Microbiology

Question 1

what are virulence factors

Answer 1

molecules produced by pathogens that contribute to the pathogenicity of the organism

Question 2

what is the pathogenesis of bacteria

Answer 2

1- Contact/entry host
2 - Adhere/Colonise and invade
3 - Evade host defences
4 - Multiply/complete its life cycle
5 - exit host
6 - release/spread
7 - reservoir of pathogens

Question 3

what is virulence

Answer 3

the capacity of a micro-organism to cause disease/damage to the hose

Question 4

what are the virulence factors

Answer 4

adhesin
invasin
impedin
aggressin 
modulin

Question 5

what is adhesin

Answer 5

enabled binding of the organism to host tissue

Question 6

what is invasin

Answer 6

enables the organism to invade a host cell/tissue

Question 7

what is impedin

Answer 7

enables the organism to avoid host defence mechanism

Question 8

what is aggressin

Answer 8

causes damage to the host directly

Question 9

what is modulin

Answer 9

induces damage to the host indirectly

Question 10

what VF are responsible for variation

Answer 10

adhesin, impedin, aggressin

Question 11

what are the VF of S.aureus

Answer 11

firbinogen binding protein
leukocidin (PVL)
TSST-1 (toxin)

Question 12

what are examples of adhesins/attachment

Answer 12

fibrinogen-binding

collagen-binding

Question 13

what helps with evasion of host defences

Answer 13

supertoxins
PVL
alpha toxin

Question 14

what is PVL

Answer 14

Panton-Valentine Leukocidin
produced by some strains of Staph Aureus
has toxicity for leukocytes
associated with severe skin infections

Question 15

what is PVL and alpha toxin linked with

Answer 15

CA-MRSA responsible for necrotising pneumonia and contagious severe skin infections

Question 16

what are superantigens

Answer 16

class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release

Question 17

what super antigen is associated with toxic shock

Answer 17

TSST-1

Question 18

what is the diagnostic criteria for toxic shock

Answer 18

fever
diffuse macular rash
hypotension
more or equal to 3 organ systems involved (liver, blood, renal, mucous membranes, GI, MSK, CNS)

Question 19

what skin infections does strep. pyogenes cause

Answer 19

impetigo
cellulitis
necrotising fasciitis
toxic shock like syndrome (TSLS)

Question 20

what is special about strep. pyogenes

Answer 20

beta haemolysis

GAS

Question 21

features of S.aureus infection

Answer 21

localised
no bacteremia
menstrual TSST-1
pyrogenic toxin

Question 22

most common toxins of S.pyogenes

Answer 22

SpeA and SpeC

Question 23

typical appearance of Staph sp.

Answer 23

Gram positive cocci in clusters

Question 24

what is the only coagulase positive Staph that appears golden

Answer 24

Staph. aureus

Question 25

what colour does coagulase neg staph appear

Answer 25

white

Question 26

what antibiotic treats staph aureus

Answer 26

flucloxacillin

Question 27

what are some toxins that staph aureus releases

Answer 27

Enterotoxin – food poisoning SSSST – staph. scalded skin syndrome toxin PVL – Panton Valentine Leukocidin

Question 28

how does strep appear

Answer 28

gram positive cocci in chains (strips)

Question 29

what are the 3 types of strep

Answer 29

β(beta)-haemolytic (complete haemolysis) α(alpha)-haemolytic (partial haemolyis) γ(gamma) or non-haemolytic (no haemolysis)

Question 30

what are the 2 alpha haemolytic strep

Answer 30

Strep pneumoniae | Strep viridans

Question 31

what skin infection does staph aureus cause

Answer 31

``` Cellulitis Infected eczema Impetigo Wound infection Staphylococcal scalded skin syndrome ```

Question 32

describe strep pyogenes

Answer 32

Beta haemolytic Group A Strep only one in the group sometimes called group A streptococcus (GAS)

Question 33

what skin diseases does strep pyogenes cause

Answer 33

Infected eczema Impetigo Cellulitis Necrotising fasciitis

Question 34

treatment for strep pyogenes

Answer 34

penicillin | flucoloxacillin also works

Question 35

what is necrotising faciitis

Answer 35

Bacterial infection spreading along fascial planes below skin surface → rapid tissue destruction

Question 36

presentation of necrotising faciitis

Answer 36

little to see on skin surface | severe pain

Question 37

tx of necrotising faciitis

Answer 37

debridement required | antibiotic depends on organims affecting

Question 38

leg ulcers always get swabbed - true or false

Answer 38

false | very rarely swabbed, only if cellulitis suspected

Question 39

what is the name for ringworm infections

Answer 39

tinea

Question 40

appearance of fungal infection

Answer 40

lesion grows outwards and heals in centre | gives ring appearance

Question 41

what type of ringworm mainly affects children

Answer 41

scalp ringwoem | tinae capitis

Question 42

what are Dermatophytes

Answer 42

fungal infections that utilize keratin

Question 43

what are the most common fungus affecting skin

Answer 43

Trichophyton rubrum | Trichophyton mentagraphytes

Question 44

fungal treatment

Answer 44

Clotrimazole cream Scalp infections - Terbinafine orally OR Itraconazole orally

Question 45

what causes infections in skin folds and what is the treatment

Answer 45

candida clotrimazole cream fluconazole oral

Question 46

what causes scabies

Answer 46

sarcoptes scabiei

Question 47

what is the incubation period for scabies

Answer 47

6 weeks

Question 48

symptoms of scabies

Answer 48

Intensely itchy rash affecting finger webs, wrists, genital area

Question 49

tx of scabies

Answer 49

``` malathion lotion, applied overnight to whole body and washed off next day benzyl benzoate (avoid in children) ```

Question 50

what are the 3 types of lice

Answer 50

``` Pediculus capitis (head louse) Pediculus corporis (body louse) a.k.a Vagabond’s disease Phthirus pubis (pubic louse) ```

Question 51

tx of lice

Answer 51

malathion