About Medical Microbiology

Question 1

What is the study of microorganisms (including bacteria, viruses, fungi and parasites) which are of medical importance and are capable of causing disease in human beings?

Answer 1

Microbiology

Question 2

What is one of the most important causes of mortality and morbidit in the population?

Answer 2

Infection

Question 3

Approximately what % of hospital patients are on antibiotics at any one time?

Answer 3

30%

Question 4

What do 1 in 10 patients acquire whilst in hospital?

Answer 4

An infection

Question 5

What is normal flora?

Answer 5

The bacteria, fungi and parasites that are usually in and on our bodies

Question 6

What do we call the bacteria, fungi and parasites that can be found in our skin, nose mouth and GI tract?

Answer 6

Normal Flora

Question 7

How much bacteria does a gram of faeces carry?

Answer 7

10 to the power of 9

Question 8

What parts of our body tend to be sterile or have defence mechanisms for bacteria?

Answer 8

Internal organs

Question 9

What stops other, pathogenic bacteria from taking a foothold, by taking up space and competing for nutrients,
aids digestion and produces essential vitamins (folic acid and vitamin K)
but can cause disease if gets into the wrong place?

Answer 9

Normal Flora

Question 10

What produces folic acid and vitamin K?

Answer 10

Normal Flora

Question 11

Name 2 advantages of normal flora:

Answer 11

Prevents other bacteria from invading (takes up space and nutrients)

Aids digestion in the gut and produces vitamin K and folic acid

Question 12

What happens if normal flora gets into the wrong place?

Answer 12

Disease

Question 13

What is contamination?

Give 2 examples

Answer 13

Presence of an organism in a culture, that was not originally in the substance
(e.g. a culture of blood contaminated with an organism from the skin
or a sample contaminated in the lab)

Question 14

What do we call a presence of an organism in a culture that was not in the original substance that has been cultured?

Answer 14

Contamination

Question 15

What do we call presence of an organism at a site that does not cause a tissue reaction (inflammation), symptoms or disease?

Answer 15

Colonisation

Question 16

What is colonisation?

Give 2 examples

Answer 16

Presence of an organism at a site that does not cause a tissue reaction (inflammation), symptoms or disease.

Normal Flora
Abnormal Flora (after a patient has received antibiotics - e.g. yeast)

Question 17

What is the process where organisms invade a body site and their multiplication initiates a tissue reaction producing symptoms/disease?

Answer 17

Infection

Question 18

What is infection?

Answer 18

The process where organisms invade a body site and their multiplication initiates a tissue reaction producing symptoms/disease.

Question 19

What are the 4 classifications of organism?

Answer 19

Viruses
Bacteria
Fungi
Parasites

Question 20

What are viruses, bacteria, fungi and parasites?

Answer 20

The 4 classes of organism that can cause disease

Question 21

Why do we classify organisms that cause disease?

3 reasons

Answer 21

Cause different DISEASES
Have different modes of TRANSMISSION
TREATMENT is different

Question 22

List the order of bacteria, fungi and viruses from smallest to largest:

Answer 22

Viruses
Bacteria
Fungi

Question 23

Which type of organism is unable to replicate independently and invades host cells, using their cellular machinery to replicate?

Answer 23

Viruses

Question 24

What are influenza, chickenpox (varicella) and herpes examples of?

Answer 24

Viruses

Question 25

What is the common cold and HIV/AIDS examples of?

Answer 25

Viruses

Question 26

Are viruses difficult to treat?

Answer 26

Yes

Question 27

How do viruses replicate?

Answer 27

By invading host cells and using their cellular machinery

Question 28

What type of organism is capable of independent replication and causes most infections seen in hospital?

Answer 28

Bacteria

Question 29

What are pneumonia, certain types of meningitis, cellulitis and UTI examples of?

Answer 29

Bacteria

Question 30

What organisms can be treated with antibiotics?

Answer 30

Bacteria

Question 31

How does bacteria replicate?

Answer 31

Independently

Question 32

What organisms are complex and large, known as eukaryotes and can be divided into yeasts and moulds?

Answer 32

Fungi

Question 33

What organisms are thrush, athletes foot, invasive and allergic aspergillosis examples of?

Answer 33

Fungi

Question 34

Most fungi diseases are opportunistic. What does this mean?

