Microbiology Flashcards
which antibiotic has a high CDIF risk
clindomycin
what is adult osteomyelitis
inflammation of bone and medially cavity
usually in long bones
how can osteomyelitis be classified
acute vs chronic (by time) -most common
contiguous vs haematogeneous (by spread)
host status eg. presence of vascular insufficiency
how is osteomyelitis confirmed
direct biopsy
diagnostic factor for osteomyelitis
if you can see tendon
how is osteomyelitis treated
await microbiological diagnosis
treat with the appropriate antibiotics
EXAM Q
no empiric antibiotics
investigations for osteomyelitis
good standard- bone biopsy
MRI
5 features of infection seen in osteomyelitis
calor rubor tumor dolor functino laesa
why does bone infection occur
due to necrosis
or a bacteria with high inoculum
what are the aims of surgery for osteomyelitis
remove infected tissue
drain and debride
how long does debrided bone take to be covered by vascularised soft tissue
6 weeks
most common sites of bone infection
prosthetic joint infection diabetic foot infection (vascular insufficiency) post-traumatic infection (open fracture) vertebral osteomyelitis haemotogeneous osteomyelitis (IVDU)
when do coagulase negative staph cause problems
mainly in people who have prosthetics, however usually just a commensal
coagulase positive staph are much much more virulent
is fever a reason to start empiric antibiotics for osteomyelitis before getting results back
no
is sepsis a reason to start empiric antibiotics in osteomyelitis
yes
what does coagulase do
clots plasma
antibiotic for staph aures
flucloxacillin
coag negative staph is golden true/false
false
coag positive staph aures is gold
coag negative staph is white
what bacterial infection open fractures
staph areas
gram negative bacteria
how to treat open fractures osteomyelitis
aggressive debridement
fixation
soft tissue cover
clinical signs of open fracture osteomyelitis
non-union and poor wound healing
when are diabetic ulcers likely to get infected
when ulcer is >2cm for >2months
what microbes infect diabetic ulcers
polymicrobial however often staph aures
treat staph aures first and if no improvement treat gram negative too
treatment for infected diabetic ulcers
probe to bone (diagnostic)
debridement and antimicrobials
what is the best diagnostic test for osteomyelitis
bone biopsy
best imaging for osteomyelitis
MRI
rely on MRI if patient cant go to theatre
how do u treat a mild diabetic ulcer infection
flucloxacillin
how to treat moderate diabetic foot ulcer infection
flucloxacillin (oral) + metronidazole (oral)
how to treat severe diabetic foot ulcer infection
flucloxacillin (IV)
Gentomycin
metronidazole
7 days (14 if blood infection, 6 weeks if osteomyelitis)
does fluclox cover MRSA
no but covered MSSA
what does metronidazole cover
anaerobes
what does gentamicin cover
gram negatives
what antibiotics cover gram positives
fluclox/vancomycin if allergic
oral switch is doxycycline (to help get patient out of hospital quicker)
what antibiotics cover gram -ve
gentamicin/aztreonam IV if severe
oral cotrimoxazole/doxycyxline
can you switch IV vancomycin to oral
no because it isn’t absorbed
used as topical treatment for bowel in cdiff
when is pseudomonas likely to be an infection
if its in bone or blood but not on skin
significant organisms to not be ignored
staph aures
group A, B C or G strep
miller group
anaerobes
what is haemotogenous osteomyelitis
bone infection from bacteria in blood
who tends to get haemitogenous osteomyelitis
IVDUs (PWID)
prepubertal children
people with central lines/dialysis
elderly
sources of infection in haemitogeneous osteomyelitis
tonsils throat teeth skin infection GI UTI mostly staph aures
if person has staph aures in blood what do you do
remove all lines
treat with IV minimum 14 days
look for endocarditis
if endocarditis 4-6 weeks
organisms found in blood of PWID
staph aures
strep viridians
unusual:
eikenella corrodes (needle lickers)
candida (heroin, or lemon juice)
causes of haemotogenous osteomyelitis in PWID
continuous
haemotogenous
direct inoculation
what organisms do people with sickle cell myelitis have
staph aures
salmonella
SAPHO (adults) and CRMO (kids)
chronic lytic regions on X-ray that look like osteomyelitis
how does vertebral osteomyelitis occur
mostly haematogenous
may be associated with epidural access or psoas access
may be associated with PWID, IV site infections, GU infections, SSTI, post op
everyone with vertebral osteomyelitis have fever true/false
false 5%
investigations for vertebral osteomyelitis
MRI, Ga-67 scan vertebral biopsy (before antibiotics)
treatment for vertebral osteomyelitis
drainage of large abscess
antimicrobials for 6 weeks minimum
expect >50% decrease in ESR
duration extended in complicated cases
why would you repeat MRI in vertebral osteomyelitis
unexplained increase in inflammatory markers
increased pain
new anatomical signs
those with vertebral tb also have pulmonary tb true/false
false
<50%
risk factors for infection of prosthetic joints
rheumatoid arthritis
diabetes
malnutrition
obesity
what are the mechanisms of infection in prosthetic joints
direct inoculation at time of surgery
manipulation of joint at time of surgery
seeding of joint at later time
what is a biofilm
a layer of bacteria which is really close to the prosthetic and grows really slowly, difficult to treat with antibiotics
where do you get biofilms
cystic fibrosis
anywhere you have metals or plastic
pathogens which infect prosthetic joints
staph aures staph epidermis propionibacterium acnes (upper limb prosthesis) rarely strep e.coli, pseudomonas fungi mycobacteria
how to diagnose prosthetic joint osteomyelitis
culture preoperative tissues
blood culture
CRP
radiology
treatment for prosthetic joint osteomyelitis
removal of prosthesis and cement
antimicrobial therapy for at least 6 weeks
re-implantation of joint after aggressive antibiotic therapy
how does septic arthritis occur
direct invasion through wound
ematogenous spread
spread from focus osteomyelitis in adjacent bone
spread from infection focus in adjacent soft tissues
symptoms of PVL producing staph aures
skin infection necrotising fascitis invasive infections bacteraemia septic arthritis
what is septic arthritis
inflammation of the joint space caused by infection
can be blood born organisms
can be extension of local infection
can be introduced directly following injection or trauma
bacterial causes of septic arthritis
staph aures streotococci coag neg staph - prosthetics neisseria gonorrhoea -sexually active haemophilia influenzae- less common now bc of vaccination
how to diagnose septic arthritis
clinical picture
joint fluid microscopy
blood culture
exclude crystals
treatment for septic arthritis
high dose flucloxacillin
if <5 years old add ceftriaxone
adjust when organism confirmed
what is pyomyositis
bacterial infection of the skeletal muscle
who gets pyomyosititis
immunosuppressed
What else can cause psyomyositis
viral - diffuse
fungal -v rare
parasites (Taenia- tape worm, trichenella (rare meat)
what is myonecrosis
flesh eating bugs causing necrosis of muscle tissue
what causes tetanus
clostridium tetani
gram +ve strictly anaerobic rods
spores
spores found in soil, gardens ect
what happens in tetanus
neurotoxin causes spastic paralysis
clinical signs of tetanus
extreme muscle spasm
spastic paralysis
what is the incubation period for tetanus
4 days - several weeks
tetanus treatment
surgical debridement antitoxin supportive measures antibiotics... penicillin/metonidazole booster vaccination
how to prevent tetanus
vaccination at 2,3,4 months
check green book
how is tetanus diagnosed
clinically
culture v difficult
