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Open AccessArticle

Prevalence of Various Vaccine Candidate Proteins in Clinical Isolates of Streptococcus pneumoniae: Characterization of the Novel Pht Fusion Proteins PhtA/B and PhtA/D

1
Department of Hygiene, Sapporo Medical University School of Medicine, Hokkaido, Sapporo 060-8556, Japan
2
Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Hokkaido, Sapporo 060-8556, Japan
*
Author to whom correspondence should be addressed.
Pathogens 2019, 8(4), 162; https://doi.org/10.3390/pathogens8040162
Received: 16 August 2019 / Revised: 9 September 2019 / Accepted: 23 September 2019 / Published: 24 September 2019
(This article belongs to the Section Human Pathogens)
Pneumococcal proteins unrelated to serotypes are considered to be candidates of antigens in next-generation vaccines. In the present study, the prevalence of vaccine candidate protein genes, along with serotypes and antimicrobial resistance determinants, was investigated in a total of 57 isolates obtained from a tertiary care hospital in Japan. All of the pediatric isolates and 76.6% of the adult isolates did not belong to PCV13 (a 13-valent pneumococcal conjugate vaccine) serotypes, and 70.2% of all isolates showed multidrug resistance. All of the isolates had ply, pavA, nanA, and nanB, and high prevalence was noted for the pspA and pspC genes (96.5% and 78.9%, respectively). Detection rates for the pneumococcal histidine triad protein (Pht) genes phtA, phtB, phtD, and phtE were 49.1%, 26.3%, 61.4%, and 100%, respectively. Two fusion-type genes, phtA/B and phtA/D, were identified, with a prevalence of 36.9% and 14.0%, respectively. These fusion types showed 78.1–90.0% nucleotide sequence identity with phtA, phtB, and phtD. The most prevalent pht profile was phtA + phtD + phtE (26.3%), followed by phtA/B + phtE (19.3%) and phtA/B + phtD + phtE (17.5%), while pht profiles including phtD and/or phtA/phtD were found in 71.9% of isolates. The present study revealed the presence of two fusion types of Pht and their unexpectedly high prevalence. These fusion types, as well as PhtA and PhtB, contained sequences similar to the B cell epitopes that have been previously reported for PhtD. View Full-Text
Keywords: Streptococcus pneumoniae; serotype; vaccine candidate proteins; pneumococcal histidine triad protein (Pht); Pht fusion proteins Streptococcus pneumoniae; serotype; vaccine candidate proteins; pneumococcal histidine triad protein (Pht); Pht fusion proteins
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Kawaguchiya, M.; Urushibara, N.; Aung, M.S.; Shinagawa, M.; Takahashi, S.; Kobayashi, N. Prevalence of Various Vaccine Candidate Proteins in Clinical Isolates of Streptococcus pneumoniae: Characterization of the Novel Pht Fusion Proteins PhtA/B and PhtA/D. Pathogens 2019, 8, 162.

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