Update of Investigation into food poisoning incidents at Pat’s Schoolhouse, The Children’s Place and Learning Vision

Investigation Findings
The investigations have traced the outbreak of food poisoning to the consumption of seafood marinara pasta supplied by the caterer to the pre-schools for lunch on 10 May 2011. The infective agent was Salmonella Enteritidis (a bacteria which can cause food poisoning), found in the stool samples collected from the affected cases. As this organism is not native to seafood but is commonly found in items such as poultry and eggs, there may have been cross-contamination of the pasta with raw food during preparation at the caterer’s premises.

Interviews with the food handlers employed by the caterer indicated that the same trays were used to hold raw and cooked foods, which may be a possible cause of cross-contamination, if the trays were not cleaned properly. Meat, seafood and poultry were also being prepared in the same area, which increases the risk of cross-contamination. 

Qi Yin

Two Catergories of Toxins!

Exotoxins  are soluble, heat-labile, proteins that usually released into the surroundings as the pathogen grows. Often exotoxins may travel from the site of infection to other body tissues or target cells in which they exert their effects. 
 Ø Exotoxins usually are

1.  Synthesized by specific bacteria that often have plasmids or prophages bearing the exotoxin genes

2.  Heat-labile proteins inactivated at 60 to 80°C.

3.  Among the most lethal substances known (toxic in very small doses [microgram per kilogram amounts]; e.g., the botulinum toxin)

Ø   Exotoxins can be divided into four types based on their structure and physiological activities. (1) One type is the AB toxin, which gets its name from the fact that the portion of the toxin (B) that binds to a host cell receptor is separate from the portion (A) that has the enzyme activity that causes the toxicity. (2) A second type, which also may be an AB toxin, consists of those toxins that affect a specific host site (nervous tissue [neurotoxins], the intestines [enterotoxins], general tissues [cytotoxins]) by acting extracellularly or intracellularly on the host cells. (3) A third type does not have separable A and B portions and acts by disorganizing host cell membranes. Examples include the leukocidins, hemolysins, and phospholipases. (4) A fourth type is the superantigen that acts by stimulating T cells to release cytokines.

Endotoxins

Gram-negative bacteria have lipopolysaccharide (LPS) in the outer membrane of their cell wall that, under certain circumstances, is toxic to specific hosts. This LPS

is bound to the bacterium and is released when the microorganism lyses [dissolution or destruction of cells]. Some is also released during bacterial multiplication. The toxic component of the LPS is the lipid portion, called lipid A. Lipid A is not a single macromolecular structure but appears to be a complex array of lipid residues. The lipid A component exhibits all the properties see characteristic 5 on p. 801) associated with endotoxicity and gram-negative bacteremia.

Bacterial endotoxins are:

1. Heat stable

2. Toxic only at high doses (milligram per kilogram amounts)

3. Weakly immunogenic

4. Generally similar, despite source

5. Usually capable of producing general systematic effects: fever (are pyrogenic), shock, blood coagulation, weakness, diarrhea, inflammation, intestinal hemorrhage, and fibrinolysis (enzymatic breakdown of fibrin, the major protein component of blood clots).

 Lansing M. Prescott, John P. Harley, Donald A. Klein (Eds.). (2005) Microbiology. Boston, Mass.: McGraw-Hill Higher Education.

Qi Yin

Detection of toxins by Reserved Passive Agglutination Assay

The Reserved Passive Agglutination Assay requires latex beads covered with a specific antibody, added to the sample and mixes them in a microtiter plate. If the particular antigen is present, agglutination will take place. The latex beads will form a diffuse pattern due to the reaction that take place between antigen and antibody. If the antigen is not present, antigen-antibody reaction will not occur and a tight button or smaller diffuse layer can be seen.

Qi Yin

Detection of Microbial toxin by enzyme-linked immunosorbent assay (ELISA)

The common kits available are, enzyme-linked immunosorbent assay (ELISA). Basically each different species of microorganism or toxin have at least one unique antigen. These antigens could be purified and used to produce specific antibodies.  The antigens and antibodies are useful and precise diagnostic tools. The enzyme-linked immunosorbent assay (ELISA) is a technique commonly used to detect the presence of that particular antigens or antibodies.  The direct ELISA utilizes antibodies to identify the existence of a specific antigen in a sample.
Firstly, a specific antibody will be attached onto the walls of a microtiter plate. Next, the sample will be added into the well to examine the presence of complementary antigen. If the particular antigen is present in the sample, it will attach to the antibodies on the surface of the well. The microtitler plate will be rinsed, and is able to remove any unbound antigen. Next, will be the addition of the monoclonal, modified antibody that is linked to an enzyme (enzyme conjugated antibody). The well will be rinsed again to remove any unbound antibodies. If the particular antigen is not there, the enzyme conjugated antibody will be washed away as it is unable to bind to the antigen. Lastly, the enzyme’s substrate will be added and its purpose is to create a colour change if the enzyme conjugated antibody had reacted with the substrate. No colour change represents a negative result.

