Propionibacterium acnes wound contamination at the time of spinal surgery.
Bacteria of the normal skin microbiota such as Propionibacterium acnes and coagulase-negative staphylococci often are dismissed as contaminants when detected in clinical samples. Propionibacterium acnes is described as a cause of spinal infection and more recently has been linked to sciatica. To date no researchers formally have examined the incidence of bacterial wound contamination during spinal surgery. Surgical specimens were removed from 79 patients having spinal surgery for analysis using agar culture detection, broth enrichment, and immunofluorescence microscopy. Bacteria were identified in 29.1% of skin samples, 21.5% of tissue samples and 16.5% of washings retrieved from operative wounds. Propionibacterium acnes was identified more frequently than Staphylococcus spp in each of the three sample types. Bacteria were detected using enrichment in 9 (11%) patients and using fluorescence microscopy in 15 (19%). The results of immunofluorescence microscopy suggest that Propionibacterium acnes detected in wounds originates from patient skin. Bacteria from contaminated wounds appeared as single cells using fluorescence microscopy; however previous work shows that bacteria from infected hip prosthesis are observed as large aggregates. Therefore, it is suggested that immunofluorescence microscopy is a useful tool to help discriminate between surgical contamination and infection.


METHODS
Diagnostic study, Level I (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.
McLorinan
Gregory C
GC
Department of Microbiology, School of Medicine, Queen's University, The Royal Victoria Hospital, Belfast, UK.
Glenn
Josephine V
JV
McMullan
Michael G
MG
Patrick
Sheila
S
D015169:Colony Count, Microbial; D005260:Female; D005500:Follow-Up Studies; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis / Q000382:microbiology*; D006801:Humans; D066298:In Vitro Techniques; D007432:Intraoperative Period; D008297:Male; D008856:Microscopy, Fluorescence; D019637:Orthopedic Procedures / Q000009:adverse effects*; D011425:Propionibacterium acnes / Q000254:growth & development / Q000302:isolation & purification* / Q000648:ultrastructure; D011446:Prospective Studies; D012867:Skin / Q000382:microbiology; D013122:Spinal Diseases / Q000601:surgery; D013131:Spine / Q000601:surgery*; D013530:Surgical Wound Infection / Q000175:diagnosis / Q000382:microbiology*