1. Bacteria and You!
Helicobacter pylori
Barry Marshal

2. Last Day Taking the steps of a clinical Microbiology laboratory
Swabbing and plating bacterial cultures
Observing colonies and performing a Gram Stain
Which bacteria will show purple, and why?
Which bacteria will show pink, and why?

3. Today
Observing Gram stain under a microscope
Bacteria + Human disease
Antibiotics and Antibiotic resistance

4. Outcomes
You will be able to see the differences between Gram positive and negative bacteria under a microscope, and identify microbial shapes.
You will understand the interactions between bacteria and humans; giving examples of both the bad and the good.
You will understand how antibiotic resistance works, and think of ways it can be controlled or prevented.

5. Bacteria + Disease
Study of Diseases- Pathology
Bacteria and other disease causing agents are known as pathogens
Table 24.4 in textbook
A look at some common and serious microbial infections

7. So, How do they do it? Bacteria can cause disease in 2 ways
Directly- attacking and digesting living cells/tissue
Indirectly- production of poisons known as toxins
Exotoxin
Endotoxin

8. Exotoxins
Toxins made from bacterial proteins
Gram positive bacteria- secrete into surrounding environment (protection mechanism)
e.g. Clostridium tetani

9. Endotoxins
Toxins made from lipids + carbohydrates (outer membrane of Gram negative bacteria)
Not released until bacterial death
Complications with Antibiotics
e.g. Escherichia coli

10. Antibiotics
Drugs that combat bacteria by interfering with various cellular functions (Table 24.5)
Can be broad spectrum (works against a variety of different bacteria) or narrow spectrum (selected group of bacterial types)

11. Antibiotic Classes
Penicillin and Cephalosporin class antibiotics interfere with cell wall synthesis
Tetracycline Class inhibits protein synthesis (used to treat acne)
Sulfonamide (Sulfa Drugs) inhibit cell metabolism

12. Kirby-Bauer disc diffusion test
Antibiotic Testing
Diffusion test
Bacteria inoculated on a plate, antibiotic test placed on agar, and the “zone size” of resistance is measured.
Automated Susceptibility testing
Bacteria are inoculated on a susceptibility testing card, machine measures optical density of wells.

13. ANTIBIOTIC RESISTANCE
MORE ON THIS NEXT WEEK (GUEST LECTURER COMING IN TO DISCUSS THIS WORLD-WIDE PROBLEM)

14. Let’s Look at some Antibiotic Testing
Suppose the plate on the piece of paper is your own antibiotic susceptibility test
If your culture was Gram positive- Use the Gram Positive sensitivity readings If Gram negative – use GN sensitivity readings
Draw the plate, along with the zone sizes of each antibiotic on your lab manual

15. To Do Now
let’s take a look at our Gram stains!
Using your lab manual, provide a scientific drawing of your bacteria
Note whether your bacteria is Gram positive or Gram negative

16. In Lab Manuals
Draw the entire F.O.V (Everything you see inside the microscope… works best if you draw a large circle in the middle of your page, and fill it in with what you see)
Keeping in mind rules for Scientific Drawings
Need to provide magnification power, actual size and magnification of drawing.

17. F.O.V

18. CALCULATIONS TOTAL MAGNIFICATION = Objective Lens x 10
ACTUAL SIZE = F.O.V diameters (use um) / # of fits across for a single cell
MAGNIFICATION (OF DRAWING) = DRAWING SIZE/ ACTUAL SIZE (SAME UNITS!!!)