Histology + Microbiology Flashcards
what microorganism is the most common pathogen of osteomyelitis
s. aureus
what tend to inflect implanted devices
biofilm
- slow growing
- bacteria coated in protein and polysacharide
what are the 3 types of implant infections
early post-op - 0-3months
Delayed - 3-24months
Late - >24months
what are the features of early post-op infection
perioperative route
fever, effusion, warmth, drinage
what are the common agents of early post-op infections
s. aureus
strep
enterococci
what are the features of delayed infection
perioperative route
persistent pain, device loosening, fistula
what are the common agents of delayed infections
coagulase-negative
staph
p.acnes
what are the features of late infection
haematogenous spread
acute or subacute
what are the common agents of late infections
s. aureus
e. coli
what is the criteria for SIRS
two or more of:
Temperature >38 or 90 beats/min
Respiratory rate >20 breaths/min or PaCO2 12,000 cells/mm3 or
what is the Tx if no SIRS
no immediate need for antibiotic treatment
wait until culture results
treatment of prosthetic joint infections
Debridement
- Retention of prosthesis (DAIR)
- Removal of prosthesis
Antiobiotcs - IV high dose
what are the bacteria of acute primary infections
S. aureus
Streptococcus spp
what are the bacteria of chronic infections
CoNS
Propionibacteria
Bacteria in abscesses or biofilms are easily treated - true or false
false
are resistant to antibiotics
what is the tayside protocol for PJI
No antibiotic pre-operatively
Minimum three bone/ tissue/ pus samples for culture
Minimum 6 weeks antibiotics before clean surgery
what antibiotic is used from gram positive and what is used if they are allergic
flucloxacillin
- if allergic vancomycin
what antibiotic is used in gram positive but Meticillin resistant organism
tecioplanin
what antibiotic is used from gram negative and what is used if they are allergic
Cotrimoxazole
- if allergic Axoicillin
what is the duration of treatment
hips - 3months
knee - 6months
how is responded assessed in PJI
Continue treatment for 2 weeks after resolution of clinical signs of infection
Repeat MRI or CT scan
what is used as prophylaxis in orthopaedics
Co amoxiclav 1.2 g peri-op & 2 post-op doses
if allergic
Co-trimoxazole
where are the nuclei situated in skeletal muscle cells
at the periphery of the fibre just under the cell membrane
what is the cell membrane called in muscle cells
sarcolemma
what are fascicles
muscle fibres grouped into bundles
what are the different connective tissues of muscle cells
epimysium - connective tissue of muscle as a whole
perimysium - around a single fascicle
endomysium - single muscle fibre
what are the units of contraction
sarcomeres
what do thousands of sarcomeres form
myofibrils
what is a type I skeletal muscle fibre
- relatively slowly contracting fibres that depend on oxidative metabolism.
- have abundant mitochondria
- resistant to fatigue
- produce relatively less force.
- Often called ‘red’ fibres.
what is a type IIA skeletal muscle fibre
- this is intermediate between the other two.
- relatively fast contracting,
- reasonably resistant to fatigue.
- uncommon
what is a type IIB skeletal muscle fibre
- fast contracting fibres that depend on anaerobic metabolism.
- few mitochondria,
- fatigue relatively easily
- produce relatively greater force. - Often called ‘white’ fibres.
how is cartilage, which is avascular, nourished
by diffusion through the extracellular matrix
how is bone nourished
blood vessels that pervade the tissue
what cells are found in cartilage and where do they live
chondrocytes
- lacuna
what are the different types of cartilage
hyaline
elastic
fibrocartilage
what is the morphology of bone
outer shell of dense cortical bone makes up the shaft (diaphysis)
Cancellous or trabecular bone occupies the ends of the bone (the epiphyses)
what are osteocytes
bone cell trapped within the bone matrix
what are osteons
fundamental functional unit of much compact bone
what is the boundary of an osteons called
cement lines
what are osteoprogenitor cells
located on bone surfaces, for example under the periosteum, these cells serve as a pool of reserve osteoblasts
what are osteoblasts
bone forming cells
found on surface of developing bone
what are osteoclasts
responsible for bone reabsorption
found on surface of bone
pathway for bone remodelling
- osteoclasts drill into bone forming a tunnel
- blood vessel grows into tunnel
- osteoblasts follow
- they lay new lamellar bone
- continues until only the space of a Haversian canal remains.
what is the basic multicellular unit
The collection of osteoclasts and osteoblasts that participate in bone remodelling
what do osteoblasts secrete
collagen, glyocsaminoglycans, proteoglycans
collectively termed osteoid
what is woven bone
during development or following a break
rather than having collagen fibres orientated all in one direction, as occurs in lamellar bone, the collagen fibres are laid down in a haphazard fashion
which is stronger - woven or lamellar bone
lamellar
what is brodie’s abscess
seen on x-ray
sign of subacute osteomyelitis
what is osteomyelitis
inflammation of bone or bone marrow
can be acute or chronic
how can acute osteomyelitis be acquired
inoculation - mostly post-trauma/open #
haematogenous - children or immunosuppressed
common bugs of osteomyelitis
staph aureus - fluxocillin
haemophilus - in children
Tx for osteomyelitis
aspirate pus
then give antibiotics
hows does chronic osteomyelitis occur
bone abscess, pus seeks its way out, either goes under periosteum or under joint.
when is goes under periosteum - becomes devascularise area
will try and compensate for dying central bone and will form bone on the outside i.e. involucrum
Ix for chronic osteomyelitis
plain X-rays - 1st line
MRI
what is ivolucrum
layer of new bone growth outside existing bone
how can septic arthritis be contracted
metaphyseal spread
inoculation
direct haematogenous
Tx for cellulitis
Flucoxacillin
Benzylpenicillin
common organisms of cellulitis
staph
strep
what is Necrotising fasciitis
life-threatening subcutaneous soft-tissue infection
symptoms/signs of NF
severe pain cellulitis fever systemic symptoms nausea and vomiting crepitations
Tx of NF
surgical debridement - get rid of dead tissues
target antibiotics or empirical if unknown organism
what is infectious arthroplasty
infection of prosthetic joint
deep infection
Ix for infected arthroplasty
CRP
joint aspiration
Bone scan - Tech 99
X-ray
what prophylaxis is done is surgery to prevent infection
Clean air theatres Local antibiotics Systemic antibiotics Duration of surgery Laminar flow
which bugs commonly cause infected arthroplasty
staphylococcus aureus (SA) staphylococcus epidermidis (SE)
