Cheap and rapid in-house method for direct identification of positive blood cultures by MALDI-TOF MS technology

Abstract

BackgroundRapid and accurate pathogen identification in blood cultures is very important for septic patients and has major consequences on morbidity and mortality rates. In recent years, matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS)-based technology has become useful for highly specific and sensitive identification of bacteria and yeasts from clinical samples including sterile body fluids. Additional in-house methods enabled direct identification from blood cultures following various preparation protocols.MethodsBlood culture (5 ml) was harvested from each positive bottle following growth identification by BACTEC™ FX system and transferred into a VACUETTE® Z Serum Sep Clot Activator tube containing an inert gel, which following centrifugation separates microorganisms from the blood cells. We used MALDI-TOF MS analysis for identification of microorganisms collected from the gel surface.ResultsPositive blood culture bottles (186) were collected. In comparison with the routine method, 99% (184/186) and 90% (168/186) of the isolates were correctly identified by the SepsiTyper kit and the in-house method, respectively. We found high concordance (Pearson coefficient = 0.7, p < 0.0001) between our in-house method and the SepsiTyper kit. Additionally, high correlation was found in sub-groups of identified bacteria, with Pearson coefficients of 0.77 (p < 0.0001), 0.67 (p < 0.0001), and 0.73 (p < 0.007) for Gram negative, Gram positive, and anaerobic bacteria, respectively.ConclusionsOur in-house method was found to be in good agreement with the SepsiTyper kit. Considering the low costs and the rapid and easy implementation of this procedure, we propose our in-house method for the direct identification of bacteria from blood cultures.

Rapid direct identification of positive paediatric blood cultures by MALDI-TOF MS technology and its clinical impact in the paediatric hospital setting

“…Whilst identification had high accuracy for Gram negative bacteria as well as S. aureus and Enterococcus spp., the method performed less well for other Gram positive organisms and yeasts, consistent with other direct MALDI-TOF MS methodologies [3,[14][15][16]. The thicker cell walls and spore-forming nature of bacilli [8,[12][13][14][15][16] and the more complex processing required to disrupt yeast cell walls [19] are likely contributors. Some studies, using more complicated and costly extraction procedures, have reported slightly higher success rates for Gram positive organisms [17,18].…”

“…The technique was inexpensive, and identification results could be obtained within 15 min of the blood culture flagging positive. Results of the in-house method were highly consistent with single colony identification for Gram-negative organisms to species and genus level (up to 99%), outperforming comparable methods in the literature which reported < 90% concordance [3,[12][13][14][15][16].…”

Rapid direct identification of positive paediatric blood cultures by MALDI-TOF MS technology and its clinical impact in the paediatric hospital setting.

“…Whilst identification had high accuracy for Gram negative bacteria as well as S. aureus and Enterococcus spp., the method performed less well for other Gram positive organisms and yeasts, consistent with other direct MALDI-TOF MS methodologies [3,[14][15][16]. The thicker cell walls and sporeforming nature of bacilli [8,12,[13][14][15][16] and the more complex processing required to disrupt yeast cell walls [19] are likely contributors. Some studies, using more complicated and costly extraction procedures, have reported slightly higher success rates for Gram positive organisms [17][18].…”

“…Results of the in-house method were highly consistent with single colony identification for Gramnegative organisms to species and genus level (up to 99%), outperforming comparable methods in the literature which reported <90% concordance [3,[12][13][14][15][16].…”

Application Of The Maldi-Tof Ms Technique For Identification Of Dermatophytes

“…Szerokie zainteresowanie tą metodą wynika z jej wysokiej dokładności, szybkości uzyskiwania wyników identyfikacji mikroorganizmów, stosunkowo niskiego kosztu analiz i prostej implementacji do laboratoriów diagnostycznych [15,49]. Niemniej jednak w literaturze naukowej dostępnych jest tylko kilka doniesień oceniających zastosowanie MALDI-TOF MS do identyfikacji dermatofitów [5,10,23,32,40,49,50] Celem niniejszej pracy jest dokonanie przeglądu piśmiennictwa traktującego o zastosowaniu techniki MALDI-TOF MS w diagnostyce dermatomykoz, ze szczególnym uwzględnieniem identyfikacji dermatofitów. Ponadto, w niniejszej pracy opisane są zalety i ograniczenia tej techniki w implementacji do rutynowego stosowania w laboratoriach mykologicznych.…”