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Microbiology 1 Flashcards

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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
metronidazole?
anaerobes
26
gram +ve cover?
fluclox (IV) vancomycin (IV) doxy (oral switch)
27
gram -ve cover?
gentamicin (IV) | cotrimoxazole/doxy (oral switch)
28
anaerobes?
metronidazole
29
is vancomycin used orally?
not really | only for C. Diff
30
general endocarditis treatment?
6 weeks IV antibiotics
31
is pseudomonas in a culture likely to be an infection?
only if its in the blood, sputum or surgical biopsy | probably not if its a skin swab
32
name some likely coloniser organisms?
``` pseudomonas E. Coli Proteus Klebsiella Enterobacter Bacillus sp Coagulase -ve staph ```
33
name some organisms which are always treated as significant
staph aureus Group A, B, C strep Milleri strep Anaerobes
34
who classically gets haematogenous osteomyelitis?
prepubertal children IV drug users people with central lines/dialysis elderly
35
sources of haematogenous osteomyelitis?
``` tonsils skin teeth GI UTI mostly staph aureus ```
36
staph aureus blood culture treatment?
minimum 14 days antibiotics | must take lines out if present or look for other source of infection
37
common types of infection in IV drug users?
``` contiguous haematogenous direct inoculation Staph aureus most commonly can be in unusual sites ```
38
what causes osteomyelitis in sickle cell disease?
staph aureus salmonella usually affects long bones but can be multifocal
39
where does bone infection occur in Gaucher's disease and what typically causes it?
tibia (can mimic bone crisis) | staph aureus
40
what is SAPHO and CRMO?
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
how does vertebral osteomyelitis usually occur?
``` mostly haematogenous can be associated with epidural abscess or psoas abscess or PWID IV infections GU infections SSTI post op ```
42
features of vertebral osteomyelitis?
only 50% have fever 90% just have pain and raised inflammatory markers <50% have raised WCC few have neurological symptoms
43
vertebral biopsy?
always biopsy before empirical antibiotics 1st biopsy not as sensitive as the 2nd open biopsy if still no answer after the 2nd
44
how is vertebral osteomyelitis treated?
drainage of paravertebral/epidural abscess antimicrobials for 6 weeks (extended if complicated) (expect >50% decrease in ESR)
45
when is MRI repeated?
increasing pain, inflammatory markers or new symptoms
46
what is Potts disease?
vertebral TB
47
what are the features of Potts disease?
often no systemic symptoms skin/soft tissue infection common wedge shaped spine deformity
48
risk factors for prosthetic joint osteomyelitis?
rheumatoid arthritis diabetes malnutrition obesity
49
is pulmonary TB associated with vertebral TB?
not always (<50%)
50
how can prosthetic joint osteomyelitis occur?
direct inoculation during surgery manipulation of joint during surgery seeding of joint at later time (e.g from a bacteraemia)
51
early vs late prosthetic joint infection?
``` early = within a month (wound sepsis) late = after 1 month (contamination during surgery) ```
52
what is biofilm?
community of bacteria that are very difficult to penetrate with antibiotics grow slowly covering prosthetic joint
53
in which disease are severe biofilms found?
CF
54
prosthetic joint osteomyelitis organisms?
``` gram +ves - staph aureus - staph epidermidis gram -ves (fungi) (mycobacteria) ```
55
how is prosthetic jont osteomyelitis diagnosed?
``` culture - perioperative tissue (multiple) - if same organism grows from many samples = significant blood culture CRP radiology ```
56
how is prosthetic joint infection osteomyelitis treated?
ideally removal of the joint therapy for 6 weeks re-implantation of joint after antibiotic therapy (not always possible)
57
plaktonic vs sessile bacteria?
``` planktonic = bacteraemia sessile = biofilm, phenotypic transformation of planktonic bacteria ```
58
reasons for septic arthritis?
inflammation of the joint space blood borne organisms extension of local infection direct innoculation
59
bacterial causes of septic arthritis?
staph aureus strep coag -ve if prosthetic Neisseria ghonorrhoea if young and sexually active
60
how is septic arthritis diagnosed?
clinical features joint fluid microscopy blood culture if pyrexial
61
how is septic arthritis treated?
presumptive flucloxacillin treatment if <5 add cephtriaxonee adjust when organisms confirmed
62
what is chikungunya?
….
63
can viruses cause septic arthritis?
yes - hep B - rubella - parovirus - alphavirus
64
what causes pyomyositis?
90% are staph but can be site specific (i.e perineal infections - think gram -ves)
65
causes of pyomyositis in temperate and tropical places?
tropical - MSSA | temperate - immunosuppressed (pseudomonas, beta strep, enterococcus)
66
causes of pyomyositis in IV drug users?
clostridium?
67
how is PVL noticed?
more sick than you expect necrotising bacteraemia/pneumonia invasive infections
68
what else can cause myositis?
viral - diffuse (HIV, rabies etc) fungal (rare) parasites (taenia etc)
69
what is polymyositis?
inflammatory disease of many muscles in the body causing weakness
70
what is myonecrosis?
destruction of tissue by infection
71
what is tetanus?
clostridium tetanis toxin causes disease gram +ve strictly anaerobic spores found in soil, gardens
72
what does tetanus do?
neurotoxin causes spastic paralysis (by preventing release of neurotransmitters) locked jaw, muscle spasm non invasive
73
inoculation period of tetanus?
4 days - several weeks
74
diagnosis of tetanus?
culture very hard so usually a clinical picture
75
how is tetanus treated?
``` surgical debridement antitoxin supportive measures antibiotics sometimes vaccine available ```
76
how are septic patients always treated?
empirically

MSK (66 decks)

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