Number of Bacteria on Different Surfaces
Materials and Methods
The nutrient agar medium was heated in the boiling water bath (100 °C), allowed cooling down to 40-50 °C, and then was poured into the sterile Petri plates. About 20 ml of the culture medium were placed into each one. The Petri plates were closed and left until the solidification of the medium. During this process, microorganisms were collected with the application of swab technique. They were obtained from the following surfaces: bathroom sink knob, light switch, elevator button, toilet handle, classroom podium, and entrance door. The sterile cotton swab was moistened with sterile water and rubbed against one of the mentioned surfaces. It allowed the microorganisms, which were present on the studied surfaces, adhere to the swab. Then, each of the Petri plates was open near the Bunsen burner, and one cotton swab was gently rubbed against the solidified nutrient agar medium. It allowed the microorganisms, which had adhered to the swab, get onto the culture medium. The procedure was performed accurately to avoid damage to the nutrient medium. In the result, each Petri plate was inseminated with the biological material from one of the studied surfaces: either bathroom sink knob, light switch, elevator button, toilet handle, classroom podium, or entrance door. The Petri plates were closed and signed in the appropriate way. They were inverted and incubated at 37 °C for 48 hours. Then, the colonies, which were growing on each Petri plate, were examined and counted. The results were compared with respect to the surfaces, from which the material had been obtained. The dirtiest and the cleanest study surfaces were identified, and the findings were compared to the …
