Microbiology

Question 1

Diagnostic methods for microbiology

Answer 1

Cel culture
Antigen or antibody detection
PCR

Question 2

3 bacterial shapes

Answer 2

Cocci (round)
Bacillus (rod-shaped)
Spirochaetes (spirals)

Question 3

What colour are gram stains?

Answer 3

Purple - positive

Pink - negative

Question 4

Organisms that don’t stain well with gram stain

Answer 4

TB (waxy coat)

Question 5

Factors required for bacterial growth

Answer 5

Food
Moisture
Correct temperature
Correct pH

Question 6

3 types of atmosphere bacteria can grow in

Answer 6

Aerobic
Microaerophikic
Anaerobic

Question 7

What is an exotoxin?

Answer 7

Produced inside cell and then exported from it

Mainly gram positive

Question 8

What is an endotoxin?

Answer 8

Part of cell wall

Mainly gram negative

Question 9

Role of toxins in sepsis

Answer 9

Cause damage to red and white blood cells causing them to become leaky. This causes BP drop affects blood clotting which can lead to sepsis

Question 10

Gram positive bacilli that can form spores

Answer 10

Clostridium (e.g. C. diff)

Bacillus sp. (e.g. anthrax)

Question 11

What are spores?

Answer 11

Inactive hardy forms of bacteria that cannot replicate but can survive adverse conditions

Question 12

Which organism is haemolysis used to classify?

Answer 12

Streptococcus

Question 13

What is alpha haemolysis?

Answer 13

Partial haemolysis

Enzymes denature haemoglobin side red blood cells causing greenish discolouration round the colony

Question 14

What is beta haemolysis?

Answer 14

Complete haemolysis

Enzymes breakdown red blood cell causing complete clearing round the colony - most pathogenic

Question 15

What is gamma haemolysis?

Answer 15

No haemolysis

Question 16

What is strep pneumonia?

Answer 16

Gram positive cocci
Commonest cause of pneumonia, also causes meningitis
Part of normal upper respiratory tract flora in many people
Majority of UK strains are still sensitive to penicillin

Question 17

What is streptococcus viridans?

Answer 17

Gram positive cocci
Group of species which are common come sales
Can cause endocarditis (infection of heart valves)

Question 18

What is group A strep (strep pyogenes)?

Answer 18

Most pathogenic of all strep.
Cause tonsillitis, necrotising fasciitis, puerperal sepsi
All strains are still sensitive to penicillin

Question 19

What are group B strep (strep. Agalactiae)?

Answer 19

Most common cause of newborn infections

Question 20

Examples of non-haemolytic strains?

Answer 20

Enterococcus
Not particularly pathogenic
Common cause of UTI
Most sensitive to amoxicillin (but not penicillin)

Question 21

What are prion proteins?

Answer 21

Infectious protein that have no DNA or RNA

Cannot be sterilised or cleaned off

Question 22

What test distinguishes staph aureus from other staph organisms?

Answer 22

Coagulase test

Staph aureus - positive - golden

Question 23

What are coagulate negative staphylococci?

Answer 23

Common skin commensals
Do not produce toxins
Common causes of prosthetic joint and prosthetic heart valve infection and catheter infection - difficult to treat with antibiotics

Question 24

What is staph aureus?

Answer 24

Produces both exotoxins (enzymes that damage cells) and endotoxins (toxins that act on the gut - food poisoning)
Strains sensitive to flucloxacillin - MSSA
Strains resistant to flucloxacillin - MRSA (also resistant to penicillins +!cephlaosporins)

Question 25

Infections caused by staph aureus

Answer 25

Commonest cause of skin, soft tissue and wound infection Commonest causes of bone and joint infection Food poisoning (enterotoxjn producing strains) Flucloxacillin is treatment of choice for MSSA

Question 26

What is Staph. aureus bacteraemia?

Answer 26

Infection in the blood stream Leads to sepsis Can spread to other sites in the body Many are hospital acquired

Question 27

Examples of gram positive strict anaerobes

Answer 27

Clostridium

Question 28

What is clostridium?

