Cicatiello, Annunziata Gaetana (2016) Characterization of Neisseria meningitidis rifampicin resistant strains: highlight on molecular mechanisms underlying the phenotypic traits associated with the RpoB H553Y substitution. [Tesi di dottorato]

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Item Type:	Tesi di dottorato
Lingua:	English
Title:	Characterization of Neisseria meningitidis rifampicin resistant strains: highlight on molecular mechanisms underlying the phenotypic traits associated with the RpoB H553Y substitution
Creators:	Creators Email Cicatiello, Annunziata Gaetana annunziatagaetana.cicatiello2@unina.it
Date:	2016
Number of Pages:	120
Institution:	Università degli Studi di Napoli Federico II
Department:	Medicina Molecolare e Biotecnologie Mediche
Scuola di dottorato:	Medicina molecolare
Dottorato:	Patologia e fisiopatologia molecolare
Ciclo di dottorato:	28
Coordinatore del Corso di dottorato:	nome email Avvedimento, Vittorio Enrico vittorioenrico.avvedimento@unina.it
Tutor:	nome email Salvatore, Paola UNSPECIFIED
Date:	2016
Number of Pages:	120
Uncontrolled Keywords:	rifampicin; resistance; Neisseria meningitidis
Settori scientifico-disciplinari del MIUR:	Area 06 - Scienze mediche > MED/07 - Microbiologia e microbiologia clinica
Date Deposited:	13 Apr 2016 10:42
Last Modified:	21 Nov 2016 11:03
URI:	http://www.fedoa.unina.it/id/eprint/10869

Abstract

Rifampicin chemoprophylaxis against Neisseria meningitidis infections led to the onset of rifampicin resistance in clinical isolates harboring point mutations in the rpoB gene, coding for the RNA polymerase β chain. These resistant strains are rare in medical practice, suggesting their decreased fitness in the human host. In this study, we isolated rifampicin-resistant rpoB mutants from hypervirulent serogroup C strain 93/4286 and analyzed their different properties, including the ability to grow and survive in different culture media and in differentiated THP-1 human monocytes and to compete with the wild-type strain in vitro. Our results demonstrate that different rpoB mutations (H553Y, H553R and S549F) may have different effects, ranging from low- to high-cost, on bacterial fitness in vitro. Moreover, we found that the S549F mutation confers temperature sensitivity, possibly explaining why it is observed very rarely in clinical isolates. Comparative high-throughput RNA sequencing analysis of bacteria grown in chemically defined medium demonstrated that the low-cost H553Y substitution resulted in global transcriptional changes that functionally mimic the stringent response. Interestingly, many virulence-associated genes, including those coding for meningococcal type IV pili, porin A, adhesins/invasins, IgA protease, two-partner secretion system HrpA/HrpB, enzymes involved in resistance to oxidative injury, lipooligosaccharide sialylation, and capsular polysaccharide biosynthesis, were down regulated in the H553Y mutant compared to their level of regulation in the wild-type strain. These data might account for the reduced capacity of H553Y mutant to grow and survive in differentiated THP-1 cells and explain the rarity of this mutant in clinical isolates.

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