Microbiology

Question 1

what colour do gram positive stain

Answer 1

purple

Question 2

what colour do gram negative stain

Answer 2

pink

Question 3

what is an opportunistic pathogen

Answer 3

probably only cause infection in immunocompromised individuals

Question 4

define pathogenicity

Answer 4

ability of microorganism to produce disease

Question 5

define virulence

Answer 5

degree of pathogenicity of organism (how well it can cause disease)

Question 6

how do bacteria replicate

Answer 6

by binary fission

Question 7

what are the 3 types of atmosphere

Answer 7

• aerobic (in O2)
• anaerobic (no O2)
• microaerophillic (reduced O2 and enriched co2)

Question 8

what are exotoxins

Answer 8

produced by gram positive

- produced inside cell

Question 9

what are endotoxins

Answer 9

produced by gram negative

- part of gram -ve cell wall

Question 10

what are the 2 types of fungi and their properties

Answer 10

• Yeast (single cells and reproduce by budding): Candida

- Mould (produce sporins): Aspergillus

Question 11

what are the gram positive cocci

Answer 11

• streptococcus
• staphylococcus
• enterococcus

Question 12

what are the properties of streptococcus

Answer 12

• aerobic
• chains of cocci
• alpha haemolysis (partial), step pneumonia & viridans
• beta haemolysis (complete), Group A strep (throat/skin), Group B (neonatal meningitis

Question 13

what are the properties of staphylococcus

Answer 13

• cocci clusters
• coagulase positive (golden), Staph. Aureus in wound/skin infections
• Use flucloxacilllin for this
• coagulase negative (white), staph. epidermidis (prosthetic heart valves, catheter infection)

Question 14

what are the properties of enterococcus

Answer 14

• aerobic
• cocci chains
• non-haemolytic
• common UTI cause

Question 15

what are the stages of developing a fever

Answer 15

• antigen attacks macrophages
• release cytokine
• travel to anterior hypothalamus
• releases prostaglandin E.
• this resets body temperature
• body perceives it as cold so shivers to conserve heat
• FEVER… growth of pathogens slowed if temperature increases

Question 16

types of gram negative bacteria

Answer 16

• gram negative cocci
• coliforms
• strict aerobes
• haemophilus influenzae
• gram negative anaerobic bacilli
• mycobacteria

Question 17

what are the properties of coliforms

Answer 17

• gram negative bacilli
• gut commensals: E.Coli
• gut pathogens: Salmonella
• gentamicin is 1st line ABX

Question 18

what are the properties of strict aerobes

Answer 18

• gram negative bacilli

- eg legionella

Question 19

what are the properties of haemophilus influenzae

Answer 19

• gram negative bacilli

- common for chest infection, especially COPD exacerbations

Question 20

name a gram positive anaerobic bacilli

Answer 20

Clostridium spp

Question 21

name a gram negative anaerobic bacilli

Answer 21

bacteroides spp.

• normal gut commensals
• use metronidazole

Question 22

what are the properties of mycobacteria

Answer 22

• thick waxy outer coat

- TB

Question 23

how is DNA transferred by transformation

Answer 23

DNA transferred from dead bacteria to alive bacteria from the extracellular environment

Question 24

how is DNA transferred by transduction (bacteriophage)

Answer 24

transfer DNA through bacteriophage as vectors

Question 25

how is DNA transferred by conjugation

Answer 25

DNA transferred to from bacteria in physical contact using a sex pilus

Question 26

what are the 5 I's of infection

Answer 26

- inhalation - indigestion - intercourse - inoculations - mother to Infant

Question 27

what are bactericidal and bacteriostatic antibiotics

Answer 27

``` bactericidal = kills bacteria bacteriostatic = inhibits bacterial growth ```

Question 28

what spectrum can antibiotics be

Answer 28

broad eg tetracycline | narrow eg penicillin

Question 29

what antibiotics work on the cell wall

Answer 29

- penicillins - cephalosporins - glycopeptides

Question 30

for gram positive organisms they have a ___ PG layer and a ___ phospholipid bilayer

Answer 30

- thick | - single

Question 31

for gram negative organisms they have a ___ PG layer and ___ phospholipid bilayers

Answer 31

- thin | - 2

Question 32

what are the properties of penicillin

Answer 32

- are beta-lactam - bactericidal - may cause type 1 hypersensitivity - Eg, flucloxacillin (narrow s.), co-amoxiclav (broad s.), temocillin, amoxicillin.

Question 33

flucloxacillin is used for...

Answer 33

skin infections and soft tissue infections

Question 34

what are the properties of cephalosporins

Answer 34

- beta-lactam - bactericidal - may induce c.difficile growth

Question 35

what are the properties of glycopeptides

Answer 35

- NOT beta-lactam - bactericidal - only work on gram positive organisms - eg vancomycin

Question 36

what antibiotics inhibit protein synthesis

Answer 36

- macrolides - tetracyclines - aminoglycosides

Question 37

what are the properties of macrolides

Answer 37

- exreted via biliary tract - bacteriostatic - eg clarithromycin

Question 38

what are the properties of tetracyclines

Answer 38

- bacteriostatic - excreted via biliary tract - can destruct intestinal flora - eg doxycycline

Question 39

what are the properties of aminoglycosides

Answer 39

- bactericidal - act on gram negative organisms - eg Gentamicin

Question 40

what antibiotics work on bacterial DNA

Answer 40

- metronidazole - trimethoprim - floroquinolones

Question 41

what are the properties of metronidazole

Answer 41

- used for anaerobic organisms | - interacts with alcohol

Question 42

what are the properties of trimethoprim

Answer 42

- inhibits folic acid synthesis

Question 43

what are the properties of fluoroquinolones

Answer 43

- prevent supercoiling of DNA - bactericidal - promote C.difficile growth - eg ciprofloxacin

Question 44

what are the 4 C's to be avoided

Answer 44

- clindamycin - cephalosporins - co-amoxiclav - ciprofloxacin (fluoroquinolones)

Question 45

what are the stages of viral replication

Answer 45

- attachment (ligand>receptor) - entry via endocytosis - uncoating (viral nucleic acid released) - nucleic acid and protein synthesis - assembly (nucleic acid and proteins package together) - release: budding or lysis

Question 46

how do budding and lysis occur

Answer 46

- budding = viruses released in envelope derived from host cell's membrane - lysis = viruses accumulate until cell bursts - lysis kills the cell