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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
5 techniques for diagnosis of viral infection
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
what does ELISA look for
viral antigen
27
what does PCR look for
nucleic acid detection
28
sample examples for fungal infections
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
sample collection for dermatophyte culture
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
how to collect nails
by clipping can scrape away heavily keratinised structures to access deeper portions and disinfect claw surface with alcohol
31
how to sample open skin lesions
without disinfection or cleaning as it may remove or kill the organism of interest
32
specifics about samples for fungal isolation
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
what is serological reaction
isolation and identifying the causative agent, or demonstrating antibodies or antigens in tested blood serum
34
why are serological methods good
more reliable for latent and chronic infections than isolation of causative agent quicker for viral diagnosis verify immune status of the animal
35
when are antibodies detectable in blood titre
7th day post infection
36
If both samples show equal titre of antibodies it means
they are antibodies that have remained from a previous infection (residual antibody titre)
37
how much blood for serological testing
10ml to get 5ml of serum
38
how is blood collected for serological testing
in sterile tube
39
where to take blood from pig
cranial vena cava jugular ear vessels
40
where to take blood from poultry
wing vein - v. ulnaris
41
where to take blood dogs and cat s
cephalic vein - front leg medial/lateral saphenous vein - hind leg femoral vein - hind leg
42
samples for chemical toxicological testing from live animals
10ml full blood 50ml+ urine faeces vomit milk sample
43
samples form chemical toxicology from dead animals
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
silage samples for toxicology
3-5kg
45
grain or fodder sample for toxicology
1kg
46
water samples for toxicology
can be frozen but must not melt before they get to lab
47
what is transport medium
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
how to take sample for CEM
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
organ samples
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
interpreting results
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
how to get enteritis pathogens
faeces physiologically contain a large number of species Salmonella, Campylobacter, Clostridium etc need specific conditions for isolation - microaerophilic/anaerobid or selective culture medium
52
aspergillosis interpretation
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
organ/tissue for pathohistology
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
what is a poison
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
what is a toxin
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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