Microbiology

Question 1

What are the examples of bone bacteria?

Answer 1

Staphyloccus aureus
Myobacterium tuberculosis

Question 2

what are the examples of joint infections?

Answer 2

Staphyloccus aureus
Staphyloccus epidermidis (prosthetic)
Various anaerobic bacteria

Question 3

What are the examples of the muscles infection?

Answer 3

Streptococcus pyogenes
Clostridium perfingens

Question 4

What are the causes of osteomylitis?

Answer 4

Staphyloccus aureus
Myobacterium tuberculosis

Question 5

What are the routes of bone infection?

Answer 5

Hematogenous osteomyelitis
Direct spread
Traumatic osteomyelitis

Question 6

How does hematogenous spread in children?

Answer 6

Metaphysis of long bones

Question 7

How does hematogenous spread in adult?

Answer 7

Vertebral osteomyelitis and discitis

Question 8

What is the pathogenesis of acute osteomyelitis in childrem?

Answer 8

A) During an episode of bactermia, bacteria are deposited in the metaphysis from the metaphyseal vessels (nutrient artery and vein)
B) A focus of infection develops in the metaphysis, which leads to cellulitis in the bone marrow
C) Exudate under pressure is forced laterally through the haversian systems and colkmann canals and into the cortex of the bone, where it can lift or rupture through the periosteum

Question 9

What causes the localization of osteomyelitis?

Answer 9

The high turnover and increased vascularisation during growth

Question 10

What are the characteristics of acute inflammation?

Answer 10

Infiltration by granulocytes
Increased vascular permeability

Question 11

What is the morphology of the staphylococcus species?

Answer 11

Gram-positive cocci arranged in clusters

Question 12

What are further tests needed for staphylococcus species?

Answer 12

Coagulase test

Question 13

What is a biofilm?

Answer 13

A community of microorganisms in a structural matrix usually adherent to an abiotic surface; these microbes within the biofilm structure can evade both antibiotic therapy as well as the natural defenses of the host

Question 14

Why are biofilms associated with prosthetics?

Answer 14

These abiotic artificial surfaces offer a ready interface to which individual bacteria may attach and eventually form a biofilm

Question 15

What is the pathogenesis of biofilms?

Answer 15

Sluggish flow at the metaphysis
Adhesion of S.aureus
Acute inflammation at the site
Avoidance of host defence
Growth in biofilm
Necrosis of tissue
Abscess formation
Further necrosis due to compromised blood supply

Question 16

What is osteomyelitis ?

Answer 16

An inflammation of the medullary and cortical portions of bone, includig periosteum

Question 17

What are the types of osteomyelitis?

Answer 17

Pyogenic osteomyelitis
Tuberculous osteomyelitis
Syphiitic osteomyelitis

Question 18

What is the main causitive agent of acute pyogenic osteomyelitis?

Answer 18

Bacteria
Most commonly staphylococcus aureus
In neonates its aused by E coli and group B streptococci

Question 19

What are the predisposing factors of osteoyelitis?

Answer 19

Debilitating diseases
Bone or joint prostheses
Immunodeficiency

Question 20

What are the routes of infection of osteomyelitis?

Answer 20

Hematogenous dissemination (most common in children in developing countries)
Direct extension from adjacent septic arthritis or soft tissue abscesses
Traumatic implantation following compound fracture, surgical prosthesis, implants

Question 21

What are the risk factors for development of haematogenous osteomyelitis?

Answer 21

Infants and young children
Elderly patients
IV drug abusers
Central venous catheters
Joint disease
Immuno-suppression
Trauma

Question 22

What are the basic pathologic changes in osteomyelitis?

Answer 22

Suppuration, ischemic necrosis, healing by fibrosis and bony repair

Question 23

What are the common causative organisms of haematogenous osteomyelitis in nenates, children and adults?

Answer 23

Neonates: S. aureus, Group B strep, E. coli
Children (haematogenous): S. aureus, s. pyogenes
Adults: S. aureus, streptococi

Question 24

What are the common causative organisms of haematogenous osteomyelitis in sickle cell disease and thalassaemia, immuno-compromise, implant-associated infections?

Answer 24

Sickle cell disease, thalassaemia: salmonella species
Immuno-compromise: s. aureus, mixed infections including E. coli and pseudomonas spp
Implant-associated infections: Coagulase-negative staphyloccocci, mixed infections

Question 25

What are the rare causes of haematogenous ostemomyelitis?

Answer 25

TB, fungi, Brucela sp.

Question 26

What is the effect of bacterial seeding?

Answer 26

Bacteria proliferate and induce an acute inflammatory reaction The excessive neutrophils liberate enzymes and oxygen free radicals --> increased marrow cavity pressure --> compression of vessels --> bone necrosis

Question 27

What is the sequence of events of osteomyelitis?

Answer 27

Infection usyally starts at the metaphyseal marrow of long bones Terminal branches of metaphyseal artery from loops at the level of the growth plate These end up i irregular venous sinusoids That is why the circulation is lsow ad turbulent at this point. This leads to easy bacterial seeding

Question 28

What are the drugs used for treatment of osteomyelitis in case of MSSA and MRSA?

Answer 28

MSSA : Flucloxacillin + fucidic acid or clindamycin MRSA: Vancomycin or teicoplanin + fucidic acid, or clindamycin

Question 29

What are the drugs used to treat osteomyelitis in case of Streptococci, E. coli or pseudomonass spp. infection?

Answer 29

Streptococci: Amoxycilin, ceftriaxone, vanomycin E.coli: Ceftriaxone, ciprofloxacin Pseudomonas spp.: Ceftazdime, ciprofloxacin, piperacillin-tazobactam osteomyelitis- antibiotic

Question 30

What is the duration of osteomyelitis treatment?

Answer 30

Acute: 6 weeks Chronic: 12 weeks Acute in children: 2-4 weeks