Infections on surfaces

Question 1

What is a surface?

Answer 1

Interface between solid and either liquid or gas

Question 2

Viruses present on skin

Answer 2

Papilloma

Herpes simplex

Question 3

Gram positive bacteria on skin

Answer 3

Staph Aureus
Coagulase negative staphylococci
Corynebacterium (accidental contamination usually)

Question 4

Gram negatice bacteria on skin

Answer 4

Enterobacteriaceae

usually below waist as contamination from GI tract

Question 5

Fungi present on skin

Answer 5

Yeasts (single celled eg Candida)

Dermatophytes (multicell eg ringworm)

Question 6

Parasites

Answer 6

usually around hair follicles

Mites

Question 7

Bacteria wiped out by antibiotics causing…

Answer 7

Lactobacilli wiped out of vagina
Candida albicans overgrows
= yeast infection

Clostridum difficile overgrowth in gut
= inflammation and perforation of gut

Question 8

What is microbiota?

Answer 8

Commensals

harmless usually, helpful to make vitamins and prevent colonisation of pathogens

Question 9

When is microbiota harmful?

Answer 9

When transferred to other sites

Question 10

How do people get infections?

Answer 10

Invasion (strep pyrogens = pharyngitis)
Migration (E coli = UTI)
Innoculation (CN staphloccocus = prosthetic joint infection)
Haematogenous (Strep viridans = infective endocarditis)

Question 11

External natural surface infections

Answer 11

Cellulitis
Pharyngitis
Conjunctivitis
Gastroenteritis
UTI 
Pneumonia

Question 12

Internal surface infections

Answer 12

Endocarditis
Vasculitis
Septic arthritis
Osteomyelitis
Empyema (pleural sac infection)

Question 13

Prosthetic surface infections

Answer 13

IV lines
Catheters
Prosthetic joints
Cardiac valves
Pacing wires
Endovascular grafts
Ventriculo-peritoneal shunts

Question 14

What are <1 year after prosthetic valve endocarditis cases caused by?

Answer 14

Coagulase negative staphylococcus

Question 15

What are >1 year prosthetic valve endocarditis caused by?

Answer 15

same as Native valve endocarditis:

Viridans
Streptococci
Enterococci
Staph aureus 
Candida

Question 16

Causes of prosthetic joint infections

Answer 16

Coagulase negative staphlococcus

Staphylococcus aureus

Question 17

Cardiac pacing wire endocarditis causes

Answer 17

Coagulase negative staphylococcus

Staphyloccocus Aureus

Question 18

Pathogenesis of infection at surfaces

Answer 18

Adherence to host cell
Biofilm formed
Invasion/multiply
Host response

Question 19

Types of host response to infections at surface

Answer 19

pyogenic = neutrophils and pus
Granulomatous = fibroblasts, lymphocytes, nodular legions

Question 20

How do pathogens adhere to cells?

Answer 20

Pilli

Question 21

What are biofilms?

Answer 21

Microbial communities encased in extracellular matrix

Question 22

What do biofilms do?

Answer 22

Protect the bacteria by oreventing phagocytosis, antibodies and complement recognition/binding of receptors

Question 23

What is quorum sensing?

Answer 23

Communication between bacteria via chemicals

Question 24

What does quorum sensing control?

Answer 24

sporulation
biofilm formation
virulance factor secretion

Question 25

3 components of quorum sensing

Answer 25

Autoinducers (AI) are signalling molecules
Cytoplasmic/cell surface receptors
Gene expression (cooperate behaviours and produce more AI)

Question 26

Virulance factors exotoxins

Answer 26

Cytolytic
AB toxins
Superantigens
Enzymes 
BIOFILM production

Question 27

Investigations of infections on surface

Answer 27

Tissue/prosthetic valve sonication (shake to remove) and culture
Blood culture

Question 28

Treatment of infections on surface

Answer 28

Antibacterials
Remove prosthetic material
Surgery (resect infected material)

Question 29

Challenges of treatment on infections at surface

Answer 29

Poor antibacterial penetration into biofilm
Low metabolic activity of biofilm microorganisms
Dangers/difficulties of surgery

Question 30

Prevention of infections at natural surface

Answer 30

Maintain surface integrity
Prevent bacterial colonisation
Remove colonising bacteria

Question 31

Prevention of infections on prosthetic surface

Answer 31

Prevent contamination (aseptic)
Inhibit surface colonisation
Remove colonising bacteria

Question 32

Stages of forming biofilm

Answer 32

Surface attachment (reversible/irriversible)
Microcolonies (cell proliferation and aggregation)
Macrocolonies (mushroom and tower like, cell detachment)