Microbiology - Monoarticular joint pain

Question 1

How can joints become infected

Answer 1

By the haematogenous route
Directly following trauma or surgery
Usually immunologically mediated instead of microbial invasion

Question 2

What does bacterial arthritis usually affect

Answer 2

The hip or knee in all age groups

Question 3

What kind of bacteria usually causes bacterial arthritis

Answer 3

Gram +ve cocci

Question 4

ReA

Answer 4

Pathogen responsible is at distant site and causes a ‘reactive arthritis’
Infection present
No live organisms present
Microbial structures present

Question 5

What does ReA and arthralgia occur after

Answer 5

Certain enteric bacterial infections e.g Campylobacter, Yersinia, salmonellae

Question 6

Bacteria causing septic arthritis

Answer 6

Staph. aureus, Streptococci (Group A and B), Mycobacterium tuberculous

Circulating bacteria sometimes localises in joints

Question 7

What can Staph aureus cause

Answer 7

Skin/ soft tissue infection

Question 8

What may bacteraemia cause

Answer 8

Seeding in distant sites

Osteomyelitis
Septic arthritis
Infective endocarditis

Question 9

What will 14 days treatment of bacteraemia prevent

Answer 9

Sequelae incl OM

Question 10

Risk factors of septic arthritis

Answer 10

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

Question 11

Pathogenesis of septic arthritis

Answer 11

Haematogenous 
Dissemination from OM 
Spread from adjacent soft tissue 
Puncture or injection (esp. corticosteroids)
Penetrating trauma

Question 12

Presentation of septic arthritis

Answer 12

Fever 
Joint pain 
Limitation of movement 
Swelling 
Joint effusion

Question 13

Acute OM

Answer 13

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

Question 14

What is the result of OM

Answer 14

A painful, tender bone lesion and a general febrile illness

Question 15

Acute OM tends to be a disease of …

Answer 15

A disease of children and adolescents, may follow non-penetrating injury to bone

Question 16

Diagnosis of OM

Answer 16

Blood cultures taken before start of antimicrobial therapy or bone biopsy if an open lesion
Periosteal reaction and bone loss may be visible radiologically

Question 17

When does OM become chronic

Answer 17

When there’s a necrotic bone fragment to act as continued source of infection

Question 18

What may be necessary with serious OM

Answer 18

Surgical intervention of debridement
Drainage
Prolonged courses of Abx

Question 19

Paediatric septic arthritis

Answer 19

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

Question 20

Septic bursitis

Answer 20

Superficial bursae are commonly infected (pre-patellar and olecranon bursae)
Underlying joint infection is not common
Acute or receptive trauma

Question 21

What is septic bursitis caused by

Answer 21

Staph aureus

Question 22

Treatment of septic bursitis

Answer 22

Drainage

Abx

Question 23

Prosthetic joint infection

Answer 23

Early or late onset
Bacterial adhesion to biomaterial
Cannot be treated w/ out usually removing material

Question 24

DAIR procedure in treating prosthetic joint infections

Answer 24

Debridement
Abx (12 weeks)
Irrigation
Retention

involves a two-stage revision

Question 25

Results of prosthetic infection

Answer 25

``` Periosteal reaction Scattered patches of osteolysis Generalised bone resorption w/out implant wear Transcortical sinus tracts Implant loosening Scalloping ```

Question 26

Athrocentesis

Answer 26

Procedure done to remove the synovial fluid accumulated around the joints Immediate send off to lab for M, C & S

Question 27

Amount of fluid in healthy knee

Answer 27

< 3ml

Question 28

Amount of fluid in knee w/ infl

Answer 28

>25ml

Question 29

M, C & S

Answer 29

Microscopy Culture Sensitivities

Question 30

Cause of acute onset of prosthetic joint infection

Answer 30

Staph. aureus | Gram +ve

Question 31

Causes of delayed onset of prosthetic joint infection

Answer 31

Low virulence organisms

Question 32

Classification of joint effusions

Answer 32

Normal Non - infl Infl Septic

Question 33

Features of normal joint effusions

Answer 33

Clear, colourless, viscous <200 WBCs/mm^3 <25% PMNs

Question 34

Features of non-infl joint effusions

Answer 34

Clear, yellow, viscous 200-2,000 WBC/mm3 <25% PMNs

Question 35

Features of infl joint effusions

Answer 35

Cloudy, yellow, watery Glucose may be low 2,000 - 100,000 WBC/mm3 >50% PMNs

Question 36

Features of septic joint effusions

Answer 36

Purulent Glucose very low 80,000 WBC/mm3 >90% PMNs

Question 37

Synovial fluid analysis

Answer 37

Cell count and differential Crystals Culture and sensitivity Cytology (if malignancy suspected)

Question 38

What does management of bacterial joint diseases depend on

Answer 38

Extent of disease Host factors Organism

Question 39

Choosing the right Abx

Answer 39

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

Question 40

Gram +ve cocci

Answer 40

Streptococci | Staphylococci

Question 41

Gram +ve rods

Answer 41

Listeria

Question 42

Gram -ve cocci

Answer 42

Neisseria

Question 43

Gram -ve rods

Answer 43

E. coli Pseudomonas aeruginosa Haemophilus influenza

Question 44

What drug can be given for MRSA

Answer 44

Vancomycin | Trough levels should be 15 -20