were subsequently named stachybotryotoxicosis. Stachybotrys chartarum, conidiophores and spores as seen under a microscopeStachybotryotoxicosis has also been reported in farm workers who handled contaminated straw. Recent studies have shown spores of Stachybotrys chartarum to contain high concentrations of highly toxic mycotoxins. In 1993-1994 an outbreak of pulmonary hemorrhage in infants in Cleveland, Ohio,USA, was initially attributed to Stachybotrys chartarum. Since this incidence, this mould has received a lot of media attention in North America and has been given various names such as “toxic mould” and “black mould”. Although studies associating the outbreak with this mould were later reviewed and thought not to provide enough evidence to associate the disease with Stachybotrys chartarum, there are still no studies to date to prove or disapprove this claim.

Do you have a mould question? Send it to My Question.

Sampling for Airborne Mould: When Should One Use Viable, Non-viable or Both Methods?

An air quality investigation may require determining airborne mould (spores and hyphal fragments) concentration. Air can either be sampled onto some growth media for culture analysis or on a sticky surface or a filter membrane for direct microscopic examination. It is sometimes debated as to whether one should take non-viable samples, viable samples or a combination of the two. Either method can be used without the other or both can be used together (at the same time) depending on the objectives of the investigation.

Due to lack of standardization some terminologies used in air sampling are technically incorrect or misleading. Let’s discuss these terms first.

Non-viable Air Samples
“Non-viable air samples” refer to samples that are taken on some sticky media or on a filter membrane or tape and subsequently examined directly under a microscope for enumeration and identification of mould spores and hyphal fragments without culturing. In other words, the samples are taken for analyses by direct microscopic examination (DME). Results are presented as a listing of various categories of moulds and the corresponding number of spores or hyphal fragments per cubic meter of air (Spores/m3). This term is technically inaccurate since viable and non-viable propagules are indistinguishable under the microscope and hence both are enumerated.

Viable Air Samples
“Viable air samples” refer to samples that are taken on some growth media and subsequently incubated for mould propagules (spores and/or hyphal fragments) to germinate and form colonies. The resulting colonies are then enumerated and/or transferred to other media for identification to genus or species. Results are presented as a listing of the recovered moulds and their corresponding number of colony forming units per cubic meter of air (CFU/m3). That is, the analysis of viable air samples involves culturing. The term is also technically inaccurate because some (sometimes most) of the propagules impacted on the growth media may not germinate not because they are not viable but because of the selectivity of the growth media used, competition from fast growing moulds or that some moulds can only grow on living hosts.

Spore traps
“Spore traps” is commonly used to refer to non-viable air samples. However, whether sampling is done for culture analysis with an RCS, Andersen or for DME with Air-O-Cell or other similar cassettes it involves spore trapping. “Spore traps” is therefore applicable to both viable and non-viable samples.

When should one use viable, non-viable or both sampling methods?

The easiest way to decide on this is first to define the objectives of air sampling, data required from sample analysis and the questions these data are meant to answer. The objective might be broad or very specific.

  • When to use non-viable sampling

If the objective of air sampling was to have an idea of how contaminated the air is, then the data required would be total counts. Non-viable samples would then be the best to take because counting includes both those propagules that can grow on laboratory media and those which cannot grow either because they are dead or would not grow on the selected media. Non-viable sampling may also be selected when the objective of air sampling is to determine the total counts for airborne spores prior to and after remediation to assess the effectiveness of remediation. In this case viable air samples would not be necessary.

  • When to use viable sampling

If the objective of air sampling was to find whether the air contains a specific species of mould e.g., Aspergillus fumigatus, then identification to species would be required. Since non-viable analysis would not distinguish A. fumigatus from other Aspergillus species and not even from Penicillium species and related genera, then sampling for viable analysis would be selected. For detecting a specific species, a selective media that would support the growth of the mould of interest would also be selected. If identification to species was required for a broad range of moulds, then media that support growth of a wide range of moulds would be selected.

  • When to use both non-viable and viable sampling

If the objective of air sampling was to determine the total airborne mould concentration and at the same time determine the proportion of viable propagules, then both sampling methods would be used. This would possibly be the case in hospitals where concern is not only the total concentration of airborne mould but also the viable species present.

