Virulence-Associated Characteristics of Serotype 14 and Serogroup 9 Streptococcus pneumoniae Clones Circulating in Brazil: Association of Penicillin Non-susceptibility With Transparent Colony Phenotype Variants.

Tatiana C A Pinto,Lúcia M Teixeira,Natália S Costa,Camille A B Moura,Aline R V Souza,Fabíola C O Kegele,Sandrine E C M Pina,Laura M A Oliveira,Vânia L C Merquior,Ana Caroline N Botelho,José M Peralta

doi:10.3389/fmicb.2020.02009

Abstract

Streptococcus pneumoniae remains a major agent of invasive diseases, especially in children and the elderly. The presence of pneumococcal capsule, pneumococcal surface protein A (PspA), and pilus type 1 (PI-1) and the ability of colony phase variation are assumed to play important roles in the virulence potential of this microorganism. Differences in the capsular polysaccharide allow the characterization of more than 90 pneumococcal serotypes; among them, serotype 14 and serogroup 9 stand out due to their prevalence in the pre- pneumococcal conjugate vaccine era and frequent association with penicillin non-susceptibility. Here we investigated the distribution of PI-1 and pspA genes and colony phase variants among 315 S. pneumoniae isolates belonging to serotype 14 and serogroup 9, recovered over 20 years in Brazil, and correlated these characteristics with penicillin susceptibility and genotype as determined by multilocus sequence typing. All strains were shown to carry pspA genes, with those of family 2 (pspA2) being the most common, and nearly half of the strains harbored P1-1 genes. The pspA gene family and the presence of PI-1 genes were conserved features among strains belonging to a given clone. A trend for increasing the occurrence of pspA2 and PI-1 genes over the period of investigation was observed, and it coincided with the dissemination of CC156 (Spain9V-3) clone in Brazil, suggesting a role for these virulence attributes in the establishment and the persistence of this successful clone. Opaque variant was the colony phenotype most frequently observed, regardless of clonal type. On the other hand, the transparent variant was more commonly associated with penicillin-non-susceptible pneumococci and with strains presenting evidence of recombination events involving the genes coding for polysaccharide capsule and PspA, suggesting that pneumococcal transparent variants may present a higher ability to acquire exogenous DNA. The results bring to light new information about the virulence potentials of serotype 14 and serogroup 9 S. pneumoniae isolates representing the major clones that have been associated with the emergence and the dissemination of antimicrobial resistance in our setting since the late 1980s.

Highlights

Streptococcus pneumoniae is a leading cause of invasive infections and can asymptomatically colonize the upper respiratory tract of variable numbers of individuals (Weiser et al, 2018)
In the present study, we have evaluated the distribution of three virulenceassociated characteristics, among S. pneumoniae isolates belonging to major clones of serotype 14 or serogroup 9 circulating in Brazil, which were recognized to be responsible for the emergence and the expansion of penicillin non-susceptibility in our setting
The presence of pilus type 1 (PI-1) coding genes was evaluated among all 315 pneumococcal strains included in the study and among the reference strains of five PMEN clones

Summary

INTRODUCTION

Streptococcus pneumoniae is a leading cause of invasive infections and can asymptomatically colonize the upper respiratory tract of variable numbers of individuals (Weiser et al, 2018). The virulence of S. pneumoniae is associated with phase variation, a phenomenon characterized by the expression of two colony phenotypes, opaque and transparent. In Brazil, we have shown that four major clonal complexes (CC) were responsible for the emergence and the dissemination of antimicrobial resistance among S. pneumoniae strains of serotypes 14 and 9 circulating in the country since the late 1980s (Pinto et al, 2016). In the present study, we have evaluated the distribution of three virulenceassociated characteristics (presence of pspA and PI-1 coding genes, as well as colony phase variation phenotypes), among S. pneumoniae isolates belonging to major clones of serotype 14 or serogroup 9 circulating in Brazil, which were recognized to be responsible for the emergence and the expansion of penicillin non-susceptibility in our setting

MATERIALS AND METHODS

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT