Collection

• The veterinarians primary responsibility in diagnosis of a pathogenic agent is to collect a clinical specimen and submit it to the lab in a manner as the agent remains viable and is not overgrown by contaminants.
• Tissue blocks for collection of specimens are approximately 4 x 4 x 2 cm.
• Abscesses can be collected by scraping the abscess wall or the wall itself plus pus.
• Exudates such as joint fluids, endocardial fluid, etc., can be collected aseptically by sterile syringe.
• Swab collection for specimens can be done using a swab-transport system, such as Culturette.
• All tissues, organs, pus, must be maintained cold (refrigerator temperature) during shipment or transport.
• Feces should be placed in transport media (such as Cary-Blair, 10% suspension), and can then be transported at room temperature.
• The use of aseptic technique in collecting specimens cannot be overemphasized as many pathogenic bacteria are fastidious and slow growing.
• Enteric bacteria rapidly disseminate throughout the tissues after death, making collection of specimens from an animal that has been dead for an unknown period of time difficult to interpret.
• Anaerobic Culture can be carried out for organisms such as Clostridia, Fusobacterium, Bacteroides, Peptostreptococcus, and many others.
• Samples contaminated with normal flora, such as intestinal contents, oropharyngeal swabs or washings, and skin, are not suitable for anaerobic culture as contaminated sites all contain anaerobic bacteria.
• If samples cannot reach the laboratory within 30 min., they should be transported in an anaerobic transport system.
• If swabs must be used they should be submitted in commercial anaerobic transport swabs and maintained at 4°C, if not processed immediately.
• Large pieces of tissue (6 X 6 X 6 cm) will usually maintain an anaerobic environment, but should be kept at 4°C and processed as soon as possible.
• Smaller pieces of tissue (or other specimens) should be maintained in an anaerobic transport bag until processing can be done.
• The success of culture for anaerobes is heavily dependent on samples taken from a living or recently dead animal, excluding air from the samples in transit, and maintaining at 4°C.
• Culture under anaerobic conditions as soon as possible is essential.
• Conventional culture is done using urine culture media.
• If in doubt, the culture should be repeated.
• Urine culture is reported as 1+-4+, with 1+ indicating no growth and 4+ indicating a high bacterial count.
• Fresh and formalin-fixed samples for histopathology are essential if ubiquitous organisms, such as Aspergillus fumigatus, are to be identified.
• Uterine Infections are investigated for all bacteria and fungi known to cause abortion in a particular animal species.
• Most urinary tract infections will have a bacterial burden of greater than 10^5 CFU/ml.
• Examples of bacteria known to cause abortion include Campylobacter sp., Brucella sp., Leptospira sp., H. somni, mycoplasmas, Listeria sp., A. pyogenes, Aspergillus sp., Zygomycetes and others.
• Anaerobes and filamentous fungi are rare.
• Blood cultures are done by shaving and prepping the skin aseptically with antiseptic, such as betadine and alcohol, and collecting three blood samples approximately 1 hour apart.
• From a cystocentesis, any number >10^3 CFU/ml is significant.
• Leptospirosis can be identified by centrifuging and examining the urine immediately, diluting and culturing the urine, or collecting blood for serology.
• Infertility investigations should cover Cattle: Campylobacter fetus, and opportunistic aerobes (e.g Histophilus somni ), and Mares: Coliforms (especially Klebsiella ), other opportunist aerobes (such as streptococci, fungi, and Taylorella equigenitalis ).
• Preferred samples for fetal examination include Placenta plus cotyledons (fixed and fresh) or uterine discharge (fresh), Fetal stomach contents (fresh), plus fetal lung, liver, kidney, and spleen (fixed and fresh), and Midstream urine for leptospirosis.
• The most common bacteria isolated from the urinary tract are enterics (e.g E. coli, enterococci, Proteus), as well as Pseudomonas, staphylococci, and occasionally yeasts.
• After 24 hrs incubation the colonies are counted and the number of CFU/ml is estimated.
• The bottles are examined for turbidity and gram-stained and cultured onto chocolate agar.
• Both maternal and fetal samples should be submitted when possible.
• Mastitis can be diagnosed by culture of milk samples, which can easily be contaminated by organisms from outside the udder, so it is essential that a good collection technique is used.
• The collection should be made into sterile narrow-necked bottles.
• Urinary Tract Infections can be diagnosed by collecting specimens (usually urine) by cystocentesis, catheter, or voided.
• Specimens should be refrigerated if they cannot be cultured immediately and must be cultured within 6 hrs, even if kept at refrigerator temperature.
• The history should include: species of animals which are affected, breed, age, vaccinations, number of animals of same species on premises, number of animals sick, symptoms, location of lesions, duration of problem, suspected condition, treatments, samples submitted.
• Gram-negative nonlactose fermentors include Pseudomonas aeruginosa.