Epidemiology and Public Health Microbiology Practical Report : Scenario - Nursing Assignment

Internal Code : MAS4445

Nursing Assignment

Scenario 1: The food poisoning outbreak was a result from contaminated milk used in the custard due to Bacillus cereus spores surviving through pasteurisation (Kotiranta, Lounatmaa & Haapasalo 2000). This has been demonstrated in a Japanese outbreak of Bacillus cereus in 1991 (Lund, Baird-Parker & Gould 1999). Further cooking methods were insufficient to kill the spores or vegetative organisms. To confirm this, a sample of the milk/dairy products used in the making of the rice pudding would need to be analysed separately. It is also likely that inadequate storage conditions contributed to the growth of the organisms to an extent where illness is observed (AIFST Inc. NSW Branch, Food Microbiology Group 2003). Although B. Cereus is common in milk, outbreaks involving contaminated milk are not frequent and are less likely than scenario two due to the low numbers of organisms present (Fratamico, Bhunia &; Smith 2005). Scenario 2: The food poisoning outbreak was a result of rice contaminated with Bacillus cereus spores or vegetative organisms which survived through the cooking process and then grew to large numbers through incorrect storage methods (Kotiranta, Lounatmaa & Haapasalo 2000). There are two primary contributory factors in this scenario. Firstly due to the volume of rice being cooked it is likely that there was not a uniform heat distribution in the cooking pot and is likely that some parts of the rice never reached a high enough temperature to kill both Bacillus cereus organisms and its spores. Secondly, the slow cooling process facilitates rapid B. cereus growth (AIFST Inc. NSW Branch, Food Microbiology Group 2003). B. cereus is a food borne illness ubiquitous in nature and as a result preventative measures involves good food handling methods. Firstly, it is important to keep cold prepared food under refrigeration (below 5°C) and hot foods above 60°C. This is because Bacillus cereus tends to grow best between 30 and 37 degrees Celsius but can grow in environments as low as 5°C and as high as 55°C (Fratamico, P.M., Bhunia, A.K. & Smith, J. L. 2005). Thus keeping the prepared food in the upper and low extremes of this range greatly reduces the likelihood of Bacillus cereus related infections. Furthermore maximal toxin production is at room temperature (20°C -25°C) so if food was to be left out there is an increased likelihood that a future eater would become sick. Secondly, food should not be prepared too far in advance and basic hygiene and compliance with the Australian and New Zealand Food Standards Code (Australian Government 2011) be upheld. There is a strong likelihood of errors involved in this report in regards to experimental procedure. More specifically: incorrect aseptic techniques leading to contamination, incorrect observations and poor laboratory skills (including gram staining). However the pooling of class data allowed for a better validation of results. The use of questionnaires can provide incorrect information as the response is generated by that person alone. Information provided by individual medical examinations could help provide more accurate and substantiated information, however, this is not practical for large numbers of cases. Laboratory testing indicates that Bacillus cereus is the causative agent in this food poising outbreak. Although presumptive identification of B. cereus on PEMBA and then further lipid globule testing meets the Australian standard for identification of B. cereus (AIFST Inc. NSW branch Food Microbiology Group 2003), further confirmatory tests including immunological assays, strain typing and antibiotic susceptibility tests could be performed in the future for increased validity of results (Kotiranta, Lounatmaa & Haapasalo 2000).