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Infectious Colloquium > sampling and submission of lab samples > Flashcards

sampling and submission of lab samples Flashcards

1
Q

what are laboratory diagnostics?

A

a set of physical, chemical, toxicological, microscopic, pathanatomical, bacteriological, virological, mycological, hematological, biochemical, immunological, parasitological and molecular tests

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2
Q

samples can come from

A

live animals - sick or healthy
dead animals
from animal environment - living or non living

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3
Q

5 main laboratory groups

A
  1. microbiological - bacteriological, virological and mycological
  2. serological
  3. pathohistological
  4. blood assay - whole blood and biochemistry
  5. chemical-toxicological
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4
Q

microbiological tests include

A

bacteriological, virological, mycological

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5
Q

general principles on sample collection

A

-take samples ASAP (especially for viral or enteric bacteria)
- collect samples form in contact animals too
- collect specimens as aseptically as possible

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6
Q

how much blood for serology

A

at least 5ml

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7
Q

how much tissue sample

A

approximately 2cm3

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8
Q

what to put on the form for the lab

A
  1. name and address, protocol number and date
  2. name, surname, address and number of owner
  3. data on animal - species, sex, breed, age, signs, name, microchip number etc
  4. list of materials sent and date of sampling
  5. type fo lab assay
  6. clinical diagnosis - disease suspicion, possible pathological and morphological charges
  7. epizootiological data and data on treatment - drugs, duration
  8. name, surname and signature of person who sent material
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9
Q

best lab test for bacterial infection

A

direct microscopic exam of exudate
can get info on number, morphological characteristics and gram staining properties of microorganisms and host cellular response

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10
Q

specimen collection for bacterial infection

A
  • collect from actual site of infection with minimum contamination
  • transport to lab without contamination or change in relative number of bacteria
  • if biopsy or FNA, skin decontamination does before
  • collect aș early as possible in disease process
  • get specimen before atb given if possible
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11
Q

swab should never be submitted from

A

currettings, biopsy material, fluid (esp urine) or surgically removed tissue

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12
Q

how to transport swabs

A

in a transport medium or in humidified transporting chamber
because bacteria susceptible to desiccation during transport

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13
Q

transporting anaerobes

A

need special transport devices to prevent exposure to lethal concentration of oxygen

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14
Q

when should blood be taken

A

first blood culture specimen taken at onset of fever
or take 3-4 cultures within 1-3h - if more than one culture yields the same organism it is probably significant

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15
Q

when would you consider contamination of mid stream voided urine

A

when less than 10 5 cfg/ml are isolated

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16
Q

best way to sample urine

A

cystocentesis

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17
Q

when to collect urine by catheterisation

A

when it will be performed for diagnostic or therapeutic reasons anyway

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18
Q

how to store urine sample

A

in sterile capped syringe or capped container/tube
if not cultured within 1-2h, must be in fridge for max 8h

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19
Q

how to collect transudate/exudate samples

A

sterile needle and syringe
antiseptic prep of skin
specimen put in anaerobic transport device
if a wash is used - can’t contain any bacteriostatic preservative
buffered solution eg lactated ringers solution is best as isotonic saline can be acidic

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20
Q

collection of faeces

A

2-3g preferred amount
in clean, sealed, leak proof containers

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21
Q

tissue sample collection

A

abscess sample should contain pus and abscess wall
should be placed (unfixed and without preservative) in sealed, leak proof and sterile container
in fridge if delay to lab

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22
Q

consideration when taking samples from necropsy

A

take samples for microbiology first as excessive tissue sampling and exposure can cause additional contamination

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23
Q

what does susceptibility tests measure

A

lowest concentration of antimicrobial required to macroscopically inhibit the growth of the microorganism
MIC - minimum inhibitory concentration

24
Q

samples for viral disease transport

A

refrigerate if short term shipment 12-48h
if long term shipment, sample should be frozen and shipped don wet ice
tissues for histopathology and IHC should be fixed in buffered formalin

25
Q

5 techniques for diagnosis of viral infection

A
  1. virus isolation in cell culture
  2. electron microscopy
  3. specific viral antigen detection by immunologic methods (ELISA, fluorescent antibody, IHC)
  4. nucleic acid detection (PCR and in situ hybridisation)
  5. serologic testing for specific viral antibodies
26
Q

what does ELISA look for

A

viral antigen

27
Q

what does PCR look for

A

nucleic acid detection

28
Q

sample examples for fungal infections

A

from active site of infection
systemic mycoses usually from resp tract so lung tissue or airway exudate
if disseminated infection - maybe urine or bone marrow
non systemic specimens - nasal sinus, abscess, cornea, catheter, hair and nail

