Skin and Soft Tissue Infections Flashcards
(120 cards)
1
Q
name the layers of the skin
A
stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum basale
2
Q
what is the infection site in the epidermis?
A
impetigo
3
Q
what is the infection site in the dermis and upper subcut fat?
A
folliculitis
erysipelas
4
Q
what is the infection site in the lower dermis and upper sub cut fat?
A
cellulitis
5
Q
what is the infection site in the lower subcut fat and muscle fascia
A
necrotising fascitis
6
Q
organisms causing impetigo
A
s. aureus
strep pyogenes
7
Q
organisms causing folliculitis
A
s. aureus
8
Q
organisms causing erysipelas
A
strep pyogenes
9
Q
organisms causing cellultitis
A
strep pyogenes (common)
s. aureus (uncommon)
h. influenzae (rare)
10
Q
organisms causing necrotising fascitis?
A
strep pyogenes
mixed bowel flora
11
Q
what is impetigo?
A
superficial skin infection
12
Q
what does impetigo look like?
A
multiple vesicular lesions on an arythematous base
golden crust
13
Q
causes of impetigo
A
most common s. aureus
less common strep pyogenes
14
Q
what age is most affected by impetigo ?
A
2-5 yrs
15
Q
how infectious is impetigo ?
A
highly
16
Q
where does impetigo occur?
A
exposed parts of the body including face, extremities, scalp
17
Q
predisposing factors for impetigo
A
skin abrasions minor trauma burns poor hygiene insect bites chickenpox eczema atopic dermatitis
18
Q
treatment of impetigo
A
small area - topical antibiotics
large area - topical and oral antibiotics - flucloxacillin
19
Q
what is erysipelas?
A
infection of the upper dermis
20
Q
features of erysipelas?
A
painful, read area (no central clearning)
associated fever
regional lymphadenopathy and lymphangitis
typically has distinct elevated borders
21
Q
most common cause of erysipelas
A
strep pyogenes
22
Q
where does erysipelas occur?
A
70-80% - lower limbs
5-20% - face
areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, DM
23
Q
what is the recurrence rate for erysipelas?
A
30% within 3 years
24
Q
what is cellulitis?
A
diffuse skin infection involving deep dermis and subcutaneous fat
25
how does cellulitis present?
spreading erythematous area with no distinct borders
26
most common causes of cellulitis
strep pyogenes
| staph aureus
27
features of cellulitis
fever
| regional lymphadenopathy and lymphangitis
28
predisoposing factors for cellulitis
DM
tinea pedis
lymphoedema
29
treatment of erysipelas and cellulitis
combination of anti-staphylococcal and anti-streptococcal antibiotics
in extensive disease, admission for IV antibiotics
30
name the hair-associated infections
folliculitis
furunculosis
carbuncles
31
features of folliculitis
circumscribed, pustular infection of a hair follicle
up to 5mm in diameter
small red papules
central area of purulence that may rupture and drain
32
where is folliculitis typically found?
head
back
buttocks
extremities
33
most common cause of folliculitis
staph aureus
34
features of furunculosis
furuncles commonly referred tto as boils
single hair follicle associated inflammatory nodule
extending into dermis and SC tissue
may spontaneously drain purulent material
35
where does furunculosis commonly affect?
moist, hairy, friction prone areas of the body - face, axilla, neck, buttocks
36
most common organism causing furunculosis
staph aureus
37
systemic symptoms of furunculosis
uncommon
38
risk factors for furunculosis
```
obesity
DM
atopic dermatitis
chronic kidney disease
corticosteroid use
```
39
when does a carbuncle occur?
when infection extends to involve multiple furuncles
40
where are carbuncles often found?
back of neck
| posterior trunk or thigh
41
features of carbuncle
multiseptated abscesses
| purulent material may be expressed from multiple sites
42
systemic symptoms of carbuncle
common
43
treatment of folliculitis
no treatment or topical antibiotics
44
treatment of furunculosis
no treatment or topical antibiotics
| if not improving oral antibiotics
45
treatment of carbuncle
often require admission to hospital, surgery and IV antibiotics
46
where can necrotising fasciitis occur?
