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Dr. Jackson Kung’u (PhD)- Mold Specialist.
Phone: 905-290-9101
Mobile: 437-556-0254

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Archives for 2008

Listeria Testing

Listeria is a deadly bacterium found in unpasteurized dairy products, raw vegetables and meats, and processed foods, including deli meats and hot dogs. A recent outbreak of listeriosis claimed at least 20 lives and left several others sick.

To safeguard the public, the Canadian Food Inspection Agency (CFIA) is proposing new rules for Listeria testing. The proposed new rules include two new tests that food processing plants would have to perform:

  • Testing for Listeria near production lines such as ceilings and floors
  • Testing for Listeria on surfaces that come in contact with meat, including countertops and slicing machines.

If Listeria monocytogenes is detected, the company would have to place the meat in quarantine, clean the facilities and then re-test. If a re-test comes up positive, the company would have to test a random sample of the quarantined meat for Listeria.

If the quarantined meat tests positive, it would have to be destroyed.

The new rules would also require companies to report positive Listeria findings to CFIA.

Click CFIA to launch new listeria testing protocols for more details.

Bacteria in the Refrigerator

Cold winds are blowing and the winter of 2008 is already here. In Canada, winter means eating and celebrating the season. We have Christmas parties and winter wine festivals, light festivals and many others. And when extreme cold and snow blows, for lots of us here, it also means hibernating. As we tend to go out lesser and lesser, we end up stocking our freezers and refrigerators with all varieties of foods – canned, frozen, ready-to-eat meals and lots more. That is why we`ll discuss about refrigerator hygiene and food safety in homes and work places.

We all know that foods are stored in refrigerators or freezers to prevent spoilage, but what if the refrigerator itself is not clean? Refrigeration slows microbial growth. Micro-organisms are omnipresent. They are in the soil, air, water, and the foods we eat. In presence of nutrients (food), moisture, and favourable temperatures, micro-organisms grow rapidly, increasing in numbers to the point where some types of bacteria can cause illness. If your refrigerator is not clean, it may become a breeding ground for such bacteria.

Micro-organisms that can grow at cold temperatures are called psychrophiles. Psychrophilic microbes can tolerate, survive and thrive at low to extremely low temperatures. This explains why food products still go bad in refrigerators. The microbes that are found in glaciers, in the Arctics and the Antarctics are pyschrophiles and so are the ones in your freezer. Another group called psychotrophs, is capable of growth at room temperature as well as low temperatures. This means that they can survive at temperatures ranging from 0°C to 25°C.

So how can bacteria harm you?
Improperly processed or packed meats and other foods can be contaminated with psychotrophic bacteria and moulds. The bacteria may also be present in unhygienic conditions in refrigerators or freezers. So when you eat foods contaminated with such bacteria, they will grow in your body and exhibit  pathogenic conditions. Some bacteria may not be harmful themselves but they release toxins into the food which causes food poisoning. Bacteria such as some Coliforms, Pseudomonas sp., Vibrio sp. and Listeria sp. and moulds such as Penicillium and Cladosporium sp. are all known to survive low temperatures and become harmful once they are inside the human body.

And what do you do to protect yourself from food poisoning?
The following practices can safeguard you and your family from food poisoning (see the links below for details):

  • Keep your refrigerators clean by wipping up spills immediately, cleaning surfaces thoroughly with hot, soapy water and then rinsing.
  • throw out perishable and expired foods that should no longer be eaten. A general rule of thumb for refrigerator storage for cooked leftovers is 4 days; raw poultry and ground meats, 1 to 2 days.
  • Verify the temperature of the refrigerator. Refrigerators should be set to maintain a temperature of 40 °F or below.

If you suspect bacterial contamination in your home or office refrigerator, send us swabs of suspect areas and we’ll detect the bacteria and moulds for you. For more details, visit www.moldbacteria.com or call us at 905-290-9101. Follow the food safety and refrigeration rules and enjoy the coming celebration season!

  1. References:
    Food Microbiology and Laboratory Practice. Bell Chris, P Neaves, and W. P. Anthony. Blackwell Publishing. 2005. ISBN 0-632-06381-5

Edited by: Dr. Jackson Kung’u, PhD.

Air Sampling

Air sampling is one of the tools used in mold investigation. The primary objective of mold investigation is to determine the extent of mold growth and subsequently its potential effect on indoor air quality. Air sampling helps to termine whether or not visible mold growth has degraded indoor air quality. It may also help to detect the presence of hidden mold growth. Some investigators use air sampling to determine the effectiveness of remediation. This is achieved by taking air samples before and after remediation.