Qi Yin

More about GM food and its use

The most common GM food according to the International Service for the Acquisition of Agri-biotech Applications (ISAAA) in 2008 are GM soybean, GM maize, GM cotton and lastly GM canola. Theses for ingredients are the crops that take up to 99% of the global hectarage of GM crops. Also in 2008 25 countries have been reported by the ISAAA to have been commercially cultivating GM crops. Other countries though not involved in the cultivation of such crops, do have regulatory approvals for GM crops to be imported to their county for food and feed use. Altogether since 1996 to 2008 around 670 countries have been granted the approval to either cultivate GM crops or have them imported.

With the cultivation of GM crops, cost spent on growing these crops should reduce due to the lesser use of herbicides and pesticides and also lesser lost of crops. However due to regulations and consumer’s rights, labelling is in fact mandatory in most countries which increases the cost of the GM food or ingredient. Then cost is not only needed to paste a little sticker on the product but mainly to maintain the credibility of the labelling system. Therefore due to this the cost of GM food or ingredients may in fact be more expensive than non-GM foods or ingredients.

Lina

Contreversial Issues of GM Foods #4 - Religious and Ethical Concerns

GM foods are mainly seen as unnatural foods due to their production by the transferring of genes from one species to another. This could lead to objections of the consumption of animal genes in plants and vice versa. Using genes from animals in plant foods may pose ethical, philosophical or religious problems. For example vegetarians are concerned about consuming vegetables that contain animal genes which will then violate their religious beliefs. Another example eating traces of genetic material from pork could be a problem for certain religious or cultural groups such as the Muslims.

Lina

Contreversial Issues of GM Foods #3 - Food Safety

The non GM foods that contain allergens, pesticide residues and microbiological contaminants used for the extraction of their genes to create GM food can eventually lead to contaminated GM product. There is also the development of resistance to antibiotics. If any of the genes encoded for antibiotic resistance enters the food chain and is eaten by consumers, there is a chance that this can affect the gut micro flora and would adversely affect the efficacy of antibiotics administered orally.

 Lina

Contreversial Issues of GM Foods #2 - Consumer's Rights

Consumer’s right is the right given to consumers to have access to various detailed information regarding GM food so that they would be able to make informed choices upon purchasing of the GM product. However, the problem is that most consumers are denied this access to information needed to make decision on GM foods. This is because of their limited access to education such as in developing countries. In Singapore, a body that watches out for consumer’s right is the Consumers Association of Singapore.

In order to provide customers with their rights, GM foods should be properly labelled.

 

Lina

Contreversial Issues of GM Foods #1 - Environmental Concerns

One of the risks is the risk of GM foods to the environment. With the production of GM crops that reduces the use of herbicides due to their resistance to certain herbicides, there is an increase in the growth of weeds that are now resistant to the herbicides too. This can cause many future environmental problems for farmers in the future such as increase use of herbicides which could eventually lead to water and soil contamination. 

Besides this, another disadvantage that has arisen due to GM foods is pesticide resistant insects. Insects would overcome whatever pesticides used and in this case it is the BT toxins produced by GM crops.

It seems that large scale growth of GM crops can affect the balance of biodiversity, wildlife and also the environment as it may alter the whole life cycles of thing, such as the unintentional poisoning of species of insects that are ecologically beneficial to the plants. Not only that, animals that depend on this insects as food would also be affected this could result in major loss of fauna biodiversity. 

 Lina

Benefit of GM Foods #3 - Better Nutritional Value

One other benefit of the growth of GM crops is the production of foods with better nutritional value. This is also known as nutritional enhancement. With the injecting of certain nutrient genes from other sources into foods commonly eaten, this can improve the nutritional intake and status of developing countries. Also now crops have better resistance to diseases as microorganisms such fungi and bacteria are common causes of plant disease.

Lina