Name: 6. Clinical Connection: Often, whether or not a pa number of eells of the

Question

Name: 6. Clinical Connection: Often, whether or not a pa number of eells of the pathogen that the potential host is exposed to. This is callet dose. Generally, this is expressed as the IDs, or the number of cells that would be n is able to cause disease depends on the cause disease in 50% of the hosts exposed to it. Chart1: Here is data on typical counts of bacteria from untreated wastewater( coming from your house and entering a sewage treatment plant) (this is what is Bacteria Per LITER: 100,000,000 cells 1,000 cells 10,000 cells Fecal coliform (aka E col) Salmonella Sal lla (a) Use the data in Chart 1 to figure out how many cells are in Hint I L 1000 ml 1 ml of wastewater Bacteria Cells/ml Fecal coliform (aka E coll) Salmonella Shigella (b) Based on the population count of each bacteria above, if you set up serial dilutions and plate counts exactly as we did in class, which plate would be the countable plate? Because all of our numbers are multiples of 10, you can assume that the countable plate will have 100 colonies. Bacteria Dilution of countable plate Fecal coliform (aka E coli) Salmonella Shigella Chart 2: Here is some data on infective dose for several Gram-negative intestinal pathogens which are often ingested through contaminated food or water. (Data from www.ews.msu edwdocumens Yates presensation pd) Bacteria E coli Salmonella IDse 1,000,000 cells 10,000 cells 10 cells Shigella (c) Using the data in Chart 2 and the cells/ml data you calculated, determine how much of the untreated water (in ml) would you need to ingest in order to receive the infectious dose for each of the 3 pathogens? Bacteria ml of water needed to ingest infectious dose Fecal coliform (aka E. coli) Salmonella Shigella 139

Explanation / Answer

Answer chart 1

a. E.coli-100000

Salmonella-1

Shigella-10

b. E.coli-106

Salmonella-101

Shigella-102

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