Usefulness of MALDI-TOF MS as a Diagnostic Tool for the Identification of Streptococcus Species Recovered from Clinical Specimens of Pigs

• Published in: PloS one 2017-01, Vol.12 (1), p.e0170784-e0170784
• Main Authors: Pérez-Sancho, Marta, Vela, Ana I, García-Seco, Teresa, González, Sergio, Domínguez, Lucas, Fernández-Garayzábal, Jose Francisco
• Format: Article
• Language: English
• Subjects: Animals; Bacterial Typing Techniques - instrumentation; Bacterial Typing Techniques - methods; Biology and Life Sciences; Desorption; Diagnostic software; Diagnostic systems; Diseases and pests; Genetic aspects; Genotype; Genotyping; Hogs; Identification and classification; Ions; Lasers; Mass spectrometry; Medical diagnosis; Medicine and Health Sciences; Physical Sciences; Physiological aspects; Pneumonia - diagnosis; Pneumonia - microbiology; Pneumonia - veterinary; Research and Analysis Methods; RNA, Ribosomal, 16S - genetics; Sensitivity and Specificity; Sepsis - diagnosis; Sepsis - microbiology; Sepsis - veterinary; Septicemia; Sequence Analysis, DNA; Species; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Streptococcal Infections - diagnosis; Streptococcal Infections - microbiology; Streptococcal Infections - veterinary; Streptococcus; Streptococcus - classification; Streptococcus - genetics; Streptococcus - isolation & purification; Streptococcus infections; Streptococcus suis; Suidae; Swine; Swine Diseases - diagnosis; Swine Diseases - microbiology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0170784

The application of MALDI-TOF MS for identifying streptococcal isolates recovered from clinical specimens of diseased pigs was evaluated. For this proposal, the MALDI BDAL Database (Bruker Daltoniks, Germany) was supplemented with the main spectrum profiles (MSP) of the reference strains of S. porci, S. porcorum and S. plurextorum associated with pneumonia and septicemia. Although these three species showed similar MALDI profiles, several peaks were recognized that can be useful for their differentiation: S. porci (4113, 6133, 7975 and 8228 m/z Da), S. plurextorum (3979, 4078, 4665, 6164, 6491, 6812, 7959 and 9330 m/z Da) and S. porcorum (3385, 3954, 4190, 6772, 7908, and 8381 m/z Da). After adding these MSPs, an evaluation was conducted to determine the accuracy of MALDI-TOF MS for the identification of streptococci from diseased pigs using 74 field isolates. Isolates were identified as S. suis, S. porcinus, S. dysgalactiae, S. hyovaginalis, S. porcorum, S. alactolyticus, S. hyointestinalis and S. orisratti. This is the first time that the latter three species have been reported from clinical specimens of pigs. Overall, there was good concordance (95.9%) between the results obtained from MALDI-TOF MS identification (best hint) and those from genotyping. Our results demonstrate the good performance of MALDI-TOF MS (100% sensitivity and specificity) for identifying most of the species of streptococci that can frequently be isolated from diseased pigs. However, conflicting results were observed in the correct identification of some isolates of S. dysgalactiae and S. alactolyticus.