Analysis Of The Relatedness Of Cooked Food Cold Storage And Bacteria Detection And Study On The Effects Of Microwave Sterilization On Food

Food-borne disease is the infected and toxic disease that is caused by the food eaten in human body. It is a worldwide important public health problem. Food poisoning is the most typical foodborne disease. Bacterial food poisoning is the most among all kinds of food poisoning. In China, the studies about antimicrobial resistant of pathogens in food were much less compared with the clinical pathogens and epidemiology.It is necessary to study the antimicrobial resistance of pathogen in food. PFGE typing can reflect the tested bacteria epidemiological relevance effectively.Microwave on food sterilization application. In daily life, people often store cooked food in the refrigerator and heat it in the microwave oven before eating. It is important to study these issues that the effectively refrigerating time of cooked food in the refrigerator, antimicrobial susceptibility, strain-relatedness of the same bacteria, time-effect of household microwave oven sterilization on cooked food for the prevention of the occurrence of food poisoning and effective treatment.PART ONE Relatedness of cooked food cold storage and bacteria detectionObject:1.To understand the cooked food in the refrigerator had bacterial growth time;2.To understand the antimicrobial susceptibility of bacteria recoverd from refrigerated food;3.To understand the strain-relatedness of the same bacteria.Method:1.A total of60hot food were sampled from the canteen of three level of first-class hospital in tianjin from June to August2010～2011.Each is about300g.In a closed high pressure sterilization lunch box.Then to separate bateria after cooked food storage in the refrigerator for0、24、48、72hours.Bacteria isolation and aerobic plate count detection refer to food microbiological examination (GB4789-2010).Identification of bacteria was by common bacterial identification manual.2.Antimicrobial susceptibility of levofloxacin,ciprofloxacin,floxacin, cefepime,ceftazidime, amikacin, piperacillin, cefotaxime, cefoperazone, ceftriaxone, Piperacillin/tazobactam, gentamycin for Gram-negative bacteria and penicilin, oxzacilin,ampicilin,cefazolin,ciprofloxacin,gatifloxacin,chloramphenicol,lincomycin, gentamycin, ceftriaxone, imipenem, erythromycin for Gram-positive bacteria were determined by Kirby-Bauer method.3. Pulsed Field Gel Electrophoresis(PFGE) analysis:The15strains of Escherichia coli and7strains of Proteus vulgaris were genotyped by PFGE with XbaI、SfiI-digested chromosomal DNA, respectively. Result:1.In indoor environment, the average temperature of26degrees, the average relative humidity of75%;under the condition of cooked food refrigerator,16(26.67%)、17(28.33%)、17(28.33%)、10(16.67%) cooked food were separated bacteria after storage in the refrigerator for0、24、48and72hours, respectively.7West Hu flesh(100%)、eggplant flesh(100%)、moo Shu pork(87.50%)、celery meat(87.50%) isolate bacteria in the frozen24hours, respectively.The predominant bateria:Enterobacteriaceae (63.33%); Aureus(11.67%), Micrococcus(10.00%), Pseudomonas(8.33%) and Bacillus subtilis(6.67%) are minor. Aerobic plate counts0.32×105～12.00×105cfu/g.31food (51.67%) exceeded GB2726-2005standard for cooked meat products shall(subject to less than8.0×104cfu/g).2.Drug sensitivity: Resistance rate of15strains of Escherichia coli to levofloxacin, ciprofloxacin, floxacin, amikacin, cefoperazone, gentamycin werel3.33%、13.33%、13.33%6.67%、6.67%、13.33%, respectively.Resistance rate of8strains of Proteus vulgaris to gentamycin is12.50%.3.15strains of Escherichia coli could be falled into14types, each line has9～18belt type, the similarity coefficient is21.10%～91.20%;8strains of Proteus vulgaris could be falled into7types, each line has14～19belt type, the similarity coefficient is34.50%～100%.Conclusions:Bacteria will all grow after the cooked food in the refrigerator for72hours and resistant to antibiotic in lower level.PFGE display strains showed a greater genetic diwersity. PART TWO Time-effect of household microwave oven sterilization on cooked foodObject:To understand time-effect of household microwave oven sterilization on cooked food. Method:To heat cooked food of300g with microwave oven, then isolation and culture of bateria. Result:Heating for1and2minutes, cooked food had bateria growth. heating for3mnutes, a temperature of75degree, cooked food had no bacteria growth. Conclusion:Household microwave oven sterilize on300g cooked food effectively for3minutes, temperature reaches75degree.