Food Hygiene Essentials

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In my last article on the subject of bacteria (shigella) I described some bacterial terminology in lay man’s terms to help you to understand the scientific terminology. Today I would like to touch a little upon the subject of how we categorize bacteria. There are many species of bacteria and the have evolved in many different ways. Each has found a niche in the evolutionary ladder and they have adapted themselves to be able to live in a vast variety of different conditions. What I want to do is to go through some of the different conditions in which bacteria live and by which bacteria are categorized.

The first three categories I am going to describe relate to different temperature conditions in which bacteria can be found and by which they are categorized for having this quality.

Psicrophilic. Psicro in Greek means low. Psicrophilic bacteria are ones which prefer to function at low temperatures. Normally speaking, low temperatures means below 5 degrees Celsius. The advantage that these bacteria have by utilizing cold conditions is that there are very few other bacteria that can compete with them at this temperature. From a food hygiene perspective these are the bacteria which cause refrigerator spoilage. If you have ever notices a slightly slimy surface to food that is kept at low temperatures this sliminess can be caused by psicrophilic bacteria. Normally these are not considered to be pathogenic bacteria but if you are particularly sensitive eating food that has been affected by psychrophylic bacteria can cause mild to medium stomach upset.

Mesophilic. Mesophilic bacteria are once which prefer to perform their metabolic functions at a moderate temperature range. This means that this category of bacteria is active between temperatures of 10 degrees Celsius to 40 degrees Celsius. many processes in the food industry, particularly the cheese industry, and most fermentation processes occur within this temperature range. This is also the temperature at which the vast majority of pathogenic bacteria function and therefore this presents the need for close control of bacteria action within the cheese and fermentation industries. Mistakes in this area would definitely cost lives. It is also the temperature at which most bacteria attack our bodies.

Thermophilic. Thermophilic bacteria are bacteria which have developed the ability to operate their metabolic functions at high temperatures. Bacteria of this classification can survives in temperatures in excess of 100 degrees Celsius. Some bacteria of this classification are used in the food industry and some are found in nature. In processes of controlled rotting the development of thermophilic bacteria is undesirable because they will break the materials down too much. This can be caused in the manufacture of compost by giving too much food. By giving too much food the temperature rises, the desirable bacteria are killed as well as the worms and the thermophilic bacteria turn the entire compost heap into useless mush.

The next three categories that I would like to discuss refers to the chemical environment in which bacteria live with respect to levels of acidity. Bacteria have developed the ability to survive in a wide range of acidic or non acidic conditions. Many such bacteria by acting in different acidic or non acidic climates become desirable from an industrial point of view. Many industrial processes rely upon bacterial activity for the production of the end product. This is true of the food and non food industries. However, some conditions become the target zone of pathogenic bacteria.

Basophilic. Bacteria which thrive in a basophilic climate are bacteria which prefer to live in a base of alkali environment. The level of which depends upon the specific species of bacteria. Some pathogenic bacteria become pathogenically active in alkali environments particularly bacteria which break down the proteins in meat and fish. They have developed this ability because ammonia is produced in decomposing flesh which is an alkali. In saying that many industrial processes are dependant upon basophilic bacteria.

Normophilic. Normophilic bacteria are ones which perform their metabolic functions at a neutral PH level or there about. Bacteria wich are active within this climate include many types of pathogens. You may remember that we have already talked about the fact that most pathogenic bacteria cannot remain active when acidity levels are raised and PH is lowered. We can therefore state that a great many pathogens function in mesophilic, normophilic conditions. If you think about it this is logical because the acidic conditions within a body are more of less neutral. The bacteria have become suited to the environment in which they are designed to exist.

Acidophile. Bacteria which have developed to survive within an acidophile environment are ones which perform their metabolic function in a strong acid environment. Again, bacteria such as these have evolved in nature to continue the degradation of matter when conditions become too acidic for normophilc bacteria. This category of bacteria is also used extensively throughout industry for a great many purposes. Not many bacteria within this group are pathogens.

The third category of bacteria about which I would like to discuss with you refers to how the bacteria relates to the use of oxygen. by this I mean can the bacteria survive with or without the presence of oxygen. Most pathogenic bacteria exist in an anaerobic environment or can change from an aerobic environment to an anaerobic one depending on the environment in which it is trapped.

