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Year 2 > Microbiology of MSK infections > Flashcards

Microbiology of MSK infections Flashcards

1
Q

What is the most common cause of osteomyelitis?

A

Staph aureus

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2
Q

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

A

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

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3
Q

What are the first line treatment choices for coliform infection?

A 
Gentamicin 
Ceftriaxone (try to avoid)
Ciprafloxacin (oral but try to avoid)
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4
Q

What makes infection of implanted devices so hard to treat?

A

Biofilm formation

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5
Q

What is a biofilm?

A

Bacterial growth coated in protein and polysaccharides

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6
Q

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

A

Reduce pH

Reduce oxygen availability

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7
Q

What are the three types of implant infection?

A

Early post-op
Delayed
Late

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8
Q

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

A

Staph aureus
Streptococci
Enterococci

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9
Q

Which bacteria tend to cause delayed implant infections?

A

Coag. negative staph

P. acnes

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10
Q

Which bacteria tend to cause late implant infections?

A

Staph aureus

E.coli

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11
Q

Describe the time frame for each type of implant infection

A

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

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12
Q

How does an early implant infection present?

A

Fever
Effusion
Warmth
Drainage

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13
Q

How does a delayed implant infection present?

A

Persistant pain
Device loosening
Fistula

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14
Q

How does a late implant infection present?

A

Acute OR subacute

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15
Q

Describe the route of infection for each type of implant infection

A

Early - perioperative
Delayed - perioperative
Late - haematogenous

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16
Q

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

A

Temperature >38 OR 90

Respiratory rate >20 OR PaCO2 12,000 OR

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17
Q

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

A

False - SIRS is only acute

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18
Q

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

A

Presence of SIRS - immediate treatment

Absence of SIRS - delay until specimens cultured

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19
Q

How are prosthetic joint infections treated?

A

Debride joint

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

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20
Q

What are the two surgical options for prosthetic joint infection?

A

Debride and retain prosthetics (DAIR)

Debride and remove prosthetic (one or two stage)

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21
Q

What are the most common acute prosthetic joint infections?

A

Staph aureus

Strep

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22
Q

What are the most common chronic prosthetic joint infections?

A

Coag negative staph

Propionibacteria

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23
Q

What type of samples are obtained in PJI? Why?

A

Bone samples - reflect the infecting organism

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24
Q

How are gram positive joint infections treated?

A

Flucloxacillin/vancomycin

Teicoplanin (if resistant)

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25
Q

How are gram negative joint infections treated?

A

Co-trimoxazole

Amoxicillin

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26
Q

How long does DAIR treatment take?

A

4 weeks + 8 weeks

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27
Q

How long does one stage treatment take?

A

4 weeks + 6 weeks

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28
Q

How long does two stage treatment take?

A

6 weeks + 6 weeks

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29
Q

How long does hip treatment take?

A

3 months (12 weeks)

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30
Q

How long does knee treatment take?

A

6 months (24 weeks)

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31
Q

Is CPR always elevated?

A

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

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32
Q

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

A

2 weeks

CT/MRI

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33
Q

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

A

2 years post treatment

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34
Q

Describe surgical prophylaxis

A

Give dose 60min pre surgery

Stop dose within 24 hours post surgery

35
Q

What surgical prophylaxis is given in orthopaedics?

A

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

Eradicate MRSA pre-op

36
Q

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

A 
Immunosuppression
Diabetes
Implants 
IV drug user 
Sickle cell anaemia
37
Q

Which BJI pathogen is common in children

A

Kingella

38
Q

How does a BJI present acutely?

A

Fever
Inflammation over the affected joint
Reduced mobility/fixed immobilisation

39
Q

How does a BJI present acutely in a child?

A

Listless
Not feeding
Not playing
Cranky

40
Q

What is septic arthritis?

A

Infection of a joint space

41
Q

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

A

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

42
Q

Which organisms tend to be involved in septic arthritis?

A

Staph aureus
Strep

H. influenzae (children)
Gonorrhoea

43
Q

How is septic arthritis diagnosed?

A 
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
Q

How is septic arthritis treated? How long for?