anywhere
47
predisposing conditions for necrotising fasciitis
```
DM
surgery
trauma
peripheral vascular disease
skin popping
```
48
what is type 1 necrotising fasciitis?
mixed aerobic and anaerobic (diabetic foot infection, Fournier's gangene)
49
type 1 necrotising fasciitis causative agents
```
streptococci
staphylococci
enterococci
gram negative bacilli
clostridium
```
50
what is type 2 necrotising fasciitis?
monomicrobial
51
type 2 necrotising fasciitis causative agents
strep pyogenes
52
features of necrotising fasciitis
rapid onset
sequential development of erythema, extensive oedema, and severe unremitting pain
haemorrhagic bullae, skin necrosis and crepitus
fever, hypotension, tachycardia, delirium and multiorgan failure
53
what feature is highly suggestive of necrotising fasciitis?
anaesthesia at site of infection
54
treatment of necrotising fasciitis
surgery
| broad spectrum antibiotics - flucloxacillin, gentamicin, clindamycin
55
mortality from necrotising fasciitis
17-40%
56
what is pyomyositis?
purulent infection deep within striated muscle, often manifesting as an abscess
57
what is pyomyositis often secondary to?
seeding into damafed muscle
58
multipe sites of pyomyositis are involved in what %?
15%
59
common sites of pyomyositis
```
thigh
calf
arms
gluteal region
chest wall
psoas muscle
```
60
features of pyomyositis
fever, pain, woody induration of affected muscle
61
if pyomyositis is untreatmed it can lead to?
septic shock and death
62
predisposing factors of pyomyositis
```
DM
HIV
immunicompromised
IVDU
rheumatological diseases
malignancy
liver cirrhosis
```
63
commonest cause of pyomyositis
staph aureus
64
other organisms causing pyomyositis
gram +ve/-ve
TB
fungi
65
investigation of pyomyositis
CT
| MRI
66
treatment of pyomyositis
drainage with antbiotics
67
what are bursae?
small sac-like cavities that contain fluid and are lined by synovial membrane
68
where are bursae found?
subcutaneously between bony prominences or tendons
69
what do bursae do?
facilitated movement with reduced friction
70
most common sites of septic bursitis
patellar
| olecranon
71
septic bursitis is infection often originating where?
adjacent skin
72
predisposing factors for septic bursitis
```
RA
alcoholism
DM
IVDU
immunospuression
renal insufficiency
```
73
features of septic bursitis
peribursal cellullitis, swelling and warth
| fever and pain on movement
74
diagnosis of septic bursitis
aspiration of the fluid
75
most common cause of septic bursitis
staph aureus
76
other causes of septic bursitis
gram -ve
mycobacteria
vrucella
77
what is infectious tenosynovitis?
infection of the synovial sheaths that surround tendons
78
where is infectious tenosynovitis most common?
flexor muscle associated tendons
| tendons of hands
79
what is the most common initiating event of infectious tenosynovitis?
penetrating trauma
80
most common cause of infectious tenosynovitis
staph aureus
| streptococci
81
what causes chronic infectious tenosynovitis?
mycobacterium
| fungi
82
what may infectious tenosynovitis cause?
disseminated gonococcal infection
83
presentation of infectious tenosynovitis
erythematous fusiform swelling of finger
held in a semiflexed position
tenderness over the length of the tendon sheath and pain with extension
84
treatment of infectious tenosynovitis
empiric antibiotics
| hand surgeon review
85
toxin mediated syndromes are often due to?
superantigens
86
mechanism of toxin mediated syndromes
• Group of pyrogenic exotoxins
• Do not activate immune system via normal
contact between APC and T cells
• Superantigens bypass this and attach directly to
the T cell receptors activating up to 20% of the
total pool of T cells instead of the normal
1/10,000
• Massive burst in cytokine release
• Leads to endothelial leakage, haemodynamic
shock, multi-organ failure and ?death
87
causes of toxin mediated syndromes
staph aureus - TSST1, ETA and ETB
| strep pyogenes - TSST1
88
what can cause toxic shock syndrome?
