Question

2. What other ways might be used to close test tubes, still retaining a sound bacteriologic technique? 3. How would you protect culture medium from lint in a liter Erlenmeyer flask in which the cotton plug had to be large? 4. Explain your preference of method for the sterilization of : A hypodermic needle, rubber gloves, talcum powder, paraffin oil, a soldered test tube rack of metal, plugged test tubes, a package of surgical gowns, an egg medium, discarded glassware to be washed, bottles of water, and a solution of dextrose

Please give me answers..

Answer 1

Ans. 2) For doing sound bacteriological technique in test tube, we can either cover test tubes with cotton plug or by aluminium foil. While doing sound technique, high vibration is produced which cause the medium to vibrate, so it is important to note that the culture should not be filled upto the brim.

Ans. 3) for preventing medium from lint, cotton plug can be covered by white bandage, as it prevent the fall of cotton fiber and also give it a fixed stable shape. Cotton plug should not be touched in the medium as it can contaminate the medium. Cultute medium should usually filled approximately one fouth of the flask to help it from touching cotton plug, as when we autoclave the medium it will boil and if medium is fully filled it may touch the cotton plug. Also there should be enough space for steam, because if medium is fully filled then during autoclave steam can pressure the the cotton plug causing it to pop out.

Ans. 4) there are different methods for sterilization of different type of items and material, moist heat and dry heat. Moist heat sterilization is generally done in autoclave, it is used for glasswares and other substances that are not affected by vapour. Dry heat sterilization is generally done in hot air oven, it is used for powders, oils and other substances that are sensitive to moist heat.

Hypodermic needles : best way to sterilize needle is by autoclave for about 15 -20 minutes. In autoclave temperature (121°) and pressure (15 lb) is maintained which help to sterilize the material. It can also be sterilized by rubing the alcohol, take pure absolute alcohol and rub the needle before using it.

Rubber goloves : it can also be sterilized by autoclave at 10 lb pressure. Wrapped the gloves in aluminum foil, as direct autoclaving can melt it, and autoclave it. Before autoclave you can also wash the gloves with soap and water. It can also be sterilized by absolute alcohol.

Talcum powder : dry item like powder can be sterilized by dry heat sterilization in hot air oven. Ideal temperature of the oven needs to reach is at least 160°C and the contents need to be regulated at this heat for 45 to 60 minutes.

Paraffin oil : it can also be sterilized by hot air oven at 160° - 170° C for 1-2 hrs.

Test tube rack of metal : test tube rack can be autoclaved by covering it with aluminum foil. It can also be washed with soap and water and then sterilized in hot air oven and wiped by absolute alcohol. Dry heat sterilization is better way of sterlizing it.

Plugged test tube : best way to sterilize it is by covering the plug by foil to prevent it from becoming wet and autoclave it.

Surgical gown : autoclave is better way to sterilize it at 121° C at 15 lb pressure. Cover the gown so that it won't become wet by vapour. We can also sterilize it by dry heat to ensure proper dryin of gown.

Egg medium : any kind of medium is sterilized using autoclave at 121° C temperature and 15lb pressure for 15 - 20 minutes.

Discarded glassware : discarded glassware are first washed properly with detergents and dried up. After it properly get dried it is autoclaved for 20 minutes. Even before discarding, first autoclave it so that all microorganisms are died, and then discard the culture.

Bottle of water : bottle of water can be sterlized by autoclave. But it is necessary to lossen the cap or, it is possible, the bottle can explode as the temperature is raised above the boiling point.

Solution of dextrox : by autoclaving he dextros solution, it can be decomposed by high heat and result in colour change, t is better to filter instead. It can be sterilize by passing through a 0.2 micron filter.