Interpretation of Air Sample Results

Interpretation of air sample results can at times be very difficult. However, having a clear objective, prior to air sampling can make results interpretation easy.

As often stated, fungal spores are present in virtually all environments including indoors. Therefore, presence of some fungal spores indoors is considered normal. Generally, for well maintained mechanically ventilated buildings, airborne spores should be qualitatively similar but quantitatively lower than the outdoors. For naturally ventilated buildings, the airborne spore concentration and their diversity in the indoor air is similar to that of outdoor air.

For both mechanically and naturally ventilated buildings, presence of airborne spores of molds usually found in indoors, in numbers significantly higher than those of outdoors, is an indication of indoors sources of mold growth.

Interpretation of air samples collected primarily to determine whether there was mold growth indoors is therefore based on a comparison of concentrations and categories of spores in outdoor and indoor samples. Significant counts of species present indoors and absent (or in lower counts) outdoors suggest the source for those species is indoors. In the absence of any visible mold growth, further investigation would be required to determine the source and extent of any hidden mold growth.

It’s important to note that the conclusion derived from air sample results should always be backed by visual inspection and the building history.

Biodeterioration

Biodeterioration is a terminology used to describe any undesirable change in the properties of a material caused by the vital activities of organisms.

Fungal growth requires suitable temperature, moisture and air (oxygen). Fungi are heterotrophs that acquire nutrients by absorption. They secrete hydrolytic enzymes (exoenzymes) and acids to decompose complex molecules into simpler ones that can be absorbed and used as nutrients. Hence, they are believed to be potential contributors to biodeterioration of different kinds of materials containing cellulose, silicate mineral (mica and orthoclase), iron and magnesium-bearing minerals (biotite, olivine, pyroxene) etc.

Fungi cause biodeterioration to many materials including:

  • building materials
  • animal feeds
  • electrical equipment
  • food including meat, fruits and grains
  • fuel including jet fuel
  • glass and optical equipments
  • gunpowder
  • leather
  • monuments
  • paint
  • paper
  • tobacco etc.

 How are Fungi involved in biodeterioration?

The rate of biodeterioration depend on prevailing environmental conditions and the fungus involved. There are different mechanisms of biodegradation. These include microbial corrosion, hydrocarbon degradation and biodegradation of cellulose.  Aspergillus niger, Chaetomium globosum, Scopulariopsis brevicaulis, Trichoderma koningii, Trichothecium roseum and Eurotium chevalieri are cellulolytic fungi. Their efficiency to degradate cellulosic (cellulose containing) materials is due to their ability to produce large amounts of cellulase enzymes. 

Stachybotrys chartarum is a common fungus growing on paper (such as that covering gypsum wallboard) in damp buildings.

Some fungi cause blue stain and soft rot of wood, discolouration and loss of strength of cotton materials.  Many fungi spoil food in storage. Aspergillus flavus grows on peanuts and many other substrates, producing a mycotoxin called aflatoxin, which contaminate food and causes liver damage. Fusarium graminearum grows on feed corn and produces the  mycotoxin zearalenone that causes oestrogenic syndrome in animals.

Through the action of excreted oxalic and citric acids fungi can deteriorate marble, limestone, granite and basalt. Several species of fungi are involved in biodeterioration of stone monuments in different countries. Some of these fungi are Aspergillus elegans, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger, Aspergillus versicolor, Alternaria sp, Cladosporium cladosporioides, Cladosporium sphaerospermum, Cunninghamella  echinulata, Curvularia lunata, Fusarium roseum,  Gliocladium virens, Penicillium crustosum, Penicillium glabrum, Penicillium chrysogenum (=Penicillium notatum), Rhizopus arrhizus.

Biodeterioration is a problem worldwide. Several control measures have been applied to prevent the biodeterioration. These include use of fungicides, biological control, prevention of biodeterioration by control of environmental conditions, periodic cleaning of dirt, dust and spores, and use of radiation.

Spore Trapping And Counting

Spore trapping and counting is extensively used in crop protection to:

  • determine the concentration of pathogenic spores carried by wind
  • forecast a disease outbreak
  • get facts about periodicity of spore showers on crops as one of several infection requirements
  • determine correct timing of protectant sprays and other control measures. 

Spore trapping and counting also provide useful information about airborne spores that cause respiratory allergies such as rhinitis, asthma, and farmers’ lung disease. In building environments, spore counting and trapping can be used for detecting dry rot or other hidden mould. Although there are no acceptable levels of airborne fungal concentration in indoor environment, spore trapping and counting can also help in determining if occupants were potentially exposed to high levels of allergenic fungal spores.