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Bacteria

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.

Legionella

Apart from the global economic chaos, Ontario also seems to have been affected by a series of nasty bugs. First, it was the Listeriosis outbreak in Toronto and GTA last month. Then, the E.coli outbreak in North Bay and now it is Legionella. An update released by the Peel Public Health in September says that there has been an increase in legionellosis cases noted in Peel and other jurisdictions around the Golden Horseshoe. Hamilton Public Health also confirms seven cases of legionellosis since August 2008.

So, what is Legionella?
Legionella bacteria (gram negative, poorly staining rods) are naturally found in the environment, usually in water. They may be found in water distribution systems of hospitals, hotels, ships, public buildings, homes and commercial facilities. They can survive for several months in a wet environment and multiply in the presence of algae, protozoa and organic matter.  Legionella acquired its name after a July, 1976 outbreak among people attending a convention of the American Legion in Philadelphia. The mystery disease sickened 221 persons, causing 34 deaths. The causative agent was identified by scientists at the Centres for Disease Control and Prevention (CDC) and subsequently named Legionella.

Symptoms
Legionella pneumophila is the causative agent of the legionellosis disease which presents itself in two forms:

  • Legionnaires’ disease – the more severe pneumonic form
  • Pontiac fever – the milder non-pneumonic illness

Legionnaires’ disease is a type of pneumonia that may be mild to fatal. Symptoms include high fevers, chills, nausea, cough and headache. There may be memory loss or a change in mental status. Pontiac fever is not associated with pneumonia and is milder. Symptoms include fever and headache.

Transmission
Legionella infections are acquired exclusively from environmental sources – through inhalation of contaminated aerosols – mist droplets containing the bacteria. These aerosols are formed from cooling towers, large central air conditioning systems, domestic hot-water systems, showers and faucets, fountains and similar water environments. Natural sources of Legionella include freshwater ponds and creeks. Legionella can travel at far as 6 km from its source by airborne spread. It is not spread from person to person. Older people (65 years or more) or immunocompromised patients are more susceptible to the infection.

Control
Legionella infection can be best reduced by good engineering practices in the operation and maintenance of air and water handling systems as emphasized by ASHRAE – American Society of Heating, Refrigerating and Air Conditioning Engineers. Common measures taken are cooling tower maintenance, increased heat shock treatments and use of biocides. Water treatment, prevention of scaling and algal build-up, periodic cleaning and maintenance of equipment are highly recommended.

Monitoring and Sampling
Air, water, sludge and sediments can be sampled for detection of Legionella. For sampling Legionella in water systems, several locations are recommended.  Water at bottom drain and outlet pipes, water from hot and cold faucets, tanks, humidifiers, spas and fountains can be sampled in sterile containers and sent to the lab for analysis at the earliest. Swabs are recommended for surfaces like inside of faucets and shower heads or any surface showing biofilm formation. Culturable air sampling is done by using air sampling pumps that draw air directly onto culture media which can be further analysed for the presence of Legionella after incubation and other tests.

For further information and a detailed protocol on Legionella sampling, call us at 905-290-9101 or e-mail us at info@moldbacteria.com.

Edited By: Dr. Jackson Kung’u, PhD.

How to collect bacteria samples

Various methods can be used to collect bacteria samples. The procedure will depend on what is being sampled and the type of data required. One may may be interested in a specific bacterium, in which case the method of sampling should be suitable for the recovery of that specific organism.

Sampling from surfaces

Sampling of bacteria from surfaces is usually performed using sterile swabs. Results from this test could be as simple as presence or absense of the bacterium of interest for example E. coli or Legionella. The test could also be detailed to include the amount of the bacterium present. It’s important to know how to collect samples for these different levels of analysis. If quantification is required, it’s important to swab a known surface area, for example 100 cm square. In this case the results would be expressed as “Number of colony forming units” per unit area.

Sampling bacteria samples from the air

To sample bacteria from the air, the air is impacted on some suitable growth media.   The media to use will be determined by the type of bacteria being sampled for. If one is interested on a specific type of bacterium then a media that is selective for that bacterium should be used. To sample for the general population of bacteria in the air, then a media that can support the growth of many types of bacteria such as  tryptic soy agar (TSA) should be used. Results are given as colony forming units per cubic meter of air.

