Microbiology and Pathogens

Question 1

What is a pathogen?

Answer 1

A microorganism that causes disease

Question 2

What is gram positive bacteria?

Answer 2

Thicker layer of peptidoglycan, so they hold the stain better

Question 3

What does pathogenic mean?

Answer 3

Capable of causing disease in other organisms
-not all bacteria are pathogenic

Question 4

How do bacteria cause disease?

Answer 4

-Toxin production = bacteria release chemical toxins causing cell damage
-Tissue invasion = growing and dividing in tissues which disrupts the tissues normal functions

Question 5

What is an endotoxin?

Answer 5

-In the lipid part of the lipopolyssaccharide
-Attach to the bacteria’s cell wall
-Cause cell damage around the site of infection
-Form on gram negative bacteria

Question 6

What is an exotoxin?

Answer 6

-They are soluble proteins so are free to move around the body
-Produced by gram positive and negative bacteria
-Can act as enzymes, enzyme inhibitors or bind to proteins

Question 7

Why do we use a bunsen burner?

Answer 7

To create an upward draft keeping aerosols from landing on your work

Question 8

What does culturing micro organisms mean?

Answer 8

Growing them
-Scientists do this to study micro organisms better and further

Question 9

What is a growth medium?

Answer 9

Contains the right levels of nutrients and oxygen for the micro organisms to grow
-liquid nutrient broth = used to grow bacteria in a liquid medium
-nutrient agar = used to grow bacteria on a solid medium

Question 10

Why do we use different agars?

Answer 10

Used to grow different micro organisms

Question 11

What is an aseptic technique?

Answer 11

Techniques aiming to avoid contamination to and from the bacteria

Question 12

How to set up an aseptic technique?

Answer 12

1. spray and wipe work surfaces with virkon
2. collect a laminate which has been soaked in virkon
3. set up a bunsen burner on a roaring blue flame
4. sterilise equipment before and after work
5. make sure the growth medium is autoclaved before use
6. be organised (keep equipment close to the bunsen burner to reduce contamination)
7. make sure hands are thoroughly washed before beginning to work

Question 13

Why are aseptic techniques important?

Answer 13

-Microbiologists want to study a pure culture that is not contaminated by any micro organisms from the environment
-Contaminates may be pathogenic
-Harmless micro organisms can mature/mutate to become harmful

Question 14

How do you inoculate an agar plate?

Answer 14

-Use a marker to draw on the bottom of the agar to split it in half
-Inoculate one half with distilled water
-Inoculate the other with bacterium

Question 15

What are the steps of inoculation?

Answer 15

-Sterilise the metal inoculating loop by putting it through the hottest part of the flame (it will glow red)
-Unscrew the lid of the bacterium using the pinky-palm method
-Put the neck of the bottle through the flame
-Place inoculating loop into the bacterium then onto the agar plate in a zigzag movement
-Close the plate then reflame the inoculating loop

Question 16

How to bacteria reproduce?

Answer 16

Binary fission when conditions are favourable
-a method of asexual reproduction

Question 17

What is generation time?

Answer 17

The time between bacterial divisions

Question 18

What is a growth constant?

Answer 18

The number of times the population will double in one unit of time

Question 19

What are the phases of bacteria?

Answer 19

-Lag phase = where bacteria adapt to their new environment and are not yet reproducing to their maximum rate
-Log phase (exponential phase) = rate of reproduction is close to maximum
-Stationary phase = total growth rate is 0, the number of new cells formed is equal to the number dying
-Death phase = reproduction almost stopped and cell death is increasing

Question 20

Why does exponential growth not continue?

Answer 20

-Reduction of new nutrients
-Build up of waste products, inhibit further growth and begin producing poison cells
e.g carbon dioxide will build up and change the pH of the culture where growth can’t occur

Question 21

What is a logarithmic scale?

Answer 21

Useful for displaying bacterial growth when large numbers are achieved

Question 22

What is a haemocytometer?

Answer 22

Used to count individual cells, it is a special microscope slide with two viewing chambers

Question 23

What do antibiotics do?

Answer 23

Target bacterial cell processes by disrupting the biochemistry of bacterial cells but not host cells

Question 24

What are bacteriostatic antibiotics?

Answer 24

-Prevent further bacterial cell growth
-Relies on the hosts immune system to destroy remaining cells
-Not suitable for people with suppressed immune systems

Question 25

What are bactericidal antibiotics?

Answer 25

-Destroys almost all of the pathogens present
-Suitable for those with suppressed immune systems

Question 26

What are the types of bacteriostatic antibiotics?

Answer 26

-Antimetabolites = prevent nucleic acid formation so the bacteria’s DNA cannot be synthesised and the bacteria cannot divide
-Protein synthesis inhibitors = prevents transcription and translation

Question 27

What are the types of bactericidal antibiotics?

Answer 27

-Cell wall agents = prevents cell wall linking so the cell wall is weak and lyses
-Cell membrane agents = creates holes in the membrane so too much water enters the cells
-DNA gyrase inhibitors = DNA cannot coil and won’t fit into the cell

Question 28

What is the purpose of a control disk?

Answer 28

-It is sterile and soaked in distilled water
-Shows the antimicrobial properties are because of the antibiotic not the disk

Question 29

What is antibiotic resistance?

Answer 29

Bacteria evolve in response to antibiotics so are no longer affected by them

Question 30

How does antibiotic resistance happen?

Answer 30

-Mutations may occur during respiration which can change the way the antibiotic binds to the bacteria, making the drug less effective
-These mutations will increase due to natural selection

Question 31

Why does antibiotic resistance happen?

Answer 31

-Incorrect dosage of antibiotic
-Not completing the course
-Not appropriate for certain conditions
-Not many new antibiotics are being developed