Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1325 page)

   Special Collection and Transport Instructions

   Fluid aspiration is performed after preparation of the puncture site in a manner consistent with a preparation of a surgical site. Submission of specimens from drainage devices is discouraged because of the high incidence of contamination with endogenous flora; direct collection of the sterile fluid is recommended.

   Collection of the maximum amount of fluid from the infected site is recommended. Blood culture bottles may be inoculated and is recommended for patients with spontaneous bacterial peritonitis, but a small amount of fluid should be retained for Gram stain and for special culture inoculation, if needed.

   Swabs should not be used for fluid collection.

   Place fluid into sterile transport tubes; small-volume specimens, or several milliliters from large-volume specimens, should be placed into an anaerobic transport tube. Note: Specimens transported under anaerobic conditions are acceptable for inoculation of cultures for aerobic bacterial, mycobacterial, and fungal cultures.

   Submission of several specimens prior to antibiotic therapy may significantly improve sensitivity of culture detection.

   The use of anticoagulants is discouraged because of possible inhibition of some pathogens. If anticoagulation is required, heparin or SPS is recommended.

   Transport specimens at room temperature; do not refrigerate or freeze specimens.

   Interpretation

   
Expected results:
No growth. Infection is not excluded by a negative culture, especially after initiation antibiotic therapy. Uncommon, fastidious pathogens may not be isolated in culture without inoculation of special media.

   
Positive cultures
indicate infection of the sterile site, but cultures that may be contaminated with endogenous flora must be interpreted with caution in the context of quantity or bacterial growth, purity of culture, Gram stain findings, and clinical signs and symptoms. Infected peritoneal fluid may yield numerous aerobic and anaerobic pathogens. Extensive identification and susceptibility testing are usually not clinically useful: final results are often not available until well into therapy, and empirical treatment is usually effective.

Suggested Readings

Atkins BL, Athanasou N, Deeks JJ, et al.; the Osiris Collaborative Study Group. Prospective evaluation of criteria for microbiologic diagnosis of prosthetic-joint infection at revision arthroplasty.
J Clin Microbiol.
1998;36:2932–2939.

Baselski V, Beavis KG, Bell M, et al.
Clinical Microbiology Procedures Handbook
, 3rd ed. Editor in Chief: Lynne S. Garcia, Washington, DC: ASM Press; 2010.

Bernard L, Pron B, Vaugnat A, et al.; the Groupe d’Etude sur l’Osteite. The value of suction drainage fluid culture during aseptic and septic orthopedic surgery: a prospective study of 901 patients.
Clin Infect Dis.
2002;34:46–49.