Intro to Microbiology

Question 1

Eukaryotic species

Answer 1

A group of closely related organisms that breed among themselves

Question 2

Prokaryotic species

Answer 2

A population of cells w/ similar characteristics

Question 3

Clone

Answer 3

Population of cells derived from a single cell

Question 4

Strain

Answer 4

Genetically different cells within a clone

Question 5

Viral species

Answer 5

Population of viruses w/ similar characteristics that occupies a particular ecological niche

Question 6

Gram stain +ve and -ve

Answer 6

Bacteria to be characterised as Gram +ve if they retain the violet dye (peptidoglycan layer) or Gram -ve if they don’t (lipopolysaccharide layer)

Question 7

Process of the Gram stain

Answer 7

Crystal violet –> iodine treatment –> decolorisation

Question 8

Microorganism shapes

Answer 8

Round cells are called cocci (sing. coccus)

Rod-shaped cells are bacilli (bacillus)

Question 9

Acid Fast Bacilli stain

Answer 9

Mycobacteria aren’t stained during gram test due to mycolic acid layer in membrane. Waxy layer that is v. thick and very dense so doesn’t even pick up pink colour

Question 10

Process of acid fast bacilli stain

Answer 10

Apply primary stain of carbolfuschin for 30 seconds
Heat fix cells to the slide using the flame
Decolorize with acid alcohol for 15-20 seconds
Apply counterstain of methylene blue for 30 seconds then rinse excess stain

Question 11

Other ways to classify bacteria

Answer 11

Classification by phenotype
Classification by genotype
Classification by analytical methods

Question 12

Classification of bacteria by phenotype

Answer 12

How they behave w/ diff substrates/ Abx

Latex agglutination

Question 13

Classification of bacteria by genotype

Answer 13

G + C ratio
DNA hybridisation
DNA fragment analysis
Whole genome sequencing

Question 14

Classification of bacteria by analytical methods

Answer 14

Whole cell lipids
Cell wall
Whole cell protein (proteomics)

Question 15

Mycoses

Answer 15

Infections caused by fungi

Question 16

Arguments for viruses being living

Answer 16

Can mutate
Reproduce, only in living host cells
Respond to environmental stress

Question 17

Arguments for viruses being non-living

Answer 17

Acellular; no cytoplasm or cellular organelles
Carry out no metabolism on their own – use host mechanisms. New viral components are synthesized and assembled within infected host cell
Vast majority of viruses possess either DNA or RNA not both

Question 18

Prions

Answer 18

Protein containing particles w/ no detectable nucleic acid
‘Slow’ infectious diseases
Highly resistant infectious agent
No inflammation or immune response in affected

Question 19

Antibiotic susceptibility

Answer 19

Create ‘lawn’ of bacteria
Add filter disc w/ known quantity of antibiotic
Inhibition of growth around disc
‘Cut - off’ size of zone correlates to conc. of antibiotic in blood following normal dose

Question 20

Non-culture methods

Answer 20

Look for antigen
Look for antibody
Look for genome

Question 21

Looking for antigen

Answer 21

Known antibody will bind to antigen in sample
ELISA
Immunofluorescence

Question 22

Looking for antibody

Answer 22

Know antigen will bind to antibody in sample
ELISA
CFT

Question 23

Looking for genome

Answer 23

PCR: detect known sequence of DNA/RNA within sample

‘Fingerprinting’: compare DNA fragments w/ reference stains

Question 24

Examples of Abx resistant microorganisms

Answer 24

MRSA
C. difficile
ESBL bacteria
VRE

Question 25

MRSA

Answer 25

A Staphylococcus aureus that is methicillin and therefore penicillin, flucloxacillin resistant

Question 26

C. difficile

Answer 26

Anaerobic bacterium that lives in gut | Can become deregulated via the use of broad-spectrum antibiotics and overgrow causing pseudomembranes and colitis

Question 27

ESBL bacteria

Answer 27

Extended Spectrum Beta-lactamases Gram -ve Enterobacteriaceae that are resistant to all penicillin-based Abx Usually complicate urinary catheter and in situ drains

Question 28

VRE

Answer 28

Vancomycin-resistant enterococcus Commensal bacteria but can cause infections of the urinary tract, the bloodstream, or of wounds associated w/ catheters or surgical procedures Usually causes infections on hosp

Question 29

Causes of antibiotic resistance

Answer 29

Over-prescription of antibiotics Patients not finishing entire antibiotics course Antibiotics in livestock and fish farming Poor infection control in healthcare settings Poor hygiene and sanitation Absence of new antibiotics being discovered

Question 30

How do organisms cause disease

Answer 30

Invasion and damage to host cells; cell death and infl response --> toxin production (systemic or local) ---> response to infection; "immune mediated"

Question 31

Types of innate defences

Answer 31

Mechanical Chemical Cellular

Question 32

Mechanical innate defences

Answer 32

Respiratory tract GI tract Skin

Question 33

Respiratory tract as a mechanical innate defence

Answer 33

``` Nasal hair URT anatomy Secretions Epithelial sloughing Muscociliary apparatus Expulsion ```

Question 34

Muscocilliary expulsions

Answer 34

Uses motion of ciliated epithelium to bring out bacteria

Question 35

GI tract as mechanical innate defence

Answer 35

Secretions Epithelial sloughing Peristalsis Elimination

Question 36

Skin as mechanical innate defence

Answer 36

Waterproofing | Tight junctions

Question 37

Chemical innate defences

Answer 37

Lysozyme Iron binding proteins e.g. lactoferrin Defensins e.g. cathelicidins Surfactant

Question 38

Chain of infection

Answer 38

Microbe ----> Reservoir ---> Escape route ----> Transmission ---> Point of entry ---> Host ---->

Question 39

Reservoir

Answer 39

Place where infection is prevalent | Can be animal

Question 40

Esacpe route

Answer 40

How microbe spreads from reservoir

Question 41

What does the environment classify

Answer 41

Transmissibility of viruses by the environment they spread from

Question 42

Airborne spread

Answer 42

``` Tiny particles 1-5 micrometres Cough aerosol Remain suspended in air indefinitely Can reach alveoli easily Low numbers but high virulence organisms e.g. TB, measles ```

Question 43

Droplet spread

Answer 43

Remain suspended for 17 mins Deposit in upper airway 1m spread Impact on mucous membrane

Question 44

Person to person transmission

Answer 44

``` Direct contacts - skin to skin Faecal-oral Inhalation Sexual transmission Blood to blood Vertical ```

Question 45

Examples of vertical transmission

Answer 45

Mother to foetus | Mother to baby

Question 46

Fomite

Answer 46

An inanimate object that is capable of transmitting infectious organisms from one individual to another e.g. keyboard

Question 47

Vertical transmission routes

Answer 47

Mother's bloodstream Mother's genital tract Breast-feeding

Question 48

What your does Gram-ve bacteria stain

Answer 48

Pink