A

Flucloxacillin

Ceftriazone if

45
Q

What is osteomyelitis?

A

Inflammation of bone/medullary cavity

46
Q

Which bones tend to be affected by osteomyelitis?

A

Long bones

Vertebrae

47
Q

Which pathogens tend to be involved in acute osteomyelitis?

A

S. aureus

Strep

48
Q

Which pathogens tend to be involved in chronic osteomyelitis?

A

TB
Pseudomonas
Salmonella
Coliforms

49
Q

When might osteomyelitis reoccur?

A

Inefficient treatment

50
Q

Incidence os osteomyelitis is increasing in children. T/F

A

True

51
Q

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

A

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

52
Q

Define the timeframe of acute osteomyeltis

A
53
Q

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

A

Haematogenous

54
Q

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

A

Hip
Shoulder
Ankle
Elbow

Metaphyses are found within the joint space

55
Q

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

A

They have blood vessels connecting the metaphysis to the epiphysis

56
Q

Chronic osteomyeltis has a higher risk of which complications?

A

Abscess
Septicaemia
Permanent bone deformity

57
Q

How should chronic osteomyelitis be managed?

A

Antibiotic treatment according to culture results (if no SIRS)

58
Q

How is osteomyelitis diagnosed and managed? How long for?

A

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

4-8 weeks

59
Q

What are the risk factors for prosthetic joint infections?

A

Diabetes
Rheumatoid arthritis
Malnutrition
Obesity

60
Q

Coagulate negative staph are skin commensals. T/F

A

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

61
Q

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

A

Most infecting organisms are skin commensals

Multiple tissue and bone cultures

62
Q

How can PJI be diagnosed?

A 
Multiple tissue/bone cultures
Blood culture (RARELY +VE)
Inflammatory markers
FBC
Imaging
63
Q

How is PJI treated?

A

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

64
Q

What is necrotising fasciitis?

A

Severe infection of subcutaneous soft tissues

65
Q

How common is necrotising fasciitis?

A

Uncommon

66
Q

How often to people die from necrotising fasciitis?

A

High mortality (rapidly progressive)

67
Q

Where are the common sites of necrotising fasciitis infection?

A

Abdominal wall
Perineum
Limbs
Post-op wounds

68
Q

How does necrotising fasciitis present?

A

Highly painful
Minimal signs of inflammation
Systemic symptoms
Rapid expansion

69
Q

Describe type 1 and type 2 necrotising fasciitis

A

Type 1 - anaerobes (synergistic gangrene)

Type 2 - group A strep

70
Q

How can necortising fasciitis be diagnosed?

A 
Clinical
Swabs + biopsy --> microbiology, gram stain, culture
Blood culture
Inflammatory markers
FBC
71
Q

How is necrotising fasciitis managed?

A

Debridement

Antibiotics

72
Q

Which antibiotics are given in type 1 necrotising fasciitis?

A

Pip-taz
Clindamycin
Gentamicin

73
Q

Which antibiotics are given in type 2 necrotising fasciitis?

A

Penicillin & clindamycin

74
Q

Necrotising faciitis requires droplet protection. T/F

A

False - contact precautions

75
Q

Which pathogen is responsible for gas gangrene?

A

Clostridium perfringens

76
Q

Describe the pathogenesis of gas gangrene

A

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

77
Q

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

A

Crepitus

78
Q

How is gas gangrene managed?

A

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

79
Q

What pathogen causes tetanus?

A

Clostridium tetani

80
Q

Where can tetanus bacteria be found?

A

Animal mouths
Soil
Rust

81
Q

How does tetanus present? Why?

A

Spastic paralysis
Lock jaw

Produces a neurotoxin which prevents release of neurotransmitters

82
Q

How long is the incubation period of tetanus?

A

4 days - several weeks

83
Q

How is tetanus treated?

A 
Debridgement
Anti-toxin
Supportive
Penicillin/metronidazole 
Toxoid booster vaccination
84
Q

When are the tetanus vaccines given?

A

2, 3 & 4 months

Year 2 (72 decks)

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