Obligate aerobic. An obligate aerobic bacteria is one which must have the presence of free oxygen around it. Many industrial processes rely upon bacteria of this category.

Obligate anaerobic. Obligate anaerobic bacteria are bacteria which for the most part cannot tolerate an oxygen rich environment and perform all their metabolic functions through fermentation. Some bacteria from this category are pathogens.

Facultative anaerobic bacteria are ones which can switch from an oxygen rich environment to an environment devoid of oxygen and back again as the need arises. Many pathogenic bacteria belong to this category. By belonging to this niche facultative anaerobic bacteria have ensured the ability to survive even when conditions change.

Now that you have this information look up different bacterial species on the Internet and see if you can distinguish pathogenic bacteria in several of the different categories stated here.

Most of us in the western world think of dysentery or “Shigella” as a disease of the summer months. Have you ever thought why? Firstly, is it true? Is dysentery a disease of the summer months?

Ok, now I’m going to confuse you a little more because the answer is yes and no. No because dysentery is not only a disease of the summer months and yes because it is mostly proliferated throughout the western world during the summer months, but why?

Dysentery is a disease that is spread via contaminated food and water. A lot of our summer produce is picked in warmer regions of the world where the water sourses osed to irrigate and to wash produce before packing may not be of the best quality and may contain many contaminants. In addition, workers who pick and pack produce may be carriers of certain types of dysentery causing bacteria.

Another major cause of dysentery during summer months for westerner’s is travelling to warmer climates. Whereas locals in many areas of the world may have developed immunities to many bacterial and protozoic species, all of these may be new for us. By being tempted to eat as the locals do we are often exposing ourselves to sources of food and water contamination.

Dysentery is caused by several major causes lets have a look at a couple of them.

Bacterial Dysentery. Bacterial dysentery is caused primarily by the bacterium Shigella dysenteriae. The disease it causes is called shigellosis. This bacterium is a gram negative, non motile, rod shaped, non spore forming facultative anaerobic species that produces a toxin called shiga toxin which is what causes the reaction which we know as dysentery.

Allow me to translate that mouthful of scientific jargon for you. Firstly Gram testing is a form of bacterial staining devised by a man called Mr. Gram which adheres to proteinous outer shells but not to fatty shells. As the vast majority of gram negative bacteria have a Lipopolysaccharide outer shell the dye will not stick, therefore the bacteria are classified as gram negative. Non motile means that they have no mechanism by which they can propel themselves within the medium they are in. Non spore forming means that the bacterium does not have the capability of reducing it’s structural size to permit it to survive periods when conditions are not suitable for bacterial growth, hibernating in short. Facultative anaerobic means that it can live in an oxygen rich environment or in one which is void of oxygen. It is usually when in the anaerobic phase that facultative bacteria will produce their toxins.

The symptoms of dysentery are high fever, vomiting, diarrhea, severe dehydration. Shega toxin is a potentially deadly toxin. Patients with dysentery may experience projectile diarrhoea and projectile vomiting simmultaneously. This is a very unpleasant condition which I have experienced personally. With this disease fluid intake is vital even if that means via infusion and a strict hygiene regeme is vital to rule out the possibility of re infection. Recovery usually takes anything between one to two weeks but in many areas of the world high mortality is common due to improper conditions with which to treat this condition. Mortality rate is particularly high in children and the elderly.

Amoebic Dysentery. This form of dysentery is also spread by the ingestion of contaminated food and water. It is caused by a cyst forming amoebic species. The disease is called intestinal amoebiasis.

This disease is most common in the developing world but not only. One case was reported in St. Petersburg which is quite close to the artic circle. Both bacterial and Ameobic Dysentery are prevelant in developing countries and often get confused. Most cases of travellers dysentary are in fact bacterial or viral in origin. Amoebic dysentery is a parasitical disorder and will not be effected by antibiotics. This form of dysentery may cause infection and enlargening of the liver and blood in stools. Other symptoms remain very much the same as in bacterial dysentery. Metronidazole is the preferred treatment for Amoebic Dysentaty.

Note. Not all species of amoebae are cyst forming.