Serotype distribution and genetic characteristics of invasive streptococcus pneumoniae in southern Vietnam between 2009-2017

Abstract

Streptococcus pneumoniae (S. pneumoniae) is the main etiologic agent of many life-threatening infections which result in significant mortality, particularly in children less than 5 years old. Although more than 95 pneumococcal serotypes were identified, little data on epidemiology of pneumococcal diseases is available in Vietnam. The aim of this study was to characterize invasive pneumococcal isolates from children in Southern Vietnam from 2009 to 2017 by both serotypes and sequence types (STs). Using multiplex polymerase chain reaction, 7 serogroups/types were determined among 34 isolates, with the most prevalent being 6A/B (41.2%), 19F (29.4%), 14 (14.7%), and 23F (5.9%). 8 isolates could not be characterized by multilocus sequencing typing (MLST), which might be due to an alteration in ddl gene. Among the remaining 26 isolates, 17 STs were found, accounting for 2 clonal groups and 13 singletons. The most common was ST 95 (15.4%). 6 new STs were discovered, 1 of which had 2 novel alleles and the other 5 had new combinations of known alleles. Comparison with the global S. pneumoniae MLST database revealed 15 clonal complexes and 2 singletons among 17 STs, the majority of which (69.2%) are related to international antibiotic resistant clones as well as their variants. In conclusion, a significant proportion of pneumococcal conjugate vaccine serotypes and international clones, as well as novel clones emerged from Vietnam, are responsible for invasive pneumococcal diseases among children in Southern Vietnam between 2009 – 2017. Keywords: Streptococcus pneumoniae, invasive pneumococcal disease, children, serotyping, MLST.