tampons
| small skin infections due to staph aureus
89
diagnostic criteria for staphlococcal TSS
• Fever
• Hypotension
• Diffuse macular rash
• Three of the following organs involved
• Liver, blood, renal, gatrointestinal, CNS, muscular
• Isolation of Staph aureus from mucosal or
normally sterile sites
• Production of TSST1 by isolate
• Development of antibody to toxin during
convalescence
90
streptococcal TSS is almost always associated with?
streptococci in deep seated infections such as erysipelas or necrotising fasciitis
91
mortality rate of strep and staph TSS
5% staph
| 50% strep
92
treatment of strep TSS
urgent surgical debridement
93
treatment of TSS
```
remove offending agent e.g. tampon
IV fluids
ionotropes
antibiotics
IV immunoglobulins
```
94
what is staphylococcal scalded skin syndrome?
infection due to a particular strain of staph aureus producing the exfoliative toxin A or B
95
what is staphylococcal scalded skin syndrome characterised by?
widespread bullae and skin exfoliation
96
who gets staphylococcal scalded skin syndrome?
children but rarely adults
97
treatment of staphylococcal scalded skin syndrome
IV fluids and antimicrobials
98
mortality rate of staphylococcal scalded skin syndrome
3% in children
| higher in adults who are often immunosuppressed
99
what is panton-valentine leucocidin toxin?
gamma haemolysin
100
panton-valentine leucocidin toxin can be transferred from?
one strain of staph aureus to another including MRSA
101
what can panton-valentine leucocidin toxin cause?
SSTI
| haemorrhagic pneumonia
102
who gets panton-valentine leucocidin toxin?
children and young adults
103
presentation of panton-valentine leucocidin toxin
recurrent boils which are difficult to treat
104
treatment of panton-valentine leucocidin toxin
antibiotics that reduce toxin production
105
IV catheter associated infections are what kind of infections?
nosocomial
106
what do IV catheter associated infections normally start as and progress to
start as locall SST inflammation progressing to cellulitis and even tissue necrosis
107
risk factors for IV catheter associated infections
continuous infusion > 24 hrs
cannula in situ > 72 hrs
cannula in LL
patients with neurological/neurosurgical problems
108
most common organism IV catheter associated infections
Staph aureus
109
what does staph aureus in IV catheter associated infections form?
biofilm which spills into blood stream
110
where can IV catheter associated infections end up?
endcocarditis
| osteomyelitis
111
diagnosis of IV catheter associated infections
clinically or by positive blood cultures
112
treatment of IV catheter associated infections
remove cannula
express pus from the thrombophlebitis
antibiotics for 14 days
echocardiogram
113
prevention of IV catheter associated infections
– Do not leave unused cannula
– Do not insert cannulae unless you are using them
– Change cannulae every 72 hours
– Monitor for thrombophlebitis
– Use aseptic technique when inserting cannulae
114
describe the classification of surgical wounds: class 1
clean wound
| resp, alimentary, genital or infected urinary systems not entered
115
describe the classification of surgical wounds: class 2
clean-contaminated wound
| resp, alimentary, genital or infected urinary systems entered but no unusual contamination
116
describe the classification of surgical wounds: class 3
contaminated wound
| open, fresh accidental wounds or gross spillage from the GIT
117
describe the classification of surgical wounds: class 4
infected wound
| existing clinical infection, infection present before the operation
118
causes of SSI
* Staph aureus (incl MSSA and MRSA)
* Coagulase negative Staphylococci
* Enterococcus
* Escherichia coli
* Pseudomonas aeruginosa
* Enterobacter
* Streptococci
* Fungi
* Anaerobes
119
risk factors for SSI: patient associated
```
– Diabetes
– Smoking
– Obesity
– Malnutrition
– Concurrent steroid use
– Colonisation with Staph aureus
```
120
risk factors for SSI: procedural factors
```
– Shaving of site the night prior to procedure
– Improper preoperative skin preparation
– Improper antimicrobial prophylaxis
– Break in sterile technique
– Inadequate theatre ventilation
– Perioperative hypoxia
```
