Dear Innocent,

All stools for lab exam require preservation in a formalin fixative and PVA or equivalent immediately after collection. Use tight sealing sterile containers or tubes of transport medium that will maintain viability, prevent drying out of the specimen/swab, and prevent overgrowth of nonpathogenic microorganisms. It is important to label the container with the patient’s name and source. The inoculated containers should show no leakage.

http://www.questdiagnostics.com/home/physicians/testing-services/specialists/hospitals-lab-staff/specimen-handling/infectious-diseases-microbiology.html

The following text gives more details on the storage and transport of stool:

To ensure that these diagnostic advances can be used most effectively, earlier recommendations for collecting stool specimens must be updated. Because appropriate specimen-collection methods for viral, bacterial, and parasitic agents differ, the sections below are divided into guidelines by category of agent. II. PROCEDURES FOR COLLECTING SPECIMENS

Stool (See Table 1)

General guidelines

Timing. Begin collecting stool specimens immediately

after being notified of an outbreak, since delay may impede identification of the causative agent. To permit diagnosis of certain viral agents, specimens must be collected during the first 48 hours of illness.

b. Quantity. Collect diarrheal stool samples from at least 10 ill persons (assuming that at least that number are involved in the outbreak). For outbreaks thought to be of viral origin, collect large-volume stool specimens (at least a urine cupful).

2. Methods for collection and storage

Viruses. Place each diarrheal stool specimen, of as

large a quantity as can be obtained (preferably, at least 10 cc), in a leak-proof, clean, dry container, and refrigerate at 4 C. Instructing patients to catch stool specimens in plastic kitchen wrap draped across the back half of the toilet under the toilet seat may facilitate collection of stool specimens. Do not freeze specimens if EM examination is anticipated.

b. Bacteria. Collect at least two rectal swabs or swabs of fresh stools from each patient and place swabs in refrigerated (i.e., chilled 1-2 hours before use) Cary-Blair transport medium. When obtaining swabs from a patient, first moisten each rectal swab in the holding medium, insert the moistened swab into the rectum 1 to 1-1/2 inches, rotate the swab gently, and then return the swab to the same tube of holding medium. Try to ensure that visible fecal material is present on each swab. After obtaining the two fecal swabs, insert both into the same tube of medium and push them to the bottom of the tube. Break off and discard the excess top portion of the swab sticks.

IMPORTANT: Refrigerate or freeze tubes after specimens are placed in them. If specimens will be examined within 48 hours after collection, they can be refrigerated; however, if specimens must be held longer than 48 hours, freeze them as soon as possible after they are collected. Although storage in an ultra-low freezer (-70 C) is preferable, storage in a home-type freezer (if it is properly set at -20 C) is acceptable for short periods.

c. Parasites. Mix fresh bulk-stool specimens thoroughly with each of two preservatives, 10% formalin and polyvinyl alcohol (PVA) fixative,* at a ratio of 1 part stool to 3 parts preservative. If there is a delay in obtaining the preservatives, refrigerate untreated stool specimens at 4 C (do not freeze) for up to 48 hours. Once preserved, the specimens can be stored and transported at room temperature or refrigerated. Do not freeze.

3. Transportation (specimen handling)

Refrigerated specimens. Enclose each specimen in a

secure container (e.g., urine cup, Cary-Blair medium tube), to which has been affixed a waterproof label. Place this container in a waterproof bag with tissue, towels, or other blotting material to absorb any leakage. Batch specimen containers, pack with ice or frozen refrigerant packs in an insulated box, and send by overnight mail scheduled to be delivered during business hours on a weekday, if possible. Submit a list of specimens and a CDC Identification Form 50.34 for each specimen.

b. Frozen specimens (for bacterial testing only). So that they remain frozen, ship frozen specimens on dry ice. Use enough dry ice to keep the specimen frozen until it is received at the laboratory that will process it (i.e., enough dry ice to fill one-third to one-half of the shipping container). Do not allow glass tubes to be in direct contact with dry ice; place a layer of paper or other material between the tubes and the dry ice. To prevent excess exposure of specimens to carbon dioxide, tighten the screw caps on the Cary-Blair tubes and seal them with electrical tape, or seal the specimens in a plastic bag within the container of dry ice.

https://www.cdc.gov/mmwr/preview/mmwrhtml/00001829.htm

Hoping this will be helpful,

Rafik