Microbiology - Monoarticular joint pain Flashcards
How can joints become infected
By the haematogenous route
Directly following trauma or surgery
Usually immunologically mediated instead of microbial invasion
What does bacterial arthritis usually affect
The hip or knee in all age groups
What kind of bacteria usually causes bacterial arthritis
Gram +ve cocci
ReA
Pathogen responsible is at distant site and causes a ‘reactive arthritis’
Infection present
No live organisms present
Microbial structures present
What does ReA and arthralgia occur after
Certain enteric bacterial infections e.g Campylobacter, Yersinia, salmonellae
Bacteria causing septic arthritis
Staph. aureus, Streptococci (Group A and B), Mycobacterium tuberculous
Circulating bacteria sometimes localises in joints
What can Staph aureus cause
Skin/ soft tissue infection
What may bacteraemia cause
Seeding in distant sites
Osteomyelitis
Septic arthritis
Infective endocarditis
What will 14 days treatment of bacteraemia prevent
Sequelae incl OM
Risk factors of septic arthritis
Age > 80 yrs. and children Comorbid conditions (esp. diabetes) Joint damage from arthritis Prosthetic joint Skin infection Immune suppression (malignancy or treatment) Cirrhosis Chronic renal failure and haemodialysis IV drug abuse
Pathogenesis of septic arthritis
Haematogenous Dissemination from OM Spread from adjacent soft tissue Puncture or injection (esp. corticosteroids) Penetrating trauma
Presentation of septic arthritis
Fever Joint pain Limitation of movement Swelling Joint effusion
Acute OM
Bone can be infected by adjacent infection or haematogenous
Involves the growing end of a long bone, where localization of circulating bacteria is promoted by sprouting capillary loops adjacent to epiphyseal growth plates
What is the result of OM
A painful, tender bone lesion and a general febrile illness
Acute OM tends to be a disease of …
A disease of children and adolescents, may follow non-penetrating injury to bone
Diagnosis of OM
Blood cultures taken before start of antimicrobial therapy or bone biopsy if an open lesion
Periosteal reaction and bone loss may be visible radiologically
When does OM become chronic
When there’s a necrotic bone fragment to act as continued source of infection
What may be necessary with serious OM
Surgical intervention of debridement
Drainage
Prolonged courses of Abx
Paediatric septic arthritis
Neonates and young children often have coexisting septic arthritis and OM
Bony cortex is thin, and periosteum is loose
Blood vessels connecting metaphysis and epiphysis serve as conduit by which bony infection may easily reach the joint space
Septic bursitis
Superficial bursae are commonly infected (pre-patellar and olecranon bursae)
Underlying joint infection is not common
Acute or receptive trauma
What is septic bursitis caused by
Staph aureus
Treatment of septic bursitis
Drainage
Abx
Prosthetic joint infection
Early or late onset
Bacterial adhesion to biomaterial
Cannot be treated w/ out usually removing material
DAIR procedure in treating prosthetic joint infections
Debridement
Abx (12 weeks)
Irrigation
Retention
involves a two-stage revision
Results of prosthetic infection
Periosteal reaction Scattered patches of osteolysis Generalised bone resorption w/out implant wear Transcortical sinus tracts Implant loosening Scalloping
Athrocentesis
Procedure done to remove the synovial fluid accumulated around the joints
Immediate send off to lab for M, C & S
Amount of fluid in healthy knee
< 3ml
Amount of fluid in knee w/ infl
> 25ml
M, C & S
Microscopy
Culture
Sensitivities
Cause of acute onset of prosthetic joint infection
Staph. aureus
Gram +ve
Causes of delayed onset of prosthetic joint infection
Low virulence organisms
Classification of joint effusions
Normal
Non - infl
Infl
Septic
Features of normal joint effusions
Clear, colourless, viscous
<200 WBCs/mm^3
<25% PMNs
Features of non-infl joint effusions
Clear, yellow, viscous
200-2,000 WBC/mm3
<25% PMNs
Features of infl joint effusions
Cloudy, yellow, watery
Glucose may be low
2,000 - 100,000 WBC/mm3
>50% PMNs
Features of septic joint effusions
Purulent
Glucose very low
80,000 WBC/mm3
>90% PMNs
Synovial fluid analysis
Cell count and differential
Crystals
Culture and sensitivity
Cytology (if malignancy suspected)
What does management of bacterial joint diseases depend on
Extent of disease
Host factors
Organism
Choosing the right Abx
Is the bug susceptible
Does the antibiotic get into the bone?
Oral bioavailability? Relatively long-term treatment – side effects?
Can I give it to my patient – children, concurrent therapy
Gram +ve cocci
Streptococci
Staphylococci
Gram +ve rods
Listeria
Gram -ve cocci
Neisseria
Gram -ve rods
E. coli
Pseudomonas aeruginosa
Haemophilus influenza
What drug can be given for MRSA
Vancomycin
Trough levels should be 15 -20
