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Identification of clinical Streptococcus pneumoniae isolates among other alpha and nonhemolytic streptococci by use of the Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry system.

ABSTRACT: Discrimination between Streptococcus pneumoniae and its close relatives of the viridans group is a common difficulty in matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry-based identification. In the present study, the performances of the Vitek MS MALDI-TOF mass spectrometry system were assessed using 334 pneumococci, 166 other S. mitis group streptococci, 184 non-S. mitis group streptococci, and 19 related alpha- and nonhemolytic aerobic Gram-positive catalase-negative coccal isolates. Pneumococci had been identified by means of optochin susceptibility and bile solubility or serotyping, and other isolates mainly by use of RapidID32 Strep strips. In case of discordant or low-discrimination results, genotypic methods were used. The sensitivity of the Vitek MS for the identification of S. pneumoniae was 99.1%, since only three bile-insoluble isolates were misidentified as Streptococcus mitis/Streptococcus oralis. Conversely, two optochin-resistant pneumococci were correctly identified (specificity, 100%). Three Streptococcus pseudopneumoniae isolates were also correctly identified. Among nonpneumococcal isolates, 90.8% (n = 335) were correctly identified to the species or subspecies level and 2.4% (n = 9) at the group level. For the remaining 25 isolates, the Vitek MS proposed a bacterial species included in the list of possible species suggested by genotypic methods, except for 4 isolates which were not identified due to the absence of the species in the database. According to our study, the Vitek MS displays performance similar to that of the optochin susceptibility test for routine identification of pneumococcal isolates. Moreover, the Vitek MS is efficient for the identification of other viridans group streptococci and related isolates, provided that the species are included in the database.

SUBMITTER: Dubois D

PROVIDER: S-EPMC3716079 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Identification of clinical Streptococcus pneumoniae isolates among other alpha and nonhemolytic streptococci by use of the Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry system.

Dubois Damien D Segonds Christine C Prere Marie-Françoise MF Marty Nicole N Oswald Eric E

Journal of clinical microbiology 20130410 6

Discrimination between Streptococcus pneumoniae and its close relatives of the viridans group is a common difficulty in matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry-based identification. In the present study, the performances of the Vitek MS MALDI-TOF mass spectrometry system were assessed using 334 pneumococci, 166 other S. mitis group streptococci, 184 non-S. mitis group streptococci, and 19 related alpha- and nonhemolytic aerobic Gram-positive catal ...[more]

PMID: 23576536

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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 clinical Streptococcus pneumoniae isolates among other alpha and nonhemolytic streptococci by use of the Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry system.

Publications

Identification of clinical Streptococcus pneumoniae isolates among other alpha and nonhemolytic streptococci by use of the Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry system.

Similar Datasets

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