Infection Tests

Question 1

System specific infection symptoms

Answer 1

Cough (respiratory)
Neck stiffness (CNS)
Bony pain (orthopaedic)
Skin pain/redness (skin and soft tissue)
Dysuria (urinary)

Question 2

Non-specific infection symptoms

Answer 2

Fever/ “burning up”
Shaking episodes/chills
Sweating/night sweats
Feeling muddled/confused

Question 3

Social history regarding infection

Answer 3

To help identify potential pathogens
Travel (inside or outside UK with details if outside UK)
Occupation (farmer, fishmonger, vet, air steward etc.)
Animal contact (which animals)
Hobbies/pasttimes
Sexual history

Question 4

System specific signs of infection

Answer 4

Lung crackles (respiratory)
Meningism (clinical syndrome of headache, neck stiffness, and photophobia, often with nausea and vomiting) (CNS)
Bony tenderness (orthopaedic)
Skin erythema (SST)
Loin tenderness (urinary)

Question 5

Non-specific signs of infection

Answer 5

Pyrexia
Witnessed rigor/chills
Sweating
Confusion

Question 6

FBC findings in bacterial infection

Answer 6

Possible anaemia if chronic
Raised WCC (can be low in severe sepsis)
Normal or low lymphocytes
Raised neutrophils

Question 7

FBC findings in viral infection

Answer 7

Possible anaemia if chronic
Normal WCC (can be low in severe sepsis)
Raised lymphocytes
Normal neutrophils

Question 8

Normal C-reactive protein

Answer 8

<5mg/l

Raised in infection

Question 9

Normal procalcitonin

Answer 9

<0.5μg/l

Question 10

Reasons to use testing

Answer 10

To improve outcome
To provide epidemiological data
Otherwise testing should not be used

Question 11

What does serology test for?

Answer 11

An antibody response

Question 12

Direct detection

Answer 12

Detection of a whole organism, antigen or genomic material

Question 13

Principles of culturing

Answer 13

Isolation of viable pathogen enables:
Identification (immediate or by further testing)
Typing (to establish organism relatedness)
Sensitivity testing (to direct antimicrobial therapy)
Not applicable to non cultivable microorganisms
Needs to be done before antibiotics are started

Question 14

Gram-negative stain colour

Answer 14

Pink (or colour of counter-stain)

Question 15

Gram-positive stain colour

Answer 15

Purple

Question 16

Principle of sensitivity testing

Answer 16

Requires viable microorganisms (usually bacteria or fungi)
Culture of microorganism in presence of antimicrobial agent
Work out if the concentration of antimicrobial that will be available in the body is high enough to kill the microorganism
Solid or liquid media

Question 17

Uses of sensitivity testing

Answer 17

To inform decisions on targeted antimicrobial therapy (initial treatment is usually empiric, with subsequent being targeted)

Question 18

Limitations of sensitivity testing

Answer 18

Correlation between antimicrobial sensitivity and clinical response is not absolute

Question 19

Uses of culture

Answer 19

Establishes the presence of a microorganism at a specific site
Allows the use of empiric and targeted antimicrobial therapy
Provides epidemiological and typing information

Question 20

Limitations of culture

Answer 20

Is usually slower than direct detection (days)

Question 21

Principles of direct detection

Answer 21

Detection of whole organism via microscopy or detection of component of organism, via antigen or nucleic acid

Question 22

Uses of direct detection

Answer 22

Establishes the presence of a microorganism at a particular site (both cultivable and non-cultivable)
Allows the use of appropriate empiric antimicrobial therapy
Is usually the fastest diagnostic method

Question 23

Limitations of direct detection

Answer 23

Does not give any information on antimicrobial susceptibility or typing

Question 24

Principle of immunological tests

Answer 24

Detection of immune response to infection
Antibody detection:
IgM
Seroconversion (change from negative to positive result in subsequent tests)
Fourfold rise in titre

Question 25

Uses of antibody testing

Answer 25

Confirms exposure to a specific microorganism (cultivable and non-cultivable microorganisms)

Question 26

Limitations of antibody testing

Answer 26

Is restricted to patients with a detectable antibody response
Is retrospective (often too late to inform antimicrobial therapy decisions)