Answer Happy

Tips for Success • Students should not wash their hands during the day before beginning this exercise. If you have a dog at home, give it a good petting before you leave home! Materials (per Team of Two or Four) 4 sterile swabs Inoculating loop 1 tube of sterile water I sterile surgical scrub brush • Regular soap • Betadine or antiseptic soap 4 trypticase soy agar (TSA) plates Procedure Period 1 1. Label your plates 1, 2, 3, and 4" Label each with the initials of the person whose hands are being washed and swabbed. Mark the bottom of each plate into quadrants 2. For plate 1, swab a portion of your nondominant palm below your little (fifth) finger and all of the palmar surface of your little finger with a moistened swab (be sure to rotate the swab, so that you get all sides of the cotton tip coated). Use this swab like an inoculating loop to streak the first quadrant of the plate. Use overlapping strokes to cover the entire quadrant (figure 26.20). 3. In quadrant 4. touch the tip of your little finger on the agar surface (the nail can penetrate the agar but don't mash it completely with your fingertip). Use your flamed inoculating loop to streak the sec ond and third quadrants of the plate for isolation (figure 26.2). 4. For plate 2, wash your hands by rubbing them together with warm tap water and soap. Rinse your hands and shake the excess - water off in the sink. Swab a portion of your nondominant palm below your wedding ring (fourth) finger (figure 26.2b) and all of the palmar surface of your fourth finger. Swab quadrants 1, 2, and 3 as shown in figure 26.24. Quadrant 1- streak with swab from hand Quadrant 4- touch fingertip Quadrant 2- isolation streak with loop Quadrant 3- isolation streak with loop (a) (b) Figure 26.2 (a) Layout for inoculating the plates; (b) swabbing for plate 2
5. In quadrant 4, gently press the tip of your fourth finger into the agar. Use your flamed inoculating loop to streak the second and third quadrants of the plate for isolation as you did for plate 1. 6. For plate 3, unwrap the sterile surgical scrub brush. Scrub your hand with brush, soap, and warm tap water. Rinse your hands and shake the excess water off in the sink. Swab a portion of your nondominant palm below your middle (third) finger and all of the palmar surface of your middle finger. Swab quadrants 1, 2, and 3 as shown in figure 26.20 7. In quadrant 4, gently press the tip of your third finger into the agar Use your flamed inoculating loop to streak the second and third t quadrants of the plate for isolation as you did for plates 1 and 2. 8. For plate 4, scrub your hand with a brush, antiseptic (such as povidone iodine [Betadine]) or antiseptic soap, and warm tap water. Rinse your hands and shake the excess water off in the sink. Swab a portion of your nondominant palm below your index (second) finger and all of the palmar surface of your second finger. Swab quadrants 1, 2, and 3 as shown in figure 26 2a. 9. In quadrant 4. gently press the tip of your second finger into the agar. Use your flamed inoculating loop to streak the second and third. quadrants of the plate for isolation as you did for the other plates. 10. Invert your plates stack them, and incubate at 37°C. Period 2 1. Examine your plates. Look for both the quantity and diversity of bacteria on each plate.. 2. If instructed by your professor, you may Gram stain some of the isolated colonies 3. Record your results. Results and Interpretation Plate 1 is unwashed skin and should show both resident (normal biota) and transient organisms. Compare plate 1 to the other plates (figure 26.3a, b) and see if you can determine which are the transients. Plate 2 is from skin following the use of a soap or surfactant. Compare this to plate 1. Plate 3 involves the use of a surfactant with the addition of friction from the scrub brush. Plate 4 is made after the use of an antiseptic. Did it reduce the overall number of organisms? Several bacteria, which can be normal skin biota, are shown in figure 26.3c-e. M (a) (b) (d) Figure 26.3 Abundance and diversity of skin microbiota. Colonies from plate 1 (a) and plate 2 (b): These bacteria are normal biota of the skin. (c) Staphylococcus epidermidis has whitish colonies and is very commonly seen. (d) Less common but more dangerous is Staphylococcus aureus, which is yellowish. (e) Micrococcus luteus is found on fewer people than Staphylococcus and has distinctly yellow colonies.
Interpretation and Questions 1. What difference did you see between the unwashed and washed skin? Between the use of a scrub brush and no scrub brush) 2. What effects did you see from the use of an antiseptic rather than soap? paiderW bash! 3. It is estimated that students and other humans shed 1.5 million skin cells per hour. What problems might that create in the microbiology lab or surgical suite?
Lab result 4-3 MH