Grandview Medical Center

It takes at least 18-24 hours incubation before there are any culture results available

It takes 48-72 hours from the receipt of a specimen before susceptibility studies are available.

CULTURES:

1. Positive cultures are reported as soon as identified with at least a probable identification of the organism.  Complete identification of the organism will follow as the organism grows to the “complete identification stage”.  (The “complete identification stage” varies among organisms and source site.)
2. Cultures are not reported as “no growth” or “negative” until the following:
   1. Urine  –- 24 hours is No growth;  a minimum of 2 days if  growth is identified
   2. Throat – 42 hours
   3. GC cultures –- 3 days
   4. Blood cultures –  5 days
   5. CSF –- 72 hours
   6. Wound – 2-3 days
   7. Sterile body fluids – 72 hours
   8. Stool – up to 4 days
   9. Other routine cultures –- 2 days
   10. Anaerobic cultures –- 7 days
   11. AFB cultures –- 6 weeks
   12. Fungus cultures  –   4 weeks
3. Gram stains made on sputum cultures are held for 7 days
4. Positive blood cultures will have a gram stain performed and called to the patient’s nurse, agency, or physician if the patient came to us for the culture draw

MYCOLOBACTERIOLOGY (AFB):

1. Specimens are sent to a reference lab for testing
2. Reports for AFB smears (direct and concentrated) are generally issued within 48 hours of receipt of the specimen to the reference lab
3. Most Mycobacterium (including M. tuberculosis) are slow growers and generally require at least two to three weeks to produce visible growth.  As soon as growth of AFB is observed, a preliminary report will be issued.
4. AFB cultures are observed for 6 weeks before being signed out as negative by the reference lab.

MYCOLOGY (FUNGUS):

1. Specimens are sent to a reference lab for testing
2. Fungi will be identified as completely as possible by the reference lab
3. Preliminary reports will be issued prior to final identification if pathogenic fungi are present
4. Because all fungi may be pathogenic given the proper clinical circumstances, all fungi, even though usually considered non-pathogenic aerial contaminants, will be identified as completely as possible
5. Fungus cultures are observed for 4 weeks before being signed out as negative by the reference lab

ANTIBIOTIC SUSCEPTIBILITY TESTING:

1. Antibiotic susceptibility testing is routinely performed on any bacterium isolated from clinical material which may contribute to an infectious process warranting chemotherapy, if susceptibility cannot be reliably predicted from knowledge of its identity.  The choice of antibiotics tested shall be appropriate for both the organism being tested and the site from which the organism has been isolated.  The National Committee has established such standards for Clinical Laboratory Studies.
2. Unless isolated from a sterile site, routine susceptibility tests are not needed when resistance has not been described in the chemotherapeutic agent of choice, e.g. Streptococcus pyogenes to penicillin.
3. Susceptibility tests are also to be avoided on normal flora in their natural habitat, and on organisms that are not known to play a pathogenic role.
4. Antibiotic susceptibility testing is not performed on fastidious or slow growing organisms or on organisms for which such testing has not been standardized.  The pathologist is available for consultation regarding the choice of antibiotics to treat such organisms.
5. The choice of antibiotics for susceptibility testing reflects the “family” concept, i.e. using one member of a family of antibiotics as a representative.  This concept does not apply to the members of the aminoglycoside family of antibiotics.
6. Susceptibility testing is routinely performed on the following:
   1. Sputum  –  All gram negative rods, Streptococcus pneumoniae, and Staphylococcus aureus in moderate to heavy growth
   2. Wounds and fluids  –  All gram negative rods, Enterococcus, Staphylococcus, Streptococcus, and Listeria
   3. Urine  –  All gram negative rods, Enterococcus, Staphylococcus, and Listeria in quantities greater than 10,000 colonies/ml
   4. Blood and Spinal fluid  –  All organisms
7. Susceptibility testing is NOT routinely performed on the following:
   1. All organisms whose susceptibility can be reliably predicted from knowledge of its identity
   2. Contaminated urines (more than three organisms present)
   3. Anaerobes (Most anaerobes are sensitive to penicillin except for Bacteroides fragilis. B. fragilis should be treated with chloramphenicol or clindamycin.  Erythromycin or tetracycline may be effective.  Anaerobes generally do not respond well to aminoglycosides.)
   4. If susceptibility testing on anaerobes is requested by the physician, these plates will be sent to a reference lab.