Molecular Characterization of Pneumococcal Surface Protein A (PspA), Serotype Distribution and Antibiotic Susceptibility of Streptococcus pneumoniae Strains Isolated from Pakistan

Abstract

IntroductionPakistan has one of the highest burdens of pneumococcal diseases in the world, but unfortunately studies in this demanding research area are limited in the region. Pneumococcal surface protein A (PspA) is the next generation pneumococcal vaccine candidate as the protein locates on the Streptococcus pneumoniae surface. Its gene, pspA, might be encoded by all pneumococci, and the protein has proven immunogenicity. The molecular characterization of PspA, pneumococcal serotype distribution and antibiotic susceptibility are important for regional diversity studies.MethodsIn this study, we examined 38 pneumococcal isolates from pneumococcal diseased (pneumonia/meningitis) patients blood or cerebrospinal fluid. There were no specific inclusion or exclusion criteria, but all the individuals [ages 1 month to 12 years (male/female)] had undergone no antibiotic treatment in at least the past 3 months and had no vaccination history. We investigated the serotype distribution, antibiotic susceptibility, prevalence of the PspA family and its active domain's fusion, expression and antigenicity.ResultsOur finding shows that serotype 19F is the most prevalent (23.6%) followed by 18B (15.78%) (non-vaccine type) in all isolated pneumococcal strains. All strains were susceptible to chloramphenicol and linezolid, while 80% were resistant to gentamycin. Genotyping revealed that ~ 80% (N = 31/38) of pneumococcal strains produce PspA belonging to family 2 and clade 3. We further selected three active domains of PspA (family 2 and clade 3) by in silico analysis, merged together into a fusion gene for expression study, and its antigenicity was analyzed by Western blotting.ConclusionSerotypes 19F and 18B (non-vaccine type) are the most prevalent in the Pakistani pneumococcal isolates. The PspA family 2 proteins produced by Pakistani pneumococcal isolates have high sequence homologies with each other and differ from those produced by strains isolated in the rest of the world. The PspA fusion peptide had a proven antigenic response in western blotting, with no considerable correlation among pneumococcal serotypes, antibiotic susceptibility and PspA family/clade distribution.Electronic supplementary materialThe online version of this article (10.1007/s40121-018-0195-0) contains supplementary material, which is available to authorized users.

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“…They both demonstrated safety ( 354 ), but PspA antigen’s immunogenicity was low ( 355 ) whereas the inactivated pneumolysin was found to be immunogenic and effective in eliciting protective immune response ( 356 ). PspA is considered an ideal protein candidate because reports indicate that PspA family 2 is commonly found in S. pneumoniae strains ( 357 ). For example, in Pakistan most strains of pneumococci have PspA genes ( 357 ).…”

“…PspA is considered an ideal protein candidate because reports indicate that PspA family 2 is commonly found in S. pneumoniae strains ( 357 ). For example, in Pakistan most strains of pneumococci have PspA genes ( 357 ). These protein vaccines can provide an extra preventative method once developed and will require thorough analysis of regulation and what regulatory issues may be faced ( 358 ).…”