Microbiology of MSK infections Flashcards Preview

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Flashcards in Microbiology of MSK infections Deck (84):
1

What is the most common cause of osteomyelitis?

Staph aureus

2

What are the first line treatment choices for staph/strep infection?

Flucloxacillin
Vancomycin (pen allergic)
Clindamycin (virulent strain requiring anti-toxin)

3

What are the first line treatment choices for coliform infection?

Gentamicin
Ceftriaxone (try to avoid)
Ciprafloxacin (oral but try to avoid)

4

What makes infection of implanted devices so hard to treat?

Biofilm formation

5

What is a biofilm?

Bacterial growth coated in protein and polysaccharides

6

How do biofilms affect the environment of the area they've infected?

Reduce pH
Reduce oxygen availability

7

What are the three types of implant infection?

Early post-op
Delayed
Late

8

Which bacteria tend to cause early post-op implant infections?

Staph aureus
Streptococci
Enterococci

9

Which bacteria tend to cause delayed implant infections?

Coag. negative staph
P. acnes

10

Which bacteria tend to cause late implant infections?

Staph aureus
E.coli

11

Describe the time frame for each type of implant infection

Early post op - 0-3 mnth
Delayed - 3-24 mnth
Late - >24 mnth

12

How does an early implant infection present?

Fever
Effusion
Warmth
Drainage

13

How does a delayed implant infection present?

Persistant pain
Device loosening
Fistula

14

How does a late implant infection present?

Acute OR subacute

15

Describe the route of infection for each type of implant infection

Early - perioperative
Delayed - perioperative
Late - haematogenous

16

What is the diagnostic criteria for systemic inflammatory response syndrome (SIRS)?

Temperature >38 OR 90
Respiratory rate >20 OR PaCO2 12,000 OR

17

SIRS is an ongoing response in chronic infections. T/F

False - SIRS is only acute

18

What defines the need for immediate antibiotic treatment of a patient?

Presence of SIRS - immediate treatment
Absence of SIRS - delay until specimens cultured

19

How are prosthetic joint infections treated?

Debride joint
Long course of high dose (+/- IV) antibiotics

20

What are the two surgical options for prosthetic joint infection?

Debride and retain prosthetics (DAIR)
Debride and remove prosthetic (one or two stage)

21

What are the most common acute prosthetic joint infections?

Staph aureus
Strep

22

What are the most common chronic prosthetic joint infections?

Coag negative staph
Propionibacteria

23

What type of samples are obtained in PJI? Why?

Bone samples - reflect the infecting organism

24

How are gram positive joint infections treated?

Flucloxacillin/vancomycin
Teicoplanin (if resistant)

25

How are gram negative joint infections treated?

Co-trimoxazole
Amoxicillin

26

How long does DAIR treatment take?

4 weeks + 8 weeks

27

How long does one stage treatment take?

4 weeks + 6 weeks

28

How long does two stage treatment take?

6 weeks + 6 weeks

29

How long does hip treatment take?

3 months (12 weeks)

30

How long does knee treatment take?

6 months (24 weeks)

31

Is CPR always elevated?

No -
Usually normal in chronic infections
Can be influenced by underlying diseases
Can be influenced by surgery

32

How long should PJI treatment be continued after resolution of clinical symptoms and signs? What should then be done?

2 weeks
CT/MRI

33

When can we be sure of a clinical cure following PJI?

2 years post treatment

34

Describe surgical prophylaxis

Give dose 60min pre surgery
Stop dose within 24 hours post surgery

35

What surgical prophylaxis is given in orthopaedics?

Co-amoxiclav/co-tramoxazole peri op and two post op doses
Eradicate MRSA pre-op

36

What are the underlying risk factors for bone and joint infections (BJI)?

Immunosuppression
Diabetes
Implants
IV drug user
Sickle cell anaemia

37

Which BJI pathogen is common in children

Kingella

38

How does a BJI present acutely?

Fever
Inflammation over the affected joint
Reduced mobility/fixed immobilisation

39

How does a BJI present acutely in a child?

Listless
Not feeding
Not playing
Cranky

40

What is septic arthritis?

Infection of a joint space

41

What are the possible routes of infection with regard to septic arthritis?

Haematogenous
Contiguous (bone-bone)
Direct inoculation (injection, trauma, etc)

42

Which organisms tend to be involved in septic arthritis?

Staph aureus
Strep

H. influenzae (children)
Gonorrhoea

43

How is septic arthritis diagnosed?

