6: Microbiology Part 2

Question 1

The fitting of which materials may lead to infection?

Answer 1

Prosthetic joints

Question 2

What are some risk factors for prosthetic joint infection?

Answer 2

Immunosuppression - rheumatoid arthritis

Diabetes

Malnutrition

Obesity

Question 3

What is a biofilm?

Answer 3

Community of different organisms getting up in there and having fun etc.

Question 4

Orthopaedic theatres are strictly controlled to prevent infection.

What are two mechanisms of prosthetic joint infection at the time of surgery?

Answer 4

Direct inoculation using instruments

Manipulation of joint by surgeons

Seeding of joint by something else

Question 5

If prosthetic joint occurs early (i.e within a month), what is it likely associated with?

Answer 5

Haematoma / sepsis

Question 6

If prosthetic joint infection occurs late (i.e after a month), what is the likely cause?

Answer 6

Contamination during surgery (?why)

Question 7

Biofilms produce a thick ___ which antibiotics struggle to penetrate?

Answer 7

mucus

Question 8

Which organisms tends to cause prosthetic joint infection?

Answer 8

Staph. aureus still

but also Staph. epidermidis due to involvement of prosthesis

Question 9

Which organism, found in the skin of the upper limb, may rarely be responsible for upper limb prosthetic joint infections?

Answer 9

Proprionibacterium spp.

Question 10

Before antibiotics are given, what should be taken from a suspected prosthetic joint infection?

Answer 10

Biopsy (as always)

Question 11

Coagulase negative Staph. tend to be treated as contaminants unless the patient has what?

Answer 11

Prosthesis

Question 12

How are prosthetic joint infections treated?

Answer 12

Remove / replace the joint

Antimicrobial therapy (fluclox for the Coag +ve, vancomycin for Coag -ve)

Question 13

If a patient with prosthetic joint infection is elderly and can’t tolerate surgery, what may be done to treat them?

Answer 13

Cleaning / debridement

prognosis is poor

DAIR

Question 14

Which drug is added to normal antibiotic therapy for prosthetic joint infections?

Why?

Is the drug ever used by itself?

Answer 14

Rifampicin

Helps other antibiotic to penetrate slime produced by biofilm

No, as Staph. aureus will develop resistance to it

Question 15

(rearrange) How is septic arthritis diagnosed?

Answer 15

Aspiration of joint fluid via needle

Question 16

r From which other infections can septic arthritis develop?

Answer 16

Cellulitis

Osteomyelitis

Question 17

r What is the duration of antibiotic therapy for septic arthritis?

Answer 17

4 weeks

Question 18

What is septic arthritis?

Answer 18

Inflammation of joint space due to infection

Question 19

What organisms tend to cause septic arthritis?

Answer 19

Staph. aureus

Streptococci

Coagulase negative Staph. (prosthetic joints)

Neisseria gonorrhoea

Question 20

Which specific toxin, produced by both MSSA and MRSA, makes patients very sick?

Answer 20

PVL

Question 21

What drug is used to treat PVL-producing Staph. aureus?

Answer 21

Flucloxacillin

Question 22

What is sent to the lab for microscopy to diagnose septic arthritis?

Answer 22

Joint fluid

Question 23

Which metabolic diseases mimic septic arthritis?

How would you tell from the fluid?

Answer 23

Crystal arthropathy (gout and pseudogout)

Crystals in the fluid

Question 24

What drug is used to treat septic arthritis?

Answer 24

Flucloxicillin (Vancomycin in MRSA, clindamycin in allergies)

+/- ceftriaxone in patients < 5yrs to cover Haemophilus influenzae

Question 25

What other pathogen can cause arthritis?

Answer 25

**Viruses**

Question 26

People with viral arthritis will present with ___ symptoms.

Answer 26

**viral** look up what these are, presumably fever

Question 27

What is **pyomyositis**?

Answer 27

**Muscle inflammation** caused by **infection**

Question 28

90% of pyomyositis cases are caused by **(*Staphylococci* / *Streptococci*)**.

Answer 28

***Staphylococci***

Question 29

How is pyomyositis treated?

Answer 29

**Surgery to debride as much pus / necrotic tissue as possible**

Question 30

Why are antibiotics an afterthought in severe pyomyositis?

Answer 30

**Antibiotics don't penetrate necrotic tissue and pus**

Question 31

What is the main symptom of pyomyositis?

Answer 31

**Pain** **Redness**

Question 32

What is the difference between **pyomyositis** and **myositis**?

Answer 32

**Pyomyositis** - bacterial, focal **Myositis** - viral, diffuse

Question 33

**Tetanus** is mainly a **(bacterial / toxin) - mediated disease.**

Answer 33

**Toxin-mediated**

Question 34

What is the organism responsible for tetanus?

Answer 34

***Clostridium tetani***

Question 35

more on c. tetani

Question 36

What are the classic symptoms of tetanus?

Answer 36

**Lockjaw** and **muscle spasm** triggered by **loud noises** and **bright lights**

Question 37

How is tetanus treated?

Answer 37

**Surgical debridement** of wound(s) **Antitoxin** **Supportive** - benzodiazepines, anaesthetics, nutrition & fluids

Question 38

Are tetanus survivors immune to the disease? What should the next step be?

Answer 38

**No** **Tetanus vaccination**