Introduction: Pakistan 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.
Methods: In this study, we examined 38 pneumococcal
isolates from pneumococcal diseased
(pneumonia/meningitis) patients bloo... More
Introduction: Pakistan 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.
Methods: In 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.
Results: Our 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.
Conclusion: Serotypes 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.