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ALT CULTURE CLUB TOPIC
MICROBIOLOGY
COLLECTION AND HANDLING SPECIMENS
Generally, a bacteriology report can indicate only what has been found by microscopic and cultural examination. An etiological diagnosis is thus confirmed or denied. Failure to isolate the causative organism, is not necessarily the fault of inadequate technical methods. It is frequently the result of faulty collecting technique.
The following are general considerations regarding the collection of material for culture:
1. Whenever possible, specimens should be obtained before antibiotics or other antimicrobial agents have been administered. A purulent spinal fluid will reveal no bacterial pathogens on smear or culture when an antibiotic has been given within the previous 24 hours. Also, in a patient with salmonellosis will invariably show a negative stool culture if the specimen has been collected while the patient was receiving suppressive antibacterial therapy, only to reveal a positive culture several days after the therapy has been terminated.
2. If the culture has been taken after the initiation of antibiotics, the laboratory should be informed, so that specific inhibitory measures, such as adding penicillinase, or merely diluting the specimen may be carried out.
3. The material should be collected where the suspected organism is most likely to be found, and with as little external contamination as possible. This is particularly true of draining lesions containing coagulase positive staphylococci - in which the phage typing of the primary infecting strain is different from that of a surface contact strain which may grow out.
4. The stage of the disease at which the specimen is collected for culture. Examples, enteric pathogens are present in much greater number during acute or diarrheal stage of intestinal infections. Viruses responsible for causing meningoencephalitis are isolated from cerebrospinal fluid (CSF) with greater frequency when the fluid is obtained during the onset of the disease rather than at a time when the symptom of acute illness have subsided.
5. With regards to the patient, he or she should have full instructions, and his or her cooperation should be encouraged by the technician or ward attendant.
6. Specimens should be of a quantity sufficient to permit complete examination.
7. The specimen should be placed in sterile containers that precludes subsequent contamination of patient, nurse or the technician who will do the examination.
8. Provision must be made for prompt delivery of specimens to the laboratory.
9. Addition of preservatives is not advisable.
10. Proper identification or labels in the proper container.
11. The specimen should be place to its proper media immediately.
SPECIMENS FOR CULTURE
1. Throat and nasopharyngeal
2. CSF
3. Urine
4. Sputum
5. Skin - lesions, wounds, exudates
6. Blood
7. Ear - mastoid, sinuses, antrum
8. Eye - conjunctiva
9. Urethral, vaginal, prostatic
10. Stool
11. Gastric washing
12. Surgical tissues
13. Fungi - skin, hair, nail
There may be occasions when it is necessary to submit specimens to a reference laboratory in a distant place. Thus requiring shipment by mail or express. In virus containing material, such as CSF, stools, tissue, throat, the specimen should be frozen and shipped in dry ice. Whole blood is not frozen. Rather, the serum is separated and sent in sterile tube. Freezing and thawing would result in extensive hemolysis, rendering the serum unsatisfactory. If culture slant of an isolated organism (i.e., AFB culture for complete identification) is to be sent, postal regulations require that they be shipped in glass container stored with leakproof rubber stopper. The glass container is then completely wrapped in absorbent packing material placed in a cylindrical sheet metal box. Double mailing containers should always be used when the specimen is considered a biohazard.
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