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MMB > 025) Bacterial Infections of Bones, Joints and Muscles > Flashcards

025) Bacterial Infections of Bones, Joints and Muscles Flashcards

1
Q

Describe organism’s morphology and name it

A

Staphylococcus species

  • Gram-positive cocci arranged in clusters
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2
Q

Staphylococcus are catalase (+/-) bacteria

A

Catalase (+)

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3
Q

How can catalase + staphylococcy be further classified ?

A

By Coagulase test

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4
Q

Coagulase (+) staphylococcy ?

A

Staph. aureus

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5
Q

Coagulase (-) staphylococcy ?

A

-S. epidermidis

-S. saprophyticus

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6
Q

…. Causes ~75% of cases of osteomyelitis

A

Staph. aureus (coagulase positive)

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7
Q

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

A

Staph. epidermidis (Coagulase-negative)

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8
Q

Virulence factors of Staph. aureus ?

A

• Coagulase

• Staphylokinase

• Leucocidins

• Hyaluronidase

• Haemolysins

• Epidermolytic toxins

• Enterotoxins

• Toxic shock toxin

• Biofilm production

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9
Q

Invasins of Staph. aureus ?

A

• Staphylokinase

• Leucocidins

• Hyaluronidase

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10
Q

Exotoxins of Staph. aureus ?

A

• Epidermolytic toxins

• Enterotoxins

• Toxic shock toxin

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11
Q

Major Virulence factor of Coagulase -ve Staphylococci ?

A

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

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12
Q

Pathogenesis of S. aureus osteomyelitis ?

A

• 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

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13
Q

Treatment of S. aureus osteomyelitis ?

A

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

  • CHEMOTHERAPY :
    Vigorous use of antibacterial agents ;

•Flucloxacillin +/- Fusidic acid (Fucidin) or

•Teicoplanin

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14
Q

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

A

(6-8 weeks)

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15
Q

Treatment of pott’s disease ?

A
  • 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)
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16
Q

Pott’s disease treatment often needs …. Time

A

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

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17
Q

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

A

3 to 6

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18
Q

How can Catalase (-) Streptococcus be further classified ?

A

Haemolysis

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19
Q

Beta haemolytic Streptococcy ?

A

-S. Pyogenes (GAS)

-S. Agalactiae (GBS)

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20
Q

Alpha haemolytic Streptococcy ?

A

-S. pneumoniae

-S. viridans

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21
Q

what’s the haemolysis ?

A

Gamma

22
Q

Name organism and describe morphology

A

Streptococcus pyogenes (GAS) ;

Morphology: Gram-positive cocci, arranged in chains

23
Q

Virulence factors of Strep pyogenes ?

A

• 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

24
Q

Adhesion factors of Strep pyogenes ?

A

• M-protein – adhesin, antiphagocytic

• Lipoteichoic acid – adhesin

• Fibronectin-binding protein (Protein-F)

25
Q

Invasion factors of Strep pyogenes ?

A

• Streptococcal pyrogenic exotoxins A,B,C superantigens

• Streptolysin, O, S – haemolysins

• Streptokinase

• DN’ase

• Hyaluronidase

• Proteases e.g. C5a peptidase

26
Q

Superantigens are often produced by :

A

Staphylococci, Group A Streptococci and Mycoplasmas

27
Q

How does Superantigens cause damage ?

A

• Potent immunomodulators (overstimulation of the immune system)

• Overproduction of cytokines ……………Tissue Damage

• Divert T cells into polyclonal activation which is immunologically unhelpful.

28
Q

Cells secreting TNF, IL-1 ?

A

macrophages, fibroblasts

29
Q

Cells secreting IL-8 ?

A

epithelial cells

30
Q

Cells secreting Histamine ?

A

Mast cells

31
Q

What secretes NAD dehydrogenase ?

A

mitochondria

32
Q

Cells secreting Leucotrienes, prostaglandins ?

A

all cells

33
Q

Pathogenesis of Streptococcal infections ?

A

• Penetrate tissue

• Adherence

• Avoid host defenses

• Produce enzymes/toxins to destroy tissue

• Cause thrombosis of perforating arteries

• Activate immune cells non-specifically

34
Q

Cellulitis ?

A
35
Q

Comment on the demarcation of cellulitis

A

an irregular line of demarcation (not well demarcated)

36
Q

Pathogens of Necrotizing fasciitis ?

A

• Streptococcus pyogenes (group A strep)

(flesh-eating bacteria)

• Mixed infections with facultative anaerobes

• Rarely other organisms e.g. E. coli

37
Q

Presentations of Necrotizing fasciitis ?

A

• Acute inflammatory response

• Very painful

• Erythema spreads rapidly

• Patient is “toxic”

38
Q

Treatment of S. pyogenes infections ?

A

• Penicillins are the drugs of choice benzylpenicillin (BP)

39
Q

Treatment of S. pyogenes Necrotizing fasciitis ?

A

• Prompt Radical excision of necrotic tissue (surgical debridement)

• Aggressive Local and systemic antibiotics –

clindamycin + BP

40
Q

Pathogens of Gas Gangrene ?

A

• Clostridium perfringens

• Mixed facultative and strict anaerobes

41
Q

Presentations of Gas Gangrene ?

A

• Dark red skin with large bullae

• Very painful

• Erythema spreads

• Patient is “toxic”

• Very little inflammation

42
Q

comment on morphology and define the organism

A

Clostridium perfringens ;

Gram-positive rods

43
Q

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

A

Clostridium perfringens

44
Q

…… Can form spores (under unfavourable conditions)

A

Clostridium perfringens

45
Q

While most Clostridiums are saccharolytic , others are …..

A

proteolytic

46
Q

Clostridium perfringens is a strict (aerobe/anaerobe)

A

Anaerobe

47
Q

Virulence Factors of Clostridium perfringens ?

A

1-Exotoxins

2- Spreading enzymes: Collagenase & Hyaluronidase

48
Q

Exotoxins of Clostridium perfringens ?

A

(~17 all with Greek letters)

• Alpha toxin :(phospholipase C or Lecithinase)
• Theta toxin: O 2 labile hemolysin

49
Q

Pathogenesis of Clostridium perfringens ?

A
50
Q

Treatment of Clostridium perfringens (Gas gangrene) ?

A
  • surgical debridement

• Hyperbaric oxygen chamber

• Benzylpenicillin is an adjunctive therapy not an alternative to surgery

51
Q

What is Hyperbaric oxygen chamber/therapy ?

A

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.

MMB (72 decks)

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