Coastline Community College
Bacillus cereus is a Gram-positive, facultative aerobic, spore-forming, rod-shaped bacterium that is widely distributed among the environment.
The reason for identification of unknown bacteria was to help students recognize different bacteria through different biochemical tests and characteristics. This is important in the medical field because identification of unknown bacteria can help treat a patient by knowing the contributing source of a disease. Also, knowledge of different bacteria helped others make antibiotics that are used today.
Bacillus cereus, a commonly occurring pathogen which can survive in remarkably hostile conditions, is typically found in soil. B. cereus has been recognized as an agent of food poisoning since 1955. The natural environmental reservoir for B. cereus consists of decaying organic matter, fresh and marine waters, vegetables and fomites, and the intestinal tract of invertebrates, from which soil and food products may become contaminated, leading to the transient colonization of the human intestine. Illness associated with B. cereus can occur when heat-resistant B. cereus endospores survive cooking. If the food is then inadequately refrigerated or held for extended periods at improper temperatures the endospores can germinate and multiply. Once the spores germinate, the vegetative cells can multiply and produce illness causing enterotoxins. Bacillus cereus is known to cause two distinctly different types of food-borne illness. The first type of illness, referred to as the Rapid-onset (Emetic) Vomiting-type, is characterized by nausea and vomiting. The incubation period ranges from 1 to 6 hours. Both the symptomology and incubation period mirror those of Staphylococcus aureus. The second type of illness, generally referred to as the Slow-onset Diarrheal-type, is characterized by diarrhea and
References: McCarthy, A.L., Stevens, S.K., & Weber, R.A. Bacillus Cereus Fact Sheet (2013) Food Safety Counsel. Retrieved from http://www.foodsafetycounsel.com/food-safety-law/common-food-borne-pathogens/bacillus-cereus/ Todar, K Dichotomous Key, Coastline Community College Microbiology Lab. Personal photograph by author. 2013. EMB Positive and Negative results. Digital image. Flickriver.com. Flickriver Viewer Software, 2007. Web. 3 Nov. 2013. An endospore stain of Bacillus cereus using malachite green. Digital image. Academic.missouriwestern.edu. N.p., n.d. Web. 3 Nov. 2013. Hahn, Brittany. Phenyl Ethyl Alcohol agar. Digital image. Studyblue.com. STUDYBLUE INC., 22 Apr. 2013. Web. 3 Nov. 2013. Reynolds, Jackie. Selective and differential media. Digital image. Www.microbelibrary.org). Kern Community College District, 12 Sept. 2011. Web. 3 Nov. 2013. Rose, Scott. B. cereus simple stain. Digital image. Napa Valley College. The Western Association of Schools and Colleges Designated Hispanic Serving Institution (HSI), US Department of Education, n.d. Web. 5 Nov. 2013. Rose, Scott. Gram Stain B. cereus. Digital image. Napa Valley College. The Western Association of Schools and Colleges Designated Hispanic Serving Institution (HSI), US Department of Education, n.d. Web. 3 Nov. 2013.