Infections Flashcards
where in MSK system can you get infection
bone infections
joint and synovial fluid
muscle infections
what is osteomyelitis
inflammation of the bone and medullary cavity- usually located in one of the long bones
how can you classify osteomyelitis
acute/chronic
by spread: contiguous (adjacent to where infection started)/ haematogenous (PWIDs, bacteriaemia)
host status (vascualr insufficiency, host susceptibility)
what is the risk of using clindamycin
c diff infection
how do you treat bone infection
surgical debridement- remove pus, dead/ infected bone and drain pus
antimicrobials
what localised symptoms suggest bone infection
if you can probe to the bone or see the bone
calorm rubor, tumour, dolor, function laesa
how do you confirm bone infection
gold standard= bone biopsy
cross secotional imaging
when do you give antibiotics
when you get microbial diagnosis (unless patient septic)
when does a bone infection occur
bone highly resistant to infection, only occurs with necrosis +/- high innoculum
how long does osteomyelitis take to recover
6 weeks of therapy
what cultures can be done
percutaneous aspirate, deep surgical cultures
when do coagulase negative organisms cause infections
usually commensals, cause infection in patients with metal/ plastic inside bodies (e.g. prosthetic)
what can cause osteomyelitis
open fractures
diabetes/ vascular insufficiency
haematogenous osteomyelitis (PWIDs, disseminate infection)
vertebral osteomyelitis (form of HO above)
prosthetic joint infection
specific hosts and pathogens
how is staph aureus treated
flucloxacillin
is staph aureus coagulase positive or negative
positive
what type of infection does an open fracture cause
contiguous
what bug infects open fractures
staph aureus and aerobic gram negative bacteria
what is the early management of an open fracture
aggressive debridement, fixation and soft tissue cover
what is the clue to an infected open fracture
non union and poor wound healing
does diabetes/ venous insufficiency cause contiguous or haematogenous infection
contiguous
what bug usually causes diabetic/ vascular insufficiency
often polymicrobial but predominantly staph aureus
can also be streptococci, enterobacteria, obligate anaerobes and MRSA
if severe think obligate anaerobes
what scans can be done for osteomylelitis
plain radiograph, if no characteristic pathological findings then MRI
how long do you treat skin or skin and soft tissue diabetic/ vascular infection
7 days
how long do you treat bacteraemia for
14 days
how long do you treat osteomyelitis for
6 weeks
what microbials does gentamicin cover
gram negative bacilli not not anaerobes
what antibiotics for gram positive cover
flucloxacillin IV
or vancomycin if penicillin allergic
oral switch
doxycyline
what antibiotics for gram negative cover
gentamicin/ aztreonam IV if severe
oral cotrimoxazole/ doxycyline
what antibiotic for anaerobes
metronidazole
what organisms commonly cause osteomylitis
staph aureus
group A,B,C or G streptococcus
milleri group
anaerobes
name 7 likely red herring colonisers
pseudomonas aeruginosa escherichia coli proteus enterobacter bacillus sp coagulase negative straphylcocci
why do you not switch IV vancomycin to oral in osteomyelitis
as not absorbed
how long is endocarditis treated for
6 weeks injectable therapy
who gets haematogeneous osteomyelitis
prepubertal children, PWIDs, central lines/dialysis/elderly
when does the first day of treatment 914 days IV antibiotics) start for people with haematogeneous osteomyelitis
first day of negative blood culture results
what organisms commonly cause PWID haematogeneous osteomyelitis
staphylococcus, streptococci
what organisms commonly cause dialysis patients HO infections
staph aureus (most common), aerobic gram negatives
what pathogens cause sickle cell osteomyelitis
salmonella
staph aureus
what is gauchers disease and its clinical features
lysosomal storage disorder
may mimic bone crisis (if sterile)
often affects tibia
if infected= staph aureus
what is seen clinically in SAPHO and CRMO
raised inflammatory marker, lytic lesions on x-rays, pus cultures exclude osteomyelitis
who most gets SAPHO and CRMO
SAPHO adults
CRMO kids
(mostly chest wall, plevis or spine)
what organisms cause vertebral osteomyelitis
staph aureus
gram neg aerobic bacilli
streptococcus spp
mycobacterium tuberculosis
is vertebral osteomyelitis contiguous or haematogenous
mostly haematogeneous
what are the clinical presentations of vertebral osteomyelitis
50% have fever
90% have insidious pain and tenderness
90% raise inflam markers
what is the bets way to diagnose vertebral osteomyelitis
biopsy and MRI
how do you treat vertebral osteo
drain large paravetebral/ epidural adbscesses
antimicrobials for 6 weeks
do you get systemic symptoms with skeletal tuberculosis
not usually, confined to spine
what are the risk factors for infection in prosthetic joints
rheumatoid arthritis
diabetes
malnutrition
obesity
what is the mechanisms of prosthetic joint infection
direct inoculation during surgery
manipulation of joint during surgery
seeding of joint at later date
what is the difference between planktonic vs sessile bacteria
planktonic- bacteraemia
sessile- grow into bio film which has protective extracellular matrix making it hard to abscess with antibiotics
what pathogens cause prosthetic joint infection
gram +ve
- staph aureus
- staph epidermis
gram -ve
- escherichia coli
- pseudomonas aeruginosa
fungi
mycobacteria sp
what is the treatment for infection of prosthetic joint infection
ideally remove prosthesis and cement- re-implantation after aggressive antibiotic therapy
how do you treat coagulase negative staph epidermis
vancomycin
what is the oral switch for vancomycin
doxycycline
what are the sources of infection for septic arthritis
penetrating wound
hematogenous spread
adjacent infected soft tissues/ bone
what bacteria cause septic arthitis
staph aureus streptococci coag neg strep (prosthetic joints) neisseria gonorrheae haemophilus influenzae
what infections does PVL producing staph aureus cause
skin infections
peumonia
bacteraemia
septic arthritis
what is septic arthritis
inflammation of the joint space caused by infection
what are the symptoms of septic arthitis
severe pain, red, hot swollen, pus limited movement
what is the treatment for septic arthiritis
presumptive treatment for staph aureus- flucloxacillin
what is bursitis
is inflammation and swelling of a bursa. A bursa is a fluid-filled sac which forms under the skin, usually over the joints, and acts as a cushion between the tendons and bones.
what is pyomyositis
bacterial infection of the skeletal muscles
what are 90% of bacterial pyomyositis caused by
staphylococcal
what else can cause myosisitis
viral, protozoa, parasites, fungal
what causes myonecrosis
‘flesh eating bugs’
what bug causes teanus- describe it
clostridium tetani- gram +ve, strictly anaerobic rods, produces spores (drumstick shaped) found in soil, gardens etc
what does the tetanus neurotoxin do
causes spastic paralysis- binds to inhibitory neurones preventing the release of neurotransmitters- lock jaw, muscle spasm
what is the treatment for tetanus
surgical debridement
antitoxin
supportive measures antibiotics
booster vaccination (survivors are not immune)
how long does debrided bone take to be covered by vascularised soft tissue
6 weeks
