Dr Jackson Kung'u- Mold Specialist

Helping People Resolve Mold Problems

Contact Us

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

Home | MBL Blog

MBL Blog

Listeriosis in humans and animals

Listeriosis is currently in the Canadian news, having caused a number of deaths following contamination of meat and meat products. But what is listeriosis? It’s a disease caused by species of the bacterium Listeria. There are 6 species of Listeria widely distributed in nature. Listeria monocytogenesis the causative agent of listeriosis, however other species are also pathogenic. For example, Listeria ivanovii is an animal pathogen and in rare cases cause human infection. Even though, human infection is rare, the fatality is high, about 25-30% of cases would die.

Sources of Infection

The sources of infection are food and water contaminated with soil, sewage or any other material containing Listeria. Most outbreaks are caused by eating foods from animal origin e.g. hot dogs, deli meats, cooked poultry, raw milk, cheeses, raw and smoked fish.  Unlike many other bacteria, Listeria can survive and multiply on foods being stored in the refrigerator.

Symptoms of Listeriosis in human

Listeriosis in humans is characterised by a long incubation period of up to 70 days after exposure. However, many people can be asymptomatic carriers of Listeria but few of them develop listeriosis. The symptoms of listeriosis in humans include vomiting, nausea, abdominal pain, severe headache, diarrhea or sometimes constipation with persistent fever. Pregnant women, children and old people are more likely to get listeriosis than other healthy adults. It is probable that Listeria can be transferred to unborn babies through placenta of infected pregnant women and also to newborn babies through milk.

Listeriosis “Circling disease” in animals

Listeriosis affects a wide range of animals and birds. Persistent fever, abortion and circling due to encephalitis are the common symptoms. The disease is highly sever and fatal in small ruminants. Listeria monocytogenes  can be excreted in the milk of either aborting or apparently healthy cows, ewes, and goats. Listeriosis in dogs and cats are mainly visceral and septicaemic “gastroenteritis and fever”.

How to reduce the risk of infection

To reduce the risk of infection, the following practices are recommended:

  • Thoroughly cleaning and sanitizing all surfaces used for food preparation
  • Thoroughly cleaning fruits and vegetables before eating them
  • Defrosting food in cold water or in the microwave, but never at room temperature
  • Keeping the temperature inside refrigerator under 4°C to avoid multiplication of Listeriain foods if they are already contaminated with Listeria.

 

Therapeutic treatment

Listeria monocytogenesis sensitive to penicillin (the drug of choice), cefotaxime, azithromycin and trimethoprim/sulphonamide. It is recommended to test the antimicrobial sensitivity of the isolated Listeria.

Article by: Dr. Zakaria Saleh, PhD 

References:
Health Canada, http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/food-aliment/listeria-eng.php
Wikipedia, http://en.wikipedia.org/wiki/Listeriosis
The Merck Veterinary Manual, 50th Anniversary Edition

Sick Building Syndrome

What is Sick Building syndrome?

Sick Building Syndrome (SBS) is a term used to describe situations in which building occupants experience acute health symptoms that appear to be linked to the time spent in a building with no specific cause that can be identified. The complaints may be localized in a particular room or zone, or may be widespread throughout the building. SBS related complaints have increased in recent years and result when a building is operated or maintained in a manner that is inconsistent with its original design or prescribed operating procedures. Sometimes indoor air problems are a result of poor building design or occupant activities.

Indicators

Occupants of sick building syndrome buildings complain of symptoms associated with acute discomfort, e.g., headache, eye, nose, or throat irritation, dry cough, dry or itchy skin, dizziness and nausea, difficulty in concentrating, fatigue and sensitivity to odors. The cause of the symptoms is not known. Most of the complainants report relief soon after leaving the building.

Possible Causes

Many factors contribute to the sick building syndrome and sometimes it is difficult to pinpoint the cause.

  • Inadequate ventilation: This implies insufficient outside air, insufficient airflow and inadequate circulation. An improper system design or operation, and occupant tampering with HVAC system may be the cause.
  • Chemical contaminants from indoor sources: Copying and printing machines, computers, carpets, furnishings, cleaning materials, smoke, paints, adhesives, caulking, perfumes, hairsprays, solvents emit  VOCs or volatile organic compounds that affect indoor air quality.
  • Chemical contaminants from outdoor sources: Pollutants from motor vehicle exhausts; plumbing vents, and building exhausts (e.g., bathrooms and kitchens) can enter the building through poorly located air intake vents, windows, and other openings or a nearby garage.
  • Biological contaminants: Bacteria, molds, pollen and viruses are types of biological contaminants. These contaminants may breed in humid and damp conditions, stagnant water that has accumulated in ducts, humidifiers and drain pans, or where water has collected on ceiling tiles, carpeting, or insulation. Sometimes insects or bird droppings can be a source of biological contaminants. Physical symptoms related to biological contamination include cough, chest tightness, fever, chills, muscle aches, and allergic responses such as mucous membrane irritation and upper respiratory congestion.

