Assessment of matrix-assisted laser desorption ionization-time of flight mass spectrometry for identification and biotyping of the pathogenic oomycete Pythium insidiosum

Abstract

MALDI-TOF MS has been successfully used for identification and biotyping of P. insidiosum. The obtained mass spectral database allows clinical microbiology laboratories, well-equipped with a MALDI-TOF mass spectrometer, to conveniently identify P. insidiosum, without requiring any pathogen-specific reagents (i.e., antigen, antibody or primers).

New insights on evolutionary aspects of Pythium insidiosum and other peronosporaleans

“…53 It is thus important to evaluate the spectra of each of the different phylogenetic clusters for an accurate identification of the P insidiosum complex. [53][54][55] Even so, the paraphyletic status of P insidiosum Thai isolates in relation to American ones support the scenario in which American isolates or species derive from Asian ones. 12 In this case, it seems plausible that the Great American Interchange played a role in the geodispersal of P insidiosum about 3-2.6 Mya.…”

“…and Phytopythium litorale , respectively . It is thus important to evaluate the spectra of each of the different phylogenetic clusters for an accurate identification of the P insidiosum complex …”

An accurate identification of Pythium insidiosum complex using MALDI-TOF, requires representative spectra of each of its four phylogenetic clusters

“…It is important to mention that two papers using the MALDI-TOF approach to identify P. insidiosum from clinical samples, missed by Bernheim et al (2019), appeared in the last two years (Krajaejun et al, 2018;Mani et al, 2019). These papers highlighted the importance of MALDI-TOF in the identification of submerged filamentous colonies from cases of superficial or systemic suspected pythiosis infections in humans and animals.…”

“…These papers highlighted the importance of MALDI-TOF in the identification of submerged filamentous colonies from cases of superficial or systemic suspected pythiosis infections in humans and animals. Oddly, one of the two research papers appeared in IJID, 2018 Vol 77, pages 61-67 (Krajaejun et al, 2018).…”

“…These investigators, using MALDI-TOF, tested 52 P. insidiosum isolates from all over the world and concluded that for an accurate identification of P. insidiosum complex, MALDI-TOF should include the spectra of each of the different phylogenetic clusters reported earlier by Schurko et al (2003). Krajaejun et al (2018) (see above) concluded also that the inclusion of at least a member of each of the phylogenetic clusters is of fundamental importance for an accurate identification of P. insidiosum complex. Thus, Bernheim et al (2019) was not the first report suggesting this approach for the identification of P. insidiosum and, based on early findings (Krajaejun et al, 2018;Mani et al, 2019), a spectrum generated from a single P. insidiosum isolate would likely generate a large number of false negatives.…”