Capsule Typing of Haemophilus influenzae by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

• Published in: Emerging infectious diseases Vol. 24; no. 3; pp. 443 - 452
• Main Authors: Månsson, Viktor, Gilsdorf, Janet R, Kahlmeter, Gunnar, Kilian, Mogens, Kroll, J Simon, Riesbeck, Kristian, Resman, Fredrik
• Format: Journal Article
• Language: English
• Published: United States U.S. National Center for Infectious Diseases 01.03.2018; Centers for Disease Control and Prevention
• Subjects: Analysis; bacteria; bacterial capsules; Bacterial Capsules - genetics; bacterial typing; Bacterial Typing Techniques; Basic Medicine; Biological markers; capsule typing; Clinical Medicine; Evolution, Molecular; Genetic Linkage; Haemophilus Infections - microbiology; Haemophilus influenzae; Haemophilus influenzae - classification; Haemophilus influenzae - genetics; Infectious Medicine; Infektionsmedicin; Klinisk medicin; Mass spectrometry; Medical and Health Sciences; Medicin och hälsovetenskap; Medicinska och farmaceutiska grundvetenskaper; Methods; Microbiology in the medical area; Mikrobiologi inom det medicinska området; Multilocus Sequence Typing; Polymerase Chain Reaction; Reproducibility of Results; Sensitivity and Specificity; serotyping; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; epidemiology; serotyping; Sweden; bacterial capsules; bacteria; vaccines; capsule typing; MALDI-TOF mass spectrometry; matrix-assisted laser desorption/ionization mass spectrometry; Haemophilus influenzae; respiratory infections; bacterial typing
• ISSN: 1080-6040; 1080-6059
• DOI: 10.3201/eid2403.170459

Encapsulated Haemophilus influenzae strains belong to type-specific genetic lineages. Reliable capsule typing requires PCR, but a more efficient method would be useful. We evaluated capsule typing by using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Isolates of all capsule types (a-f and nontypeable; n = 258) and isogenic capsule transformants (types a-d) were investigated. Principal component and biomarker analyses of mass spectra showed clustering, and mass peaks correlated with capsule type-specific genetic lineages. We used 31 selected isolates to construct a capsule typing database. Validation with the remaining isolates (n = 227) showed 100% sensitivity and 92.2% specificity for encapsulated strains (a-f; n = 61). Blinded validation of a supplemented database (n = 50) using clinical isolates (n = 126) showed 100% sensitivity and 100% specificity for encapsulated strains (b, e, and f; n = 28). MALDI-TOF mass spectrometry is an accurate method for capsule typing of H. influenzae.