Histology + Microbiology

Question 1

what microorganism is the most common pathogen of osteomyelitis

Answer 1

s. aureus

Question 2

what tend to inflect implanted devices

Answer 2

biofilm

• slow growing
• bacteria coated in protein and polysacharide

Question 3

what are the 3 types of implant infections

Answer 3

early post-op - 0-3months
Delayed - 3-24months
Late - >24months

Question 4

what are the features of early post-op infection

Answer 4

perioperative route

fever, effusion, warmth, drinage

Question 5

what are the common agents of early post-op infections

Answer 5

s. aureus
strep
enterococci

Question 6

what are the features of delayed infection

Answer 6

perioperative route

persistent pain, device loosening, fistula

Question 7

what are the common agents of delayed infections

Answer 7

coagulase-negative
staph
p.acnes

Question 8

what are the features of late infection

Answer 8

haematogenous spread

acute or subacute

Question 9

what are the common agents of late infections

Answer 9

s. aureus

e. coli

Question 10

what is the criteria for SIRS

Answer 10

two or more of:
Temperature >38 or 90 beats/min
Respiratory rate >20 breaths/min or PaCO2 12,000 cells/mm3 or

Question 11

what is the Tx if no SIRS

Answer 11

no immediate need for antibiotic treatment

wait until culture results

Question 12

treatment of prosthetic joint infections

Answer 12

Debridement
- Retention of prosthesis (DAIR)
- Removal of prosthesis
Antiobiotcs - IV high dose

Question 13

what are the bacteria of acute primary infections

Answer 13

S. aureus

Streptococcus spp

Question 14

what are the bacteria of chronic infections

Answer 14

CoNS

Propionibacteria

Question 15

Bacteria in abscesses or biofilms are easily treated - true or false

Answer 15

false

are resistant to antibiotics

Question 16

what is the tayside protocol for PJI

Answer 16

No antibiotic pre-operatively
Minimum three bone/ tissue/ pus samples for culture
Minimum 6 weeks antibiotics before clean surgery

Question 17

what antibiotic is used from gram positive and what is used if they are allergic

Answer 17

flucloxacillin

- if allergic vancomycin

Question 18

what antibiotic is used in gram positive but Meticillin resistant organism

Answer 18

tecioplanin

Question 19

what antibiotic is used from gram negative and what is used if they are allergic

Answer 19

Cotrimoxazole

- if allergic Axoicillin

Question 20

what is the duration of treatment

Answer 20

hips - 3months

knee - 6months

Question 21

how is responded assessed in PJI

Answer 21

Continue treatment for 2 weeks after resolution of clinical signs of infection
Repeat MRI or CT scan

Question 22

what is used as prophylaxis in orthopaedics

Answer 22

Co amoxiclav 1.2 g peri-op & 2 post-op doses
if allergic
Co-trimoxazole

Question 23

where are the nuclei situated in skeletal muscle cells

Answer 23

at the periphery of the fibre just under the cell membrane

Question 24

what is the cell membrane called in muscle cells

Answer 24

sarcolemma

Question 25

what are fascicles

Answer 25

muscle fibres grouped into bundles

Question 26

what are the different connective tissues of muscle cells

Answer 26

epimysium - connective tissue of muscle as a whole perimysium - around a single fascicle endomysium - single muscle fibre

Question 27

what are the units of contraction

Answer 27

sarcomeres

Question 28

what do thousands of sarcomeres form

Answer 28

myofibrils

Question 29

what is a type I skeletal muscle fibre

Answer 29

- relatively slowly contracting fibres that depend on oxidative metabolism. - have abundant mitochondria - resistant to fatigue - produce relatively less force. - Often called ‘red’ fibres.

Question 30

what is a type IIA skeletal muscle fibre

Answer 30

- this is intermediate between the other two. - relatively fast contracting, - reasonably resistant to fatigue. - uncommon

Question 31

what is a type IIB skeletal muscle fibre

Answer 31

- fast contracting fibres that depend on anaerobic metabolism. - few mitochondria, - fatigue relatively easily - produce relatively greater force. - Often called ‘white’ fibres.

