025) Bacterial Infections of Bones, Joints and Muscles

Question 1

Describe organism’s morphology and name it

Answer 1

Staphylococcus species

• Gram-positive cocci arranged in clusters

Question 2

Staphylococcus are catalase (+/-) bacteria

Answer 2

Catalase (+)

Question 3

How can catalase + staphylococcy be further classified ?

Answer 3

By Coagulase test

Question 4

Coagulase (+) staphylococcy ?

Answer 4

Staph. aureus

Question 5

Coagulase (-) staphylococcy ?

Answer 5

-S. epidermidis

-S. saprophyticus

Question 6

…. Causes ~75% of cases of osteomyelitis

Answer 6

Staph. aureus (coagulase positive)

Question 7

…… are skin commensals that cause most cases of osteomyelitis associated with prosthetic joints.

Answer 7

Staph. epidermidis (Coagulase-negative)

Question 8

Virulence factors of Staph. aureus ?

Answer 8

• Coagulase

• Staphylokinase

• Leucocidins

• Hyaluronidase

• Haemolysins

• Epidermolytic toxins

• Enterotoxins

• Toxic shock toxin

• Biofilm production

Question 9

Invasins of Staph. aureus ?

Answer 9

• Staphylokinase

• Leucocidins

• Hyaluronidase

Question 10

Exotoxins of Staph. aureus ?

Answer 10

• Epidermolytic toxins

• Enterotoxins

• Toxic shock toxin

Question 11

Major Virulence factor of Coagulase -ve Staphylococci ?

Answer 11

• Biofilm production – cause 10-40% of prosthetic hip infections

Question 12

Pathogenesis of S. aureus osteomyelitis ?

Answer 12

• Sluggish flow at the metaphysis

• Adhesion of S. aureus

• Acute inflammation at the site

• Avoidance of host defences

• Growth in biofilm

• Necrosis of tissue

• Abscess formation

• Further necrosis due to compromised blood supply

Question 13

Treatment of S. aureus osteomyelitis ?

Answer 13

-SURGERY :
Drainage (release) any pus WITHOUT DELAY
and :

• CHEMOTHERAPY :
  Vigorous use of antibacterial agents ;

•Flucloxacillin +/- Fusidic acid (Fucidin) or

•Teicoplanin

Question 14

CHEMOTHERAPY of staph.aures ostemomyolitis needs to be continued for…. Weeks

Answer 14

(6-8 weeks)

Question 15

Treatment of pott’s disease ?

Answer 15

• CHEMOTHERAPY :
  Treatment for at least 6 months and possibly up to 9–12 months for extensive bone infections eg rifampicin + izonaziad + pyrazinamide + ethambutol (2months or more) then rifampicin and izonaziad (up to 10 months)

Question 16

Pott’s disease treatment often needs …. Time

Answer 16

Treatment for at least 6 months and possibly up to 9–12 months for extensive bone infections

Question 17

In Management of Septic Arthritis : Antimicrobials must be continued for…… weeks

Answer 17

3 to 6

Question 18

How can Catalase (-) Streptococcus be further classified ?

Answer 18

Haemolysis

Question 19

Beta haemolytic Streptococcy ?

Answer 19

-S. Pyogenes (GAS)

-S. Agalactiae (GBS)

Question 20

Alpha haemolytic Streptococcy ?

Answer 20

-S. pneumoniae

-S. viridans

Question 21

what’s the haemolysis ?

Answer 21

Gamma

Question 22

Name organism and describe morphology

Answer 22

Streptococcus pyogenes (GAS) ;

Morphology: Gram-positive cocci, arranged in chains

Question 23

Virulence factors of Strep pyogenes ?

Answer 23

• M-protein – adhesin, antiphagocytic

• Lipoteichoic acid – adhesin

• Fibronectin-binding protein (Protein-F)

• Streptococcal pyrogenic exotoxins A,B,C superantigens

• Streptolysin, O, S – haemolysins

• Streptokinase

• DN’ase

• Hyaluronidase

• Proteases e.g. C5a peptidase

Question 24

Adhesion factors of Strep pyogenes ?

