Microbiology Flashcards

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1
Q

what are virulence factors

A

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

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2
Q

what is the pathogenesis of bacteria

A
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
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3
Q

what is virulence

A

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

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4
Q

what are the virulence factors

A
adhesin
invasin
impedin
aggressin 
modulin
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5
Q

what is adhesin

A

enabled binding of the organism to host tissue

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6
Q

what is invasin

A

enables the organism to invade a host cell/tissue

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7
Q

what is impedin

A

enables the organism to avoid host defence mechanism

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8
Q

what is aggressin

A

causes damage to the host directly

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9
Q

what is modulin

A

induces damage to the host indirectly

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10
Q

what VF are responsible for variation

A

adhesin, impedin, aggressin

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11
Q

what are the VF of S.aureus

A

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

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12
Q

what are examples of adhesins/attachment

A

fibrinogen-binding

collagen-binding

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13
Q

what helps with evasion of host defences

A

supertoxins
PVL
alpha toxin

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14
Q

what is PVL

A

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

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15
Q

what is PVL and alpha toxin linked with

A

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

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16
Q

what are superantigens

A

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

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17
Q

what super antigen is associated with toxic shock

A

TSST-1

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18
Q

what is the diagnostic criteria for toxic shock

A

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

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19
Q

what skin infections does strep. pyogenes cause

A

impetigo
cellulitis
necrotising fasciitis
toxic shock like syndrome (TSLS)

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20
Q

what is special about strep. pyogenes

A

beta haemolysis

GAS

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21
Q

features of S.aureus infection

A

localised
no bacteremia
menstrual TSST-1
pyrogenic toxin

22
Q

most common toxins of S.pyogenes

A

SpeA and SpeC

23
Q

typical appearance of Staph sp.

A

Gram positive cocci in clusters

24
Q

what is the only coagulase positive Staph that appears golden

A

Staph. aureus

25
Q

what colour does coagulase neg staph appear

A

white

26
Q

what antibiotic treats staph aureus

A

flucloxacillin

27
Q

what are some toxins that staph aureus releases

A

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

28
Q

how does strep appear

A

gram positive cocci in chains (strips)

29
Q

what are the 3 types of strep

A

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

30
Q

what are the 2 alpha haemolytic strep

A

Strep pneumoniae

Strep viridans

31
Q

what skin infection does staph aureus cause

A
Cellulitis
Infected eczema
Impetigo
Wound infection
Staphylococcal scalded skin syndrome
32
Q

describe strep pyogenes

A

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

33
Q

what skin diseases does strep pyogenes cause

A

Infected eczema
Impetigo
Cellulitis
Necrotising fasciitis

34
Q

treatment for strep pyogenes

A

penicillin

flucoloxacillin also works

35
Q

what is necrotising faciitis

A

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

36
Q

presentation of necrotising faciitis

A

little to see on skin surface

severe pain

37
Q

tx of necrotising faciitis

A

debridement required

antibiotic depends on organims affecting

38
Q

leg ulcers always get swabbed - true or false

A

false

very rarely swabbed, only if cellulitis suspected

39
Q

what is the name for ringworm infections

A

tinea

40
Q

appearance of fungal infection

A

lesion grows outwards and heals in centre

gives ring appearance

41
Q

what type of ringworm mainly affects children

A

scalp ringwoem

tinae capitis

42
Q

what are Dermatophytes

A

fungal infections that utilize keratin

43
Q

what are the most common fungus affecting skin

A

Trichophyton rubrum

Trichophyton mentagraphytes

44
Q

fungal treatment

A

Clotrimazole cream

Scalp infections - Terbinafine orally OR Itraconazole orally

45
Q

what causes infections in skin folds and what is the treatment

A

candida
clotrimazole cream
fluconazole oral

46
Q

what causes scabies

A

sarcoptes scabiei

47
Q

what is the incubation period for scabies

A

6 weeks

48
Q

symptoms of scabies

A

Intensely itchy rash affecting finger webs, wrists, genital area

49
Q

tx of scabies

A
malathion lotion, applied overnight to whole body and washed off next day
benzyl benzoate (avoid in children)
50
Q

what are the 3 types of lice

A
Pediculus capitis (head louse)
Pediculus corporis (body louse)
a.k.a Vagabond’s disease
Phthirus pubis (pubic louse)
51
Q

tx of lice

A

malathion