234. Clinical Impact of Provider Notification of Positive Blood Culture Results:  Use of MALDI-TOF MS for Gram-Negative Bacilli Speciation Directly from Blood Culture Bottles
Session: Poster Abstract Session: Diagnostic Microbiology
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Background:

Matrix-Assisted Laser Desorption Ionization – Time of Flight (MALDI-TOF) mass spectrometry (MS) has shown promise in reducing time to identification of organisms grown in blood cultures (BC) which currently requires 24-48 hours. We performed a provider notification study following MALDI-TOF identification of Gram-negative bacilli (GNB) in positive BC.

Methods:

Case patients were identified prospectively via monitoring BC positive for GNB.  BC fluid from charcoal-containing bottles was processed for MALDI-TOF identification.  The Infectious Disease consultant was notified of the genus (and species if available) of the isolate.  After discharge, cases were evaluated for time to administration of effective antibiotic therapy and outcomes.  Controls were identified retrospectively and matched for pathogen and whether initial antibiotic therapy was ineffective and changed to effective therapy at the time of final susceptibility reporting.

Results:

Fifty-three case patients were included in the study.  The MALDI-TOF results correlated 100% of the time with the final standard phenotype results.  The Infectious Disease consultant modified the antibiotic regimen from ineffective to effective antibiotics based on the MALDI-TOF results in 5 (9.4%) of the case patients.  Sixteen historical control patients were identified with 10 matched for species and 6 matched for Enterobacteriaceae.  One anaerobe could not be matched.  The mean time to administration of effective antibiotic therapy between cases (31.2±9.5 hours) and controls (63.9±25.8 hours) was statistically significant (p<0.0001).  The CWIC values were not significant between the two groups (2.20±1.64 vs 2.25±1.57).  There was no difference in mortality or discharge location between the two groups.

Conclusion:

MALDI-TOF demonstrates a rapid and effective method for genus and species identification of Gram-negative pathogens directly from blood culture bottles containing charcoal.  While only a few cases benefited from a change to effective antibiotic management, the time to that change was highly significant.  Due to our small numbers, the impact on outcomes was limited.  Larger additional studies will be needed to demonstrate the clinical benefit of this powerful and cost-effective device.

Mona Al Fares, MD1, Kathleen Riederer, BS, MT2, Susan Szpunar, PhD2, Kristian Cruz, BS2 and Joel Fishbain, MD3, (1)Infectious Diseases, St John Hospital and Medical Center, Grosse Pointe Woods, MI, (2)Graduate Medical Education, St. John Hospital and Medical Center, Grosse Pointe Woods, MI, (3)Infectious Diseases, St. John Hospital and Medical Center, Grosse Pointe Woods, MI

Disclosures:

M. Al Fares, None

K. Riederer, None

S. Szpunar, None

K. Cruz, None

J. Fishbain, None

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