Blood Stream Infections

Question 1

what is the mortality rate of severe sepsis?

Answer 1

28-50%

Question 2

why is the incidence of severe sepsis anticipated to increase?

Answer 2

due to the disproportionate growth of elderly americans and the high incidence of sepsis in these patients

Question 3

how do infection and colonization differ?

Answer 3

infection is microorganisms in a normally sterile site while colonization is on an epithelial surface

Question 4

what is the difference between bacteremia and sepsis?

Answer 4

bacteremia only implies that there is bacteria in the blood stream. it may be of no consequence

Question 5

what is the classification for systemic inflammatory response syndrome?

Answer 5

must have two or more of the following:
temperature over 38 or under 36C, tachycardia, tachypnea (over 20 or CO2 less than 32 mmHg), and WBC over 12k or under 4k (may also have >10% bands)

Question 6

what is sepsis?

Answer 6

SIRS associated with proven or clinically suspected infection

Question 7

define hypotension

Answer 7

systolic bp of 40 mmHg from baseline

Question 8

what is severe sepsis?

Answer 8

sepsis associated with dysfunction of organs distant from the site of infection, hypoperfusion or hypotension. Hypotension is reversible by administering fluids

Question 9

what abnormalities are typically included in severe sepsis?

Answer 9

lactic acidosis, oliguria, altered mental status, thrombocytopenia and acute lung injury.

Question 10

define septic shock.

Answer 10

sepsis with hypotension that does not respond to fluid resuscitation and requires vasopressor therapy. There are perfusion abnormalities also seen in severe sepsis

Question 11

what does refractory septic shock describe?

Answer 11

septic shock that lasts for greater than one hour and does not respond to vasopressor admin

Question 12

what causes SIRS?

Answer 12

the body’s response to an inciting event (not the direct effect of the event)- cytokines and dysregulation of inflammation

Question 13

what is the cause of mortality with sepsis?

Answer 13

multiple organ dysfunction syndrome

Question 14

how is septic shock initiated?

Answer 14

LPS of gram negative bacteria is recognized by TLR4. This activates the cell and promotes the production of inflammatory mediators

Question 15

other than the immune system, what else is dysregulated in SIRS and sepsis?

Answer 15

the coagulation system

Question 16

what molecule can be tracked to identify and watch the progression of sepsis?

Answer 16

procalcitonin level is elevated in sepsis. it is stimulated by endotoxin

Question 17

what is transient bacteremia? what causes it, typically?

Answer 17

it lasts for minutes or a few hours, often when manipulating a nonsterile body part or at the onset of acute bacterial infections

Question 18

what is intermittent bacteremia?

Answer 18

bacteremia of the same microorganism that goes through cycles of clearance and recurrence

Question 19

what is the cause of intermittent bacteremia?

Answer 19

associated with undrained, closed space infections (abscesses) or focal infections

Question 20

how is persistent bacteremia categorized?

Answer 20

bacteremia that is detectable over a long period of time

Question 21

what are some infections that cause persistent bacteremia?

Answer 21

infective endocarditis and other intravascular infections. Also occurs during early stages of systemic bacterial infections

Question 22

what is a primary blood stream infection?

Answer 22

a BSI without a documented primary source of infection (the source is intravascular)

Question 23

what organisms are associated with endocarditis?

Answer 23

staph aureus, streptococci and coagulase negative staph. among several others

Question 24

who is at risk for developing infective endocarditis?

Answer 24

IV drug abusers and individuals who have heart valve damage

Question 25

what is a mycotic aneurysm?

Answer 25

damage to endothelial cells by inflammatory reaction to infection. results from an infection by staph, strep or salmonella, of the aortic wall

Question 26

what is suppurative thrombophlebitis? where does it occur most frequently?

Answer 26

venous thrombosis associated with bacteremia and inflammation. occurs most frequently with IV catheter or PICC lines

Question 27

what do catheter associated bloodstream infections colonize?

Answer 27

colonize dwelling catheters that provide more accessible long term venous access for blood testing and treatment.

Question 28

what is a secondary blood stream infection?

Answer 28

a BSI that has a documented portal of bacterial entry or a known associated site of infection

Question 29

what two infections of the elderly may lead to a bsi?

Answer 29

UTIS and bacterial pneumonias

Question 30

how is bacteremia detected?

Answer 30

by culturing blood (most sensitive method) prior to initiation of antimicrobials

Question 31

when are circumstances in which blood cultures are especially important?

Answer 31

sepsis, meningitis, osteomyelitis, arthritis and endocarditis

Question 32

how many blood cultures are necessary to detect bacteremia?

Answer 32

must have at least two sets of blood cultures with large volumes of blood from seperate sites at the same time. a total of 3 over 24 hours is usually adequate

Question 33

what is the typical concentration of bacteria in the blood of a patient with bacteremia?

Answer 33

generally less than 1 bacterial cell/ mL of blood

Question 34

what does a blood culture set consist of?

Answer 34

an aerobic bottle and an anaerobic bottle, each inoculated with 10 mL of blood

Question 35

what percentage of bacteremias are detected with one set of blood cultures? two? three?

Answer 35

1- 80%
2- 90%
3- 99%

Question 36

why is it important to avoid contamination of blood culture samples?

Answer 36

because normal skin flora may cause systemic diseases and it would be impossible to distinguish the two if the sample was contaminated.

Question 37

what is one method that would avoid contamination of blood samples?

Answer 37

by avoiding use of existing IV lines for culture collection

Question 38

how long does a lab hold the blood culture? when are bacteremia cases generally detected? why are they held longer?

Answer 38

held for 5 days but most cases detected in the first 48 hours. Some organisms take a longer time so they are held for a longer times