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MSK > Microbiology 1 > Flashcards

Microbiology 1 Flashcards

1
Q

what is osteomyelitis?

A

inflammation of bone and medullary cavity

usually in ling bones

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2
Q

how can osteomyelitis be classified?

A

acute/chronic
contiguous/haematogenous spread
host status (e.g presence of vascular insufficiency)
usually the first two

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3
Q

how can osteomyelitis be diagnosed in general terms?

A

direct (biopsy)

indirect (wound swabs, blood cultures but not as good, cross sectional imaging)

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4
Q

how is osteomyelitis generally treated?

A

debridement
antimicrobials
- not an emergency unless they have sepsis

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5
Q

what is a diagnostic factor of osteomyelitis

A

if you can see a tendon

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6
Q

are empirical antibiotics used in osteomyelitis?

A

NO

not until a biopsy has been performed and you know the specific pathogen (unless they have sepsis)

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7
Q

what causes infection in the bone?

A

bone is generally resistant to infection so would need to be necrosis of bone or very virulent organism

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8
Q

describe the principles of surgery for osteomyelitis

A

remove infected tissue
drain
debride
6 weeks of treatment as debrided bone takes 6 weeks to be covered in soft tissue? (can be a variety of treatments i.e - IV then oral)

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9
Q

where does bone infection tend to occur? (6)

A
  • open fractures
  • diabetes/vascular insufficiency
  • haematogenous osteomyelitis
  • vertebral osteomyelitis
  • prosthetic joint infection
  • specific hosts and pathogens
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10
Q

which staph causes most problems?

A 
coagulase positive
coagulase negative (epidermidis) doesn't usually cause problems unless the person has a metal/plastic prosthetic (not virulent)
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11
Q

name 2 appropriate bone cultures

A

percutaneous aspirate

deep surgical cultures

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12
Q

coagulase +ve vs -ve result in test tube?

A

+ve clots

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13
Q

how does infection occur in open fractures (bone pierces skin) and give a clinical clue of this?

A

contiguous infection
non-union of bones
poor wound healing

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14
Q

early management of open fracture infection?

A

aggressive debridement

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15
Q

when is a diabetic ulcer likely to get infected?

A

> 2cm for >2 months

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16
Q

is diabetic ulcer polymicrobial?

A

yes as its rotting flesh

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17
Q

how is diabetic osteomyelitis diagnosed?

A

bone probe (surface swab not useful as too many bugs present)

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18
Q

how is diabetic osteomyelitis treated?

A

debridement
antimicrobials
antibiotics after probe so you know

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19
Q

best diagnosis of osteomyelitis and infecting organism?

A

bone biopsy and culture

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20
Q

best imaging for osteomyelitis?

A

MRI (X rays can show changes after a long time)

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21
Q

mild, moderate and severe diabetic ulcer treatment?

A

mild - flucloxacillin
mod - flucloxacillin _ metronidazole
severe - flucloxacillin + metronidazole + gentamicin

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22
Q

how long is treatment maintained for infection?

A

7 days
14 if blood infection
6 weeks if osteomyelitis
DURATIONS IMPORTANT

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23
Q

vancomycin?

A

MRSA

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24
Q

gentamicin?

A

gram -ves

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25
Q

metronidazole?

A

anaerobes

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26
Q

gram +ve cover?

A

fluclox (IV)
vancomycin (IV)
doxy (oral switch)

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27
Q

gram -ve cover?

A

gentamicin (IV)

cotrimoxazole/doxy (oral switch)

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28
Q

anaerobes?

A

metronidazole

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29
Q

is vancomycin used orally?

A

not really

only for C. Diff

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30
Q

general endocarditis treatment?

A

6 weeks IV antibiotics

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31
Q

is pseudomonas in a culture likely to be an infection?

A

only if its in the blood, sputum or surgical biopsy

probably not if its a skin swab

32
Q

name some likely coloniser organisms?

A 
pseudomonas
E. Coli
Proteus
Klebsiella
Enterobacter
Bacillus sp
Coagulase -ve staph
33
Q

name some organisms which are always treated as significant

A

staph aureus
Group A, B, C strep Milleri strep
Anaerobes

34
Q

who classically gets haematogenous osteomyelitis?

A

prepubertal children
IV drug users
people with central lines/dialysis
elderly

35
Q

sources of haematogenous osteomyelitis?

A 
tonsils
skin
teeth
GI
UTI
mostly staph aureus
36
Q

staph aureus blood culture treatment?

A

minimum 14 days antibiotics

must take lines out if present or look for other source of infection

37
Q

common types of infection in IV drug users?

A 
contiguous
haematogenous
direct inoculation
Staph aureus most commonly
can be in unusual sites
38
Q

what causes osteomyelitis in sickle cell disease?

A

staph aureus
salmonella
usually affects long bones but can be multifocal

39
Q

where does bone infection occur in Gaucher’s disease and what typically causes it?

