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MSK > Microbiology; Bone & Joint Infection > Flashcards

Microbiology; Bone & Joint Infection Flashcards

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1
Q

Osteomyelitis

  • what is it
  • classifications
A

> Inflammation of bone and medullary cavity (long bones very common)

> Classifications
- acute/chronic

  • contiguous/ haematogenous
  • Host status - presence of vascular insufficiency
  • Penetrating trauma. car crash, surgery
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2
Q

Contiguous osteomyelitis

A

Adjacent to source of infection e.g. cellulitis

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3
Q

Haematogenous Ostemyolitis

A

Through the blood

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4
Q

Clinical approach to infection

  • direct and indirect confirmation
A

> Clinical suspicion

> Confirmation that they have the infection

  • indirect (imaging, MRI)
  • direct (surgical sample)

> Debride what needs to be debrided

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5
Q

Indirect confirmation of infection

what is the gold standard?

A

Imaging

MRI is the gold standard

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6
Q

Direct confirmation of infection

A

Surgical sample/ bone biopsy (gold standard)

Microbiology and histologically.

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7
Q

What antibiotics should you NOT use?

A

Empirical antibiotics (broad spectrum) without microbiological samples

UNLESS

Sepsis (tachycardia, hypothermic)

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8
Q

Causes of Osteomyelitis (main)

A
  1. Open fractures
  2. Diabetes/ vascular insufficiency
  3. Haematogenous osteomyelitis
  4. Vertebral osteomyelitis
  5. Prosthetic joint infection
  6. Specific hosts and pathogens
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9
Q

What materials do coagulase negative staphylococcus love?

A

Plastic and metal

Endocarditis

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10
Q

What are the 5 Cs Abx?

A

CEPHALOSPROINS,

CLINDAMYCIN,

CIPROFLOXACIN [QUINOLONES] ,

CO-AMOXICLAV,

CLARITHROMYCIN [ MACROLIDES]

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11
Q

Open fractures –> osteomyelitis

A

Contiguous infection

Early management is key (aggressive debridement, fixation and soft tissue cover)

Clinical clue - non union (not healed, not joined back together) and poor wound healing

Staph aureus and aerobic gram negative bacteria

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12
Q

Antibiotic for Staph aureus??

A

Flucloxacillin
Fluclox
Fluclox

(if allergic - vancomycin)

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13
Q

Diabetes/ venous insufficiency –> osteomyelitis

A

Often contiguous.

Clawed toes.

Cavus deformity with increased pressure under metatarsal heads.

Pressure on the bone and the skin are not what they should be
–> pressure ulcers which become infected –> osteomyelitis

Polymicrobial

“Probe to bone”

Treatment
- debridement and antimicrobials

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14
Q

Haematogenous osteomyelitis

> common in
diagnosis

A

> Prupubertal children

> People who inject drugs

> Central lines/dialysis/ elderly

Diagnosis

  • Must suspect there is an infection (history) – localised symptoms
  • Patient medical history and epidemiology matter
  • Examination (probe to bone/ visible bone, rule of 2s)

Gold standard is bone biopsy/ MRI

Await microbiological diagnosis
- unless sepsis

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15
Q

People who inject drugs

  • epidemiology
  • organisms
A

> Epidemiology
- contiguous; haematogenous; direct innoculation

> Organisms

  • staphylococcus
  • streptococci
  • Pseudomonas
  • Candida
  • Eikenella corrodens (needle lickers)
  • Mycobacterium tuberculosis
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16
Q

Dialysis patients and osteomyelitis

  • epidemiology
  • pathogens
A

Lines being taken in and out all of the time

> Epidemiology

High staphylococcal colonisation rates

Comorbidities (peripheral vascular diseae, diabetes)

> Pathogens

  • Staph aureus
  • aerobic gram negatives
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17
Q

Osteitis pubis

A

> Urogynae procedures predispose to bacterial causes

> Aseptic osteitis pubis

  • triggered by surgery
  • can be up to 18 months later
  • athletes can get it
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18
Q

Clavicle Osteo

A

3% of osteomyelitis

Risk factors

  • neck surgery
  • subclavian vein catheterisation
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19
Q

Sickle cell osteomyelitis

Epidemiology
Pathogens

A 
> 12% homozygous get osteomyelitis 
> acute long bone osteomyelitis
> Can be MULTIFOCAL 
> Nb infarction
> Septic arthritis

Pathogens

  • salmonella
  • staph aureus
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20
Q

Gaucher’s disease

A

> Epidemiology

  • lysosomal storage disorder
  • may mimic bone crisis
  • often affects the tibia

> Pathogens

  • sterile if bone crisis
  • if infected, staph aureus
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21
Q

