INFECTIOUS AGENTS - Bloodstream Infections and Sepsis

Question 1

Define bacteraemia

Answer 1

The presence of bacteria in the blood (often transient and asymptomatic)

Question 2

Define septicaemia

Answer 2

The presence of bacteria in the blood with clinical symptoms

Question 3

Describe the three different types of bacteraemia

Answer 3

Transient - temporary bacteria in the bloodstream
Intermittent - random release of bacteria into the bloodstream
Continuous -constant presence of bacteria in the bloodstream

Question 4

What often causes transient bacteraemia?

Answer 4

Dental surgery

Question 5

What does SIRS stand for?

Answer 5

Systemic inflammatory response syndrome

Question 6

(T/F) SIRS parameters only apply to infectious aetiology

Answer 6

FALSE. SIRS can apply to almost any aetiology

Question 7

In veterinary practice, what is used to diagnose septic shock?

Answer 7

Presence of an infection and the presence of two or more SIRS parameters

Question 8

What are the four SIRS parameters?

Answer 8

• Heart rate
• Respiratory rate
• Temperature
• Leukocyte count

Question 9

Define ‘uncomplicated infections’

Answer 9

Localised infections with no systemic features

Question 10

Define sepsis

Answer 10

Systemic inflammatory response (SIRS + infection)

Question 11

Define severe sepsis

Answer 11

Sepsis induced organ dysfunction or organ hypo-perfusion (not enough O2 reaching the organs)

Question 12

Define septic shock

Answer 12

Sepsis induced hypotension (low Bp) not responding to fluid resuscitation

Question 13

What can cause symptoms of septic shock but a negative blood culture result?

Answer 13

A localised infection that has resulted in the release of bacterial components/secretions into the bloodstream

Question 14

What are some bacterial components that can cause sepsis if released into the bloodstream?

Answer 14

• Lipid A (LPS)
• Peptidoglycan
• Lipoteichoic acid

Question 15

Describe briefly the sepsis cascade and the physiological consequences of sepsis

Answer 15

1. UNCOMPLICATED INFECTION: Localised infection
2. SEPSIS: Systemic inflammatory response in response to the infection
3. Secretion of inflammatory mediators and activation of the coagulation cascade causing endothelial dysfunction and microvascular thrombosis
4. SEVERE SEPSIS: Imbalance between oxygen consumption and delivery causing hypo-perfusion, ischaemia and acute organ dysfunction
5. SEPTIC SHOCK: Refractory hypotension and and multi-system organ failure which won’t respond to fluid resuscitation

Question 16

What causes toxic shock syndrome?

Answer 16

The secretion of specific bacterial toxins known as superantigens. Superantigens cross link between antigen presenting cells and T- cells to induce T-cell proliferation and massive cytokine production causing a systemic inflammatory response

Question 17

How should sepsis be treated?

Answer 17

Maintenance of normal physiological parameters/homeostasis

• Fluid therapy: maintain venous and arterial pressures to restore cardiovascular stability and improve O2 delivery to the organs
• Respiratory support: the use of ventilators/O2 to improve O2 delivery to the organs
• Renal support: Dialysis if renal failure begins to occur
• Antimicrobial therapy within ONE HOUR of sepsis diagnosis

Question 18

Define primary viraemia

Answer 18

The initial spread of a virus in the bloodstream to the virus’ target organ. Primary viraemia is clinically silent

Question 19

Define secondary viraemia

Answer 19

When there is viral infection of additional tissues via the bloodstream, replication of the virus within those tissues and re-entry of the virus into the bloodstream causing sepsis