Moist heat kills all of the following except: September 2009

Ans. A: Coxiella burnetti Moist heat is used in the autoclave, a high-pressure device in which steam is superheated. The autoclave is the standard instrument for preparing microbial media and for sterilizing instruments such as syringes, hospital garb, blankets, intravenous solutions, and myriad other items Most vegetating microorganisms are killed within two or three minutes, but over two or three hours may be required for destruction of bacterial spores. In moist heat, the microbial proteins undergo denaturation, a process in which the three-dimensional form of the protein reves to a two-dimensional form, and the protein breaks down. Coxialla burnetti: It can also present in a spore-like phase. The spores are resistant to heat, desiccation and multiple disinfectants, which allow the organism to remain ble for prolonged periods of time. For example, the bacterium can survive in cold temperatures in stored meat for 1 month and in skimmed milk at room temperature for 40 months.