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Microorganisms Can Cause Food Poisoning Biology Essay

Microorganisms can cause food poisoning in different ways and one of the ways that food can be cross contaminated is through food contact surfaces. The survival of bacteria on food contact surfaces increases the risk of cross-contamination of these microorganisms to food (Cesare, et al, 2003). The risk has been considered to be lowered when the surfaces are dry because bacterial growth would be reduced. However, some non-spore-forming bacteria might be able to stand with the dry conditions on surfaces for a long period of time (Lindsay and Von Holy, 1999). Cleaning of food preparation surface is difficult because many microorganisms can adhere to these surfaces and may concentrate in places that remain moist (Kusumaningrum et al, 2003).

Microbiological risk assessment can be described s a structured process that is used to determine the inherent risks associated with microbiological hazards be it physical, chemical or biological in food (Forsythe, 2007). Its goal is to characterize the likelihood as well as the nature of harm that results from human exposure to agents in food and uses both quantitative and qualitative data. In the microbiological risk assessment four distinct steps must be taken and these include hazard identification that involves the collection, organization and analysis or evaluation of data collected concerning a given pathogen (WHO, 2009). After identifying the hazard, it is characterized where the relationship between effects and the pathogen is identified. The third step is exposure analysis and assessment that is concerned with determining how much of a microorganism has been ingested in a food serving (Brown, 2002). Lastly, microbiological risk assessment involves risk characterization that involves the evaluation of information related to the risk. The aim of the microbial risk assessment is to provide useful and organized information for policy and decision makers to come up with interventions that can enhance the improvement of public health and minimize the occurrence of food borne diseases (WHO, 2009).

Food Cross Contamination

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Have you ever suffered from food poisoning? A lot of people have experienced food poisoning in their lives but not yet successfully determined the causes. According to Alfaro, (2012) one of the main causes of food poisoning is cross contamination. This happens when bacteria or other microorganisms are spread from one food item to another from unwashed hands, surfaces, knives, kitchen utensils and any other items. Identifying the cause is the only way to help in prevention of incidences of food poisoning. This paper discusses how cross contamination occurs and the various strategies employed in preventing it.

Microorganisms are very small diseases carrying that are not visible by the naked eye. This makes it hard for individuals to notice whether they are carrying them, their presence or when they have spread to the food. There are numerous ways that can lead to accumulation of bacteria; not washing hands after visiting the toilet and handling any dirty equipment. Dirty households also harbour germs and bacteria and eating food that is not well prepared or fruits that are not washed. Preventing food cross contamination will ensure good health since it will keep food poisoning at bay. This means that an individual will be healthy and able to carry out the day to day activities (Alfaro, 2012).

Preventing food cross contamination requires practicing food safety habits that are easy to learn and follow. Human negligence heavily influences the causes of food poisoning, this is because a lot of people are very ignorant or are not aware of these very simple practices. Some of these practices should be followed when shopping, storing, preparing and serving food. According to Minnesota Department of Health, (2012) they include:

Shopping for food: The different food products or types should be separated when shopping. For instance, raw beef should be separated from the bread or milk packets.

Storing food: Foods like raw beef, sea foods and poultry should be refrigerated in plastic bags that can be sealed so as to prevent their raw juices, which carry bacteria, from dripping into other foods. Food like eggs should be refrigerated immediately after purchase.

Preparing food: A cook should ensure that he/ she prepares food in a very clean environment so as to prevent the spread of germs and bacteria. The cook should first clean the cooking surface and utensils before preparing food, then the hands. A clean cutting board and cutting utensils should be used when preparing the food to stop the spread of microorganisms. If any food needs to be marinated, this should be done in the fridge but not in any cooking surface. All the vegetables and fruits need to washed and rinsed properly with enough water before cooking.

Serving food: Clean plates should be used when serving food. Cutting boards that had been used to cut raw meat should never be used for serving food as they may still be carrying bacteria.