Possible Solutions to Sick Building Syndrome

In order to overcome sick building syndrome, a detailed indoor air quality investigation is a prime requirement. This involves identifying underlying causes and determining corrective actions. It begins with gathering information on the following:

  • the occupants’ activities
  • the HVAC system
  • possible pollutant pathways
  • possible contaminant sources.

Once the information is available, air sampling may be conducted to assess the level and types of chemical and biological contaminants. Moulds are serious biological contaminants that severely affect the indoor air quality. They can cause many health related symptoms like allergies, cough, cold, irritation, nausea, fatigue and fevers. Mould can be sampled using a simple air pump or a tape. You may refer the following link for a demonstration on Air Sampling for mould:
http://www.moldbacteria.com/presentations/index.html

Primary assessment confirms presence and further tests reveal the identity of moulds. This could help draw conclusions on factors that contribute to sick building syndrome. Based on all information and evidence gathered, a strategic solution may be developed. Pollution source removal and air cleaning would be the basic approach. Proper ventilation rates and air distribution can help minimise SBS. Effective communication between building occupants, management and maintenance personnel can help find the causes and consequences of sick building syndrome. Awareness about indoor air quality issues can aid in overcoming the sick building syndrome.

Testing Carpets For Mold

Carpets are reservoirs of health hazard particulates including mold spores, dust mites, and animal hair. These particulates are allergenic to some people when inhaled. Mold spores are very tiny and easily become airborne when the carpet is disturbed as people walk in the house or when the carpet is being cleaned.

Cleaning the carpet with a good vacuum cleaner on regular basis significantly reduces the number of settled mold spores and other particulates. In fact there is no need to test carpets for mold if they are well maintained.

Carpets can be tested for:

  • Settled mold spores
  • Mold growth.

To test a carpet for settled spores a dust sample is required. Dust can be collected from an area of 1 square meter. It’s important to ensure that enough dust is collected to enable the laboratory perform both culture analysis and direct microscopic examination of the dust.  

When is it necessary to test a carpet for mold growth? You can test a carpet for mold growth following water damage if the carpet was not completely dried within 48 hours. This test may involve cutting a piece of carpet from the affected area and sending it to the laboratory for testing.

Monitoring And Documenting Air Quality

Monitoring and documenting air quality, especially in hospitals, pharmaceutical, cosmetics, and food industries environments is very important. Contamination of these environments can originate from nearby or far away sewage plants, landfill sites, and waste separation plants. Therefore, monitoring on a regular basis of air quality in operating rooms, production lines, and other controlled areas is critical.

To assess the level of microbial contamination in the air, air is sampled for analysis by direct microscopy (sometimes referred to as nonviable analyses) or by culture analysis. For direct microscopy, the air is sampled using various cassettes including Air O Cell, Allergenco, Millipore filters and others. The samples are examined at between 600 and 900X magnification.  Fungal spores and mycelial/hyphal fragments are enumerated. Millipore filters are first cleared using acetone and fixed with triacetine and then analysed in a similar manner as the Air-O-Cell or Allergenco samples. The filters have a major advantage over the other spore traps in that, having a large surface area, they can be used in highly contaminated environments, where other spore traps would easily be overloaded with dust thus rendering them difficult to analyse.

Direct microscopic analysis of air samples allows determination of total spore counts regardless of whether the spores were dead or alive. In hospital environments both dead and living spores are of concern because even if the spores were dead, they could be as toxigenic or allergenic just like living spores.

To sample air for culture analysis requires the air to be impacted on suitable agar media. Commonly used types of samplers are the Reuter Centrifugal Sampler (RCS) and the Andersen samplers. However there are many other samplers.  The air is impacted on media such as MEA and DG18. Culturable air samples are incubated for 3-5 days and the resulting colonies counted. The colonies are then transferred onto suitable agar media for identification. In general, number of fungal propagules determined by cultural method is far much smaller (1-50% of total counts in some cases) than the total number of spores and fungal propagules determined by direct microscopic examination.

To assesss air for bacterial contamination, a general purpose media such as Tryptic Soy Agar (TSA) can be used. However, if sampling for a specific type of bacterium such as Legionella spp, then a selective media such as Buffered Charcoal Yeast Extract (BCYE) Agar is recommended.

Chaetomium

Chaetomium species are strong producers of the enzyme cellulase. They are, therefore, adapted to growing on cellulosic (cellulose containing) materials. They thrive particularly on paper, straw and cotton. Chaetomium species have caused problems in libraries, military equipment and food. Apart from causing spoilage of various materials, they are also producers of mycotoxins. Because of their strong ability to biodegrade organic materials, several strains are used in mold growth testing.

The species commonly encountered in chronically water-damaged buildings is Chaetomium globosum. Chaetomium globosum is also a common “weed” of mushroom beds, where it inhibits the growth of cultivated mushrooms.