Usefulness of matrix-assisted laser desorption ionization time-of-flight mass spectrometry to identify pathogens, including polymicrobial samples, directly from blood culture broths

Abstract

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (TOF-MS) is now widely used to detect pathogens in clinical settings in Japan. Here, we report the ability of TOF-MS to detect bacteria from blood culture (BC) broths, and compare the efficacy of TOF-MS to that of conventional culture methods. Bacteria were correctly detected from 63 monomicrobial samples within 80 minutes; results matched those obtained by conventional BC methods, although the conventional methods took 2–3 days. In addition to the 63 monomicrobial samples, another three polymicrobial samples were tested; notably, the infecting bacteria were not correctly identified in two of these three samples. To better assess the TOF-MS detection of polymicrobial samples, we tested various ratios of mixed broth samples, including combinations of the bacteria that we were unable to detect in clinical samples. Combinations of Enterobacter cloacae and Pseudomonas aeruginosa were correctly detected at a culture ratio of 2:1, but not in the 3:1 mixture. These results suggested that TOF-MS is a strong tool for the rapid and correct detection of pathogens from monomicrobial BC samples, though results need to be carefully checked when handling known or suspected polymicrobial samples.

Evaluation of blood culture broths with lysis buffer to directly identify specific pathogens by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry methods

“…For this comparison of MALDI-TOF MS results with those obtained by routine techniques from clinical samples, E. coli was the one detected most frequently. 6 …”

“… 12 , 13 For example, monomicrobial BCs with Streptococcus oralis/mitis that were misidentified as S. pneumoniae , similar to our study. 6 However, TOF-MS could detect the pathogens immediately at least at the genus levels, and finally contribute to early administration of antibiotics, survival of the patients, and cost-effectiveness. Therefore, we should use TOF-MS with caution, especially in sepsis with community-acquired pneumonia cases because S. pneumoniae and H. influenzae were representative pathogens of community-acquired pneumonia.…”

“…Direct identification of bacteria by MALDI-TOF MS from both positive aerobic and anaerobic bottles (Bruker Daltonics, Bremen, Germany) was performed serially in parallel with the routine protocol at the clinical laboratory of Tohoku Medical and Pharmaceutical University Hospital; these tests were performed from July 2014 to December 2017. 3 , 6 After subculturing on agar plates, any positive BC was simultaneously assessed for bacterial identification using conventional procedures, including MicroScan Walkaway panels (Beckman Coulter, Jersey City, NJ, USA), and, if necessary, complementary individual biochemical or enzymatic tests. We performed each experiment 5–10 times.…”

<p>Evaluation of agar culture plates to efficiently identify small colony variants of methicillin-resistant <em>Staphylococcus aureus</em></p>

“…The identification of bacteria by MALDI-TOF MS also was performed serially in parallel with the phenotypic characterization described above. The MALDI-TOF MS was performed at the clinical laboratory of Tohoku Medical and Pharmaceutical University Hospital according to a standard protocol and using Bruker Daltonics equipment (Bremen, Germany) 10,11. The positive colonies were simultaneously assessed for bacterial identification using conventional procedures, including MicroScan Walkaway panels (Beckman Coulter, Jersey City, NJ, USA), and complementary individual biochemical or enzymatic tests.…”

Surface-Enhanced Raman Scattering (SERS) in Microbiology: Illumination and Enhancement of the Microbial World

“…These integrated analyses play a central role in understanding complex biochemical and biological mechanisms to facilitate comprehensive identification, discrimination and more interestingly, functional analysis of microbes. [16][17][18] To achieve this challenging task, many researchers have successfully demonstrated the application of various analytical platforms, including molecular techniques, 17 matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, 19,20 and whole-organism metabolic fingerprinting techniques, 21 for extensive microbial analysis. Here, we discuss the technological advancements, limitations, and current and potential future applications of vibrational spectroscopy, with particular emphasis on surface-enhanced Raman scattering (SERS), as a global biochemical fingerprinting technique to complement existing knowledge in microbial characterization.…”