To successfully stop the spread of microorganisms from one food item to another or a surface, food should be handled properly from the point of buying, storing and preparing. Where appropriate the food needs to cleaned and rinsed properly before preparing plus the cook needs to clean his/her hands. The food should be cooked properly so as to kill the bacteria present in the food (Minnesota Department of Health, 2012). This will ensure that any person that consumes the food is free from food poisoning.

Microbial Survival on Food Contact Surface

Microbial food poisoning causes a lot of suffering and financial loss all over the world. As a result of this it has become significantly important to identify the factors that increase the risk of food poisoning from harmful microbial (Kusumaningrum et. al, 2003). The question to bear in mind is how microorganisms survive on food contact surfaces such as stainless steel and other factors that affect this survival. This paper aims at understanding on the mechanisms of microbial adhesion on contact surfaces such as steel so as to come up with relevant and effective strategies for control, and reduce the level of suffering on human being as well as financial losses incurred when seeking treatment (Baranyi & Tamplin, 2004). This paper shows that there is a relationship between the characteristics of the microorganisms and environment surrounding them which affect their survival and multiplication on surfaces (Cohen, 2004).

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The major source of potential harmful pathogens in the home environment as well as other food processing environments have been seen to the contaminated water, food, air, infected persons, pets and in some cases, insects  (Kusumaningrum et. al, 2003). Under conditions that are favorable such as temperature, relative humidity and pH, microorganisms are able to survive and in addition to this, replicate to a large extent (Cohen, 2004). This replication and survival increases the risk of contamination. In the kitchen food borne infection may arise as a result of incorrect food storage especially with respect to temperature conditions, poor or inadequate controlled cooking procedures and methods that may encourage the persistence of microorganisms in food stuffs, as well as contamination of both raw and cooked food prior to consumption (Kusumaningrum et. al, 2003). Contamination can also be passed on from kitchen equipment including utensils when contacting food. This often occurs in cases where these equipment, utensils as well as kitchen surfaces are not properly cleaned and sanitized before coming into contact with food (Cohen, 2004).

The ability of microorganisms on the food contact surfaces greatly compromises the hygienic levels of these very surfaces. If the hygienic standards are compromised such as cleaning kitchen surfaces and utensils with no soap and disinfectant will create a dirty environment that will encourage the growth and spread of the disease causing pathogens (Baranyi & Tamplin, 2004). Surface physiochemical characteristics of the pathogen and also the materials such as roughness and hydrophobicity are determinant during the very initial stages .The pathogenic adhesion to contact surfaces is also determined by the growth stage of the microorganisms as well as the nutrient availability in the surrounding medium, temperature and pH of the medium as has been mentioned before, ionic concentration as well as the cell strictures which is inclusive of Extracellular Polymeric Substances (EPS). Roughness and hydrophobicity of contact surfaces can be easily altered. The rate of absorption of pathogens on surfaces differs according to the material that the contact surface is made of. Research on the prevalence of microorganisms on surfaces has indicated that the higher the value of roughness, the greater the adhesion probability.  However, in the case of Listeria monocytogenes, however this is not entirely true. In other words, the pathogen's adhesion to a biotic contact surface is not directly and absolutely dependent to the substratum roughness and hydrophobicity (Cohen, 2004).

Retention of microorganisms on food contact surfaces such as stainless steel raises the chances of cross contamination of these microorganisms to food. When the surfaces are dry, the risk has been seen to be lower. A Partial explanation of this is that bacterial growth and survival would be reduced in dry environments. It is of significant importance to mention that there is some non-spore forming microorganisms that may withstand dry conditions on stainless steel surfaces, or any other container surface for that matter for extensive time periods (Baranyi & Tamplin, 2004).

Cells adherence to such container surfaces like steel are not easily removed by normal cleaning procedures (Kusumaningrum et. al, 2003). It is also of significant importance to mention that for impervious surfaces like glass, stainless steel, polystyrene and ceramic, the surface type does not have so much effect on the survival of the microorganisms, but the nature of the suspension fluid in which the cells are dried (Baranyi & Tamplin, 2004).