Answer 24

• M-protein – adhesin, antiphagocytic

• Lipoteichoic acid – adhesin

• Fibronectin-binding protein (Protein-F)

Question 25

Invasion factors of Strep pyogenes ?

Answer 25

• Streptococcal pyrogenic exotoxins A,B,C superantigens • Streptolysin, O, S – haemolysins • Streptokinase • DN’ase • Hyaluronidase • Proteases e.g. C5a peptidase

Question 26

Superantigens are often produced by :

Answer 26

Staphylococci, Group A Streptococci and Mycoplasmas

Question 27

How does Superantigens cause damage ?

Answer 27

• Potent immunomodulators (overstimulation of the immune system) • Overproduction of cytokines ……………Tissue Damage • Divert T cells into polyclonal activation which is immunologically unhelpful.

Question 28

Cells secreting TNF, IL-1 ?

Answer 28

macrophages, fibroblasts

Question 29

Cells secreting IL-8 ?

Answer 29

epithelial cells

Question 30

Cells secreting Histamine ?

Answer 30

Mast cells

Question 31

What secretes NAD dehydrogenase ?

Answer 31

mitochondria

Question 32

Cells secreting Leucotrienes, prostaglandins ?

Answer 32

all cells

Question 33

Pathogenesis of Streptococcal infections ?

Answer 33

• Penetrate tissue • Adherence • Avoid host defenses • Produce enzymes/toxins to destroy tissue • Cause thrombosis of perforating arteries • Activate immune cells non-specifically

Question 34

Cellulitis ?

Answer 34

Question 35

Comment on the demarcation of cellulitis

Answer 35

an irregular line of demarcation (not well demarcated)

Question 36

Pathogens of Necrotizing fasciitis ?

Answer 36

• Streptococcus pyogenes (group A strep) (flesh-eating bacteria) • Mixed infections with facultative anaerobes • Rarely other organisms e.g. E. coli

Question 37

Presentations of Necrotizing fasciitis ?

Answer 37

• Acute inflammatory response • Very painful • Erythema spreads rapidly • Patient is “toxic”

Question 38

Treatment of S. pyogenes infections ?

Answer 38

• Penicillins are the drugs of choice benzylpenicillin (BP)

Question 39

Treatment of S. pyogenes Necrotizing fasciitis ?

Answer 39

• Prompt Radical excision of necrotic tissue (surgical debridement) • Aggressive Local and systemic antibiotics – clindamycin + BP

Question 40

Pathogens of Gas Gangrene ?

Answer 40

• Clostridium perfringens • Mixed facultative and strict anaerobes

Question 41

Presentations of Gas Gangrene ?

Answer 41

• Dark red skin with large bullae • Very painful • Erythema spreads • Patient is “toxic” • Very little inflammation

Question 42

comment on morphology and define the organism

Answer 42

Clostridium perfringens ; Gram-positive rods

Question 43

……. Produces acid and gas by fermentation of carbohydrates (saccharolytic)

Answer 43

Clostridium perfringens

Question 44

…… Can form spores (under unfavourable conditions)

Answer 44

Clostridium perfringens

Question 45

While most Clostridiums are saccharolytic , others are …..

Answer 45

proteolytic

Question 46

Clostridium perfringens is a strict (aerobe/anaerobe)

Answer 46

Anaerobe

Question 47

Virulence Factors of Clostridium perfringens ?

Answer 47

1-Exotoxins 2- Spreading enzymes: Collagenase & Hyaluronidase

Question 48

Exotoxins of Clostridium perfringens ?

Answer 48

(~17 all with Greek letters) • Alpha toxin :(phospholipase C or Lecithinase) • Theta toxin: O 2 labile hemolysin

Question 49

Pathogenesis of Clostridium perfringens ?

Answer 49

Question 50

Treatment of Clostridium perfringens (Gas gangrene) ?

Answer 50

- surgical debridement • Hyperbaric oxygen chamber • Benzylpenicillin is an adjunctive therapy not an alternative to surgery

Question 51

What is Hyperbaric oxygen chamber/therapy ?

Answer 51

Hyperbaric oxygen therapy increases the amount of oxygen your blood can carry. With repeated scheduled treatments, the temporary extra high oxygen levels encourage normal tissue oxygen levels, even after the therapy is completed.