Molekularna epidemiologija in patogeneza invazivne neonatalne okužbe z bakterijo Streptococcus agalactiae v Sloveniji, 2011-2016

Perme, Tina (author), Ihan, Alojz (mentor), Jeverica, Samo (comentor)

Streptococcus agalactiae (streptokok skupine B ali SGB) je najpogostejši povzročitelj invazivne neonatalne okužbe v razvitih državah. Za preprečevanje okužbe uporabljamo obporodno antibiotično profilakso, ki je v Sloveniji indicirana na podlagi prisotnosti dejavnikov tveganja. Za preučevanje sorodnosti med posameznimi izolati SGB in genetske strukture bakterijske populacije uporabljamo številne metode, med njimi metodo sekvenciranja multiplih lokusov (MLST), s katero izolate razvrstimo v sekvenčne tipe (ST), ki se združujejo v klonske komplekse (CC), in v zadnjem času pogosteje tudi metodo sekvenciranja celotnega genoma (WGS). Dodatno lahko uporabimo tudi metodo CRISPR. V razvitem svetu je zaskrbljujoč porast invazivnih neonatalnih okužb, povzročenih s hipervirulentnim sevom SGB serotipa III ST-17. Glavni virulentni dejavnik SGB je kapsularni polisaharid. Glede na izražanje različice polisaharida lahko SGB razdelimo v 10 različnih serotipov. Za razvoj kolonizacije in invazivne okužbe so pomembni tudi drugi virulentni dejavniki, med njimi številni površinski proteini, kot so pili, proteini iz družine ALP, peptidaza C5a, Lmb, Fbs, Srr in Bib. Za virulenco hipervirulentnega seva SGB ST-17 sta posebej pomembna proteina HvgA in Srr-2, ki omogočata meningealni tropizem. Problematika invazivne neonatalne okužbe s SGB je v Sloveniji slabo raziskana, prav tako poznavanje fenotipskih in genotipskih značilnosti izolatov. Z raziskavo smo želeli fenotipsko in genotipsko primerjati zbrane invazivne izolate in skupino kolonizacijskih izolatov SGB ter opredeliti značilnosti bakterijske populacije pred uvedbo univerzalnega presejanja v nosečnosti. V to retrospektivno kohortno raziskavo smo vključili izolate 101 otroka z invazivno okužbo (n=114 izolatov) med leti 2001 in 2018. Kontrolno skupino so predstavljali kolonizacijski izolati 70 nosečnic (n=71). Zbrali smo podatke o osnovnih kliničnih značilnostih otrok, odpornosti izolatov na antibiotike in kapsularnem serotipu. S pomočjo WGS smo izolatom določili ST in CC, prisotnost genov za virulentne dejavnike in opravili filogenetsko analizo. Kot dodatno metodo tipizacije smo uporabili metodo CRISPR. Med invazivnimi izolati jih je bilo 41,6 % povezanih z zgodnjo okužbo, 58,4 % pa s pozno okužbo. Vsi izolati so bili občutljivi na penicilin. Skupno smo zaznali 7 različnih serotipov (Ia, Ib, II-V in VIII), med katerimi je prevladoval serotip III (60 %). Zaznali smo 29 različnih ST, ki so se razvrstili v 6 CC. Tako med invazivnimi kot kolonizacijskimi izolati je prevladoval hipervirulentni klon CC-17 (67,3 % ter 32,9 %; p

• Language: Slovenian
• Keywords: streptokok skupine B, SGB, hipervirulentni CC-17, neonatalna okužba, molekularna epidemiologija, virulentni dejavniki, Slovenija
• Work type: Doctoral dissertation
• Organization: MF - Faculty of Medicine
• Year: 2021
• PID: 20.500.12556/RUL-126275
• COBISS.SI-ID: 63505667
• Publication date in RUL: 14.04.2021

Secondary language

• Language: English
• Title: Molecular epidemiology and pathogenesis of invasive neonatal infection with Streptococcus agalactiae in Slovenia, 2011-2016

Abstract

Group B streptococcus (GBS) is the leading cause of invasive neonatal disease in the developed world. Intrapartum antibiotic prophylaxis is currently the only modality for prevention of GBS disease. In Slovenia, prophylaxis is administered based on the presence of risk factors. Several genotypic methods are available for studying the relationships between isolates and the genetic structure of bacterial population. The two most widely used are multilocus sequence typing and whole genome sequencing (WGS), which enable us to classify bacterial isolates into sequence types (ST), which cluster into clonal complexes (CC). Recently, CRISPR method has been studied as a possible tool for typing and subtyping. An increase in the incidence of neonatal disease caused by the hypervirulent GBS serotype III ST-17 has been described in recent years. Polysaccharide capsule is the main virulent factor of GBS. Based on the capsular antigen, GBS can be divided into ten distinct serotypes. However, a variety of other virulent factors have been implicated in the development of colonisation and invasive disease, such as pili, Alp family proteins, C5a peptidase, Lmb, Fbs, Srr and Bib. Virulent factors of the hypervirulent clone GBS ST-17 include HvgA and Srr-2, which confer meningeal tropism. The problem of GBS disease as well as phenotypic and genotypic characteristics of GBS isolates in Slovenia are not well studied. Our research aimed to phenotypically and genotypically compare invasive and colonising GBS isolates and determine a baseline GBS population characteristics before the implementation of universal screening. 114 invasive GBS isolates and 71 colonising isolates were analysed for basic clinical characteristics, antimicrobial susceptibility and capsular serotype. WGS was performed to assign ST and CC, virulent factors and phylogeny. CRISPR was performed for typing. Among invasive isolates, 41.6 % and 58.4 % were responsible for early onset (EOD) and late onset (LOD) disease, respectively. All isolates were susceptible to penicillin. Overall, 7 serotypes were identified (Ia, Ib, II-V and VIII), serotype III being the most common (60 %). 29 STs were detected that were grouped into 6 CCs. CC-17 was predominant among both invasive and colonising isolates with 67.3 % and 32.9 %, respectively (p

• Keywords: group B Streptococcus, GBS, hypervirulent CC-17, neonatal infection, molecular epidemiology, virulence factors, Slovenia