First Report of Streptococcus agalactiae Meningitis in a Non-Pregnant Adult in Italy

This study, for the first time in Italy, analyses by WGS a Streptococcus agalactiae strain isolated from a non-pregnant adult affected by meningitis and without common risk factors. The S. agalactiae strain was classified as a serotype II (SS2), sequence type ST569. Molecular characterization evidenced the presence of resistance genes to tetracycline and macrolide (tet(M) and mre(A)) and several virulence genes coding for adhesion and immune evasion factors (bca, cps family, neu family, scpB, gbs family, pil family and hylB), toxins (cfa/cfb, cyl family), pro-inflammatory factors (lepA), and two homologous genes that contributed to bacterial escape from the host immune system (lmb, luxS). SNPs analysis showed 18 different alleles, with 9 missense SNP mutations related to genes involved in cellular metabolism (dhaS, ftsE, ligA, nrdD and secA), virulence (bgrR and galE) and antimicrobial resistance (glpK and mutL). SNPs in glpK and mutL genes might reduce susceptibility to drugs. The SNPs analysis highlighted the presence of mutations conferring pathogenicity to the strain. The evidence in this study could explain the development of meningitis in a healthy patient. This case highlights the importance of using molecular methods to characterize the complete genome of a bacterial species that could seriously affect human health.