Prevention and Diagnosis of Bacillus Ceseus - Term Paper Example

Introduction Bacillus cereus is a type of prokaryote that has been in existence in the environment for millions of years but cannot be seen from the naked eyes. Their existence can be traced back through the study of fossils. They are found to have strong resistance towards physical and chemical conditions that ‘enable them to survive or thrive in harsh environments, ranging from desert sands and hot springs to Arctic soils and from fresh waters to marine sediments’ (microbiologybytes.com). Predominantly classified as bacteria, Bacillus cereus is found to contaminate food items and raw food, causing food poisoning amongst human-beings. Since they are able to adapt to wide ranging climate conditions and resistant to factors like heat, radiation, under-sub-zero conditions, disinfectants, they are difficult to get rid off easily through common medicine. The bacteria are transmitted through untreated water, contaminated food and unhygienic living conditions which are most suited for the growth of these harmful bacteria. Taxonomy Kingdom: Bacteria Phylum: Firmicutes Class: Bacilli Order: Bacillales Family: Bacillaceae Genus: Bacillus Species: cereus (Todar, 2004) Cell type Bacillus cereus is a unicelullar micro organism that does not have a well defined cell wall. They are 1 µm wide, 5-10 µm long rod like microbes that have endospores with aerobic or anaerobic characteristics and commonly arranged singly or in short chains. They have photosynthesis pigments that provide them with unique color and endow them with features of plants, whereby, under microscope, they appear as refractile objects. The endospore features help them to survive extreme conditions. The tough outer covering of spores is made up of keratin which is resistant to heat and chemicals. Under spore staining procedures, they are observed as green spores differentiated with pink vegetative cells. Bacillus cereus spore stain (Todar, 2004) Special Characteristics 1. They are gram positive. The gram stain features of the bacteria has become useful index for developing anti-biotic drugs that helps to identify and isolate the harmful bacteria and make it ineffective. 2. They are motile. 3. They have beta haemolytic activity and have non rhizoid growth. 4. They are toxic and produce one emetic toxin (ETE) and three different enterotoxins: HBL, Nhe and EntK, two out of which are responsible for causing food poisoning (Todar, 2004). They contaminate by making holes in the membranes. 5. They have asexual type of reproduction by binary fission or budding. They have horizontal gene transfer because the cells replicate and divide themselves, thus producing exact copy of them. Relevance to society They are highly relevant to society because of their prevalent and harmful presence in the atmosphere. They can be found in untreated water, air, soil and decaying food items. Their toxic producing property is responsible for causing common food poisoning. Also the fact that it can be found in so many different types of food items, makes it highly relevant for human society. They are also known to cause other diseases of eyes and skin infection vis-à-vis severe keratitis, endophtalmitis, panophtalmitis and infection of wounds. Food poisoning Outbreaks of food-borne illness have been associated with boiled and cooked rice, cooked meats, and cooked vegetables (Harmon, Goepfert and Bennett, 1992). They are mostly responsible for causing two types of food poisoning: emetic syndrome or vomiting; and diarrhoeal infection. Emetic syndrome is followed my nausea and vomiting. The symptoms normally appear after 1-6 hours after consumption of contaminated food items which have been kept at varying temperature. The food items, which are quick fried after being kept at ambivalent temperature, provide facilitating environment to the bacteria to germinate and infect the food items. The emetic syndrome is produced by toxin called cereulide that is found only in emetic strain. It is normally cured within 24 hours. Rice is found to be the most prevalent food that causes this infection but cheese, potato, pasta, pudding, pastries, salads etc. are also associated with this infection. Diarrhoeal infection is characterized by abdominal pain followed by watery diarrhea within 8 to 16 hours of consumption of improperly cooked food. The sickness is not serious and symptoms normally persist for about 24 hours. The most commonly food items associated