Sampling for bacteria from water

Testing water for bacteria involves collecting a water sample in a sterile container and sending it to the lab for testing. The test results may just indicate the presence/absence of the bacterium of interest or may be detailed to include the amount present in terms of colony forming units per mililitre.

E.coli

Here we go again…talking about E.coli. Just a few days ago, we heard about the outbreak in North Bay, Ontario where the number of confirmed and suspected cases of E. coli O157:H7 poisoning has risen to 159. The source of the bacterium has been linked to a fast food restaurant this time.

So what is this E.coli and why is it so important? You can’t see it, smell it or taste it. But it can leave you fighting for your life, especially if your immune system is weak or compromised. E. coli or Escherichia coli (named after Escherich who first discovered it) are a type of bacteria commonly found in the intestines of animals and humans. There are hundreds of strains of the bacterium, but E. coli O157:H7 is possibly the most dangerous as it produces a powerful toxin that can cause severe illness.

E. coli O157:H7 was first recognized in the United States in 1982, when an outbreak of severe, bloody diarrhoea was traced to contaminated hamburgers. It was then called the “hamburger disease.” E. coli O157:H7 can contaminate ground beef during the butchering process. If it is present in the intestines of the slaughtered animal, it can get into the meat as it is ground into hamburger.

Canada’s worst-ever E. coli outbreak occurred in  Walkerton, Ontario in May 2000, after the bacteria got into the town’s water supply. More than 2,300 people were affected. The source of the contamination was manure spread on a farmer’s field near one of the town’s wells. Health authorities across the country normally deal with a few thousand cases of E. coli illness every year.

Sources of E. coli
E. coli comes from human and animal wastes. During precipitation, E. coli may be washed into creeks, rivers, streams, lakes, or groundwater. When these are used as sources of drinking water — and the water is not treated or inadequately treated — E. coli may end up in drinking water. This is what we call the sewage or fecal contamination of water. It indicates that the water is not fit for human consumption.

Although the bacteria are mainly found in meats, it is also present in unpasteurized milk and fruit juices, ham, turkey, chicken, roast beef, sandwich meats, raw vegetables, fruits and cheese. Once someone has eaten contaminated food, the infection can be passed from person-to-person, and by hand-to-mouth contact. The bacteria are most often spread from person-to-person.

Symptoms
These are characterized by severe abdominal cramping that can appear within hours of eating any contaminated food but could also take up to 10 days to show up. Some people may also be afflicted with bloody diarrhoea or non-bloody diarrhoea, nausea and fever. Some people may show no symptoms at all, but can still carry the bacteria and pass it on to people who will become sick.

Precautionary Measures
Since most cases of E. coli infections are contagious (passed from person to person), good personal hygiene is critical to protecting yourself.

  • Wash your hands thoroughly and frequently.
  • Don’t handle food if you are suffering from diarrhoea.
  • Wash raw fruits and vegetables thoroughly before cooking or cutting them.
  • Sanitize food preparation surfaces and utensils.
  • Anyone known to be infected with E. coli, should not share dishes, cutlery or glasses with anyone else. Their towels, face cloths and bedding should be washed separately in hot water and bleach.
  • Call your family doctor for any unusual symptoms that you notice in your health or that of your family.

Some of the proper food handling techniques to minimize exposure to E.coli include:

  • Refrigerate or freeze meat as soon as possible after buying it and then thaw frozen meat in the refrigerator, not on the counter.
  • Use a digital food thermometer when cooking ground beef, which should be cooked to an internal temperature of at least 71 C (160 F).
  • Serve cooked meat immediately or keep it hot (60 C or 140 F).
  • Clean and sanitize countertops and utensils after contact with raw meat.
  • Don’t store raw and cooked food together.
  • If you marinate meat, don’t use the liquid as a dip or to pour over cooked meat.
  • Drink only pasteurized milk or juice fruit juices. 
  • Drink water from a supply known to be safe. If you have a private water supply (well) it should be tested several times a year.

If you need further information on E.coli or performing a water quality test, please visit our web-site www.moldbacteria.com or call us at 905-290-9101.

Article by: Sneha Panchal, M.Sc.