SAPHO & CRMO

A

Synovitis Acne Pustulosis Hyperostosis Osteitis (adults)

Chronic recurrent multifocal osteomyelitis (Kids)

History plus culture samples crucial to exclude osteomyelitis

Raised inflammatory markers

Lytic lesions of X rays

Antibiotic and non antibiotic treatments

Multiple episodes of osteomyelitis at different sites - consider these

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22
Q

SAPHO (adults)

CRMO (kids)

> Epidemiology
Sites involved

A

> Epidemiology

  • fever, weight loss, generalised malaise
  • multifocal osteitis
  • self limited
  • exacerbation/ remissions
  • genetic
  • Propionibacterium role

> Sites involved

  • 63% chest wall
  • 40% pelvis
  • 33% spine
  • 6% lower limb

5 or so active lesions

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23
Q

Vertebral osteomyelitis

  • spondylodiscitis
  • disc space infection
A 
> Haematogenous
> May be associated with
- PWID
- IV site infections
- GU infections
- SSTI
- Post operative

Clinical

Fever
Insidious pain and tenderness
Neurological signs
Raised inflammatory markers
<50% raised white cell count
32% abnormal plain film
MRI

Treatment

Drainage of large paravertebral/ epidural abscesses

Antimicrobials for 6 weeks

Expect >50% decrease in ESR

Duration extended in complicated cases

MRI repeated only if

  • unexplained increase in inflammatory markers
  • increasing pain
  • new anatomically related signs/symptoms
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24
Q

