Taking good samples

What are the guidelines for good sample collection?

Collect specimen aseptically

Take samples as soon as possible

Collect an adequate amount of sample within ethical guidelines

Separate multiple samples to prevent cross-contamination

Choose correct transport medium

Label specimen container

Immediate storage after sample collection

Sealing sample and packing

Temperature control during transportation

Send to laboratory as soon as possible

Hazardous waste disposal

What is the role of a vet in bacteriology?

Sample collection, correct sample handling, specimen labelling, sending specimens for culture and identification.

What tools are used for sample collection?

Swabs e.b charcoal or dry (not recommended for bacteria) , sterile containers and toothbrushes.

How do you take an aerobic culture?

• Most sample sites are acceptable for aerobic culture.

• Samples are typically collected using sterile swabs with Amies transport gel/with charcoal.

• Biopsy specimens should be sent in sterile container; sterile physiological saline can be added to keep the tissue from drying out.

• Do not submit syringes; specimens collected by syringe should be aseptically transferred to a sterile tube.

• Specimens should be refrigerated up pick up and transported with a cold pack

How do you take an anaerobic culture?

. As a general sampling guideline, anaerobes are usually collected from a warm, moist environment that are low/no oxygen.

. When collecting samples for anaerobic culture, try to avoid any exposure to oxygen or allowing the sample to become dry.

. Obtain specimens from deceased animals within four hours of death.

. Samples obtain 4hours< are usually unsuitable for anaerobic culture=rapid post-mortem invasion of tissues by anaerobes from the GIT.

. Acceptable anaerobic samples include tissue, several millilitres of fluid in a sterile container or a swab in appropriate transport medium.

. After collection, specimens should be kept at room temperature, if possible, out of direct sunlight.

. Samples for anaerobic culture should arrive at the laboratory as soon as possible after collection

How do you take a fungal culture?

• Samples submitted include hair, skin and tissues from infected sources.

• If both fungal and bacterial culture is required, submit an adequate amount of sample for both tests or submit separate samples for each culture.

• Swab samples are inadequate for fungal diagnosis.

• The toothbrush method works well for collecting hair fungal specimens.

• For both skin and hair samples, sterile containers are most appropriate for collection and transport.

• DO NOT use paraffin oil to aid in the collection of these types of specimens.

• After collection, refrigerate sample until transported to laboratory. Do not freeze.

• Stringent transportation conditions are not required for samples for fungal identification

What are the specific sampling rules for blood?

• Blood culture is considered the “gold standard” investigation for the detection of micro-organisms in blood.

• Specimens for blood culture require aseptic collection into specialised vacuum tubes containing growth medium.

• Do not use tubes with citrate, EDTA, oxalate or heparin as an anticoagulant for blood.

• Best practice is to take a minimum of two sets of blood samples from separate venipunctures at various stages of illness.

• Mitigate for transient bacteraemia.

• Hold cultures at room temperature until they can be transported to the laboratory- NEVER refrigerate inoculated blood culture bottles!

• Transport the inoculated bottles to a laboratory as quickly as possible, preferably within 2 hours (CLSI)

BLOOD FOR CULTURE SHOULD BE DRAWN BY VEINS NOT ARTERIES

Where would you put a synovial fluid sample?

Injection of SF in blood culture bottles is the gold standard for the diagnosis of septic arthritis.

What should you do with samples from abscesses?

For Abscesses, if pus is present, aspirate this material with a sterile syringe and needle and transfer to a sterile universal container.

What are the specific sampling rules for tissues?

• Fresh as possible! Obtain tissues from necropsy or biopsy efficiently and store appropriately. If possible, cut a block of tissue approximately 2ccm.

• Do not submit in formalin or ethanol.

• If possible, take samples from solid organs before opening the GIT

What are the specific sampling rules for faeces?

• For faecal culture: sampling early in the course of the disease will yield the best results.

• Obtain from rectum or immediately after defecation; avoid contamination with urine and soil.

• Stool samples for faecal culture should be submitted in a sterile container.

• Keep at room temperature until pick up or refrigerate overnight

What are the specific sampling rules for urine?

• Collect at least 0.5mL.

• Urine specimens should be submitted in a sterile culture tube! Do not send syringes.

• Urine from cystocentesis is the preferred method.

• Free from normal flora contamination of the urinary tract.

• Catheterised samples are acceptable when performed with aseptic technique.

• A universal containing boric acid is recommended

• Free catch is acceptable if caught mid-stream.

• A universal containing boric acid is recommended

• Room temperature is sufficient if specimens can be transported within 1hour> otherwise

refrigerate urine until pickup and transport with a cold pack.

• Always state method of sampling on the submission form.

How should you take samples from the nose?

• Preferred sample types include aspirate from sinus or swab and/or wash the nasal cavity.

• Specimens should be collected in a sterile universal pot

• Nose swabs are not ideal for the examination of nasal discharge, they are sometimes received.

• If sample site is dry, moisten the swab beforehand with sterile saline.

How should you take samples from ear?

• Antibiotics or other chemotherapeutic agents should not be used in the aural canal for three hours prior to the swab being taken.

• If sampling the outer ear, clean debris from canal with saline

• Both ears should be sampled and labelled clearly as the findings from each ear may differ

How should you take samples from eyes?

• Swabs from eyes can be easily contaminated with skin microflora; remove crusts around the eye prior to sampling.

• Swab discharge material before applying any topical medication.

• If topical dyes or anaesthetics have been applied, rinse the area before taking a sample.

• Use swabs with an appropriate transport medium and refrigerate after collection

What are common reasons for sample rejection?

• Unlabelled or mislabelled specimens.

• Specimens sent in a syringe.

• Use of improper transport medium.

• Excessive transport time.

• Improper temperature during transport or storage.

• Improper collection site for test requested.

• Specimen leakage out of transport container.

What’s the general rule for other fluids?

Send the actual fluid over a swab.