CP 62 - Skin Soft Tissue Infection Flashcards Preview

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Flashcards in CP 62 - Skin Soft Tissue Infection Deck (58):
1

what are the normal layers of the skin

outer layer, epidermis, sebaceous gland, dermis, subcutaneous adipose tissue

2

what are the function of the skins

Physical barrier: chemicals, UV, micro-organisms
Homeostasis: thermoregulation, prevention of dessication electrolyte loss
Immunological function: Ag presentation and phagocytosis (Langerhans cells, lymphocytes, mononuclear phagocytic cells)

3

what are some of the normal flora of the skins?

Coagulase-negative staphylococci, Staph. aureus, Propionibacterium, Corynebacterium spp.

4

what does herpes simplex virus cause?

herpes simplex

5

what does varicella zoster virus cause?

herpes zoster - shingles

6

what is the pathogenesis of herpes simplex

vesicle formation - ulceration and release vesicle fluid containing infective particles

virus enter via sensory nerve endings and migrates along nerve to dorsal root ganglion

In latent infection viral DNA exists as “episomes” and no virus-coded proteins are present to stimulate an immune response

In reactivation it is believed that virus particles migrate outwards to sensory nerve endings and cause clinical manifestations of infection

7

what can trigger HSV reactivation

infection or stress - preceded by tingling

8

what is primary infection of HSV

in infant

9

what does HSV-2 cause?

genital herpes

10

what does HSV-1 cause ?

general herpes - ie in the mouth mainly

11

what is secondary infection of HSV

at all ages - peri-oral/genital (which can present as weeping & vesicular)

12

what is the diagnosis of HSV

clinical diagnosis or if difficult PCR for herpes virus DNA

13

what is coldsore

?

14

what is treatment of HS eg in cold sores, genital herpes, immunosuppressed patient

Cold sores
Topical acyclovir
Genital herpes, immunosuppressed patient
Oral acyclovir

15

what is the previous medical history of herpes zoster (shingles)

Previous chickenpox
“Latent” infection

Triggered by physical or emotional insult
Preceded by tingling and/or pain

Weeping, vesicular rash
Dermatomal distribution

16

what is the diagnosis of herpes zoster (shingles)

Weeping, vesicular rash
Dermatomal distribution

17

what is treatment of HZS

Oral acicolvir/valaciclovir
IV aciclovir
Depending on age of patient, immune status and severity of shingles

18

what is Molluscum contagiosum

not really troublism Causative agent

19

what is the clinical presentation of Molluscum contagiosum

Raised, pearly lesions up to 3 mm
Umbilicated

20

what is diagnosis of Molluscum contagiosum

clinical diagnosis

21

what is treatment of Molluscum contagiosum

None – lesions usually disappear in 6-18 months
Various topical preparations
Physical treatments (cryotyherapy, diathermy, laser therapy)

22

what is the general bacterial infection?

Causative agents
Mainly Staph. aureus and group A β-haemolytic streptococci (S. pyogenes)
A few others e.g. Haemophilus influenzae, Pasteurella multocida, enteric organisms and rarities

23

what is the feature of S. aureus

Gram-positive cocci in clusters, catalase-positive

Normal nasal flora in approx. 30% of pop’n

Exotoxin production

24

what type of Streptoccus pyogenes

haemolytic

Gram-positive cocci in chains, catalase-negative

Express many virulence factors

25

where does impetigo normally infect?

epidermis -Often occurs at a site of skin damage


causative agent = S. aureus, S. pyogenes or both

26

how does impetigo present clinically

Plaque-like lesions
Yellowish exudate
Thick scabs
“Honey crusted lesions”

27

how can impetigo be diagnosised

clinical diagnosis, Bacterial culture
Sensitivity testing may be useful

28

what are some of the complication of impetigo

Epidermolytic toxin production (ETA & ETB)

Manifestations -

Localised: Bullous impetigo

Generalised: Staphylococcal scalded skin syndrome (SSSS)

29

where doe erysipelas firstly infected

dermis with causative agent - S. pyogenes

30

how can erysipelas cause problem

Often occurs at a site of skin damage
Predominantly face or shin
Preceded by pain & tenderness

