Assessing impact of MALDI mass spectroscopy on reducing directed antibiotic coverage time for Gram-negative organisms

The objective of this study was to assess whether use of matrix assisted laser desorption ionization-time of flight (MALDI-TOF), through improvements in identification time, reduces time to directed antibiotic coverage. We therefore conducted a retrospective review of 377 blood cultures from hospitalized patients with gram negative bacteremia that underwent testing by MALDI-TOF compared to standard identification methods (VITEK 2) for blood cultures from January 2016 to December 2017. We found that MALDI significantly reduced time between blood culture collection to reach pathogen identification and was associated with a significantly reduced time to initiate more specific therapy, with a mean difference of 16.37 hours, 95% CI 10.05 to 22.69 (mean time 50.34 hours (+/- 21.21) vs VITEK: 66.71 hrs (+/- 27.12), p</div

Frequencies of gram-negative pathogens among patient cultures (n = 377) and percentage of cultures per testing modality.

Frequencies of gram-negative pathogens among patient cultures (n = 377) and percentage of cultures per testing modality.</p

Time to empiric prescriptions and discontinuation of empiric therapy- MALDI vs. VITEK^*.

Time to empiric prescriptions and discontinuation of empiric therapy- MALDI vs. VITEK*.</p

Mean times gram stain verbal reporting, bacterial identification and antibiotic susceptibilities^*.

Mean times gram stain verbal reporting, bacterial identification and antibiotic susceptibilities*.</p

Secondary analyses for empiric prescription and discontinuation times across MALDI vs. VITEK–enterobacteriaceae vs. Non-fermenters^*; appropriateness of therapy changes.

Secondary analyses for empiric prescription and discontinuation times across MALDI vs. VITEK–enterobacteriaceae vs. Non-fermenters*; appropriateness of therapy changes.</p

Standard Timepoints For Study Collection, Screening Culture Eligibility based on Antibiotic Prescription and Discontinuation Dates.

(A) Based on Timepoint 0 as start point, we collected time elapsed from each subsequent date (Gram Stain Verbal Report, bacterial identification and antibiotic susceptibilities). (B) Cultures associated with ≥ 1 antibiotic prescription between date of bacterial identification and date of antibiotic susceptibilities were eligible for prescription analysis. As shown in B, culture had two associated antibiotics that met criteria (Antibiotic B and C). Only timeline for Antibiotic B would have been considered, since it had earliest start time. Subsequently, difference between start date for antibiotic B and date of blood culture collection will be calculated. (C) Cultures associated with ≥ 1 antibiotic prescription discontinued between “date of bacterial identification” and “72 hours post antibiotic susceptibility” were eligible for discontinuation time analysis. Here, antibiotics A and D would be ineligible, only antibiotic B and C met the criteria. We used earliest eligible antibiotic discontinued date (i.e., antibiotic B) and calculated difference between antibiotic B stop date with respect to date of blood culture collection.</p