To help with the prevention of COVID-19, SCU campus reporters and the Department of Microbiology jointly tested the amount of bacteria on things people may use or come into contact with every day. Surprisingly, it turned out the filthiest is not cellphones as most people would think.
The Soochow investigation squad first used cotton swabs to randomly collect samples from elevator buttons, computer keyboards, classroom door handles, and students’ mobile phones. Then the swabs were placed in a test tube shaker, which would shake the bacteria off into the saline solution. Next the polluted liquid was smeared onto the agar culture medium in a petri dish, which was put in a 37-degree incubator to complete the procedure.
After four days, bacterial colonies appeared on the petri dishes for different target objects. The results showed that a total of 42 colonies appeared on the Enter key of the computer keyboard, an amount that was 21 times that on the mobile phone.
In addition to the things mentioned above, human hands should be presumably no less dirty. The Soochow team also randomly tested the amount of bacteria on the hands of seven testees, and the bacterial colonies appearing on samples of three of them soared to over one hundred, indicating that hands could be even much filthier than the computer keyboard.
The seven testees were asked to wash their hands with water, 75% alcohol, and soap, respectively, and then the amount of bacteria on their hands were examined. It was found that washing hands with just water almost equaled to not washing them at all, with both ways recording similar amounts of bacterial colonies. In contrast, the sterilizing effect of washing hands with soap came second while cleaning hands with 75% alcohol yielded the best results.
However, the chair of Soochow’s Department of Microbiology Chung-Yi Lee reminded that although disinfection alcohol has the strongest sterilizing effect, it may be harmful to human hands if used frequently. By following the steps for thorough hand-washing recommended by the government, almost 90% of bacteria or viruses can be washed away by using soap.
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