Dataset Information

Optimization of matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis for bacterial identification.

ABSTRACT: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a relatively new addition to the clinical microbiology laboratory. The performance of the MALDI Biotyper system (Bruker Daltonics) was compared to those of phenotypic and genotypic identification methods for 690 routine and referred clinical isolates representing 102 genera and 225 unique species. We systematically compared direct-smear and extraction methods on a taxonomically diverse collection of isolates. The optimal score thresholds for bacterial identification were determined, and an approach to address multiple divergent results above these thresholds was evaluated. Analysis of identification scores revealed optimal species- and genus-level identification thresholds of 1.9 and 1.7, with 91.9% and 97.0% of isolates correctly identified to species and genus levels, respectively. Not surprisingly, routinely encountered isolates showed higher concordance than did uncommon isolates. The extraction method yielded higher scores than the direct-smear method for 78.3% of isolates. Incorrect species were reported in the top 10 results for 19.4% of isolates, and although there was no obvious cutoff to eliminate all of these ambiguities, a 10% score differential between the top match and additional species may be useful to limit the need for additional testing to reach single-species-level identifications.

SUBMITTER: Khot PD

PROVIDER: S-EPMC3502975 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Streptococcus suis, particularly S. suis serotype 2 (SS2), is an important zoonotic pathogen causing meningitis in humans worldwide. Although the proper classification of the causative and pathogenic serotype is salutary for the clinical diagnosis, cross-reactions leading to the indistinguishability of serotypes by the current serotyping methods are significant limitations. In the present study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of extracted peptides was developed to improve the classification of serotype of S. suis. The peptide mass fingerprint (PMFs) database of S. suis was generated from the whole-cell peptides of 32 reference strains of S. suis isolates obtained from pigs. Thirty-two human S. suis isolates from clinical cases in Thailand were used to validate this alternative serotyping method in direct comparison to the multiplex (m)PCR approach. All reference strains, representing 32 serotypes of S. suis, exhibited their individual PMFs patterns, thus allowing differentiation from one another. Highly pathogenic SS2 and SS14 were clearly differentiated from the otherwise serologically closely related SS1/2 and SS1, respectively. The developed MALDI-TOF-MS serotyping method correctly classified the serotype in 68.8% (22/32) of the same serotype isolates generated from the PMFs database; while the validity for the clinical human isolates was 62.5% (20/32). The agreement between the MALDI-TOF-MS and mPCR serotyping was moderate with a Kappa score of 0.522, considering that mPCR could correctly serotype up to 75%. The present study demonstrated that PMFs from the developed MALDI-TOF-MS-based method could successfully discriminate the previously indistinguishable highly pathogenic SS2 and SS14 from SS1/2 and SS1, respectively. Moreover, this serotyping method distinguished pathogenic SS6, and so is an alternative approach of choice to rapidly and reliably serotype clinically pathogenic S. suis isolates.

Dataset Information

Optimization of matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis for bacterial identification.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure