Direct identification and rapid antimicrobial susceptibility testing of bacteria from positive blood culture bottles by using MALDITOFMS and Phoenix rapid AST cards

Abstract number: O537

Adam T., Gröger C., Göbel U.

Objectives: Early and appropriate antimicrobial therapy critically determines the outcome of bloodstream infections. Rapid identification (ID) and antimicrobial susceptibility testing (AST) is, hence, mandatory to adjust empirical antimicrobial therapy instituted during the first two hours after onset of symptoms. To reduce the turnaround time (TAT) aliquots from positive blood culture bottles (BC) were subjected to differential centrifugation and gel separation using BD Vacutainer SST II tubes. The preparations were used for direct identification by MALDI-TOF mass spectrometry (MS). In addition, we are optimizing a protocol for rapid AST using the Phoenix BD system.

Methods: Blood cultures were drawn from septic patients and incubated using the Bactec BD blood culture device. In the rapid arm aliquots from consecutive positive BC bottles were processed for direct identification by Mass Spectrometry using the MALDI Biotyper (Bruker) system. Controls were processed according to standard procedures, inoculation of solid media and subsequent ID and AST using the MALDI Biotyper or the Vitek 2 system (bioMérieux), respectively. In case of discrepant ID results isolates were subjected to 16S rRNA gene sequencing..

Results: So far, we have tested 115 positive BCs. Direct MALDI TOF analysis resulted in 76 (66%) species identifications showing no discrepant results when compared with identification of colonies grown from these BCs. In 9 BCs more than 1 isolate could be grown on plates. Thus, in 73% of monoinfectious BCs MALDI TOF can reveal the etiologic agent in less than 1 h.

Conclusion: As compared to conventional procedures the combined use of MALDI-TOF MS and rapid AST may significantly reduce the TAT in diagnosis of blood stream infections..

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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