Researchers Identify Pneumonia Strain’s Lineage

Streptococcus pneumoniae is a bacterial pathogen that causes many diseases, including pneumonia, meningitis, and septicemia. Though vaccines are already available for the most dominant serotypes, or “strains,” the bacterium retains the ability to transform its structure and increase its resistance to common antibiotics.

As the arms race against mutating bacteria increases, research efforts amplify to attempt identification and protection strategies against novel S. pneumoniae serotypes. In their recent work published in Lancet Microbe, researchers in France tackled one subtype called GPSC10.

Since 2000, several pneumococcal conjugate vaccines (PCVs) have been released that target S. pneumoniae serotypes. However, there are still more than 100 strains that affect both children and adults that remain to be fully understood. To address these needs, researchers have been working on the Global Pneumococcal Sequencing (GPS) project since 2011 to create a clearer picture of S. pneumoniae serotypes worldwide.

One specific serotype, 24F, has been of increasing interest to scientists due to its rise, documented by the National Reference Center for Pneumococci, France, and many other countries like the UK, Italy, Germany, Canada, Japan, and others.

To better understand the spread of serotypes 24F, researchers from the Wellcome Sanger Institute performed whole-genome sequencing on 419 examples of 24F. Most of these samples were collected from French individuals between 2003 and 2018 by the National Reference Center for Pneumococci (NRCP) and Association Clinique et Therapeutique Infantile du Val-de-Marne (ACTIV), but 91 pneumococcal serotype 24F isolates were collected from individuals in Spain by the Hospital Sant Joan de Deu. For a comparison of spread across the globe, researchers also utilized an international collection of other S. pneumoniae genomes from the Global Pneumococcal Sequencing (GPS) project for whole-genome sequencing.

“In a microbiology lab, classifying strains and testing for drug resistance are time-consuming and resource intensive,” says Dr. Stephanie Lo from the Wellcome Sanger Institute and primary author of the study. “Whole genome sequencing can now reliably infer serotype and antibiotic resistance profiles, identify where outbreaks might be occurring and track which strains mediate serotype replacement. So it’s one test that can answer a lot of different questions.”

Analysis revealed that 24F’s presence across the globe was primarily due to three different strains: GPSC10, GPSC16 and GPSC206. One of these particularly resistant strains, GPSC10, was responsible for an increase in 24F throughout France several years after the release of PCV-13, a vaccine targeting 13 serotypes of S. pneumoniae. The study was able to identify that GPSC10 can express 17 different serotypes, only six of which are currently included in PCV vaccines.

“The Streptococcus pneumoniae strain GPSC10 is something of a shapeshifter, able to express a wide range of serotypes and multidrug resistance patterns,” states Dr. Emmanuel Varon from the National Reference Center for Pneumococci, Centre Hospitalier Intercommunal de Créteil, France, and senior author of the study. “Surveillance on pneumococcal diseases, such as that implemented in France since 2001, is our best tool to evaluate the impact of vaccine policies and will allow us to detect the emergence of other non-vaccine serotypes.”

Vaccine makers have to be incredibly precise with disease intervention strategies, especially in the dominant serotypes studied. Further understanding of “superbug’” serotypes’ global spread, like S. pneumoniae GPSC10 and 24F, can arm public health organizations with the knowledge to stop disease spread in its tracks. New strains are bound to evolve as vaccine technology improves, and it’s up to researchers and scientists to stay ahead in this evolutionary arms race to prevent disease and, ultimately, save lives.