HLTC22H3 Lecture 11: Lecture 11

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beigewhale523

1 Mar 2011

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Canadian food inspection agency and dats (deli agency of montreal) don"t eat smoke meats, pepperoni, and others may be contaminated with lysteria. Lysteriosis is a food borne illness affects ppl who are vulnerable such as the elderly also affects newborns and ppl with weakened immune systems and pregnant women. Pregnant women are 20x more likely to acquire the disease than healthy adults. Lysteriosis is caused by lysteria monositogenesis lysteria can suvive and continue to grow even when in the fridge. Foods contaminated withlysteria will look, smell and taste normally. Lysteria can be killed by proper cooking methods. Dairy products, fish, meat and veggies common foods that lysteria contaminates. Ontarios crash stop hospitals more than 1/3 of ontarios hospitals (38%) spend more money than they take in. Can get a waiver if they come up with a strategy to re-balance the books (get rid of the deficits) Hospitals are supposed to work within their budget.

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Mammalian cells can be cultured for a variety of purposes, including synthesis of vaccines. They must be maintained in growth media containing all of the components required for proper cellular function to ensure their survival and propagation. Traditionally, growth media were prepared by blending a powder, such as Dulbecco's Modified Eagle Medium (DMEM) with sterile deionized water. DMEM contains glucose, buffering agents, proteins, and amino acids. Using a sterile (i.e., bacterial-, fungal-, and yeast-free) growth medium ensures proper cell growth, but sometimes the water (or powder) can become contaminated, requiring the addition of antibiotics to eliminate undesired contaminants. The culture medium is supplemented with fetal bovine serum (FBS) that contains additional growth factors required by the cells.

Suppose an aqueous stream SG0.90 contaminated with bacteria is split, with 75% being fed to a mixing unit to dissolve a powdered mixture of DMEM contaminated with the same bacteria found in the water. The ratio of impure feed water to powder entering the mixer is 4.4:1. The stream leaving the mixer (containing DMEM, water, and bacteria) is combined with the remaining 25% of the aqueous stream and fed to a filtration unit to remove all of the bacteria that have contaminated the system, a total of 20.0 kg. Once the bacteria have been removed, the sterile medium is combined with FBS and the antibiotic cocktail PSG (Penicillin-Streptomycin-L-Glutamine) in a shaking unit to generate 5000 L of growth medium SG1.2. The final composition of the growth medium is 66.0 wt% H₂O, 11.0% FBS, 8.0% PSG, and the balance DMEM.

(a)

Draw and label the process flowchart.

(b)

Do a degree-of-freedom analysis around each piece of equipment (mixer, filter, and shaker), the splitter, the mixing point, and the overall system. Based on the analysis, identify which system or piece of equipment should be the starting point for further calculations.

(c)

Calculate all of the unknown process variables.

(d)

Determine a value for (i) the mass ratio of sterile growth medium product to feed water and (ii) the mass ratio of bacteria in the water to bacteria in the powder.

Some bacteria including strains of Enterococcus and Staphylococcus, and fungi such as Candida, can survive for one to three months on a variety of materials found in hospitals, including scrub suits, lab coats, plastic aprons, and computer keyboards. They are the major causes of opportunistic infections in human.

1. Describe the meaning of opportunistic infections.

2. Indicate one body site in healthy human body where each of the above microbes may be found as normal flora.

3. Indicate example of a disease that each of the above microbes may cause in hospital patients.

4. Describe one physical and one chemical method of disinfecting objects contaminated with these microbes.

5. List 2 important practices hospital personnel can do to reduce the spread of these pathogens.

In a quadrant streak, why do you intersect the previous lines and not the ends of the streak?

Select one:

a. More cell amount variability at ends, usually higher cell population

b. Keep streaks in the middle of the plate

c. Prevent cell death

d. To maintain a mixed culture

e. To count CFUs

How should you hold the inoculating loop?

Select one:

a. Maintain it at an angle at all times

b. In a test tube rack at all times

c. Like a pencil

d. Balanced on top of the tube

e. With dish gloves

Which of the following is used in the spread plate and not the streak plate method?

Select one:

a. Glass spreading rod

b. Flame loop

c. Agar plate

d. Bunsen burner/sterile utensil

e. Starting culture to sample

What would likely happen if the inoculum was not spread adequately over the agar surface?

Select one:

a. Contamination

b. Degradation

c. Sterilization

d. Uneven distribution

e. Cells will not grow

You have a mixed culture of unknown bacteria and want to identify one of the species by several subsequent experiments (needing multiple colonies of a pure culture). You do a quadrant streak and transfer to a sterile liquid medium. What next step makes the most sense?

Select one:

a. Perform a Gram stain

b. Note all colony morphology characteristics

c. Use the spread plate method or new streak plate on an isolated colony of the plate

d. Quantify the cells

e. Repeat using the other two methods of isolation

What would likely occur if the flame loop was not sterilized between streaks on the quadrant streak method?

Select one:

a. Bacteria will not stick to the loop

b. Virus will be introduced

c. Flame loop will be too hot

d. The sample will be contaminated

e. Subsequent streaks would have more colonies

Why is the glass rod in the spread plate method put in alcohol and ignited instead of sterilized like a flame loop?

Select one:

a. Glass oxidizes

b. Glass melts

c. Glass takes longer to cool

d. Glass burns

e. Glass is more sterile

HLTC22H3 Lecture 11: Lecture 11

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