Microbiology; Bone & Joint Infection Flashcards
Osteomyelitis
- what is it
- classifications
> 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
Contiguous osteomyelitis
Adjacent to source of infection e.g. cellulitis
Haematogenous Ostemyolitis
Through the blood
Clinical approach to infection
- direct and indirect confirmation
> Clinical suspicion
> Confirmation that they have the infection
- indirect (imaging, MRI)
- direct (surgical sample)
> Debride what needs to be debrided
Indirect confirmation of infection
what is the gold standard?
Imaging
MRI is the gold standard
Direct confirmation of infection
Surgical sample/ bone biopsy (gold standard)
Microbiology and histologically.
What antibiotics should you NOT use?
Empirical antibiotics (broad spectrum) without microbiological samples
UNLESS
Sepsis (tachycardia, hypothermic)
Causes of Osteomyelitis (main)
- Open fractures
- Diabetes/ vascular insufficiency
- Haematogenous osteomyelitis
- Vertebral osteomyelitis
- Prosthetic joint infection
- Specific hosts and pathogens
What materials do coagulase negative staphylococcus love?
Plastic and metal
Endocarditis
What are the 5 Cs Abx?
CEPHALOSPROINS,
CLINDAMYCIN,
CIPROFLOXACIN [QUINOLONES] ,
CO-AMOXICLAV,
CLARITHROMYCIN [ MACROLIDES]
Open fractures –> osteomyelitis
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
Antibiotic for Staph aureus??
Flucloxacillin
Fluclox
Fluclox
(if allergic - vancomycin)
Diabetes/ venous insufficiency –> osteomyelitis
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
Haematogenous osteomyelitis
> common in
diagnosis
> 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
People who inject drugs
- epidemiology
- organisms
> Epidemiology
- contiguous; haematogenous; direct innoculation
> Organisms
- staphylococcus
- streptococci
- Pseudomonas
- Candida
- Eikenella corrodens (needle lickers)
- Mycobacterium tuberculosis
Dialysis patients and osteomyelitis
- epidemiology
- pathogens
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
Osteitis pubis
> Urogynae procedures predispose to bacterial causes
> Aseptic osteitis pubis
- triggered by surgery
- can be up to 18 months later
- athletes can get it
Clavicle Osteo
3% of osteomyelitis
Risk factors
- neck surgery
- subclavian vein catheterisation
Sickle cell osteomyelitis
Epidemiology
Pathogens
> 12% homozygous get osteomyelitis > acute long bone osteomyelitis > Can be MULTIFOCAL > Nb infarction > Septic arthritis
Pathogens
- salmonella
- staph aureus
Gaucher’s disease
> Epidemiology
- lysosomal storage disorder
- may mimic bone crisis
- often affects the tibia
> Pathogens
- sterile if bone crisis
- if infected, staph aureus
SAPHO & CRMO
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
SAPHO (adults)
CRMO (kids)
> Epidemiology
Sites involved
> 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
Vertebral osteomyelitis
- spondylodiscitis
- disc space infection
> 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
Osteomyelitis - biopsy
Avoid empiric antibiotics
First biopsy - 38-60% yield
Second biopsy - 80% sensitivity
If still no answer, consider open biopsy
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
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.
PVL-producing Staph aureus
Panton Valentine Leukocidin
Symptoms//
- Skin infections
- Necrotising pneumonia
- Invasive infections (bacteraemia, septic arthritis)
Treatment//
Flucloxacillin, clindamycin, linezolid, depending on sensitivities
Planktonic bacteria vs sessile bacteria
Planktonic - free floating. Bacteraemia
Sessile - anchored.
- phenotypic transformation of planktonic bacteria
- biofilm
- extracellular matrix
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.)
Coagulase negative staphylococci and prosthetic joint infections
> Coagulase negative staphylococci are part of normal flora
> Frequently in blood cultures
> Low virulence
What is the virulence factor of Staph epidermidis?
Slime (biofilm)
Vancomycin.
Treatment for Staph epidermidis
Vancomycin.
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.
Bacterial causes of septic arthritis
- Staph aureus
- Streptococci
- Coag neg staphylococci
- Neisseria gonorrhoea (sexually active)
- Haemophilus influenza
Neisseria gonorrhoea - Septic arthritis
Sexually active.
Deseminated bacterial infection
Multifocal
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.
What can mimic septic arthritis?
Gout and pseudo gout
Septic arthritis - treatment
> Presumptive treatment to cover Staph aureus
FLUCLOX
Less than 5 years old add Ceftriaxone
Viral arthritis - causes
Alpha virus
Rubella virus
Hepatitis B
Parvovirus B19
Pyomyositis
Bacterial
- 90% staphylococcal
- tropical: MSSA
- temperate: immunosuppressed (pseudomonas, beta haemolytic strep, enterococcus)
- clostridial infection in contaminated wounds
Tetanus
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.
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.
Tetanus- treatment
Surgical debridement
Antitoxin
Supportive measurs
Abx - penicillin, metronidazole
Booster vaccination (you are not immune to bacteria even if you have been exposed
Myositis
Viral, diffuse
- HIV, HTLV, influenza, CMV, rabies, Chikungunya and other arboviruses
- Protozoa
- Fungal
everywhere is sore
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
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
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
Virchow’s triad
Viscosity
Velocity
Vessel wall damage
Should pus be removed in osteomyelitis?
Yes
Remove the pus.
Blood doesn’t get into pus so Abx won’t get in either
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
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
Best imaging for osteomyelitis?
MRI
Xray also shows changes
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
Soft tissue infections
> Cellulitis
Fluclox (staph) & benyzlpenicillin (strep)
covers staph and strep
> Necrotising fasciitis
- treat quickly
- crepitus under skin
Small dark areas in tissue on an Xray…
Could be gas from gas forming organisms
Cellulitis
Deep skin infection; into subcutaneous fat
Erysipelas - superficial infection. restricted to dermis
Necrotising fasciitis
Infection of subcutaneous tissue
Potentially lethal
Treat immediately
Crepitus under skin
Anaerobic bacteria
Smells bad
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
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
Surgical success - bone infecitons
- what procedures are in place
Two stage revision: 80-90% control of infection
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
The 5 pillars of inflammation
Rubor Calor Dolor Tumor Functio laesa
ITPLIO
If There’s Pus Let It Out
