Antibiotic-labeled probes and microvolume fluorimetry for the rapid detection of bacterial contamination in platelet components: a preliminary report

BACKGROUND: Approximately 1 platelet in 2000 components is bacterially contaminated. Most commonly, contaminating organisms are gram positive skin saprophytes (such as Staphylococcus sp. or Bacillus sp.). A novel approach to the rapid diagnosis of gram positive contamination by the use of a fluorescence-labeled antibiotic probe with affinity for the gram positive cell was investigated. STUDY DESIGN AND METHODS: Two isolates of Staphylococcus epidermidis were inoculated into bags of Day 0 platelets. Quantitative cultures along with a semi-automated screening assay on a microvolume fluorimeter employing a fluorescence-conjugated vancomycin probe was performed for each day of storage. In addition, serial dilutions of the bacteria were added to sterile platelets to achieve a range spanning 101 to 108 CFUs per mL. RESULTS: All samples with a bacterial contamination of ≥105 CFU per mL were detected. Sterile samples were nonreactive. The entire procedure requires three pipetting steps and took less than 1 hour to perform. CONCLUSION: These preliminary results with the use of fluorescence-labeled antibiotics as probes combined with microvolume fluorimetry for the rapid detection of bacterial contamination of platelet components suggest that this is a promising approach. Further studies with additional organisms and alternative conjugates, bacteria, and antibiotics are underway.