Micro Lec 9

Question 1

Outline the features of host response to bloodstream infection

Answer 1

Involves both the innate and adaptive immune response
Phagocytic cells
- neutrophils, macrophages, eosinophils
Antibodies and complement
CRP
Iron-binding proteins

Question 2

What is C reactive protein (CRP)

Answer 2

an acute phase protein which is made and produced by the liver which responds to infection/inflammation and its levels get greatly elevated during acute inflammation, more significantly than other acute phase proteins. Levels of CRP can rise 1000 fold during sepsis. Because of this great increase during sepsis, it is commonly assessed in the laboratory as a clinical biomarker of sepsis. However, because its levels are also inflated in other inflammatory conditions, it must be used in combination with other markers.

Question 3

What is bacteraemia

Answer 3

the presence of viable bacteria circulating the bloodstream

Question 4

Outline the features of bacteraemia

Answer 4

Can be detected by isolating bacteria from blood cultures
Still detectable after 12 – 48 hours
Dental treatment, invasive medical procedures, IVDA and trauma
Brushing your teeth can result in transient bacteraemia!

Usually transient, self-limiting and inconsequential

Presents asymptomatically
- Can trigger the immune response to which can result in sepsis

Question 5

What are septicaemia and sepsis

Answer 5

Life threatening condition where the bodies response to infection can result in organ dysfunction and tissue damage

Over reactive systemic immune response that can develop into septic shock, where blood pressure drops dangerously low

Question 6

What are the symptoms of sepsis

Answer 6

Extremes of temperature; increased breathing/heart rate; confusion; discoloured skin

Question 7

slide

Answer 7

6

Question 8

What are the sepsis 6

Answer 8

1- High flow 15litres/min via non-rebreather mask. Target saturation >94%

2- At least one set of blood cultures. Consider other samples – swab sputum urine (source control)

3- Broad-spectrum antibiotics – cover gram +ve/gram –ve and anaerobes

4- Hartmann’s solution

5- Check serum lactate levels

6- May require urinary catheter

Question 9

SLIDE

Answer 9

8,9, 10, 11

Question 10

Why does microbiological analysis take longer than other laboratory results

Answer 10

due to the need for microbial growth

Question 11

What can be found in blood when diagnosis of bloodstream infection (BSI)

Answer 11

very small quantities of organisms

1-10 CFU/mL of circulating organisms during infection from CFU plating
103- 104GC/mL estimated using qPCR

Question 12

What are blood cultures intended to do

Answer 12

Confirm presence of microorganisms within the bloodstream
Identifying the microbial etiology of the infection
Determine the source of infection (i.e infective endocarditis)
Provide an organism for susceptibility testing – allows for optimisation of antimicrobial therapy

Question 13

What are important considerations when handling blood cultures

Answer 13

Taken ASAP; prior to antimicrobial administration
Process within 4 hours
Taken from veins and not arteries
Bottle culture conditions
Avoid contamination

Question 14

What can contaminated blood culture samples result in

Answer 14

increased hospital stays, increased antimicrobial use/charges, additional costings.

Question 15

What do bloods need to be taken before

Answer 15

before antimicrobial administered

Question 16

What does BacT/Alert do

Answer 16

Measures carbon dioxide levels via indicator strip at the bottom of bottle every 10 mins

Question 17

Outline the features of BacT/Alert

Answer 17

Microorganisms multiply in the media
Generating CO2

As CO2 increases, the sensor in the bottle turns from grey to yellow

Measuring the reflected light, the system monitors and detects colour changes in the sensor

Function on the system software which immediately notifies the laboratory when a positive sample is detected

Question 18

If a positive culture bottle, what should be done next

Answer 18

Vent bottle and perform:

Gram stain
Initial agar culture

Based on findings:
Inform clinician to dictate initial antimicrobial therapy
Determine the initial nature of patients infection
Can determine if infection is polymicrobial

Question 19

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Answer 19

18

Question 20

What is infective endocarditis (IE)

Answer 20

Microbial infection of the endothelial lining of the heart

Question 21

Where does IE usually manifest

Answer 21

vegetations on heart valves

Question 22

What side of the ehart is IE most commonly associated with

Answer 22

left

Question 23

What side of the heart is most commonly associated with IVDA

Answer 23

right

Question 24

What is IE most commonly caused by

Answer 24

by Staphylococci and Streptococci

Question 25

What are the first organ that go during septic shock

Answer 25

kidneys

Question 26

What are possible abnormal or damaged heart valves

Answer 26

Congenital defects Degenerative disease Rheumatic heart disease

Question 27

What are the risk factors for IE

Answer 27

Abnormal or damaged heart valves intravenous drug abusers (IVDA) Prosthetic valves and cardiac disease HIV infection Nosocomial infection

Question 28

What are the possible portals of entry for IE

Answer 28

Oral cavity – dental infections and periodontal disease Mitis group streptococci HACEK group Skin breach IVDA Skin and soft tissue infections Hematologic spread Bacteraemia Gastrointestinal - Polyps and ulcers

Question 29

What are some causative organisms part of the HACEK group

Answer 29

Haemophillus species Aggregatibacter actinomycetemcomitans Cardiobacterium hominis Eikenella corrodens Kingella kingae

Question 30

What is differential disease associated with

Answer 30

S. aureus and Viridins group streptococci

Question 31

How does VGS act as a causative organism

Answer 31

dental manipulations can release into bloodstream Produce extracellular dextran which adheres organisms to heart valve Results in sub-acute endocarditis

Question 32

How does S. aureus act as a causative organism

Answer 32

Multiple portals of entry Common with IVDA Results in acute endocarditis

Question 33

What happens during cardiac vegetations

Answer 33

Damage to the endothelial layer of the valve surface Deposition of platelets and fibrin Bacterial attachment Vegetation increases in size Continual bacteraemia Possible embolisation

Question 34

What is the Duke Criteria

Answer 34

Diagnosis is made on the fulfilment of a number of major and minor criteria

Question 35

What do you need to make diagnosis with Duke criteria

Answer 35

Need 2 major; 1 major and 3 minor or 5 minor to make diagnosis

Question 36

What are the categories of Duke criteria

Answer 36

Definite Possible Rejected

Question 37

What are the features of a major in duke criteria

Answer 37

Blood culture positive for infective endocarditis Microorganisms typically associated with IE identified from two separate blood cultures Staphylococcus aureus Viridans group streptococci HACEK group At least two positive cultures from blood drawn >12 hour apart Single positive culture for Coxiella burnettii or serological IgG antibody titre

Question 38

What does a major Duke criteria show

Answer 38

Evidence of echocardial involvement Intracardiac mass on valve or supporting structures Or mass on implanted material Abscess New vascular regurgitation

Question 39

Outline the features of minor Duke criteria

Answer 39

Predisposition Heart condition/IVDA Fever; >38°C Vascular phenomena - emboli, infarcts, aneurysms, intracranial haemorrhage, conjunctival haemorrhages, Janeway lesions Immunological - glomerulonephritis, Osler’s nodes, Roth spots, positive rheumatoid factor Microbiology/Echo not meeting major criteria

Question 40

What are the possible treatments for IE

Answer 40

Treatment ranges from 2-6 weeks depending on organism/severity of IE Beta-lactam susceptibility is key: If susceptible: flucloxacillin/ampicillin + aminoglycoside If resistant: vancomycin + aminoglycoside MRSA: vancomycin + aminoglycoside Cases can also need surgical intervention: Repair the damage of the heart valve Replacement of valve with a prosthetic Draining of abscesses which may have developed in the muscle

Question 41

What are treatments for IE based on

Answer 41

culture susceptibilities