Microbiology - Vosler - Sepsis

Question 1

What is SIRS? How is it classified? What are the symptoms? What are the value cut-offs?

Answer 1

Systemic inflammatory response syndrome

2 or more of the following:

hyperthermia or hypothermia - Temperature > 38° C or 90 beats/min

tachypnea or hyperventilation - Respiratory rate > 20 breaths/min or PaCO2 (partial pressure of CO2 in the
blood) 12,000 cells/mm3 or 10% immature (band) forms

Question 2

What differentiates sepsis from severe sepsis from septic shock?

Answer 2

Sepsis - SIRS, which has been induced by an infection

Severe sepsis - defined as having the sepsis criteria plus evidence of organ dysfunction (1 or more):
o Cardiovascular: Systolic BP 1.5 x upper normal.

Septic shock - sepsis-induced hypotension persisting despite adequate fluid resuscitation that requires the use of vassopressors. May include lactic acidosis, oliguria, altered mental status, and acute lung injury

Question 3

Is SIRS associated with infection?

Answer 3

Sometimes (sepsis) but doesn’t have to be: e.g. acute pancreatitis, autoimmune disorder, pancreatitis, vasculitis, thromboembolism,
burns, surgery

Question 4

What is TLR4? What type of bacteria have it?

Answer 4

component of gram negative bacterial cell wall - can also be release as immunologic endotoxin leading to
“cytokine storm” or “gram negative shock”

Question 5

What is bacteremia? What is the difference between primary and secondary bacteremia?

Answer 5

Cultivatable bacteria in the bloodstream - may or may not be symptomatic or lead to spesis

primary=intravascular without identifiable source of infection (e.g. Catheter Associated Bloodstream Infections, Infective endocarditis, Supprative thrombophlebitis,

secondary = intravascular bacteria with extravascular source of infection (e.g. skin infection, a catheter, pneumonia, or a urinary tract
infection)

Question 6

What are the symptoms of sepsis?

Answer 6

rapid breathing
change in mental status, such as reduced alertness or confusion (particularly in the elderly)
fever and shaking/chills or very low body temperature decreased urination
rapid pulse
nausea
vomiting
diarrhea.

Question 7

Transient bacteremia - causes?

Answer 7

minutes to hours

can be during dental procedures; after gastrointestinal biopsy; after percutaneous catheterization of the vascular system, bladder, or common bile duct; and after surgical debridement drainage

Question 8

intermittent bateremia - causes?

Answer 8

bacteremia due to the same microorganism that is detected intermittently in the same patient because of a cycle of clearance and recurrence

caused by abscesses, cholangitis, and focal infections, including pneumonia, osteomyelitis, and spondylodiscitis.

Question 9

Persistent (continuous) bacteremia - causes?

Answer 9

characteristic of infective endocarditis (IE) and
other intravascular infections, such as vascular-graft infection, a mycotic aneurysm, or an
infected thrombus. Persistent bacteremia also occurs during the early stages of systemic
bacterial infections, such as brucellosis and typhoid fever.

Question 10

infective endocarditis is what type bacteremia (primary or secondary)?

What are the two biggest risk factors?

What are the three most common associated bacteria?

Answer 10

primary - no documented source of infection and organism is intravascular

IV drug use and heart valve damage

1) Staphylococcus aureus
2) Streptococci of the viridans group
3) coagulase negative Staphylococci

Question 11

What are the most common bacteria associated with Mycotic (infectious) aneurysm

Answer 11

staphylococcus
streptococcal
salmonella

Question 12

What is Supprative thrombophlebitis

Answer 12

venous thrombosis
associated with inflammation
in the setting of bacteremia.
Peripheral vein suppurative
thrombophlebitis occurs most
frequently in the setting of an
intravenous catheter or
peripherally inserted central
venous catheter (i.e. PICC
lines).

Question 13

What is the most sensitive method for detection of bacteremia?

Answer 13

blood culture

NOTE:normal white blood count does not rule out bacteremia

Question 14

Why are multiple blood cultures, each containing large

volumes of blood, required to detect bacteremia?

Answer 14

patients with bacteremia are likely to have low quantities of bacteria in the blood (less than one
bacterial cell/mL of blood), even in the setting of severe clinical symptoms

Question 15

What is a blood culture “set”?

Answer 15

two culture bottles one for aerobic bateria, one for anaerobic bacteria

Each bottle is inoculated with 10 mL of
blood (20 mL total),

Question 16

What is the protocol for blood sampling prior to beginning antimicrobial therapy?

Answer 16

at least two sets of blood cultures taken from separate
venipuncture sites should be obtained with minutes of eachother. A total of three blood culture sets over 24
hours is usually adequate (more volume – better likelihood for detection)

 One set: 80% of bacteremia’s detected
 Two sets: 90% of bacteremia’s detected
 Three sets: 99% of bacteremia’s detected

Question 17

Does having a fever at the time of blood culture collection increases the likelyhood of detecting bacteremia?

Answer 17

NO. Fever is neither sensitive nor specific for presence of bacteria.

Question 18

What is the most common source of contamination for blood cultures? What are the agents?

What are the consequences of contamination?

Answer 18

normal skin flora

Frequent skin contaminants include coagulase negative staphylococci,
Corynebacteria (a.k.a. Diptheroids), and Propionobacteria.

bacterial skin flora can cause systemic disease. contamination can make it difficult to distinguish
between false positive results and true infection

Question 19

1) Where does primary bacteremia arise from?
a. An endovascular source
b. The lung
c. The liver
d. The gastrointestinal tract

Answer 19

a

Question 20

What type of bacteremia may result when a procedural manipulation of a
particular body site that is colonized by normal flora occurs?
a. Continuous bacteremia
b. Intermittent bacteremia
c. Transient bacteremia

Answer 20

c

Question 21

What is the most common clinical manifestation associated with continuous
bacteremia?
a. Meningitis
b. Pleurisy
c. Encephalitis
d. Endocarditis

Answer 21

d

Question 22

Which statement best describes SIRS (Systemic Inflammatory Response
Syndrome)?
a. An inflammatory response at the source / site causing bacteremia.
b. An inflammatory response that only arises in response to bacteremia.
c. An inflammatory response that occurs only in the intravascular space.
d. An abnormal generalized inflammatory reaction in organs remote from the
initial insult.

Answer 22

d

Question 23

You are interested in the microbiology culture results on one of your patients and
come to the microbiology laboratory to get an update. The microbiology
technologist tells you that your patient’s blood became positive within the past
hour and the Gram stain is showing Gram negative bacilli and the urine is
growing >100,000 CFU/mL of lactose fermenting Gram negative bacilli. The
technologist indicates that based on the colony morphology that the urine isolate
in all likelihood belongs to the Klebsiella or Enterobacter group.
a. Gram negative bacilli are so rare that they aren’t likely to cause disease
b. Gram negative bacilli do not cause urinary tract infections so the
likelihood of the two organisms is unlikely.
c. Based on the information empiric therapy to treat the BSI directed against
Klebsiella or Enterobacter is appropriate.
d. BSI’s usually resolve without antibiotic therapy, so there is no need to
pursue this situation further.

Answer 23

c