Collection Of Samples for Culture

Collection

1. Male: Cleaning the urethral meatus with plain tap water (free skin retracted), allow to dry and at least 30 ml of mid-stream urine (MSU) should be collected in a sterile container. It is better to collect the first MSU passed at the beginning of the day.
2. Female: The vulva is cleaned by cotton plug soaked with water. Labia is separated and morning mid-stream urine (MSU) should be collected in a wide mouth sterile container.
3. Children:
   • Sterile adhesive bag.
   • Suprapubic tap: Tap by fingers on the suprapubic region 1 hour after feed (one tap per second) for 10 seconds. 1-minute interval repeat the procedure.
4. Suprapubic aspiration: Occasionally necessary in acute retention of urine or unconscious patient.
5. Urethral catheterization: Rarely used in children or unconscious patients. Fresh sterile catheter should be used. Urine sample should be collected directly from the catheter, never from collecting bag.
6. Ureteric catheterization: In operation theatre during urological surgery/examination, when necessary.
7. Genitourinary tuberculosis: 3 consecutive early morning urine specimen (EMU) or 24 hours urine in a container containing 1% boric acid.

Transport

All specimens should be processed in the laboratory within 2 hours of collection; if delay is unavoidable more than two hours use one of the following.

• Refrigerate the urine at 4˚C in the same container.
• Collect and transport in a container with boric acid (0.1g/10 ml of urine).

Any way delay should not be longer than 18 hours after collection. 

Administration of drugs or antidiarrheal substances (mineral oil, barium, bismuth, magnesium, antibiotics) should be terminated at least one week before stool collection. 

• Stool container should be
  1. Clean, dry, leak proof, disinfectant free and wide necked container.
  2. A light plastic box or an especially designed glass jar attached spoon with the stopper.

• Amount of stool that is to be collected
  1. About a spoonful specimen is sufficient
  2. Transfer a portion of stool that contain mucous, pus, blood, if present.

• Send the specimen to the lab as early as possible. 

Specimens that cannot be cultured within 2 hours of collection should be placed in Cary-Blair transport medium and refrigerated immediately.

Procedure of transport:

1. With the help of a cotton swab, a portion of stool is taken.
2. Insert the swab in the container of sterile Cary – Blair transport medium.
3. Breaking of the swab stick to allow the bottle top to be replaced lightly.

For infants or other patients [if necessary ‘Rectal Swab’ may be collected]

Moisten the swab with normal saline and introduce the swab into rectum (one inch into the anal canal) and keep for 10 seconds, turn the swab several times with circular movement. Care should be taken to avoid unnecessary contamination of specimen with bacteria from anal skin.

Precaution

1. Avoid contaminating the faeces with urine or water

1. Never store in the incubator
2. Never store in the refrigerator

Swab should be collected in the morning before any mouthwash, food or drink. Mouth of the patient should be widely opened, neck flexed. Hold the head fixed. Keep the tongue down with a tongue depressor. Oral cavity should be properly illuminated with good light source. A sterile cotton swab (supplied from dept.) is rubbed vigorously over one tonsil, then uvula, other tonsil, the posterior wall of the pharynx and over any other inflamed area. Care should be taken not to touch the tongue, buccal surface or lips. Place the swab stick in the sterile container tube. It is preferable to take two swabs from the same patient. Specimen should be dispatched to the laboratory as soon as possible. 

Sample should be collected from the base of the ulcer or nodule following removal of overlying debris or surgical biopsy of deep tissues without contact with the superficial layer of the lesion. If possible two swabs should be collected. Specimens should be placed in a sterile container capped properly and send to the laboratory as early as possible. 

Patient instruction:

• Collect early morning specimen before breakfast or mouthwash.
• Rinse mouth with water before collection
• Remember that saliva and nasopharyngeal discharge are not sputum.
• Collect only the exudative material brought up from lungs after a deep production cough in a dry wide necked leak-proof container.
• Send the container as early as possible. Never refrigerate such sample.

If pulmonary tuberculosis is suspected:

• Collect a series of two early morning sputum samples on successive days.
• If not possible the 1^st sample at spot and 2^nd early morning sample.
• If a patient produces very little sputum, 24-48 hours pooled specimen is needed to yield a positive culture.

Collection and Transport

• Approximately 5-10 ml of CSF (in adult patient) should be collected in two sterile tubes (Screw-Capped).

Collect about 1 ml of CSF in tube No. 1 (for culture) and rest of the portion in tube No. 2 (for other tests).

• The specimen should be delivered to laboratory immediately.
• Do not refrigerate the sample.
• If tuberculous meningitis is suspected, 3rd tube is kept in the refrigeration undisturbed to see whether a pellicle or coagulum forms.

Genital Specimen for Women

• All specimens should be collected during pelvic examination using a speculum.
• The speculum should be moistened with warm water before use, but antiseptics or gynecological exploration should not be used.
• After inserting the speculum, cervical speculum should be wiped off with a cotton wool ball.
• A sampling swab should then be introduced into the cervical canal and rotated for at least 10 seconds before withdrawal.
• Specimen should be transported in Amies and Stuart transport media.
• For urethral discharge and genital ulcer the patient should be referred to Microbiology Department.

-    Asepsis of blood culture bottle top.

• Timing of sample collection:

1. At spike of febrile illness
2. Before antibiotic use
3. If antibiotic already started blood should be collected just before next dose of antibiotic.

• Optimal volume of blood culture:

1. For adult minimum 5-10 ml
2. For children 1-3 ml
3. For neonate 1 ml

• After collection immediately inoculate blood into culture bottle (Bed side inoculation) and send to laboratory within one hour.