Microbiology

Question 1

What drugs are used to treat staph aureus?

Answer 1

Flucloxacillin

Question 2

What drugs are used to treat staph epidermidis?

Answer 2

Vancomycin

Question 3

What drugs are used to treat step pyogenes?

Answer 3

Doxycycline

Question 4

What drugs are used to treat gram negatives?

Answer 4

Clindamycin

Question 5

What drugs are used to treat anaerobes?

Answer 5

• metronidazole

- cotrimoxazol

Question 6

Describe staph aureus

Answer 6

• common human pathogen
• produces enzymes, including coagulase, an enzyme that clots plasma
• this distinguishes it from all other staph species
• causes wound, skin, bone and joint infections
• antibiotic (ie flucloxacillin and resistant strains
• some strains produce toxins; enterotoxin, SSSST, PVL

Question 7

Describe osteomyelitis

Answer 7

• inflammation of bone and medullary cavity, usually located in one of the long bones
• classification varies; acute vs chronic, contiguous vs haematogenous, host status eg presence of vascular insufficiency, host susceptibility
• may recur after treatment

Question 8

Describe the pathogenesis of osteomyelitis

Answer 8

• terminal branches of metaphyseal arteries form loops at growth plate and enter irregular afferent venous sinusoids
• blood flow is slowed and turbulent, predisposing to bacterial seeding
• in addition, lining cells have little or no phagocytic activity
• area is catch basin for bacteria and abscess may form
• abscess, limited by growth plate, spreads transversely along volkman canals and elevates periosteum; extends subperiosteally and may invade shaft, in infants under 1 some metaphyseal arterial branches pass through growth plate, and infection may invade epiphysis and joint

Question 9

Describe the microbiology of osteomyelitis

Answer 9

• haematogenous; in children - long bones, in adults - vertebrae
• contiguous (polymicrobial); young - injuries, surgery, elderly - pressure sore, vascular insufficiency. DM - soft tissue infections
• newborn and children; staph aureus, group B step
• adults; staph aureus
• elderly; frequency of GNB increased (gram negative bacteria)

Question 10

Describe examination findings for osteomyelitis

Answer 10

• probe to bone / visible bone
• non healing ulce
• sinus

Question 11

Name investigations for osteomyelitis

Answer 11

• bloods (CRP useful to monitor response)
• imaging (xrays, MRI, CT, PET scan, bone scan)
• MRI gibes more information about bone `

Question 12

Name the principles of diagnosis for osteomyelitis

Answer 12

• suspect; patient medical history and epidemiology matter, examination (probe to bone / visible bone, no healing ulcer), investigations
• sample; gold standard is a bone biopsy, wound swabs / blood cultures not always diagnostic, histology
• treat; await microbial diagnosis, unless sepsis, acute presentation with unstable patient)