Skin and soft tissue infections Flashcards Preview

Clinical Pathology > Skin and soft tissue infections > Flashcards

Flashcards in Skin and soft tissue infections Deck (46):
1

What are the main organisms that colonise the skin?

-Coagulase-negative Staphylococci
-S Aureus
-Propionibacterium (e.g. Acnes)
-Corynebacterium

2

What is the pathogenesis of skin infections?

Inoculation
- penetrate skin with contaminated objects
- Contamination of pre-existing breach in skin surface

Other route - neuronal migration in herpes simplex

Systemic/generalised infection

3

What viral infections cause skin infections?

Herpes simplex virus

VZV - shingles

Molluscum contagiosum

Cow pox - first virus to be vaccinated

Orf- sheets/goats - purulent producing papule

4

What is the pathogenesis of the HSV?

Vesicle formation -> ulceration -> weeping vesicular lesions (virus release)

Gains entry through sensory nerve endings and remains in dorsal root ganglion

Latent = episome - no immune repose

Reactivation - migrates downward to sensory root ends and manifests

5

What are the two types of HSV infection

Primary - occurs once - usually in infancy, extensive painful lesions in mouth

Secondary - occurs time again - weeping vesicles (peri oral and genital)

6

What triggers a reactivation infection of HSV?

Stress or infection

7

What is the type of herpes that MAINLY causes a) mouth herpes; b) genital herpes

HSV1 (mouth)
HSV2 (genital)

8

How his herpes simplex virus diagnosed?

Clinical usually
Vesicle fluid releases virus (PCR detection of viral DNA)

9

What is the treatment fora) cold sores and b) genital herpes

a) topical acyclovir
b) oral acyclovir

10

What is the primary and secondary manifestations of VZV

a) chicken pox
b) shingles

11

How does latent infection of VZV present?

Shingles - weeping vesicular rash

Dermatome distribution

12

How is VZV diagnosed?

Clinical
Vesicle fluid - PCR VZV DNA

13

What is the treatment for shingles

Acyclovir/valacyclovir - Oral/IV

14

How does the molluscum contagiosum virus present?

Raised PEARLY lesions
Umbilicated

15

How is molloscum contagious diagnosed?

Clinical - very simple

16

What is the treatment for molloscum contagiosum treated?

None - usually disappear with 6-18 months

17

What are the main causative organisms for bacterial skin infections?

Staph Aureus
Strep Pyogenes

Also H influenzae, pasteurella multocida (cat/dogs)

18

What type of bacteria is staph areus? What exotoxins does it produce that are important in the context of skin infections?

Gram positive- normal nasal flora (30% pop)

-epidermolytic toxin A and B (ETA/ETB)
- Toxic shock syndrome toxin
- Paton valentine leucocidin (PVL)

19

What is the main action of strep pyogenes?

Haemolytic

20

What is the causative bacteria that cause impetigo?

S aureus
S Pyogenes

21

How does impetigo present?

Usually on face (around nose -mainly children) - infection of epidermis

Plaque-like lesions
Yellowish exudate
Thick scabs - honey comb lesions

22

How is impetigo diagnosed?

Clinical
Bacterial culture

23

What are the complications of impetigo? What is the pathogenesis?

Bullous impetigo

Staphylococcal scalded skin syndrome (SSSS)

Exotoxin - Epidermolytic toxin A&B

24

What area of skin and bodily areas mainly is effected by erysipelas?

Dermis

Face and shin

25

What is the causative bacteria for erysipelas?

S Pyogenes

26

How does erysipelas present?

Lymph node enlargement

Fever and malaise

Well demarcated inflamed lesion - red, swollen, painful, hot

27

What is cellulitis?

Infection of the skin and subcutaneous tissue?

28

What are the causative organisms for cellulitis?

P Aureus
S Pyogenes
H influenzae
Pasturella multocida (animal bites)

29

How does cellulitis present?

Site of inoculation (portal of entry may not be observable!)

Diffuse enlargement - not well demarcated - erythema (redness), swelling, tenderness, hot

Any part of body - UNILATERAL

Fever and malaise

30

How is cellulitis diagnosed?

-Clinical diagnosis
-Unilateral (discount bilateral differentials)

-Lesion swabs
-Blood cultures (rare though)

31

What is the pathogen causing anthrax?

Bacillus anthracis
- spore forming aerobic gram positive

32

Where is the source for anthrax?

Imported wool, hides, hair, drum skins

33

What is the pathogenesis of anthrax?

Inoculation through breaks in the skin

34

How does anthrax present?

Malignant pustule

35

When is anthrax lethal?

If inhaled/septicaemic

Cutaneous = readily treated

36

What are the two types of necrotising fascitis and what bacteria causes them?

Type 1 - polymicrobrial - anaerobes, gram negative bacilli (from large bowel)

Type 2 - strep pyogenes

37

How does necrotising fascitis present?

Dark, rapidly spreading necrotising lesion

Fever and malaise (very sick!)

38

What is the treatment of necrotising fascitis?

IV antibiotics
Surgical debridement

39

What is the causative organism for gas gangrene?

Clostridium perfrinigens - anaerobic gram positive

Dirty lower GI procedures/limb amputation

40

How does gas gangrene present and whats its treatment?

Subcutaneous gas
Dark rapidly spreading necrotising

IV antibiotics and limb debridement

41

When should topical/ora/IV antibiotics be used?

Topical - superficial infections e.g. impetigo erysipelas

Oral/IV = more severe - cellulitis/necrotising fascitis/gas gangrene etc

42

What is the treatment for staph aureus/strep pyogenes

Penecillin (flucloxacillin)

Allergy -erythromycin/calrithromycin vancomycin, linezoid

MRSA - vancomycin, linezoid

43

What antibiotics are used to treat anaerobic infections?

Metronidazole

44

What antibiotics should we use for necrotising facilities?

Meropenem
Clindamycin

45

What are skin fungal infections referred to as? What is there pathogenisis

Dermatophyte infections

Use keratin as nutritional substrate

46

What are the name of dermatophyte infections?

Skin
-Tina corporis
- Tina pedis (athletes foot)

Scalp
Tina capitus (ring worm)

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