Infection Tests Flashcards
what is the difference between system specific and non specific symptoms of infection
system specific - cough, respiratory; neck stiffness - CNS (meningitis); dysuria - urinary
non specific - fever, chills, sweating, feeling confused
when taking a history what are some useful identifying topics
Travel - outside/inside UK Occupation - farmer, fishmonger, vet, air steward Sexual history Hobbies - walkers and tick bites Animal contact
what are findings that are system specific vs non-specific
lung crackles - respiratory
bony tenderness - orthopaedic
skin erythema - skin and soft tissue
non-specific - pyrexia, riggers, sweating, confusion
what is fever evidence of
sign of inflammation or sign of infection
fever = temp above 38 degrees
what happens to temperature throughout the day
high during the day during hours of activity and work and low during sleep and rest
what is rigor
vigorous shaking due to infection followed by period of heat and sweatiness
(not seizure as person is conscious)
what are the only two reasons to carry out a diagnostic test
to improve outcome and to provide epidemiology data
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
Bacterial - raised WCC, normal or low lymphocytes, raised neutrophils
viral - normal WCC, raised lymphocytes, normal neutrophils
during a full blood count are Hb and WCC good markers of infection
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)
what are inflammatory markers and what do they signify
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
what can high levels of procalcitonin and CRP indicate
P - high during severe bacterial infection
CRP - marker of where there is an inflammatory response
what are some technologies that can support diagnosis testing
x rays
CT
PET
what type of infection symptom can be seen on a chest x ray
consolidation
what is blood lactate and ABG’s useful markers of
severe sepsis and respiratory failure
to discover the microbe causing the infection you need to carry out a method of diagnosis - how would you carry out a culture
isolation of the viable pathogen for identification, typing, sensitivity testing
this must be done before antibiotic treatment
what are the uses and limitations of culture as a diagnostic test
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
describe the process of gram staining in culture of microbe
distinguishes between those with bacterial cell wall contains crystal violet and those that don’t when stained and washed with acetone
what is the distinguish between gram positive and gram negative bacteria
positive - purple - retain crystal violet in peptidoglycan
negative - pink - doesn’t retain or colour of counter stain
describe the stages of sensitivity testing during a microbial culture
culture of microbe (fungi or bacteria) in the presence of antimicrobial agent
measure the zone of inhibition
what are limitations and uses of sensitivity testing in culture tests
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
what are the three main methods of microbial diagnosis
culture
direct detection
immunological test
what is direct detection
detection of whole or component of organism via microscopy
establishes presence of organism at particular site - cultivatable or not
give two methods and examples of direct detection
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
what are some limitations and benefits of direct testing
use of appropriate empiric antimicrobial therapy
does not give susceptibility or typing
usually fastest method
what is carried out during immunological testing in diagnostic test and give examples
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
what are the uses and limitations of immunological testing
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
in summary when are infection tests needed to be carried out
only if it will improve the outcome or provide epidemiological data
