title: Streptococcus agalactiaeCausing Neonatal Infections in Portugal (2005-2015): Diversification and Emergence of a CC17/PI-2b Multidrug Resistant Sublineage.
abstract: The molecular characterization of 218 GBS isolates recovered from neonatal invasive infections in Portugal in 2005-2015 revealed the existence of a small number of genetically distinct lineages that were present over a significant time-span. Serotypes III and Ia were dominant in the population, together accounting for >80% of the isolates. Clonal complex 17 included 50% of all isolates, highlighting the importance of the hypervirulent genetic lineage represented by serotype III ST17/rib/PI-1+PI-2b. Serotype Ia was represented mainly by ST23, previously reported as dominant among invasive disease in non-pregnant adults in Portugal, but also by ST24, showing an increased frequency among late-onset disease. Overall erythromycin resistance was 16%, increasing during the study period (p< 0.001). Macrolide resistance was overrepresented among CC1 and CC19 isolates (p< 0.001 andp= 0.008, respectively). While representatives of the hypervirulent CC17 lineage were mostly susceptible to macrolides, we identified for the first time in Europe a recently emerging sublineage characterized by the loss of PI-1 (CC17/PI-2b), simultaneously resistant to macrolides, lincosamides, and tetracycline, also exhibiting high-level resistance to streptomycin and kanamycin. The stability and dominance of CC17 among neonatal invasive infections in the past decades indicates that it is extremely well adapted to its niche; however emerging resistance in this genetic background may have significant implications for the prevention and management of GBS disease.
authors.affiliation: Faculdade de Medicina, Instituto de Microbiologia, Instituto de Medicina Molecular, Universidade de Lisboa Lisbon, Portugal.
authors.forename: Elisabete R
authors.initials: ER
authors.lastname: Martins
authors.affiliation: Faculdade de Medicina, Instituto de Microbiologia, Instituto de Medicina Molecular, Universidade de Lisboa Lisbon, Portugal.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Pedroso-Roussado
authors.affiliation: Faculdade de Medicina, Instituto de Microbiologia, Instituto de Medicina Molecular, Universidade de Lisboa Lisbon, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Melo-Cristino
authors.affiliation: Faculdade de Medicina, Instituto de Microbiologia, Instituto de Medicina Molecular, Universidade de Lisboa Lisbon, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Ramirez
keywords: CC17; Streptococcus agalactiae; antimicrobial resistance; invasive disease; neonates