Question 32

how is cartilage, which is avascular, nourished

Answer 32

by diffusion through the extracellular matrix

Question 33

how is bone nourished

Answer 33

blood vessels that pervade the tissue

Question 34

what cells are found in cartilage and where do they live

Answer 34

chondrocytes | - lacuna

Question 35

what are the different types of cartilage

Answer 35

hyaline elastic fibrocartilage

Question 36

what is the morphology of bone

Answer 36

outer shell of dense cortical bone makes up the shaft (diaphysis) Cancellous or trabecular bone occupies the ends of the bone (the epiphyses)

Question 37

what are osteocytes

Answer 37

bone cell trapped within the bone matrix

Question 38

what are osteons

Answer 38

fundamental functional unit of much compact bone

Question 39

what is the boundary of an osteons called

Answer 39

cement lines

Question 40

what are osteoprogenitor cells

Answer 40

located on bone surfaces, for example under the periosteum, these cells serve as a pool of reserve osteoblasts

Question 41

what are osteoblasts

Answer 41

bone forming cells | found on surface of developing bone

Question 42

what are osteoclasts

Answer 42

responsible for bone reabsorption | found on surface of bone

Question 43

pathway for bone remodelling

Answer 43

- 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.

Question 44

what is the basic multicellular unit

Answer 44

The collection of osteoclasts and osteoblasts that participate in bone remodelling

Question 45

what do osteoblasts secrete

Answer 45

collagen, glyocsaminoglycans, proteoglycans | collectively termed osteoid

Question 46

what is woven bone

Answer 46

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

Question 47

which is stronger - woven or lamellar bone

Answer 47

lamellar

Question 48

what is brodie’s abscess

Answer 48

seen on x-ray | sign of subacute osteomyelitis

Question 49

what is osteomyelitis

Answer 49

inflammation of bone or bone marrow | can be acute or chronic

Question 50

how can acute osteomyelitis be acquired

Answer 50

inoculation - mostly post-trauma/open # haematogenous - children or immunosuppressed

Question 51

common bugs of osteomyelitis

Answer 51

staph aureus - fluxocillin | haemophilus - in children

Question 52

Tx for osteomyelitis

Answer 52

aspirate pus | then give antibiotics

Question 53

hows does chronic osteomyelitis occur

Answer 53

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

Question 54

Ix for chronic osteomyelitis

Answer 54

plain X-rays - 1st line | MRI

Question 55

what is ivolucrum

Answer 55

layer of new bone growth outside existing bone

Question 56

how can septic arthritis be contracted

Answer 56

metaphyseal spread inoculation direct haematogenous

Question 57

Tx for cellulitis

Answer 57

Flucoxacillin | Benzylpenicillin

Question 58

common organisms of cellulitis

Answer 58

staph | strep

Question 59

what is Necrotising fasciitis

Answer 59

life-threatening subcutaneous soft-tissue infection

Question 60

symptoms/signs of NF

Answer 60

``` severe pain cellulitis fever systemic symptoms nausea and vomiting crepitations ```

Question 61

Tx of NF

Answer 61

surgical debridement - get rid of dead tissues | target antibiotics or empirical if unknown organism

Question 62

what is infectious arthroplasty

Answer 62

infection of prosthetic joint | deep infection

Question 63

Ix for infected arthroplasty

Answer 63

CRP joint aspiration Bone scan - Tech 99 X-ray

Question 64

what prophylaxis is done is surgery to prevent infection

Answer 64

``` Clean air theatres Local antibiotics Systemic antibiotics Duration of surgery Laminar flow ```

Question 65

which bugs commonly cause infected arthroplasty

Answer 65

``` staphylococcus aureus (SA) staphylococcus epidermidis (SE) ```