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MSK > Microbiology; Bone & Joint Infection > Flashcards

Microbiology; Bone & Joint Infection Flashcards

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
Q

Skeletal tuberculosis

  • Vertebral TB
  • Dissemination notes
A

> 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
Q

Prosthetic joint infection

  • risk factors
  • mechanism
  • infection in prosthetic joints
A

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
Q

PVL-producing Staph aureus

A

Panton Valentine Leukocidin

Symptoms//

  1. Skin infections
  2. Necrotising pneumonia
  3. Invasive infections (bacteraemia, septic arthritis)

Treatment//

Flucloxacillin, clindamycin, linezolid, depending on sensitivities

28
Q

Planktonic bacteria vs sessile bacteria

A

Planktonic - free floating. Bacteraemia

Sessile - anchored.

  • phenotypic transformation of planktonic bacteria
  • biofilm
  • extracellular matrix
29
Q

Prosthetic joints - pathogens

A

> 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
Q

Coagulase negative staphylococci and prosthetic joint infections

A

> Coagulase negative staphylococci are part of normal flora

> Frequently in blood cultures

> Low virulence

31
Q

What is the virulence factor of Staph epidermidis?

A

Slime (biofilm)

Vancomycin.

32
Q

Treatment for Staph epidermidis

A

Vancomycin.

33
Q

Septic arthritis

A

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
Q

Bacterial causes of septic arthritis

A
  • Staph aureus
  • Streptococci
  • Coag neg staphylococci
  • Neisseria gonorrhoea (sexually active)
  • Haemophilus influenza
35
Q

Neisseria gonorrhoea - Septic arthritis

A

Sexually active.

Deseminated bacterial infection

Multifocal

36
Q

Septic Arthritis - diagnosis

A

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
Q

What can mimic septic arthritis?

A

Gout and pseudo gout

38
Q

Septic arthritis - treatment

A

> Presumptive treatment to cover Staph aureus

FLUCLOX

Less than 5 years old add Ceftriaxone

39
Q

Viral arthritis - causes

A

Alpha virus
Rubella virus
Hepatitis B
Parvovirus B19

40
Q

Pyomyositis

A

Bacterial

  • 90% staphylococcal
  • tropical: MSSA
  • temperate: immunosuppressed (pseudomonas, beta haemolytic strep, enterococcus)
  • clostridial infection in contaminated wounds
41
Q

Tetanus

A

Clostridium tetani

Gm +ve strictly ANAEROBIC rods

Spores
Drumstick shape

Spores found in soil, gardens

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
Q

What can trigger tetanus spasms?

A

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
Q

Tetanus- treatment

A

Surgical debridement

Antitoxin

Supportive measurs

Abx - penicillin, metronidazole

Booster vaccination (you are not immune to bacteria even if you have been exposed

44
Q

Myositis

A

Viral, diffuse
- HIV, HTLV, influenza, CMV, rabies, Chikungunya and other arboviruses

  • Protozoa
  • Fungal

everywhere is sore

45
Q

Imaging used in Bone Infections

A

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
Q

Acute Osteomyelitis

A

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

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
Q

Virchow’s triad

A

Viscosity
Velocity
Vessel wall damage

48
Q

Should pus be removed in osteomyelitis?

A

Yes

Remove the pus.

Blood doesn’t get into pus so Abx won’t get in either

49
Q

Chronic Osteomyelitis

A

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
Q

Involucrum

A

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
Q

Best imaging for osteomyelitis?

A

MRI

Xray also shows changes

52
Q

Septic Arthritis

A

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
Q

Soft tissue infections

A

> Cellulitis
Fluclox (staph) & benyzlpenicillin (strep)

covers staph and strep

> Necrotising fasciitis

    • treat quickly
    • crepitus under skin
54
Q

Small dark areas in tissue on an Xray…

A

Could be gas from gas forming organisms

55
Q

Cellulitis

A

Deep skin infection; into subcutaneous fat

Erysipelas - superficial infection. restricted to dermis

56
Q

Necrotising fasciitis

A

Infection of subcutaneous tissue

Potentially lethal

Treat immediately

Crepitus under skin

Anaerobic bacteria

Smells bad

57
Q

Principles of treatment of bone/skin/joint infections

A

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
Q

Infected arthroplasty

  • what is it
  • questions to ask
  • tests
A

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
Q

Surgical success - bone infecitons

  • what procedures are in place
A

Two stage revision: 80-90% control of infection

60
Q

For an implant, how long should the patient be on systemic antibiotics?

A

24 hours starting with induction

Cement used in implant also contains antibiotics

> Co amoxiclav

> Fluclox + gentamicin

> Clindamycin
Co-trimoxazole

61
Q

The 5 pillars of inflammation

A 
Rubor
Calor
Dolor
Tumor
Functio laesa
62
Q

ITPLIO

A

If There’s Pus Let It Out

MSK (11 decks)

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