Microbiology

Question 1

What is a pathogen?

Answer 1

Organism that is capable of causing disease

Question 2

What is a commensal organism?

Answer 2

An organism that colonises the host but causes no disease in normal cirumstances

Question 3

What is an opportunistic pathogen?

Answer 3

Microbe that only causes disease if host defences are compromised

Question 4

What is virulence/pathogenicity?

Answer 4

The degree to which a given organism is pathogenic

Question 5

What is asymptomatic carriage?

Answer 5

When a pathogen is carried harmlessly at a tissue site where it causes no disease

Question 6

What is general rule for naming bacteria?

Answer 6

Genus first then species second

Question 7

What is the name for round bacteria?

Answer 7

Coccus

Question 8

What is the name for rod shaped bacteria?

Answer 8

Bacillus

Question 9

What colour do gram positive bacteria stain?

Answer 9

Purple (purple has 2 p’s)

Question 10

What colour do gram negative bacteria stain?

Answer 10

Pink (pink has an n in it)

Question 11

What is a diplococcus bacteria?

Answer 11

A bacterium that occurs as pairs of cocci

Question 12

Apart from by themselves or in pairs, how else can coccus bacteria occur?

Answer 12

Chain of cocci and cluster of cocci

Question 13

What ways can bacillus arrange themselves?

Answer 13

Individually, chains of rods, curved rods or spiral rods

Question 14

What is the name for curved bacillus?

Answer 14

Vibrio

Question 15

What is the name for spiral bacillus?

Answer 15

Spirochete

Question 16

What is the main 2 differences between gram positive and gram negative bacteria?

Answer 16

Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane. Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.

Question 17

What is the environment needed to kill bacteria?

Answer 17

50 years for spores) and UV light

Question 18

How longs does the average bacteria take to double?

Answer 18

Less than an hour. E. coli doubles every 20-30 minutes, but some can take up to 2 weeks.

Question 19

What is an endotoxin?

Answer 19

Lipopolysaccharides found in the cell wall of Gram-negative bacteria, which can induce inflammation and fever as an immune response in higher organisms

Question 20

What is an exotoxin?

Answer 20

Group of soluble proteins that are secreted by the bacterium, enter host cells, and catalyse the covalent modification of a host cell component(s) to alter the host cell physiology

Question 21

How is transcription in bacteria similar to transcription in eukaryotic cells?

Answer 21

Still uses RNA polymerase to create mRNA

Question 22

Is bacteria division a stable or unstable process?

Answer 22

Very unstable, prone to mutations. These can be base substitution, deletion or insertion

Question 23

Why does bacterial division instability make them hard to treat?

Answer 23

They are always changing

Question 24

What are plasmids?

Answer 24

Small, often circular DNA molecule found in bacteria and other cells

Question 25

Why are plasmids known as promiscuous?

Answer 25

They can be exchanged between cells

Question 26

What are some examples of what plasmids may contain?

Answer 26

Transfer promotion genes, plasmid maintenance genes, antibiotic or virulence determinant genes

Question 27

What are the gene transfer methods plasmids can be exchanged?

Answer 27

Transformation e.g. via plasmid, transduction e.g. via phage, conjugation e.g. via sex pilus

Question 28

What is the classification of bacteria?

Answer 28

Really complicated. Quite hard to do on flashcards, have a look at some images

Question 29

Why do gram positive bacteria stain purple?

Answer 29

The thick peptidoglycan layer cannot be easily penetrated by the solvent

Question 30

What is coagulase?

Answer 30

An enzyme produced by bacteria that clots blood plasma. Fibrin clot formation around bacteria may protect them from phagocytosis

Question 31

What are the bacterial classifications of bacteria?

Answer 31

Can be coagulase +ve or -ve

Question 32

What type of infections are coagulase -ve species important in?

Answer 32

Opportunistic infections

Question 33

What is the normal habitat for staphylococcus?

Answer 33

Nose and skin

Question 34

How is staphylococcus aureus spread?

Answer 34

Aerosol and touch

Question 35

What virulence factors do staphylococcus aureus have?

Answer 35

Pore forming toxins, proteases, toxic shock syndrome toxin and protein A

Question 36

What is MRSA resistant to?

Answer 36

Beta-lactams and many other antibiotics now

Question 37

What are the 2 types of infection caused by MRSA

Answer 37

Pyogenic (wound infections and abscesses (boils carbuncles)) and toxin mediated (scalded skin syndrome)

Question 38

What does S. epidermis cause?

Answer 38

Wound infections, boils, sinus infections, endocarditis and other inflammations. Commonly infections in debilitated prostheses

Question 39

What does S. saprophyticus cause?

Answer 39

Common cause of UTIs but also causes acute cystitis

Question 40

What is haemolysis?

Answer 40

Breakdown or destruction of red blood cells

Question 41

What is beta type haemolysis?

Answer 41

Complete lysis of red cells in the media around and under the colonies

Question 42

What causes beta haemolysis?

Answer 42

2 hemolysins O and S

Question 43

What is alpha haemolysis?

Answer 43

Reduction of the red blood cell haemoglobin to methaemoglobin in the medium surrounding the colony

Question 44

What causes alpha haemolysis?

Answer 44

Hydrogen peroxide produced by the bacterium. H2O2 reacts with Hb.

Question 45

What is a serogroup?

Answer 45

A group of serotypes having one or more antigens in common

Question 46

How can you test for Lancefield A-h and K-v serogroups?

Answer 46

Antiserum added to each group and added to the suspension of bacteria. Clumping indicates recognition

Question 47

What are the S. pyogenes virulence factors?

Answer 47

Exported factors, toxins and surface factors

Question 48

What are the infections caused by S. pyogenes?

Answer 48

Wound infections (cellulitis and puerperal fever), tonsillitis and pharyngitis, otitis media, impetigo, scarlet fever, complications (rheumatic fever)

Question 49

Where can S. pneumoniae exist normal commensally?

Answer 49

The oropharynx (30% of the population)

Question 50

What does S. pneumonia cause?

Answer 50

Pneumonia, otitis media, sinusitis and meningitis

Question 51

What are the predisposing factors that assist S. pneumonia?

Answer 51

Impaired mucus trapping (e.g. viral infection), hypogammaglobulinemia and asplenia

Question 52

What are the virulence factors of S. pneumonia?

Answer 52

Capsule, inflammatory wall constituents and cytotoxin

Question 53

Why do gram negative bacteria stain pink?

Answer 53

The thinner peptidoglycan layer allows the stain to wash out by the solvent

Question 54

What is lipopolysaccharide?

Answer 54

Major component of the wall of gram negative bacteria. Can also be classed as an endotoxin

Question 55

What are pathogenicity determinants (virulence determinant or virulence factors)?

Answer 55

Any bacteria-associated product or strategy that contributes to pathogenicity/virulence

Question 56

What are the colonisation factors?

Answer 56

Adhesions, invasins, nutrient acquisition and defence against the host