Osteomyelitis - biopsy

A

Avoid empiric antibiotics

First biopsy - 38-60% yield

Second biopsy - 80% sensitivity

If still no answer, consider open biopsy

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25
Skeletal tuberculosis - Vertebral TB - Dissemination notes
> Vertebral TB Pott's disease Often NO systemic symptoms 1/2 have skin and soft tissue infection Less than half have pulmonary TB Very destructive disease Lots of disease and deformity > Dissemination notes - in kids, check reduced receptors for IFN gamma R1, IL-12 beta 1 - In adults always offer an HIV test Where person is from and what their occupation is
26
Prosthetic joint infection - risk factors - mechanism - infection in prosthetic joints
Risk factors// - rheumatoid arthritis - diabetes - malnutrition - obesity Mechanism// - direct inoculation at time of surgery - manipulation of joint at time of surgery - seeding of joint at a later time Infection in prosthetic joints// - early... within a month. ... with haematoma/ wound sepsis - Late... after one month - contamination at time of operation Diagnosis// Culture Blood culture CRP Radiology Treatment// Ideally removal of prosthesis and cement Therapy for at least 6 weeks Re-implantation of the joint after aggressive antibiotic therapy.
27
PVL-producing Staph aureus
Panton Valentine Leukocidin Symptoms// 1. Skin infections 2. Necrotising pneumonia 3. Invasive infections (bacteraemia, septic arthritis) Treatment// Flucloxacillin, clindamycin, linezolid, depending on sensitivities
28
Planktonic bacteria vs sessile bacteria
Planktonic - free floating. Bacteraemia Sessile - anchored. - phenotypic transformation of planktonic bacteria - biofilm - extracellular matrix
29
Prosthetic joints - pathogens
> Gram positive - Staphylococcus aureus*** - Staphylococcus epidermidis*** - Propionibacterium acnes (upper limb prostheses) - rarely streptococcus sp. and enterococcus sp. > Gram negatives - E. coli, pseudomonas aeruginosa (Fungi) (Mycobacteria sp.)
30
Coagulase negative staphylococci and prosthetic joint infections
> Coagulase negative staphylococci are part of normal flora > Frequently in blood cultures > Low virulence
31
What is the virulence factor of Staph epidermidis?
Slime (biofilm) Vancomycin.
32
Treatment for Staph epidermidis
Vancomycin.
33
Septic arthritis
Inflammation of the joint space caused by infection Can be blood borne organisms Can be extension of local infection e.g. complication of infection in adjacent bone Can be introduced by direct inoculation e.g. following injection of joint or trauma.
34
Bacterial causes of septic arthritis
- Staph aureus - Streptococci - Coag neg staphylococci - Neisseria gonorrhoea (sexually active) - Haemophilus influenza
35
Neisseria gonorrhoea - Septic arthritis
Sexually active. Deseminated bacterial infection Multifocal
36
Septic Arthritis - diagnosis
Clinical picture…severe pain,red, hot swollen plus limited movement Joint fluid…… Microscopy, C&S. Blood culture if pyrexial. (Positive in 30-60% cases) Exclude crystals.
37
What can mimic septic arthritis?
Gout and pseudo gout
38
Septic arthritis - treatment
> Presumptive treatment to cover Staph aureus FLUCLOX Less than 5 years old add Ceftriaxone
39
Viral arthritis - causes
Alpha virus Rubella virus Hepatitis B Parvovirus B19
40
Pyomyositis
Bacterial - 90% staphylococcal - tropical: MSSA - temperate: immunosuppressed (pseudomonas, beta haemolytic strep, enterococcus) - clostridial infection in contaminated wounds
41
Tetanus
Clostridium tetani Gm +ve strictly ANAEROBIC rods Spores Drumstick shape Spores found in soil, gardens Think farmyard crush injuries --- Neurotoxin --> spastic paralysis - binds to inhibitory neurones, preventing release of neurotransmitters Non invasive, all toxin related 4 days - several weeks' incubation LOCK JAW, MUSCLE SPASMS -- Bright lights and loud noises can trigger tetanus spasms.
42
What can trigger tetanus spasms?
Bright light and loud noises Keep patietn far away from stimulus like these But in a lot of care - throat can spasm and can halt breathing.
43
Tetanus- treatment
Surgical debridement Antitoxin Supportive measurs Abx - penicillin, metronidazole Booster vaccination (you are not immune to bacteria even if you have been exposed
44
Myositis
Viral, diffuse - HIV, HTLV, influenza, CMV, rabies, Chikungunya and other arboviruses - Protozoa - Fungal everywhere is sore
45
Imaging used in Bone Infections
X rays - doesn't really show bone infection changes for 2-3 weeks Technetium scan - increased uptake and increased blood flow MRI - good for imaging
46
Acute Osteomyelitis
New infection in bone Mostly post traumatic/open = inoculation Children or immunosuppressed = hameatogenous (blood borne) ``` Staph aureus (usually) Haemophilis in children ``` Slow moving blood in sinusoids Virchow's triad ---- Surgery If any bits of bone don't have a good blood supply, they get put in the bin --> Bad blood supply --> ABx can't get into the bone to treat infection
47
Virchow's triad
Viscosity Velocity Vessel wall damage
48
Should pus be removed in osteomyelitis?
Yes Remove the pus. Blood doesn't get into pus so Abx won't get in either
49
Chronic Osteomyelitis
Sclerotic margin with hole and pus inside Can expand and adjacent bone can become necrotic Eventually the infection can break out and get under the periosteum Periosteum forms NEW bone (involucrum) and original bone inside dies ---- Might have a gaping hole, dripping Looks bad but may not cause loss of function or pain Unstable skin - will not heal
50
Involucrum
Layer of new bone growth outside existing bone seen in pyogenic osteomyelitis. It results from the stripping-off of the periosteum by the accumulation of pus within the bone, and new bone growing from the periosteum. Original bone dies
51
Best imaging for osteomyelitis?
MRI Xray also shows changes
52
Septic Arthritis
Pus in the joint --> get rid of this ASAP otherwise may progress to OSTEOMYELITIS Usually from inoculation From metaphysical spread Direct haemotogenous More common in children and can destroy articular cartilage
53
Soft tissue infections
> Cellulitis > Fluclox (staph) & benyzlpenicillin (strep) covers staph and strep > Necrotising fasciitis - - treat quickly - - crepitus under skin
54
Small dark areas in tissue on an Xray...
Could be gas from gas forming organisms
55
Cellulitis
Deep skin infection; into subcutaneous fat Erysipelas - superficial infection. restricted to dermis
56
Necrotising fasciitis
Infection of subcutaneous tissue Potentially lethal Treat immediately Crepitus under skin Anaerobic bacteria Smells bad
57
Principles of treatment of bone/skin/joint infections
Know what bug you're dealing with Operate if there is dead tissue or foreign body Target Abx Biopsy & debridement If there is pus, let it out
58
Infected arthroplasty - what is it - questions to ask - tests
Infection caused by inoculation by prosthetic joint DEEP infection Foreign bodies in material from a BIOFILM (slime) > Was there every a wound problem? (e.g. superficial infection, slow to heal) > Has it ever been pain free? If it has never been pain free, something is wrong. Could be infection Tests// - CRP - Joint aspiration - Bone scan - Xray
59
Surgical success - bone infecitons - what procedures are in place
Two stage revision: 80-90% control of infection
60
For an implant, how long should the patient be on systemic antibiotics?
24 hours starting with induction Cement used in implant also contains antibiotics > Co amoxiclav > Fluclox + gentamicin > Clindamycin Co-trimoxazole
61
The 5 pillars of inflammation
``` Rubor Calor Dolor Tumor Functio laesa ```
62
ITPLIO
If There's Pus Let It Out

MSK (11 decks)

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