imited information is available on the outline of
invasive diseases caused by Streptococcus pneumoniae among the
underprivileged children in India. Estimation of Invasive Pneumococcal
Disease (IPD) and Pneumonia depends mainly on hospital-based clinical
surveillance data. Data on serotype prevalence and antimicrobial
resistance of IPD have been documented in some studies in India [1-4].
Due to national inaccessibility of a central surveillance system and
appropriate laboratory facilities, the estimate of the disease burden is
The challenges in the laboratory isolation of S.
pneumoniae include the scarcity of standard culture media and
improper sampling . In addition, its isolation by conventional
culture methods is often hindered by prior antibiotic intake .
Isolation of fastidious S. pneumoniae requires suitable culture
media enriched with sheep blood, but many laboratories use human blood –
that has passed its date of expiry – which does not support the growth
of pneumococci, leading to lower isolation rates. Minimum transportation
time for culture sample has a direct effect on the yield of the pathogen
in diseased conditions. Cerebro spinal fluid (CSF) and blood should be
transported to the laboratory preferably within 1-2 hours of drawing the
sample. Published reports state fewer than 10% of patients with clinical
diagnosis of pneumonia yield a positive blood culture [5,7,8].
Presence of more than 1000 colony forming units/mL of
the organism in a sample is required for a positive antigen detection
test such as latex agglutination or counter immune electrophoresis;
therefore such assays are of limited value in detecting pneumococci in
culture negative samples . In the current issue of Indian
Pediatrics, Nisarga, et al.  found that 56 culture
negative samples were positive for S. pneumoniae by polymerase
chain reaction (PCR) using lytA as target gene. Serotyping
information of these 56 PCR positive and culture negative samples would
have provided additional information. It should be noted that various
targets have been recommended for identification of pneumococci from
cultures isolates, but these have not been tested directly on culture
negative specimens . Amplification of lytA gene has been
evaluated and expected to be present in all the virulent isolates while
few studies have demonstrated the presence of lytA and ply
gene in members of the S. mitis group . Therefore, the
presence of these genes seems to be non-specific, and it cannot be
presumed that the other members of the S.mitis group do not
possess it or may have a facsimile of gene. Hence, lyt A and
ply-based PCR does not appear to be clinically useful and
should be used cautiously to eliminate false positives from blood and
fluid samples [10,11]. Among the culture positive specimens, only 11
were tested by PCR; of these six showed the presence of lytA
gene. It would have been desirable that all the culture positive
clinical samples were tested for lytA gene in this study.
Nucleic acid amplification tests such as PCR do not require viable
bacteria for a positive assay, and are generally considered to be highly
sensitive in comparison to culture. However, the presence of PCR
inhibitors in clinical specimens can compromise the sensitivity ,
and might explain the reason for five negative PCR among culture
positives in this study. In this study, 44 % isolates of S.
pneumoniae (16/36) were resistant to trimethoprim/sulfamethoxazole;
this number is quite less compared to 87% as reported in a recent
article from India . It is to be mentioned here that a study at
Christian Medical College and Hospital (CMC) in Vellore, India, has
documented the presence of serotypes 3, 6A, and 19A during 2007-2011
. Inclusion of molecular serotyping by sequential multiplex PCR in
addition to conventional antisera-based Quellung reaction would afford a
reliable and inexpensive way to serotype four isolates and 56 clinical
samples which could not be typed in this study. It is far most important
to know serotype of all S. pneumonaie strains for implementation
of pneumococcal conjugate vaccines, and to monitor circulating strains
to consider vaccine effectiveness and subsequent substitution of
This study over two years has rendered useful
information on the incidence, clinical spectrum and serogroups of IPD in
children. Pneumococcal meningitis still remains to be a serious problem
globally in spite of potent antibiotic usage and adjunct therapy. This
study can serve as a touchstone for successful surveillance in India
since further amelioration in therapy might be futile.
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surveillance of Streptococcus pneumoniae disease in India. Invasive
Bacterial Infection Surveillance (IBIS) Group, International Clinical
Epidemiology Network (INCLEN). Lancet. 1999;353:1216-21.
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Herrera G, Kilgore PE. Establishment of population-based surveillance
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