9 - Infections on Surfaces

Question 1

What are some surfaces in the body that can have their own flora?

Answer 1

Question 2

What are some viruses that can be found on the skin?

Answer 2

- Papilloma: warts, verrucas

- Herpes Simplex: cold sores

Question 3

What fungi can be found on the skin?

Answer 3

• Yeast
• Dermatophytes

Question 4

What bacteria can be found on the skin?

Answer 4

Question 5

What is coagulate positive staphylococci?

Answer 5

Staph aureus: more likely to cause disease

Question 6

What gram bacteria are mainly found on the skin?

Answer 6

Mainly gram positive but as go below waist can find some gram negative

Question 7

What are some parasites that can be found on the skin?

Answer 7

• Mites - Headlice - Scabies

Question 8

What are some examples of external and internal natural surface infections?

Answer 8

Question 9

What are some prosthetic surfaces susceptible to infections?

Answer 9

Question 10

How can bacteria from surfaces cause infections?

Answer 10

• Invasion
• Migration
• Innoculation
• Haematogenous

Question 11

What bacteria cause prosthetic valve endocarditis?

Answer 11

- >1 year post-operation: Viridans, Streptococci, Enterococcus faecalis, Staph aureus, HÁČEK group, Candida

- <1 year post operation: coagulase negative staphylococci

Question 12

What bacteria causes native valve endocarditis?

Answer 12

Same as prosthetic >1 year post op

Question 13

What bacteria cause prosthetic joint infections?

Answer 13

Question 14

What bacteria causes cardiac pacing wire endocarditis?

Answer 14

Question 15

What is the mechanism of infection at surfaces?

Answer 15

• Adherence to host or prosthetic surface
• Biofilm formation
• Invasion and multiplication
• Host response

Question 16

What are the two responses to a surface infection?

Answer 16

- Pyogenic = pus (neutrophils)

- Graunomatous = fibroblasts, lymphocytes, macrophages, forming nodular inflammatory lesions

Question 17

What is the three steps of management of surface infections?

Answer 17

• Diagnosis
• Treatment
• Prevention

Question 18

How are surface infections diagnosed and what are some challenges with the identification?

Answer 18

Need to identify organism and it’s antimicrobial susceptibilities e.g blood cultures, tissue sonication and culture

Challenges: adherent organisms and low metabolic state/small colony variants

Question 19

How are surface infections treated and what are the challenges with treatment?

Answer 19

• Aim: Reduce bioburden and sterilise tissue
• Treatment: antibacterials, remove prosthetic material, surgery to resect infected material
• Challenges: - Poor antibacterial penetration into biofilm, low metabolic activity of biofilm microorganisms, dangers of surgery

Question 20

What are preventative measures for natural and prosthetic surfaces from surface infections?

Answer 20

Question 21

What is the process of biofilm formation?

Answer 21

• Process where microorganisms irreversibly attach to and grow on a surface and produce extracellular polymers that facilitate attachment and matrix formation

Question 22

How do different species form the same biofilm?

Answer 22

• Quorum sensing
• Autoinducers onto cell surface receptors stimulating gene expression so bacteria have coordianted behaviour to form biofilm