Module 4 To return, press back button

Day 1
Module 4a: Ubiquity: Bacteria are found everywhere.
Procedure:
- 1 plate per person. In a group of 4, one person do the air plate.
- May put several areas onto the plate. Just label it properly.
Use the sterile cotton swabs to sample areas. If the area is wet, just swab the area then smear it gently onto the plate. If the area is dry, then wet the swab with sterile solution, then swab the area, then swab the plate.

Module 4b: Handwashing
Procedure:
- Work in groups of 4 but only 2 really do anything.
-1 person washes their hands the other samples the hands.
Wash, rinse, swab.

Label plates properly.
Time wash ...............Total time
0 .............................0 swab hand swab plate. Shows start sample
30 sec......................30 sec swab hand swab plate
30 sec......................60 sec swab hand swab plate
60 sec......................2 min swab hand swab plate

Place all plates in proper holder to be incubated.

Day 2
4a: Ubiquity
- Do not open the plates. Fuzzy growths are probably fungi. these are constructed to put spores into the air.
- Note shapes, sizes, colors. These are all often very unique colony characteristics of the bacteria. See module 9 for details.
-- The bacteria observed are the bacteria that have had their growth requirements-nutrients, temperature, pH, etc.- met. But there are other bacteria that were probably present in the sampled area but did not grow. These bacteria are referred to as "viable but not culturable". This is always a consideration when analyzing samples, especially environmental samples.

4b: Hand washing
What does this experiment show? Usually experiments are designed to test a particular hypothesis. In this case, based on previous knowledge/work, the hypothesis could have been that hand washing removes bacteria. If this was the case, then one would expect that, the longer one washes, the less bacteria should be found on the hands.

- What were the results?
-- Did the number of bacteria change with wash time?
-- Did the kinds of bacteria change with wash time?
- Do the results support the idea that hand washing reduces the number of bacteria?
- Do the results mean anything?

Experimental Design:
Proper experimental design is key to whether the results have meaning.
In general, all experiments typically involve Replicates, Reproducibility, and Controls

-Replicates: There are at least 2, if not more, experimental points that make up each data point. This is to provide a better representation of what actually happened. This would compensate for mistakes, defective media, etc. For example, if 5 plates were done for a particular time point and 4 show the growth of a large amount of bacteria and one shows very little bacteria, which result better represents what happened, the 4 plates or the 1 plate.

-Controls: Need a base line to compare any results back to. In this experiment, the results could be interpreted if washing was the only factor that could affect the number of bacteria found on the hands. Is this true?

Hypothesis: As one washes the number of bacteria found on the hand decreases. Based on idea that only source of bacteria is the hand.

--Could bacteria be in the rinse water?
--Could bacteria be in the soap?
--Could the plates be contaminated?
--Could the swab be contaminated?

Other factors:

-- What if you rinsed longer or shorter a period of time?
--How big and area was swabbed. Was it standardized?
--How hard was the swab pressed into the hand?
--Was the same area of the hand swabbed?
--Was the temperature of the water the same? Hot water vs. cold water.

Reproducibility: The results have no meaning, if it cannot be repeated by you, by others, today, tomorrow, or ten years from now. If not reproducible, then need to look at whether the experiments are truly the same. Pasteur got opposite results of others. Looked like the same experiment but actually not. There were sometimes heat insensitive bacteria present.