Bacterial screening by flow cytometry offers potential for extension of platelet storage: results of 14 months of active surveillance.

BACKGROUND: Bacterial contamination is currently the major infectious hazard of platelet transfusion in developed countries. It has been demonstrated that a significant transfusion risk remains, in particular with older platelet concentrates (PCs). In 2009, the shelf life of PCs was therefore reduced in Germany to 4 days after the day of production according to Vote 38. The aim of the present study was the application and implementation of a recently developed flow cytometry-based rapid screening method (BactiFlow) for bacterial contamination at the end of PC shelf life as a routine in-process control. STUDY DESIGN AND METHODS: A total of 472 apheresis-derived PCs were tested using the BactiFlow flow cytometric assay to detect and count bacteria based on esterase activity in viable bacterial cells, while the BacT/Alert automated culture system served as the reference method. The automation potential of the flow cytometric assay was analysed by applying the semi-automated BactiFlow ALS system. RESULTS: An algorithm was developed for use in routine blood bank operations to extend the storage period of PCs. Two of the 472 apheresis PCs tested were positive in culture and identified as Propionibacterium species. One PC was positive for Staphylococcus aureus by both methods. All remaining specimens were tested negative by both methods. CONCLUSIONS: Our study demonstrates that routine bacterial testing of PCs was successfully implemented and the established algorithm proved efficient. The BactiFlow flow cytometric assay is the first rapid screening method which is suitable for a routine application combined with a high sensitivity.

Risk factors for postoperative mediastinitis due to methicillin-resistant Staphylococcus aureus.

Risk factors for developing postoperative mediastinitis (POM) due to methicillin-resistant Staphylococcus aureus (MRSA) were analyzed in a case-case control study of patients who underwent median sternotomy during the period from 1994 through 2000. Three patient groups were studied. The first consisted of 64 patients with POM due to MRSA; the second consisted of 79 patients with POM due to methicillin-susceptible S. aureus (MSSA); and the third consisted of 80 uninfected control patients. In multivariable analysis, patients who were diabetic (adjusted OR, 2.86; 95% CI, 1.22-6.70), female (OR, 2.70; 95% CI, 1.25-5.88), and >70 years old (OR, 3.43; 95% CI, 1.53-7.71) were more likely to develop POM due to MRSA. In contrast, the only independent risk factor associated with POM due to MSSA was obesity (OR, 2.49; 95% CI, 1.25-4.96). Antimicrobial prophylaxis consisted primarily of cephalosporin antibiotics (administered to 97% of the patients). Changes in perioperative antimicrobial prophylaxis, in addition to other interventions, should be considered for prevention of POM due to MRSA in targeted, high-risk populations.