31

what is the presentation of erysipelas

Examination
Fever & malaise
Well-demarcated inflamed lesion
Red, swollen, painful and hot
Lymph node enlargement

32

what is the diagnosis of eryspielas

Clinical diagnosis
Culture rarely helpful

33

where doe erysipelas firstly infected

Infection of skin and subcutaneous tissues
Causative agents include:
S. aureus
S. pyogenes
Pasteurella multocida (animal bites)
Haemophilus influenzae

34

how will cellulitis present

Fever & malaise
Diffuse inflamed lesion
Erythema, swelling, tenderness, heat

35

how can cellulitis enter the system

Site of skin penetration
Cut, graze, intravenous catheter, surgical instrument, bite (human or animal) etc.
Any part of body
Portal may not be apparent

36

how can you distinguish cellulitis from other similar condition

cellulitis is not bilacteral

37

diagnosis of cellulitis ?

- Clinical diagnosis
- Broad differential diagnosis
- Microbiology
- Lesion swabs
Positive in 85% of cases
Swab if lesion is ulcerated
- Lesion aspirates and skin biopsy (Positive in 10-20% of cases, Not recommended routinely)
Blood cultures (only Positive in only 2-4% of cases, Use if severe sepsis or systemic signs of infection)

38

how can anthrax be acquired

Acquired from imported wool, hair and animal hides - Inoculation through breaks in the skin

39

what organism can cause antrax

Bacillus anthracis - Spore-forming aerobic Gram-positive bacillus

40

what is necrotising fasciitis

Infection of skin and subcutaneous tissues

41

what is the causative organism of necrotising fasciitis

Type 1: Polymicrobial
Enteric Gram-negative bacilli
Anaerobes
Type 2: Streptococcus pyogenes

42

how does necrotising fasciitis present

Spontaneous or at site of skin penetration
Any part of body
Fever & malaise
Dark, rapidly spreading, necrotic lesion

43

what is the diagnosis of necrotising fasiitis

clinical diagnosis
Microscopy and culture
Debrided material
Blood culture - often +ve

44

what is treatment of necrotising fasciitis

Intravenous antibiotics
Surgical debridement

45

what is gas gangrene

caused by anaerobic infections

46

what is clinical feature of gas gangrene

Clinically similar to “synergistic gangrene” (polymicrobial necrotising fasciitis)
Palpable subcutaneous gas

47

when is gas gangrene normally arise

post-op eg amputation

48

what is the organism of gas gangrene

Clostridium perfringens (anaerobic Gram-positive bacillus)

49

treatment of gas gangrene

Intravenous antibiotics
Surgical debridement

50

what are the 2 organisms which causes most of the infections of the skins and soft tissue

Staph. aureus or Strep. pyogenes

51

what is the empiric therapy

Flucloxacillin

52

what is special antibiotics that is used to treat necrotising fasciitis

need to cover anaerobes, Enterobacteriaceae, streptococci and staphylococci

Meropenem + clindamycin

53

what is special antibiotics that is used to treat anaerobic infections

Include anti-anaerobic agents (e.g. metronidazole)

54

where does fungal infection normally arise

dermatophyte infection

skin eg Tinea corporis, tinea pedis (athletes foot), tinea cruris

nail - Onychomycosis

Scalp - Tinea capitis (scalp ringworm, kerion)

55

what are the common causative organism of dermatophyte infection

Dermatophyte fungi
Tricophyton spp. (e.g. T. rubrum)
Microsporum spp. (e.g. M. canis)

56

how can you diagnosis of Dermatophyte infections

Skin scrapings - microscopy & culture
Exclude other conditions e.g. psoriasis

57

what is the treatment of Dermatophyte infections

Topical or systemic antifungal agents
Depending on site & extent of infection

58

what is the treatment for Dermatophyte infections

Skin infections
Topical antifungal therapy
Clotrimazole, terbinafine

Scalp and nail infections
Systemic antifungal therapy
Terbinafine, itraconazole, griseofulvin