INFECTIOUS DISEASES: Skin and joint infections Flashcards Preview

Year 3 Medicine Block > INFECTIOUS DISEASES: Skin and joint infections > Flashcards

Flashcards in INFECTIOUS DISEASES: Skin and joint infections Deck (61)
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1
Q
A
2
Q

What is osteomyelitis?

A

Inflammation of bone and bone marrow, usually caused by bacterial infections

3
Q

Most common bacteria causing osteomyelitis?

A

Staphylococcus aureus

4
Q

Risk factors for developing osteomyelitis?

A

Open fractures
Orthopaedic operations - esp w prosthetic joints
DM - esp w diabetic foot ulcers
Peripheral arterial disease
IV drug use
Immunosuppression

5
Q

Presentation of osteomyelitis?

A

Fever

Gangrene
Pain and tenderness
Erythema
Swelling

Non-specific - w fever, lethargy, nausea and muscle aches

6
Q

Investigations to do for suspected osteomyelitis?

A

MRI - best for establishing dx

XR - not good in early disease. Signs on XR = periosteal reaction, localised osteopenia, destruction of bone

FBC - raised WCC,
CRP, ESR

Blood cultures - causative organism and find abx sensitivity.

7
Q

Management for osteomyelitis?

A

Surgical debridement of infected bone and tissues
ABx therapy- 4-6 weeks or 3-6 months in chronic osteomyselitis
If in prosthetic joint = prosthetic replacement surgery.

8
Q

BNF recommendation for abx therapy of acute osteomyelitis?

A

6 weeks flucloxacillin +/- Rifampicin or fusidic acid for first 2 weeks

Alternative of flucloxacillin = Clindamycin. If MRSA related = vancomycin or teicoplanin

9
Q

When is staph aureus likely to cause pneumonia?

A

After influenza

10
Q

What causes diabetic foot disease?

A

secondary to neuropathy and peripheral artery disease

11
Q

Why is diabetes a RF for peripheal arterial disease?

A

diabetes is RF for both microvascular and macrovascular ischaemia

12
Q

Presentation of diabetic foot infection?

A

Neuropathy: loss of sensation

Ischaemia: lack of foot pulses, reduced ABPI, intermittent claudication

Complications: calluses, ulceration, cellulits, gangrene, osteomyelitis

13
Q

What is low risk for diabetic foot disease?

A

No deformity, just calluses alone

14
Q

What is moderate risk for diabetic foot disease?

A

deformity or
• neuropathy or
• non-critical limb ischaemia

15
Q

What is high risk for diabetic foot disease?

A
  • Previous ulceration,
  • previous amputation,
  • on RRT,
  • neuropathy + non-critical limb ischaemia,
  • neuropathy + callus AND/OR defomity,
  • non-critical limb ischaemia + callus AND/OR deformity
16
Q

What is ankle brachial pressure index?

A

ratio of systolic BP in the lower legs to arms

17
Q

What are the interpretations of ABPI?

A

> 1.2: may indicate calcified, stiff arteries. This may be seen with advanced age or PAD

  1. 0 - 1.2: normal
  2. 9 - 1.0: acceptable

< 0.9: likely PAD. Values < 0.5 indicate severe disease which should be referred urgently

18
Q

What is charcots arthropathy?

A

Bones in the foot become weak–> dislocations and fractures–> changes shape of foot/ ankle

Presents with 6Ds- destruction, deformity, degeneration, dislocation, dense bones and debris)

19
Q

Define Cellulitis

A

Infection of subcutaeneous tissues and dermis

20
Q

If cellulitis extends over a joint worry there might be___1____

___2____( ortho infection) may present as cellulitis

A

If cellulitis extends over a joint worry there might be___septic arthritis____

__Osteomyelitis___(ortho infection) may present as cellulitis

21
Q

Key in cellulitis is a __1___ in the skins barrier for pathogens to enter.

A

1 Breakdown

bacteria need a point of entry

22
Q

Give examples of how skin barrier may be broken to allow bacteria to enter and cause cellulitis

A

IV drug ucer infection around venepuncture

skin trauma

eczematous skin

fungal nail infections / athletes foot (cracks between toes)

ulcers

23
Q

Who is susceptible to get cellulitis?