Answer 34

They will colonise where normal flora has been wiped out

Question 35

Name 3 reasons why we classify bacteria:

Answer 35

Cause different DISEASES Are susceptible/resistant to different ANTIBIOTICS Some are common NORMAL FLORA and others PATHOGENS

Question 36

Name the 2 main WAYS that bacteria are classified:

Answer 36

What they look like under a microscope Based on biochemical reactions (e.g. metabolising sugar)

Question 37

What are the two classifications of bacteria when gram staining?

Answer 37

Gram Positive - Purple | Gram Negative - Pink

Question 38

What shapes can we classify bacteria into once we have picked a colour?

Answer 38

Shape Coccus - round Rod - long and thin

Question 39

How many combinations of gram positive and gram negative bacteria are there?

Answer 39

4 GP Rods, GP Coccus, GN Rods, GN Coccus

Question 40

What is notable about the cell wall of gram positive bacteria and what does it have high levels of?

Answer 40

It is very thick and has high levels of peptidoglycan

Question 41

What is notable about the cell wall of Gram Negative Bacteria and what does it have low levels of?

Answer 41

It has a thin cell wall and low levels of peptidoglycan

Question 42

Name the 5 steps of Gram Staining:

Answer 42

Stain the slide with crystal violet Flood slide with Gram's iodine for 1-2min Decolourise by washing slide with acetone (2-3secs) Stain with safarnin counterstain for 2min View under microscope

Question 43

When gram staining, do you stain the slide with crystal violet or safranin counterstain first?

Answer 43

Crystal violet, you then flood with iodine, decolourise with acetone and then use safranin counterstain

Question 44

Why does Gram Positive bacteria stain purple?

Answer 44

The high levels of peptidoglycan stick to the crystal violet

Question 45

What gives us and initial identity of bacteria and can be done without growing the organism (so is quicker)?

Answer 45

Gram Staining

Question 46

What is an advantage of Gram Staining over growing a bacteria organism?

Answer 46

It is quicker

Question 47

Name 4 things we can gram stain to find what bacteria may be present:

Answer 47

Pus Joint Fluid Sputum CSF

Question 48

Do we use the same antibiotics for Gram Positive and Gram Negative Bacteria?

Answer 48

No

Question 49

Name 3 differences between Gram Positive and Gram Negative bacteria:

Answer 49

Different ANTIBIOTICS Cause different DISEASES Differ in ability to SURVIVE ENVIRONMENT (cleaning, infection control and outbreak management)

Question 50

What are clusters of Gram Positive Cocci usually characteristic of?

Answer 50

Staphylococcus spp. Like S. Aureus

Question 51

What are chains or pairs of Gram Positive Cocci usually characteristic of?

Answer 51

Streptococcus spp. - like S. pneumoniae

Question 52

S. Aureus and S. Pneumoniae can cause lung infections. Where would be a good place to get a culture for gram staining? What do you think the result would be?

Answer 52

Sputum | Gram Positive Cocci

Question 53

What are thick Gram Positive Rods usually characteristic of?

Answer 53

Clostridium spp. like C. perfringens, C. septicum and C. tetani

Question 54

What are thin Gram Positive rods usually characteristic of?

Answer 54

Listeria spp. (can cause food poisoning and could be found in a stool sample

Question 55

What are Clostridium infections and listeria infections examples of (if gram staining)?

Answer 55

Gram Positive Rods

Question 56

Name a bacteria that can be either gram positive or gram negative cocci/gram variable?

Answer 56

Coccobacilli - usually acinetobacter spp. think bacilli = silly both

Question 57

What are Gram Negative Diplococci (2 coccus) usually examples of?

Answer 57

Neiseria spp like N. meningitidis or N. gonorrhoea or Moraxella spp. or Acinetobacter spp.

Question 58

What are thin Gram Negative Rods usually characteristic of?

Answer 58

Enterobacteriacease like E.coli | cause gut infections and food poisoning

Question 59

What are Gram Negative Coccobacilli usually examples of?

Answer 59

Haemophilus spp. like H. influenzae | can cause lung infections in kids and meningitis

Question 60

What are curved Gram Negative Rods usually characteristic of?

Answer 60

Vibrio spp. or Campylobactor spp. like V. cholerae and C. jejuni

Question 61

What are thin needle shaped Gram Negative Rods usually characteristic of?

Answer 61

Fusobacterium spp.