Genetic diversity of Streptococcus pneumoniae causing meningitis and sepsis in Singapore during the first year of PCV7 implementation

Abstract

Streptococcus pneumoniae is a major cause of sepsis, meningitis and respiratory disease worldwide. Pneumococcal conjugate vaccines (PCVs) have now been implemented in many countries worldwide, including Singapore. To evaluate the effectiveness of these vaccines, pneumococcal surveillance studies are required. Detailed and unified pneumococcal epidemiology data are currently scarce in South East Asia. Thus, we present data on invasive pneumococcal (IPD) isolates from Singapore that could assist in evaluating the effectiveness of pneumococcal vaccine in Singapore. One hundred and fifty-nine invasive pneumococcal disease isolates were received by the National Public Health Laboratory in Singapore between June 2009 and August 2010. Isolates were characterized using serotyping and multilocus sequence typing. Twenty-four different serotypes were found, the most common of which were 19A, 3, 7F, 23F, 6B, 14, 8 and 19F (in rank order). One hundred and two sequence types were observed, of which 38 were novel due to new alleles or new combinations of already existing alleles. Based on the Simpson's Index of Diversity, serotypes 3, 6B and 19A were the most genetically diverse. Novel sequence types were more prevalent among conjugate vaccine serotypes 3, 19F and 23F and non-conjugate vaccine serotype 8, serogroup 15 and in non-typable isolates. We have demonstrated considerable genetic diversity among invasive pneumococci before and during the widespread use of conjugate vaccines in Singapore. Approximately half of all novel IPD clones identified in this study were non-conjugate vaccine serotypes. Although PCVs would target the most common serotypes, the high genetic diversity in non-vaccine serotypes would require further surveillance studies.

Molecular epidemiology of pneumococcal isolates from children in China

“… 25 The PCV7 coverage rate against invasive strains (62.7%) reported in this study is also similar to those of some Asian countries, such as Denmark and Singapore <65%). 26 - 28 However, this figure is lower than those observed in the United States (87%), 29 Canada, Europe (78-94%), 30 and Spain (72.3%). 31 Some researchers explained that the low percentage of PCV7-related serotypes may be due to the herd immunity effect, as reported in the United States, 32 and United Kingdom.…”

“… 33 However, unlike the situation of high vaccine inoculation rate of PCV7 in the United States and United Kingdom, the prevalence of pneumococcal strains reflects the real circulating pneumococcal strains in Chongqing since the vaccine inoculation rate is only 4.4% in this region, which is quite the same as that in Singapore. 26 The PCV13 extends the serotype coverage, and serotypes 19F, 14, 6A, 6B, 23F, 18C, 9V, 4, 1, 5, 7F, 3, and 19A were included. The present finding showed that this vaccine could cover 94.1% (48/51) of the invasive isolates, and hence indicates the potential value of PCV13 in protecting pneumococcal infections in China, specifically in Chongqing city.…”

Immunization, Antibiotic Use, and Pneumococcal Colonization Over a 15-Year Period

“…28,29 Next we observed rapid reductions in certain additional PCV13 serotypes ∼3 years after introduction of PCV13, although, notably, serotypes 19A and 3 continued to be present at low rates in 2014. Possible reasons for the persistence of 19A and 3 include genetic diversity leading to less effective immune responses 22,30,31 or selection pressure from recent antibiotic use. 32 -34 Of note, first-line penicillins continue to be the most frequently prescribed antibiotic across all age groups among young children in Massachusetts, which may result in the continued success of 19A associated with penicillin resistance.…”

Serotypes & penicillin susceptibility of Streptococcus pneumoniae isolated from children admitted to a tertiary teaching hospital in Malaysia

“…Differential ability of the serotypes to cause invasive diseases is dependent on the chemical structure of the capsular polysaccharides and rarely the thickness of the capsules 1 . Serotypes that are associated with invasive pneumococcal diseases (IPD) among children, such as 19A, 3, 7F, 23F, 11, 6A, 6B, 14, 8, 18C and 19F have been described previously 4 5 6 . Among these common serotypes in children, serotypes 19A, 3, 7F, 23F, 14 and 8 were also present in adults 5 6 .…”