A

tibia (can mimic bone crisis)

staph aureus

40
Q

what is SAPHO and CRMO?

A

Synovitis Acne Pustulosis Hyperostosis Osteitis
Chronic Reccurent Multifactoral Osteomyositis
can often me mistaken for osteomyelitis as similar symptoms and raised inflammatory markers
excluded via history and culture

41
Q

how does vertebral osteomyelitis usually occur?

A 
mostly haematogenous
can be associated with epidural abscess or psoas abscess or
PWID
IV infections
GU infections
SSTI
post op
42
Q

features of vertebral osteomyelitis?

A

only 50% have fever
90% just have pain and raised inflammatory markers
<50% have raised WCC
few have neurological symptoms

43
Q

vertebral biopsy?

A

always biopsy before empirical antibiotics
1st biopsy not as sensitive as the 2nd
open biopsy if still no answer after the 2nd

44
Q

how is vertebral osteomyelitis treated?

A

drainage of paravertebral/epidural abscess
antimicrobials for 6 weeks (extended if complicated)
(expect >50% decrease in ESR)

45
Q

when is MRI repeated?

A

increasing pain, inflammatory markers or new symptoms

46
Q

what is Potts disease?

A

vertebral TB

47
Q

what are the features of Potts disease?

A

often no systemic symptoms
skin/soft tissue infection common
wedge shaped spine deformity

48
Q

risk factors for prosthetic joint osteomyelitis?

A

rheumatoid arthritis
diabetes
malnutrition
obesity

49
Q

is pulmonary TB associated with vertebral TB?

A

not always (<50%)

50
Q

how can prosthetic joint osteomyelitis occur?

A

direct inoculation during surgery
manipulation of joint during surgery
seeding of joint at later time (e.g from a bacteraemia)

51
Q

early vs late prosthetic joint infection?

A 
early = within a month (wound sepsis)
late = after 1 month (contamination during surgery)
52
Q

what is biofilm?

A

community of bacteria that are very difficult to penetrate with antibiotics
grow slowly covering prosthetic joint

53
Q

in which disease are severe biofilms found?

A

CF

54
Q

prosthetic joint osteomyelitis organisms?

A 
gram +ves
- staph aureus
- staph epidermidis
gram -ves
(fungi)
(mycobacteria)
55
Q

how is prosthetic jont osteomyelitis diagnosed?

A 
culture
- perioperative tissue (multiple) - if same organism grows from many samples = significant
blood culture
CRP
radiology
56
Q

how is prosthetic joint infection osteomyelitis treated?

A

ideally removal of the joint
therapy for 6 weeks
re-implantation of joint after antibiotic therapy (not always possible)

57
Q

plaktonic vs sessile bacteria?

A 
planktonic = bacteraemia
sessile = biofilm, phenotypic transformation of planktonic bacteria
58
Q

reasons for septic arthritis?

A

inflammation of the joint space
blood borne organisms
extension of local infection
direct innoculation

59
Q

bacterial causes of septic arthritis?

A

staph aureus
strep
coag -ve if prosthetic
Neisseria ghonorrhoea if young and sexually active

60
Q

how is septic arthritis diagnosed?

A

clinical features
joint fluid microscopy
blood culture if pyrexial

61
Q

how is septic arthritis treated?

A

presumptive flucloxacillin treatment
if <5 add cephtriaxonee
adjust when organisms confirmed

62
Q

what is chikungunya?

A

….

63
Q

can viruses cause septic arthritis?

A

yes

  • hep B
  • rubella
  • parovirus
  • alphavirus
64
Q

what causes pyomyositis?

A

90% are staph but can be site specific (i.e perineal infections - think gram -ves)

65
Q

causes of pyomyositis in temperate and tropical places?

A

tropical - MSSA

temperate - immunosuppressed (pseudomonas, beta strep, enterococcus)

66
Q

causes of pyomyositis in IV drug users?

A

clostridium?

67
Q

how is PVL noticed?

A

more sick than you expect
necrotising bacteraemia/pneumonia
invasive infections

68
Q

what else can cause myositis?

A

viral - diffuse (HIV, rabies etc)
fungal (rare)
parasites (taenia etc)

69
Q

what is polymyositis?

A

inflammatory disease of many muscles in the body causing weakness

70
Q

what is myonecrosis?

A

destruction of tissue by infection

71
Q

what is tetanus?

A

clostridium tetanis toxin causes disease
gram +ve
strictly anaerobic
spores found in soil, gardens

72
Q

what does tetanus do?

A

neurotoxin causes spastic paralysis (by preventing release of neurotransmitters)
locked jaw, muscle spasm
non invasive

73
Q

inoculation period of tetanus?

A

4 days - several weeks

74
Q

diagnosis of tetanus?

A

culture very hard so usually a clinical picture

75
Q

how is tetanus treated?

A 
surgical debridement
antitoxin
supportive measures
antibiotics sometimes
vaccine available
76
Q

how are septic patients always treated?

A

empirically

MSK (66 decks)

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