Microbes in the blood

Question 1

what can infection be caused by?

3

Answer 1

• bacteria (bacteraemia) e.g. S. Aureus
• fungi (fungaemia) e.g. candida albicans
• viruses (viraemia) e.g. herpes simplex

Question 2

what are sources of microbes in the blood?

Answer 2

• broken skin / mucous membranes
• focus of infection in the body
• GI tract
• viral reactivation
• direct inoculation

Question 3

what does microbe mortality in the blood depend on?

Answer 3

• the source
• type of microbe
• host immune status

Question 4

what is a 1. transient present 2. intermittent presence 3. continuous presence in the blood?

Answer 4

1. in the blood for several minutes usually caused by manipulation of or surgical procedure involving infected tissues
2. transient presence associated with undrained abcess or infected biofilm
3. severe infection that has overwhelmed host defences e.g. infective endocarditis

Question 5

what are the two most common microbes in the blood stream? where are they usually acquired?

Answer 5

• E.coli bacteraemia (ECB) - healthcare associated
• S.aureus bacteraemia (SAB) - community associated

Question 6

give an example of a fungaemia and its risk factors

Answer 6

• candidaemia due to candida
• risk factors: surgical procedures, prolonged use of broad spectrum antibiotics (amolicillin)

Question 7

give an example of viraemia and what it can cause

Answer 7

• herpes simplex virus
• can cause neonatal sepsis

Question 8

what ways can you detect bacteria in the blood in a lab?

Answer 8

• automated blood culture systems - culture gets inocculated and stored in an automated incubator. incubator reads the indicator at the bottom of the vial that is sensitive to levels of CO2 produced by bacteria if it grows. when it changes colour, the machine flags it and the culture is gram stained, grown and tested
• molecular techniques - tests for 43 targets associated with bloodstream infections in one test

left: automated blood culture systems right: molecular technologies

Question 9

what is infective endocarditis? what are some predisposing causes?

Answer 9

infection of the heart valves or other areas of the endocardium
* rheumatic valvular disease
* congenital heart disease
* mitral valve prolapse with murmur
* degenerative heart disease

Question 10

what types of infective endocarditis is there?

Answer 10

• native valve endocarditis caused by streptococcal or staphylococcal species
• native valve endocarditis in IV drug users differs as younger age group, S.aureus is predominant microbe, mostly affects valves on right side, can give rise to multiple lung abcesses
• prosthetic valve endocarditis (PVE) caused by coagulase negative staphylococci, S.aureus, gram negative bacilli

Question 11

how would you prevent infective endocarditis?

Answer 11

• maintain excellent oral health
• antibiotic prophylaxis to those who are predisposed

Question 12

how does infective endocarditis relate to dentistry?

Answer 12

• endocarditis usually follows bacteraemia
• some dental procedures produce bacteraemia with microorganisms that cause IE
• these organisms are usually sensitive to antibiotics so antibiotic prophylaxis is given before treatment in those who are predisposed