with this type of infection are meat, fish, vegetables and milk where these bacteria find the most conducive environment for rapid multiplication. It is also known as long incubation type of B. cereus food poisoning. Diagnosis The diagnosis of food poisoning, caused due to either type of bacterial infection can be done in three ways: isolation of strains of the same serotype from the left-over food and vomitus of the patient; (2) isolation of large numbers of a B. cereus serotype from the suspect food or vomitus of the patient; or (3) isolation of B. cereus from suspect foods and determining their enterotoxigenicity by serological or biological tests (fda.gov). But normally when the symptoms occur almost immediately after food consumption, the presence of B. cereus toxin is assumed to cause the infection. Holbrook and Anderson described a highly selective and diagnostic medium (PEMBA) for the isolation and determination of Bacillus cereus from food (1980). Prevention 1. The food should be properly cooked at 60°C and above and not heated again and again. 2. The food should not be kept at room temperature for extended period of time but refrigerated at 7°C and below after 1-2 hours of cooking and reheated only once. 3. Hygienic conditions of cooking should be adopted and requisite precautions need to be taken so that cooked food does not come in contact with the contaminated food or raw meat etc. 4. Since storing temperature is critical factor for germination of these bacteria, especial precaution need to be taken at hospital canteen, take away meal joints and restaurant where the welfare of a large number of public is involved. 5. Slow cooking at low heat should be avoided. The effect of heat on the number of viable cells is represented by the D-value (i.e. the time in minutes at a given temperature to achieve a 90% reduction in the number of viable cells). D-values for B. cereus are presented in the Table 2: Table 1: D-values for B. cereus (at 100oC) Food type D-value (min) for B. cereus at 100oC Pumpkin pie 40 Distilled H20 5.5 Rice broth 4.2 – 6.3 * ICMSF 1996 provides an extensive list of D-Values for B. cereus under different conditions and food types. Conclusion It can be concluded that study of bacteria is extremely critical for medical science. While few of them are extremely important for various functions of other living organisms, some may also prove dangerous to the human life. The various characteristic and distinguishing features vis-à-vis morphology, gram stain, motility and physiological features help the scientists to develop antibiotics and drugs that facilitate in controlling the bacterial infections. Reference Bacillus cereus. Available from: [Accessed 19 September, 2009]. FDA. Foodborne Pathogenic Microorganisms. Available from: [Accessed 19 September, 2009]. Holbrook and Anderson. 1980. Can. J. Microbiol. 26:753-759. 1 Harmon, S. M., J. M. Goepfert, and R. W. Bennett. (1992). Bacillus cereus, p. 593-604. In C. Vanderzant, and D. F. Splittstoesser (eds.). Compendium of methods for the microbiological examination of foods, 3rd ed. American Public Health Association, Washington, D.C. International Commission on Microbiological Specifications for Foods. 1996.bacillus cereus. 20-35. In Micro-Organisms in Foods. 5. Characteristics of Microbial Pathogens. Roberts, T.A., Baird Parker, A.C. and Tompkin, R.B. eds. Published by Blackie Academic & Professional, London. Todar, Kenneth. (2004). Bacillus cereus Food Poisoning. Available from: [Accessed 19 September, 2009]. Student Name: ______________________________________ Student Number: ______________________________________ Topic/feature Comments Score Introduction Clearly states what the assignment is about and what will be presented. /3 The taxonomy Accurate description of the taxonomy and any special changes or features about the organisms clearly described /6 Cell Type Accurate description of cell type and any special features eg. prokaryotic, eukaryotic, arhaeal, fungal, bacterial etc. If the organism is a bacterium, is it Gram positive or Gram negative. Include a description of any special features about the cells. /6 Relevance to society or industry As requested in assignment question. /6 Spelling and Grammar Accurate and correct /3 Referencing Up to date and appropriate references used. Accurate referencing used in text and in Reference list. /4 Presentation Neat, logical presentation of work /2 Any special consideration on mark? Total Mark /30 Read More