Practical Diagnostic Applications in Veterinary Microbiology Flashcards
How big should tissue block specimen be? How are abscesses collected?
4 x 4 x 2 cm
scrape the abscess wall + pus
How are exudates collected? How are swabs kept uncontaminated?
(joint fluids, endocardial fluid) - aseptically by sterile syringe
use swab-transport systems, like Culturettes
How should all tissues, organs, and pus be maintained during shipment/transport? What is a major exception?
refrigerator temperature
feces
Why isn’t feces kept at refrigerator temperature for shipment/transport? How should it be preserved?
pH drops, which can kill bacteria like Salmonella
placed in trasnport media, like Cary-Blair 10% suspension, and transported at room temperature
Why is aseptic technique so important for collecting specimen?
many pathogenic bacteria are fastidious and slow-growing, so contamination can make the interpretation of results much more difficult and fail to isolate the true etiologic agent
What is the best way to collect specimen from animals that have been dead for an unknown period of time? Why?
bone marrow or rib
enteric bacteria rapidly disseminate throughout tissue after death (especially coliforms and clostridia)
Which samples are not suitable for anaerobic cultures? Why?
samples contaminated with normal flora, such as intestinal contents, oropharyngeal swabs or washings, and skin
contaminated sites will ass contain anaerobic bacteria
- pus and fluids should be collected with a needle and syringe and have air expelled
How should anaerobic cultures be shipped? Anaerobic swabs? Large pieces of tissue? Small pieces of tissue?
if they cannot reach the lab within 30 mins, they should be transported in an anaerobic transport system
within commercial anaerobic transport swabs and maintained at 4 degrees C
(6 x 6 x6 cm) - will usually hold an anaerobic environment, but should be kept at 4 degrees C and processes as soon as possible
within anaerobic transport bag until processing can be done
What 3 things does the success of culture for anaerobes depend on?
- samples taken from a living or recently dead animal
- excluding air from samples in transit and maintaining at 4 degrees C
- cultures under anaerobic conditions as soon as possible
How should specimens be collected in mastitis cases?
- good collection technique, since milk samples can be easily contaminated by organisms outside the udder
- collection into sterile narrow-necked bottles (no nonsterile containers or “whirl-bags”
- CULTURE
In what 3 ways are UTI specimen collected? Which one is least likely to result in contamination?
- cystocentesis*
- catheter
- voided
How should urine samples be maintained if they are unable to be cultured immediately? When must they be cultured?
refrigerated
within 6 hours, even if kept refrigerated
On what media are urine samples inoculated on? How is this done?
blood agar and MacConkey agar
- 10 µl from cystocentesis/catheter; 1 µl voided
- calibrated loop inoculates urine into the plates
- draw loop down the center of the plate from top to bottom
- streak back and forth through initial streak
- 24 hrs incubation and colony count
What is the bacterial burden of most UTIs? When collected from a cystocentesis?
10^5 CFU/mL
> 10^3 CFU/mL
What are the most common bacteria isolated from the urinary tract? what other 3 can be found?
enterics, like E. coli, enterococci, and Proteus
- Pseudomonas
- Staphylococci
- yeasts
anaerobes and filamentous fungi are rare
What are the main bacteria and fungi known to cause abortion?
- Campylobacter spp.
- Brucella spp.
- Leptospira spp.
- H. somnus
- Mycoplasmas
- Listeria spp.
- A. pyogenes
- Aspergillus spp.
- Zygomycetes
What samples should be collected for isolation following an abortion?
both maternal and fetal samples
- fresh and fixed for histopathology is ubiquitoius organisms like Aspergillus fumigatus is suspected
What 4 fetal samples are preferred for uterine disease?
- placenta plus cotyledons (fixed and fresh)
- uterine discharge (fresh)
- fetal stomach contents (fresh)
- fetal lung, liver, kidney, and spleen (fixed and fresh)
What are the 2 preferred ways to collect Leptospira samples if it is suspected to be the cause of the abortion?
- midstream urine - centrifuged and darkfield microscopy immediately, or dilute in cultured media
- clotted blood samples for serology at the time of abortion
What 2 specimens should be collected in suspected infertility cases? What should examinations cover in cattle and mares?
- uterine discharge or vaginal mucus
- preputial washings* or semen
CATTLE - Campylobacter fetus and opportunistic aerobes (Haemophilus somnus)
MARE - coliforms (Klebsiella), other opportunistic aerobes (Streptococci), and fungi (Taylorella equigenitalis)
How is PCR done?
- sample extract, primers, Taq polymerase, dNTPs, and other reagents are added to thermal cycler
- temperature is raised to 94 degrees C to dissociate the DNA
- temperature is lowered to 54 degrees C to anneal DNA with the primers
- temperature is raised to 72 degrees to extend new DNA
- repeated for about 30 cycles and amplified logarithmically
Gram-positive bacteria:
Gram-negative glucose fermentors:
Oxidase-positive fermentors:
Gram-negative glucose oxidizers vs. nonsaccharolytic:
