Infection Tests

Question 1

what is the difference between system specific and non specific symptoms of infection

Answer 1

system specific - cough, respiratory; neck stiffness - CNS (meningitis); dysuria - urinary

non specific - fever, chills, sweating, feeling confused

Question 2

when taking a history what are some useful identifying topics

Answer 2

Travel - outside/inside UK 
Occupation - farmer, fishmonger, vet, air steward 
Sexual history 
Hobbies - walkers and tick bites
Animal contact

Question 3

what are findings that are system specific vs non-specific

Answer 3

lung crackles - respiratory
bony tenderness - orthopaedic
skin erythema - skin and soft tissue

non-specific - pyrexia, riggers, sweating, confusion

Question 4

what is fever evidence of

Answer 4

sign of inflammation or sign of infection

fever = temp above 38 degrees

Question 5

what happens to temperature throughout the day

Answer 5

high during the day during hours of activity and work and low during sleep and rest

Question 6

what is rigor

Answer 6

vigorous shaking due to infection followed by period of heat and sweatiness
(not seizure as person is conscious)

Question 7

what are the only two reasons to carry out a diagnostic test

Answer 7

to improve outcome and to provide epidemiology data

Question 8

a full blood count is used to see if the patient has got an infection
what is the difference between viral and bacterial infection for WCC, lymphocytes and neutrophils

Answer 8

Bacterial - raised WCC, normal or low lymphocytes, raised neutrophils

viral - normal WCC, raised lymphocytes, normal neutrophils

Question 9

during a full blood count are Hb and WCC good markers of infection

Answer 9

Hb - not for infection but can be marker for anaemia of chronic disease

WCC - can be raised in infection but also many other conditions so not specific (can be lowered in severe sepsis)

Question 10

what are inflammatory markers and what do they signify

Answer 10

elements of the innate immune system
CRP - C reactive protein normal level - less than 5 mg/L
procalcitonin - normal less than 0.5 micro g / L

Question 11

what can high levels of procalcitonin and CRP indicate

Answer 11

P - high during severe bacterial infection

CRP - marker of where there is an inflammatory response

Question 12

what are some technologies that can support diagnosis testing

Answer 12

x rays
CT
PET

Question 13

what type of infection symptom can be seen on a chest x ray

Answer 13

consolidation

Question 14

what is blood lactate and ABG’s useful markers of

Answer 14

severe sepsis and respiratory failure

Question 15

to discover the microbe causing the infection you need to carry out a method of diagnosis - how would you carry out a culture

Answer 15

isolation of the viable pathogen for identification, typing, sensitivity testing
this must be done before antibiotic treatment

Question 16

what are the uses and limitations of culture as a diagnostic test

Answer 16

shows presence of microbe in that particular area eg blood culture is only from blood stream - cultivatable organisms only

use of empiric and targeted antimicrobial therapy

provides epidemiology and typing info

slower than direct detection

Question 17

describe the process of gram staining in culture of microbe

Answer 17

distinguishes between those with bacterial cell wall contains crystal violet and those that don’t when stained and washed with acetone

Question 18

what is the distinguish between gram positive and gram negative bacteria

Answer 18

positive - purple - retain crystal violet in peptidoglycan

negative - pink - doesn’t retain or colour of counter stain

Question 19

describe the stages of sensitivity testing during a microbial culture

Answer 19

culture of microbe (fungi or bacteria) in the presence of antimicrobial agent
measure the zone of inhibition

Question 20

what are limitations and uses of sensitivity testing in culture tests

Answer 20

initial treatment is empirical - based on best guess of infective microbe

subsequent treatment is targeted

correlation between antimicrobial sensitivity and clinical response is not absolute

Question 21

what are the three main methods of microbial diagnosis

Answer 21

culture
direct detection
immunological test

Question 22

what is direct detection

Answer 22

detection of whole or component of organism via microscopy

establishes presence of organism at particular site - cultivatable or not

Question 23

give two methods and examples of direct detection

Answer 23

antigen detection - legionella antigen detection
rapid results but need training and quality

nucleic acid testing - virus such as influenza (PCR testing) , streptococcus pneumonia (PCR), fungi - candida/aspergilis by PCR or nucleic acid test b

Question 24

what are some limitations and benefits of direct testing

Answer 24

use of appropriate empiric antimicrobial therapy

does not give susceptibility or typing

usually fastest method

Question 25

what is carried out during immunological testing in diagnostic test and give examples

Answer 25

detection fo immune response to pathogen ie antibody detection

IgM detection - seroconversion = changes from a - to + result from one test to the other

fourfold rise in tire - rise in concentration of antibody from one to the next

cytokines such as IFN-y high in TB

Question 26

what are the uses and limitations of immunological testing

Answer 26

confirms exposure to specific microorganism whether cultivable or not

restrictive to patients with detachable antibody response

retrospective ie often when identified patient is already ill or better

Question 27

in summary when are infection tests needed to be carried out

Answer 27

only if it will improve the outcome or provide epidemiological data