Cost-Effectiveness of Switch to Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Routine Bacterial Identification

Abstract

ᰔMatrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) allows instant identification of microorganisms by analyzing their total protein content (1-3). In September 2009, we switched from conventional biochemical techniques (mainly Vitek 2 and API strips) to MS (Microflex; Bruker Daltonics, Wissembourg, France) for routine identification of all bacterial isolates except for mycobacteria and mycoplasma. Conventional tests were only kept in case of equipment failure or maintenance (10 days per year) and for diagnosis of Streptococcus pneumoniae, beta-hemolytic streptococci, and Shigella spp., thus entailing a limited stock of identification reagents. After 18 months, we evaluated the benefits in turnaround time and cost in our 3,046-bed acute care university hospital.Our flow chart was as follows: for each isolate, a portion of 1 to 5 colonies were submitted to MS without protein extraction; if the identification score was not acceptable (Ͻ2.0), another round of MS was performed, allowing identification in 97.6% of cases. The accuracy of identification was similar to that reported in the literature (1-4). In our 18-month experience, an average of 3.4 MS tests, each costing $0.12, were required in order to identify one isolate, i.e., with an identification score of Ն2.0, resulting in $0.41 per bacterial identification at the time of study. When MS identification failed, a relevant housekeeping gene sequence (e.g., rrs, recA, sodA, or rpoB) was analyzed (83 isolates a year, compared to 138 in the pre-MS period; P Ͻ 0.05).Changes in time to results and workflow were evaluated first. Although the setup times were identical for MS and biochemical techniques, the time to identification was significantly lower with MS, as 93% and 10% of isolates, respectively, were identified within 24 h after inoculation. Early identification allowed us to select appropriate antibiotics to be tested against clinically significant isolates. Subcultures performed in order to achieve a proper inoculum for conventional techniques were drastically cut after MS was implemented, resulting in technical time and culture medium savings. However, time to susceptibility testing results was not reduced, and implementing MS did not allow us to significantly cut down technical staff. Assessable costs were compared over identical 1-year periods, before and after MS implementation. The overall savings were at least $177,090. MS identifications of 38,624 isolates between October 2009 and September 2010 cost $15,836, and conventional identification of 960 remaining isolates over the same period cost $5,374 (total, $21,210). The year before, a total of $193,754 had been spent for 33,320 isolates identified by Vitek 2 cards and API strips (mean unitary cost, $5.81). In addition, waste disposal decreased from 1,424 kg (cards, pipettes, and suspension media) to 44 kg (MS target cleansing solution and pipette tips), saving $1,794. Other assessable savings resulted from a $1,102 cut in subculture medium expenses and a $1,650...

The Genus Corynebacterium and Other Medically Relevant Coryneform-Like Bacteria

“…Matrixassisted laser desorption ionization-time of flight (MALDI-TOF) analysis is rapidly becoming a routinely used tool in many microbiology laboratories, whereby proteins liberated from bacteria are ionized and detected by a mass spectrometer (MS), the spectrum is analyzed, and its pattern is compared to entries found in a database, giving rise to a degree of match (1,29). This technology is touted as being revolutionary, because it does not require extensive training or expertise in MS or chemistry to use and the cost for consumables is described as less than US$0.50 per sample, excluding the cost of the MALDI-TOF instrument (21). Protein fingerprints are deemed to provide identification to genus and species with an accuracy which approaches that of genetic methods (1,29).…”

A commentary on the role of molecular technology and automation in clinical diagnostics

“…26 Further, MALDI-TOF is both cost and environmentally effective when compared with conventional microbiology. Gaillot et al 27 demonstrated 89.3% cost savings in the first year of MALDI-TOF use, whereby cost per isolate decreased from $5.80 to $0.50 and waste reduced from >1400 kg to <50 kg, in addition to lesser need for DNA and/or RNA sequencing and, overall, significantly enhanced time to bacterial identification. At the time of writing, microbiological testing at UHL was predominantly based on the bioMérieux ® ARIS system costing approximately €3.50 per identification, and with ca.…”

The Ongoing Revolution of MALDI-TOF Mass Spectrometry for Microbiology Reaches Tropical Africa

“…16 Most of these misidentifications can be attributed to an incomplete population of databases associated with the instrument. 1,7,18,21,22 For instance, it has recently been reported that improvements to the database enable a more reliable distinction between S. pneumoniae and viridans group streptococci. 23,24 Because the reference databases are not static and expanded regularly to fill in current gaps in identification, updates will continue to improve the performance of MALDI-TOF MS. 18 To the best of our knowledge, this study represents the first implementation and use of MALDI-TOF MS for the identification of bacteria and fungi in a hospital in tropical Africa.…”

“…1,6 Overall, it has been clearly shown that MALDI-TOF MS is less expensive than traditional methods, even when taking into account the costs of reagents, labor, performance measurements, waste disposal, microorganism prevalence, and instrument maintenance expenses as well as multiple runs and additional tests needed to maximize accuracy. 6,18,21,22 Moreover, several studies have shown the clinical benefits of using MALDI-TOF MS. This technique can provide microorganism identification up to 30 hours faster than conventional phenotypic methods; such gains in the speed of identification can have a substantial impact on patient care and management.…”