29
Q

sample collection for dermatophyte culture

A

clean lesion with 70% alcohol - not iodine as harmful to dermatophytes
scape on edge of lesion or pluck hair from edge of lesion
keep at room temp - fridge is damaging

30
Q

how to collect nails

A

by clipping
can scrape away heavily keratinised structures to access deeper portions and disinfect claw surface with alcohol

31
Q

how to sample open skin lesions

A

without disinfection or cleaning as it may remove or kill the organism of interest

32
Q

specifics about samples for fungal isolation

A

swabs are of limited value
swabs of cotton avoided - can be mistaken for hyphae
transport at room temp and processed asap of within 2h
urine can be put in fridge
most yeast will multiply in urine kept at room temp

33
Q

what is serological reaction

A

isolation and identifying the causative agent, or demonstrating antibodies or antigens in tested blood serum

34
Q

why are serological methods good

A

more reliable for latent and chronic infections than isolation of causative agent
quicker for viral diagnosis
verify immune status of the animal

35
Q

when are antibodies detectable in blood titre

A

7th day post infection

36
Q

If both samples show equal titre of antibodies it means

A

they are antibodies that have remained from a previous infection (residual antibody titre)

37
Q

how much blood for serological testing

A

10ml to get 5ml of serum

38
Q

how is blood collected for serological testing

A

in sterile tube

39
Q

where to take blood from pig

A

cranial vena cava
jugular
ear vessels

40
Q

where to take blood from poultry

A

wing vein - v. ulnaris

41
Q

where to take blood dogs and cat s

A

cephalic vein - front leg
medial/lateral saphenous vein - hind leg
femoral vein - hind leg

42
Q

samples for chemical toxicological testing from live animals

A

10ml full blood
50ml+ urine
faeces
vomit
milk sample

43
Q

samples form chemical toxicology from dead animals

A

small animal - send whole animal
large animal - 5-10ml blood and serum asap after death and 250-300g of parenchymal organs (kidney, liver, spleen, lungs, brain)

44
Q

silage samples for toxicology

A

3-5kg

45
Q

grain or fodder sample for toxicology

A

1kg

46
Q

water samples for toxicology

A

can be frozen but must not melt before they get to lab

47
Q

what is transport medium

A

has no nutritional value and does not allow for the multiplication of the pathogen but by using it we ensure the survival of the microorganism while we are taking materials until it is inoculated on to a nutrition medium in the lab

48
Q

how to take sample for CEM

A

taylorella equingenitalis is sensitive to metabolites of the bacteria present in sample and to presence of oxygen
needs a transport medium with added charcoal

49
Q

organ samples

A

sent in entire pieces or as large as possible
before inoculating on culture medium, sterilise surface to prevent the growth of contamination bacteria from outer surface

50
Q

interpreting results

A

is sample was aseptically collected with a low possibility of contamination then even small numbers of bacteria may be significant
if high chance of contamination results interpreted based on purity of the bacteriologic culture and the and quantity go bacteria isolated

51
Q

how to get enteritis pathogens

A

faeces physiologically contain a large number of species
Salmonella, Campylobacter, Clostridium etc need specific conditions for isolation - microaerophilic/anaerobid or selective culture medium

52
Q

aspergillosis interpretation

A

if one or more colonies of Aspergillus grow on plate - have to be interpreted with clinical picture
repeat sample if necessary
Aspergillus is normally found in environment (contamination) and can also be taken from nasal passages of healthy animals
has animal been treated - take samples at least 5 days after last therapy, incubation will take longer or be negative if still on therapy

53
Q

organ/tissue for pathohistology

A

cut tissue in 2 parallel incisions vertically along the surface of the organ (sugar cube shape)
place in sterile container with 10% formalin - 10x greater than volume of excised tissue

54
Q

what is a poison

A

any chemical substance or combination of chemical substances which can disturb the function of cells, tissue, organ systems and cause death of an organism

55
Q

what is a toxin

A

a chemical substance synthesised by a living organism - Clostridium tetani, Clostridium botulinum, E.coli etc which is poisonous for another organism

Infectious Colloquium (17 decks)

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