A
  • DM - hyperglyacemia
  • DM with Peripheral neuropathy - cant feel trauma
  • Obesity - pressure sores/immobility
  • IV drug users - infection / abscess around point of injection
  • PAD - poor blood flow for healing and tendancy to ulcerate
24
Q

What systemic features might point to bacteraemia rather than local infection in cellulitis?

A

fevers

sweats

rigors

25
Q

How does cellulitis present ? (to look at)

A

Erythema (red discolouration)

Warm or hot to touch

Tense

Thickened

Oedematous

Bullae (fluid-filled blisters)

A golden-yellow crust can be present and indicate a staphylococcus aureus infection

26
Q

Who is susceptible to MRSA cellulitis infection?

A

Recent hopsital admission and length of their stay

Ask: has MRSA screening been done? results please

27
Q

What are the bacteria causes of cellulitis ?

A

Staphylococcus aureus

Group A Streptococcus (mainly streptococcus pyogenes)

Group C Streptococcus (mainly Streptococcus dysgalactiae)

MRSA

28
Q

Compare the gram stain morphology of Staphylococcus and Streptococcus

A

Staph - clusters of gram +ve cocci

Strep - chains of gram +ve cocci

29
Q

Cellulitis - if there is a hx of trauma with skin penetratio what immunisation status must be checked?

A

Tetanus

consider immunisation

30
Q

If cellulitis errythema extends over a joint what do you need to assess?

A
  • Range of movement of joint
    • Septic Arthritis -pain restricts
    • Osteomyelitis LL - weight bearing reduced
  • Time course
    • start on joint or spread to joint?
  • Prosthics
    • metalwork / recent arthroscopy
31
Q
  1. What is a lifethreatening complication of cellulitis?
  2. What would you seen on plain Xray for the above?
A
  1. Necrotising fascitis
  2. Xray - may see gas bubbles within tissues
32
Q
  1. What are two differencials for an errythematous, swollen LL?
  2. Can they co-exist?
A
  1. Cellulitis / DVT
  2. Yes - think elderly immobile woman with infected venous ulcers
33
Q

What bedside investigation would you do for pt with suspected cellulitis and why?

A

Diabetic: BM - hyperglycaemia

Non Diabetics: fasting glucose

ASK : Is sliding scale of insulin needed for better glycaemic control?

34
Q

Cellulitis - how should you examine the skin?

A

Note distribution and extent of errythema

Draw around at admission - judge extent

Broken skin? check between toes

Temperature difference

palpate local lymphadenopathy

35
Q

If cellulitis includes joint - how examine?

A

Palpate for bony tenderness

Feel for effusioon

Assess passive and active range of movement

36
Q

Cellulitis - if ulcers present how to examine?

A

Is any bone visible ?

Describe ulcer (slough, exudate, necrotic tissue, margins, depth)

Metal probe to see if can reach bone - indication of bony involvement

37
Q

What lab investigations for suspected cellulitis and why?

A

Blood

  • FBC - raised WCC (neutrophilia in bacterial)
  • CRP
  • Blood cultures - organism and sensitivities

Other

  • Abscess I&D aspiration - bacterial cause
  • Joint fluid aspiration - microscopy and culture - organism
  • Deep bone biopsy - debridement see if osteomyelitis
  • Wound swab
38
Q

What imaging for suspected cellulitis?

A

Plain Xray / MRI - look for joint destruction in septic arthritis and changes associated with osteomyelitis

39
Q

Treatment for cellulitis?

A

1st line - IV / oral flucloxacillin

Allergy: IV clarithromycin or erythromycin if pregnant

40
Q

What is the classification for severity of cellulitis?

A

Eron Classification

41
Q

Outline Eron classification for cellulitis

A

Class 1 – no systemic toxicity or comorbidity

Class 2 – systemic toxicity or comorbidity

Class 3 – significant systemic toxicity or significant comorbidity

Class 4 – sepsis or life-threatening

42
Q

What are some differencials for cellulitis ( BMJ best practice)

A

Necrotising fascitis - pain ++ / necrotic bulous changes/ crepitus

Thrombophlebitis (superficial) - tender palpable cord along vein (recent catheter)

DVT- previous DVT/ hypercoag/immobile

Gout - urate, knee, 1st metatarsopharangeal

Lyme disease - ticks

Dermamtitis - demarcated/pruritis/ Hx

Fixed drug eruption - Hx rxn, well demarcated, itching burning, lips/genitals involved

43
Q

At which stages of Eron classification would you admit for IV AB?