Conclusion
These are not the only reasons why one may sample for non-viable, viable or both non-viable and viable analysis. It all depends on the objectives of air sampling, the data required and the questions these data are intended to answer. Read Interpreting Numerical Data of Viable Airborne Mould Samples and Guidelines for Interpreting Numerical Data of Non-viable (Spore Traps) and Viable Airborne Mould Samples.

To get hands-on experience on the application of these guidelines register for our Mould Training Seminars today!

Do you have a question on mould? Send it to us at Contact US.

Mold in Homes Doubles Risk of Asthma

Exposure to dampness and mold in homes as much as doubles the risk of asthma development in children, according to a study published today in the March issue of the peer-reviewed journal Environmental Health Perspectives (EHP). Researchers studied 1,984 Finnish children aged 1 to 7 years over a six-year period to see if they developed asthma. Data collection included a baseline survey administered in March 1991, as well as a follow-up survey in March 1997, asking questions about the child’s health, parents’ health, parent’s highest education level, and details of the child’s environment including exposure to environmental tobacco smoke and presence of feathery or furry pets.

The study focused particularly on four indicators or moisture or mold in homes, including mold odor, visible mold, visible moisture, and history of water damage. The presence of mold odor proved to be the only significant indicator of asthma development.

A a total of 138 children, or 7.2% of the study population, developed asthma during the study period. Having a parent with a history of allergies increased susceptibility in children. Mold odor increased the risk, the study found, independent of parents’ medical histories. In fact, children living in homes with mold odor during the initial study period were more than twice as likely to develop asthma in the following 6 years.

“These findings strengthen evidence that exposure to molds increases the risk of developing asthma in childhood,” says lead author Jouni Jaakkola, director of the University of Birmingham’s Institute for Occupational and Environmental Medicine. “They also show the importance of heredity-children of parents with asthma have a two-fold risk of asthma compared with children of nonasthmatic parents.”

Children who were exposed to moisture or mold in homes were also slightly more likely to be exposed to environmental tobacco smoke, to have feathery or furry pets, and to have parents with a lower education level. The study adds to the body of evidence linking asthma with exposure to cigarette smoke.

“This study is important for families everywhere,” says Dr. Jim Burkhart, science editor for EHP. “Anyone with young children in the home should be aware of the potentially harmful effects of long-term exposure to mold and this potential link to asthma in children.”

In addition to Jaakkola, contributing authors included Bing-Fang Hwang of the Environmental Epidemiology Unit at the University of Helsinki in Finland, and Niina Jaakkola of the Department of Health Care Administration at Diwan College of Management in Taiwan.

Funding sources for the research as reported by the authors included the Ministry of the Environment, the National Agency for Welfare and Health, the Medical Research Council of the Academy of Finland, and The Yrjö Jahnsson Foundation.

EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org.

Environmental Health Perspectives (NIEHS)
PO Box 12233, MD EC-15
Research Triangle Park, NC 27709-2233
USA
Phone 919-541-2359
niehs.nih.gov/drcpt/ehpb/home.htm

——————————————————————————–

Save time! Get the latest medical news in your email every week with our newsletter.

——————————————————————————–

Contact Our Medical News Editors

For any corrections of factual information, or to contact the editors please use our feedback form.

Please send any medical news or health news press releases to: pressrelease@medicalnewstoday.com

Salmonella food poisoning and symptoms

Salmonella food poisoning has been a growing concern in recent news. It has frequently lead to recalls of beef, salads and organic products and, even peanut butter products. Salmonella food poisoning occurs when one eats raw or undercooked foods such meat, poultry, eggs or egg products. Properly cooked food can get contaminated with Salmonella if […]

Legionella pneumophila – Guidelines for Laboratory Interpretation

Legionella pneumophila is a Gram negative, aerobic bacteria that is characterized as an opportunistic pathogen. It is the cause of Legionnaires’ Disease, a severe form of pneumonia and, it is the cause of Pontiac fever, a non-pneumonic form of L. pneumophila infection. Legionella spp.’s mode of transmission is through aerosols or aspiration of contaminated water. The Public Health […]

The Indoor Mold Is An Early Warning Device

The mold (or mould, in the Queen’s English) has been the victim of a bad press. Mention the word and it conjures up an image of something rotting or in the process of decomposition. And yet, were it not for the mold that inspired the discovery of penicillin millions of lives would have been lost. […]