Blood culture (IF FEVER)
Inflammatory markers
FBC
U&E
Lactate
Joint aspirate +/- washout --> culture
Crystals and gram stain
USS
X-ray/CT/MRI/bone scan

44

How is septic arthritis treated? How long for?

Flucloxacillin
Ceftriazone if

45

What is osteomyelitis?

Inflammation of bone/medullary cavity

46

Which bones tend to be affected by osteomyelitis?

Long bones
Vertebrae

47

Which pathogens tend to be involved in acute osteomyelitis?

S. aureus
Strep

48

Which pathogens tend to be involved in chronic osteomyelitis?

TB
Pseudomonas
Salmonella
Coliforms

49

When might osteomyelitis reoccur?

Inefficient treatment

50

Incidence os osteomyelitis is increasing in children. T/F

True

51

What are the possible routes of infection with regard to osteomyelitis?

Haematogenous
Contiguous (bone-bone)
Peripheral vascular disease associated
Prosthesis associated

52

Define the timeframe of acute osteomyeltis

53

What is the most likely route of infection in acute osteomyelitis?

Haematogenous

54

Acute osteomyelitis can become septic arthritis in which bones especially? Why?

Hip
Shoulder
Ankle
Elbow

Metaphyses are found within the joint space

55

Why are infants more at risk of osteomyelitis becoming septic arthritis?

They have blood vessels connecting the metaphysis to the epiphysis

56

Chronic osteomyeltis has a higher risk of which complications?

Abscess
Septicaemia
Permanent bone deformity

57

How should chronic osteomyelitis be managed?

Antibiotic treatment according to culture results (if no SIRS)

58

How is osteomyelitis diagnosed and managed? How long for?

Blood culture (IF FEVER)
Bone biopsy +/- washout --> culture
Empiric flucloxacillin

4-8 weeks

59

What are the risk factors for prosthetic joint infections?

Diabetes
Rheumatoid arthritis
Malnutrition
Obesity

60

Coagulate negative staph are skin commensals. T/F

True - this can make it difficult to determine whether they are contaminants or causing infections

61

Why can it be difficult to get a microbiology diagnosis of PJI? How can this be reduced?

Most infecting organisms are skin commensals
Multiple tissue and bone cultures

62

How can PJI be diagnosed?

Multiple tissue/bone cultures
Blood culture (RARELY +VE)
Inflammatory markers
FBC
Imaging

63

How is PJI treated?

Debridement
At least 6 weeks antibiotic treatment
Re-implant joint post - treatment

64

What is necrotising fasciitis?

Severe infection of subcutaneous soft tissues

65

How common is necrotising fasciitis?

Uncommon

66

How often to people die from necrotising fasciitis?

High mortality (rapidly progressive)

67

Where are the common sites of necrotising fasciitis infection?

Abdominal wall
Perineum
Limbs
Post-op wounds

68

How does necrotising fasciitis present?

Highly painful
Minimal signs of inflammation
Systemic symptoms
Rapid expansion

69

Describe type 1 and type 2 necrotising fasciitis

Type 1 - anaerobes (synergistic gangrene)
Type 2 - group A strep

70

How can necortising fasciitis be diagnosed?

Clinical
Swabs + biopsy --> microbiology, gram stain, culture
Blood culture
Inflammatory markers
FBC

71

How is necrotising fasciitis managed?

Debridement
Antibiotics

72

Which antibiotics are given in type 1 necrotising fasciitis?

Pip-taz
Clindamycin
Gentamicin

73

Which antibiotics are given in type 2 necrotising fasciitis?

Penicillin & clindamycin

74

Necrotising faciitis requires droplet protection. T/F

False - contact precautions

75

Which pathogen is responsible for gas gangrene?

Clostridium perfringens

76

Describe the pathogenesis of gas gangrene

Spores lie within tissues -->
Predisposition (dead tissue, hypoxia) -->
Multiplication -->
Accumulation of gas bubbles within tissue

77

On compression of an area with gas gangrene what can be felt?

Crepitus

78

How is gas gangrene managed?

Urgent debridement
High dose penicillin and/or metronizaole
+/- hyperbaric oxygen

79

What pathogen causes tetanus?

Clostridium tetani

80

Where can tetanus bacteria be found?

Animal mouths
Soil
Rust

81

How does tetanus present? Why?

Spastic paralysis
Lock jaw

Produces a neurotoxin which prevents release of neurotransmitters

82

How long is the incubation period of tetanus?

4 days - several weeks

83

How is tetanus treated?

Debridgement
Anti-toxin
Supportive
Penicillin/metronidazole
Toxoid booster vaccination

84

When are the tetanus vaccines given?

2, 3 & 4 months

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