Wound Culture Processing & Reporting Policy
1. Wound cultures provide more clinically relevant results if tissue, fluid or aspirates are submitted for culture. Superficial swabs with many squamous cells do not provide reliable wound culture results, since they essentially represent an “environmental” sampling. Misleading results from these sources could cause a clinician to initiate antibiotic therapy when none is required, or to limit antibiotic coverage when empiric, broad-spectrum coverage is more appropriate.
2. Gram stains will always be performed on swab specimens submitted for wound culture, even though tissue, fluid and aspirates are the preferred specimen sources.
- Swab specimens are evaluated for the presence of squamous epithelial cells (SEC), white blood cells (WBC) and bacterial morphotypes.
- Specimens with greater than 5 SECs per low-power microscopic field and no WBCs will have minimal identification of bacteria and will not have susceptibility tests performed unless clearly pathogenic bacteria are isolated and susceptibility testing is valid for the isolate(s).
- Examples of such bacteria include Group A Strep, Pseudomonas aeruginosa, MRSA, VRE, Francisella tularensis and others.
3. Usually, tissues, aspirates and fluids will be worked up more completely than specimens collected on swabs.
- The quality of the tissue, fluid and aspirate specimen is also evaluated by Gram stain for the presence of squamous epithelial cells (SEC), white blood cells (WBC) and bacterial morphotypes.
- Specimens with greater than 5 SECs per low-power microscopic field and no WBCs will receive modified work-ups. Exceptions may be made based on the specimen source (bone specimens, for example, will receive full work-ups), and/or the immunocompetence of the patient.
- No more than 3 potential pathogens will be worked up.
- Clearly pathogenic bacteria (such as Group A Strep, Pseudomonas aeruginosa, MRSA, VRE, Francisella tularensis and others) will always be identified, with susceptibility testing performed if valid for that isolate.
- Gram stain results will determine which isolates will be chosen for more extensive work-up.
4. TriCore Reference Laboratories’ complete work-up protocol is available upon request from the Infectious Diseases Department. To obtain the protocol or for any other questions, contact the department at 505-938-8879 in Albuquerque or toll-free at 800-245-3296 Ext. 8879.
1. Manual of Clinical Microbiology, American Society for Microbiology, 8th edition, 2003.
2. Clinical Microbiology Procedures Handbook, American Society for Microbiology, 2nd edition, 2004.
3. Diagnosis and Treatment of Diabetic Foot Infections, IDSA Clinical Practice Guidelines, CID: 2004; Vol. 39: pg 609-629.
4. Guidelines for the Selection of Anti-Infective Agents for Complicated Intra-abdominal Infections. IDSA Clinical Practice Guidelines, CID: 2003; Vol. 37: pg 997-1005.
5. Wound Microbiology and Associated Approaches to Wound Management, Clinical Microbiology Reviews, 2001, Vol. 14, No. 2.