The significance of contaminated surfaces in relation to potential transmission of microorganisms and pathogens to food substances is quite apparent in catering, food processing and domestic environments. Pathogen exposure on steel surfaces may occur either through direct contact with objects that are already contaminated or indirectly through airborne particles (Baranyi & Tamplin, 2004). Some microorganisms have been seen to have a tendency to attach themselves to surfaces as their primary form of survival in manmade ecosystems and nature. Examples of pathogens that are able to survive on sponges, clothes, hands, currency and utensils for hours or even days after the initial contact with the microorganism include Staphylococcus aureus, Escherichia coli, and Salmonella spp   (Kusumaningrum et. al, 2003). The risk of food-borne contamination that leads to infection is often dependent upon two major factors which are the probability of its transfer to the food that people consume and secondly, the level of contamination on the surfaces such as stainless steel. Studies show that Campylobacter jejuni, Staphylococcus aureus as well as Salmonella enteritidis are able to remain viable on the surface of stainless steel containers for hours and in some cases, days on end (Cohen, 2004). Their degrees of survival in such circumstances heavily rely on their initial numbers. These pathogens would then be transferred from the containers (steel surfaces as well as other surfaces) to food substances that human beings consume. Such surfaces may include kitchen taps, refrigerators, kettles, blenders, knives and surfaces. It has been found out that even after typical cleaning procedures have been undertaken contamination risks still remain, considering the fact that the pathogens have with time developed high resistant mechanisms and adaptive features that make them survive even in harsh environments (Kusumaningrum et. al, 2003).

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There are factors that are responsible for the adhesion of microorganisms and other pathogenic bacteria in food environments (Cohen, 2004). Microorganisms are seen to display very high strain variability when it comes to adhesion ability to contact surfaces including steel. It is presumed that in addition to the physical characteristics of the medium in question, the microorganisms possess other intrinsic factors such as adhesions cell envelopes, extracellular polymers and cell wall proteins that come into play in the adhesion of these pathogens onto contact surfaces. In light of all this, there should be development of more effective disinfection strategies to improve the degree of hygiene in food processing and preparation environments to mitigate the risk of food contamination and food borne diseases (Baranyi & Tamplin, 2004).

Pathogenic bacteria survival on food contact surface

Salmonella spp.

Most of the Salmonella spp are pathogenic bacteria which can be classified as human pathogen. Foods can become contaminated with Salmonella spp when animal manure or human fecal material is used to fertilize the fields. There are more than 2,000 strains of Salmonella. All strains are pathogenic to humans but Salmonella enterica, serovars, Typhimurium and Enteritidis are the most type of Salmonella that associated with human illness (Jay, 1996). Salmonella spp is rod in shape, motile bacterium, Gram-negative enterobacteria, catalase positive and oxidase negative. The optimal growth of Salmonella spp. on or in food with a neutral pH of 6 to 7 and will multiply in food down occurs around pH 4.05. Raw meat and poultry, eggs and egg products, shellfish, processed meat, and dried milk and cheese made from unpasteurized milk have been common sources of this microorganism. The clinical poisoning symptoms of Salmonellosis are fever, diarrhoea, abdominal pain, nausea and sometimes vomiting. Symptoms usually begin about 6 to 48 hours after ingestion of the sufficient numbers of microorganisms (Adams and Moss, 2010).

Listeria monocytogenes

Listeria monocytogenes is typically a food-borne organism and it is the important human pathogen within the genus Listeria. Listeria monocytogenes are found widely in the environment and can be isolated from soil, water and decaying vegetation. The common sources of this microorganism are dairy product such as raw and pasteurized milk and soft cheese (Adams and Moss, 2010). Listeria monocytogenes is a gram positive, nonsporeforming, oxidase negative, catalase positive, facultative anaerobic rod in shape which grows between - 0.4 and 50oC. These bacteria primarily cause listeriosis which manifestations found essentially among pregnant women, their fetuses, the elderly and immunocompromised persons, with symptoms of abortion, neonatal death, meningitis and septicaemia (Ryser and Marth, 1999).

