L10 - Infections on surfaces

Question 1

What are some surfaces where surface infections may take place? (interface between a solid and either a liquid or a gas)

Answer 1

Skin/mucosal surfaces (GI/eye/respiratory/urinary)

Question 2

Give some examples of natural surface infections

Answer 2

cellulitis/pharyngitis/arthritis/conjunctivitis/pneumonia/UTI

Question 3

Give some examples of prosthetic surface infections

Answer 3

Cardiac valves/prosthetic joints/intravascular lines/pacing wires/catheters

Question 4

What are the major gram positive and gram negative causes of surface infections?

Answer 4

Gram +ve - staph aureus/coagulase negative staph

Gram -ve - Entertobacteriaceae

Question 5

What is the major cause of prosthetic valve endocarditis if it occurs after one year?

Answer 5

Coagulase negative staphylococci (e.g. staphylococcus epidermis)

Question 6

What are the major causes of prosthetic valve endocarditis under a year?

Answer 6

Most common is viridans streptococci (e.g. strep mutans) also enterococci and staph aureus

Question 7

What is the most common cause of endocarditis?

Answer 7

A congenital bicuspid valve which should be tricuspid -> exposes fibronectin -> viridans streptococci/S. aureus can bind with fibronectin binding protein

Question 8

What are the common signs and symptoms of someone with endocarditis?

Answer 8

Poor gum state/fever/aortic murmur/Janeway lesions on palms and soles/splinter haemorrhages under nailbeds/nodules on fingers and toes/roth spots in the eye

Question 9

Biofilms can help bacteria persist in their environment and thus make it harder for antibiotics to work. Biofilms colonise medical devices well. Staph aureus is coagulase positive whilst S. epidermis is coagulase negative, both of which are common causes of device associated infections. Staphylococci are gram positive. What mechanism is used to switch bacteria to a biofilm lifestyle when the local population density reaches a certain threshold (they work together to form a biofilm)

Answer 9

quorum sensing

Question 10

What is the major cause of native endocarditis?

Answer 10

Viridans streptococci (s. mutans) - a gram positive cocci

Question 11

How would you aim to treat a prosthetic endocarditis?

Answer 11

Sterilise the tissue/antibacterials/remove prosthetic material potentially

Question 12

An echocardiogram shows a bicuspid aortic valve with a mobile mass attached. What is this?

Answer 12

turbulent flow has eroded the valve exposing thefibronectin below -> bacteria can bind and accumulate -> endocarditis

Question 13

Name two common mouth commensuals

Answer 13

haemophilius/s. mutans/neisseria/s.aureus

Question 14

What gram positive organism with chains of cocci is likely the cause of an endocarditis?

Answer 14

viridans streptococci (strep pneumoniae)

Question 15

Staph from clusters of cocci, strep form chains of cocci T/f?

Answer 15

T

Question 16

What is the major coagulase negative staph?

Answer 16

S. epidermis

Question 17

What are the major biofilm organisms and how does a biofilm help potentiate bacteria survival?

Answer 17

Staphylococci and enterococci

The ECM secreted by the members allows an ideal growth area where nutrients can be exchanged. Also bacteria in biofilms are normally metabolically inactive making it harder for antibiotics to do damage.