A
  1. If Eron stage 3 or 4 (toxic, co-morbidities ++, septic)
  2. frail, very young or immunocompromised patients.
44
Q

Causative organism(s) in Type 1 necrotising fasciitis?

A

Mixed organisms - aerobes and anaerobes.

45
Q

Pts with _______ what condition? _____ most commonly get type 1 necrotising fasciitis post surgery?

A

Pts with diabetes most commonly get type 1 necrotising fasciitis post surgery

46
Q

Difference between Cellulitis and Erysepilas in terms of where it affects the body?

A

Erysipelas - more superfical - epidermis and dermis

Cellulitis - dermis and subcut tissue

47
Q

Necrotising fasciitis can be classified according to the causative organism:

Type 1 is caused by ____________ (often occurs post-surgery in diabetics). This is the most common type

Type 2 is caused by __________

A

Type 1 is caused by mixed anaerobes and aerobes (often occurs post-surgery in diabetics). This is the most common type

Type 2 is caused by Streptococcus pyogenes

48
Q

Which organism most commonly causes erysipelas ? compare to celluitis

A

Erysipelas - Streptoccous pyogenes (group A beta -haemolytic)

Cellulitis - Staphloccoccus aureus is most common

49
Q

Risk factors for necrotising fasciitis?

A

IV drug use

Immunosupression

Diabetes mellitus - especially if being treated with SGLT-2 inhbitors

Skin factors: recent trauma, burns or soft tissue infections

50
Q

Where does Erysipelas commonly occur and who does it usually affect ?

A

Where? Most commonly on face - cheeks and periorbitally

Who? often children / elderly / immunocompromised

51
Q

Presentation of necrotizing fasciitis?

A

Acute onset

Pain at affected site on skin - pain out of proportion to physical features

Swelling at affected site

Erythema at afected site

Rapidly worsening cellulitis

Tenderness over infected tissue - even with light touch

Skin necrosis, gas gangreen, dusky - late signs

Fever and tachycardia - late signs or absent

52
Q

Management of necrotising fasciitis?

A

Urgent surgial referral debridement

IV abx (broad spec e.g meropenem).

53
Q

Define necrotising fasciitis

A

Necrotizing fasciitis — a destructive and rapidly progressive soft tissue infection that involves the deep subcutaneous tissues and fascia (and occasionally muscles), which is characterized by extensive necrosis and gangrene of the skin and underlying structures (from NICE)

54
Q

What is Septic Arthritis ?

A

Infection of the joint and synovial fluid

55
Q

What organsims cause septic arthritis?

A

Staphloccus aureus (most common cellulitis)

Strep pyogenes

Haemophilus influenzae type B (<5yrs / non working spleen)

Strep pneumoniae (no spleen / hyposplensim)

Mycobaterium tuberculosis (immunosuppressed TB in body)

56
Q

Briefly outline the pathophsyiology of septic arthritis

A

Results from either direct bacterial invasion from overlying cellutlis or osteomyelitis. Can also result from haemotoligcal spread from bacteraemia. Cabn occur following surgery e..g total hip replacement

57
Q

What are the clincial features of septic arthritis?

A

Hot

Swollen

Tender joint

Reduced rang of movement (active and passive) due to pain

Fever (more likely with haematological spread)

(NOTE: TB septic arthtirits can get COLD joint!)

58
Q

What are some RF for septic arthritis (BMJ BP)

A

OA / RA

low socioeconomic status

Prosthetic Joint

>80 yrs

Immunosuppressed (HIV/diabetes/ alcohol misuse)

concurrent infection

ulcers

recent joint surgery

interarticular injections

59
Q

What investigations would you do for septic arthritis?

A

Joint aspiration microscopy, sensitivity and culutre

WCC count of aspirate

Blood cultures

CRP / ESR / WCC

U&Es

LFTs

60
Q

How treat septic arthritis

A

THINK SEPSIS - start sepsis 6

Flucloxacillin

Penicillin allergic - Clindamycin

refer to Ortho for surgical washout if severe/ prosthetic joint removal

61
Q

What are some complications of septic arthritis

A

Damange to synovium and cartilage - osteomyelitis and arthritis

sepsis

death

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