Answer 28

Part of normal bowel flora Produces spores Produces exotoxins

Question 29

First line treatment for clostridium

Answer 29

Metronidazole (first line treatment for infections caused by anaerobes)

Question 30

What does C. diff cause?

Answer 30

Antibiotic associated diarrhoea esp. in the elderly

Question 31

What is C. perfrigens?

Answer 31

Gas gangrene Severe soft tissue infection following wound contamination (e.g. Gunshot wound)

Question 32

What is C. tetani?

Answer 32

Causes tetanus, usually fatal paralytic illness

Question 33

Examples of gram negative strict anaerobes

Answer 33

Legionella | Pseudomonas

Question 34

Examples of aerobic gram negative cocci?

Answer 34

Neisseria meningitides & Neisseria gonorrhoeae

Question 35

Examples of small gram negative aerobic bacilli?

Answer 35

Bordetella pertussis & Haemophilis influenzae

Question 36

What are coliforms?

Answer 36

Species of gram negative bacilli that look like E. coli

Question 37

2 main subtypes of aerobic gram-negative coliforms?

Answer 37

Gut commensals | Gut pathogens

Question 38

Examples of gut commensals?

Answer 38

Most strains of E. coli Klabsiella spp. Enteronacter spp. Proteus spp.

Question 39

Examples of gut pathogen commensals

Answer 39

Salmonella spp. Shigella spp. Verotoxin E. coli 0157 (outbreaks in nurseries & care homes)

Question 40

First line treatment for coliforms?

Answer 40

Gentamicin

Question 41

Examples of gram-negative microacrophilic bacilli (spiral)?

Answer 41

Vibrio cholerae, Campylobacter sp. & Heliconacter sp.

Question 42

What does Helicobacter pylori cause?

Answer 42

Gastritis & duodenal ulcers

Question 43

Examples of gram-negative strict anaerobes?

Answer 43

Bacteroides spp.

Question 44

First line treatment for anaerobes?

Answer 44

Metronidazole

Question 45

What are mycobacteria?

Answer 45

Thick waxy coat doesn't gram stain | Acid fast bacilli or acid-alcohol fast bacilli

Question 46

Examples of Spirochaetes?

Answer 46

``` Treponema pallidum (causes syphilis) Borrelianburgdorferi (causes Lyme disease) ```

Question 47

Methods of gene transfer in bacteria

Answer 47

Transformation (dead bacteria DNA taken up by living bacteria) Conjugation (bacteria sex) Transduction (viruses transfer DNA from one bacteria to another)

Question 48

General signs of infection

Answer 48

Local symptoms - pain, redness, swelling, heat, loss of function Systemic symptoms - fever, sweats rigors

Question 49

Investigations for infection

Answer 49

``` WCC (non-specific) Culture - blood - urine - stool - psoutum PCR Blood for serology (antibodies/antigen) ```

Question 50

What causes sepsis?

Answer 50

Cytokines cause blood vessels to become leaky Lower blood volume requires heart to work harder to maintain oxygenation a of tissues Blood supply to less essential organs (skin, kidneys liver) is hut down to try maintain blood supply to brain Blood clotting system is activated causing blood clotting in tiny vessels -> uses up clotting factors -> increased risk of haemorrhage

Question 51

Difference between bactericidal & bacteriostatic?

Answer 51

Bactericidal - kill bacteria | Bacteriostatic - inhibit bacterial growth

Question 52

Where in bacteria can antibiotics act?

Answer 52

Bacteria wall Bacterial ribosome Bacterial DNA

Question 53

Examples of antibiotics that act on bacterial cell walls?

Answer 53

Penicillins Cephalosporins Glycopeptides

Question 54

Examples of glycopeptides

Answer 54

Vancomycin, teicoplanin | Need to be administered IV

Question 55

Types of antibiotics that inhibit protein synthesis

Answer 55

``` Macrolides (erthromycin' clarythromycin & azithromycin) Amino glycosides (Gentamicin IV) Tetracyclines (doxycycline) ```

Question 56

Types of antibiotics that act on bacterial DNA

Answer 56

Metronidazole Trimethoprin Fluroquinolones (Ciprofloxacin)