Campylobacter spp

Campylobacter is well known as the most common reason of bacterial foodborne diarrheal disease all over the world. Campylobacter spp. is a non-spore forming, oxidase-positive, microaerophilic and Gram negative rod. These organisms are carried in the intestine of wild animals and poultry (Silva et al, 2011). Campylobacter species grows at 37°C, but not below 32°C. C. coli and C. jejuni is district from other Campylobacter species by their high optimum growth temperature (42 - 45°C). Campylobacter species cannot survive pasteurization and cooking temperature and also do not grow under temperature of 30°C (Padungton & Kaneene, 2003).

Bacillus cereus

Bacillus species are gram-positive, catalase positive, oxidase positive, rod-shaped and spore-formers that require oxygen. Bacillus cereus produces two types of intoxications and these toxins cause two types of foodborne. One type is characterized by nausea and vomiting and abdominal cramps and the other type is characterized by diarrheal and abdominal cramps (Bottone, 2010).

Staphylococcus aureus

Staphylococcus aureus is a Gram-positive coccus, facultative anaerobic, non-motile and catalase positive, coagulase positive and oxidase negative. Staphylococcus aureus is able to grow in a wide variety of foods because it able to grow in a wide range of temperature, pH and sodium chloride concentration. Staph aureus food poisoning is a leading cause of gastroenteritis that results from eating contaminated food with a toxin. Food poisoning symptoms that are caused by this type of bacteria usually appear within 1 - 6 hours after consumption of contaminated food and this symptom may include nausea, diarrhea, vomiting and mild fever. Although, contamination of Staphylococcus aureus can be avoided by follow the proper way of personal hygiene while handling foods and refrigeration of raw and cooked foods (Loir et al, 2003).

Escherichia coli

Escherichia coli are the type species of the Enterobacteriaceae family. Escherichia coli are a Gram negative non-sporing rod, oxidase negative and catalase positive. These types of bacteria live in human and animal intestines and most of the strains are harmless. E. coli O157: H7 produces a toxin which causes the most food related illness in human (Adams and Moss, 2010). E. coli O157:H7 is mainly found in cows, sheep and chickens. However, food is at risk of becoming contaminated with E. coli through cross-contamination during slaughter or throughout the meat in the grinding process. The initial poisoning symptoms of Escherichia coli are abdominal pain, diarrhea and headaches (Pennington, 2010).

Indicator organisms (coliform)

Indicator organisms such as coliforms are used in assessing food to determine quality. These types of organisms have been used to indicate the presence of the intestinal pathogens as a result of direct or indirect faecal contamination. A routine examination for pathogens and their toxins are necessary whenever epidemiological or other evidence indicate that occurrence of a particular agent in a specific type of food (Hayes, 1995). 

Swab processes

The swab method is the most processes are used for microbiological examination to detect the microbial that can survive of the food processing surface. Tests using swab method was carried out on surfaces contaminated with food born pathogen in food processing area and three types of surface were studied (stainless steel, marble, and wood), with adjacent areas being sampled before and after cleaning. All surfaces were prepared in sizes of 20 x 20 cm2 for survival experiments. The swabs were rotated while in contact with the food preparation surface. After the defined area is swabbed the swab is returned to the test tube that containing a suitable diluents to dislodge the bacteria. Serial dilutions of the swab solutions were cultured onto duplicate pour plates were prepared for each dilution using nutrient agar, and a 0.1 ml amount of the swab fluid was spread on MacConkey agar and Blood agar. The plates were incubated for 24 hours at 37oC.


The aim of this project is to identify the microbial that can survive in the food processing area such as stainless steel, marble and wood even after the cleaning procedure which can cause food cross-contamination.


The objectives of this project were:

Assess the microbiological risks affecting food processing area.

Identify the presence of pathogenic microorganism in food processing area such as stainless still, marble and wood.

Evaluate the effect of the cleaning procedure on the microbial load in the food processing area.

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