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Identification of Weissella species by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

ABSTRACT: Although some Weissella species play beneficial roles in food fermentation and in probiotic products, others such as Weissella confusa are emerging Gram-positive pathogens in immunocompromised hosts. Weissella species are difficult to identify by conventional biochemical methods and commercial automated systems and are easily misidentified as Lactobacillus and Leuconostoc species. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is increasingly being used for bacterial identification. Little, however, is known about the effectiveness of MALDI-TOF MS in identifying clinical isolates of Weissella to the species level. In this study, we evaluated whether the MALDI-TOF MS Bruker Biotyper system could accurately identify a total of 20 W. confusa and 2 W. cibaria blood isolates that had been confirmed by 16s rRNA sequencing analysis. The MALDI-TOF Biotyper system yielded no reliable identification results based on the current reference spectra for the two species (all score values <1.7). New W. confusa spectra were created by randomly selecting 3 W. confusa isolates and external validation was performed by testing the remaining 17 W. confusa isolates using the new spectra. The new main spectra projection (MSP) yielded reliable score values of >2 for all isolates with the exception of one (score value, 1.963). Our results showed that the MSPs in the current database are not sufficient for correctly identifying W. confusa or W. cibaria. Further studies including more Weissella isolates are warranted to further validate the performance of MALDI-TOF in identifying Weissella species.

SUBMITTER: Lee MR

PROVIDER: S-EPMC4633522 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Identification of Weissella species by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Lee Meng-Rui MR Tsai Chia-Jung CJ Teng Shih-Hua SH Hsueh Po-Ren PR

Frontiers in microbiology 20151105

Although some Weissella species play beneficial roles in food fermentation and in probiotic products, others such as Weissella confusa are emerging Gram-positive pathogens in immunocompromised hosts. Weissella species are difficult to identify by conventional biochemical methods and commercial automated systems and are easily misidentified as Lactobacillus and Leuconostoc species. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is increasingly being us ...[more]

PMID: 26594208

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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

Identification of Weissella species by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Publications

Identification of Weissella species by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

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