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Authors
Abstract(s)
As leveduras do género Candida são fungos que causam desde infeções superficiais até infeções
sistémicas profundas, podendo apresentar uma letalidade elevada. Candida parapsilosis causa infeções
principalmente em pacientes imunocomprometidos, recém-nascidos e transplantados. A resistência ao
fluconazol em C. parapsilosis tem vindo a emergir em diferentes países, sendo esta uma temática de
interesse e elevada preocupação. Considerando a grande relevância de C. parapsilosis como agente
etiológico de infeções sistémicas associadas a casos de surtos hospitalares e atendendo à emergência de
resistência ao fluconazol, este estudo visa calcular a frequência de resistência ao fluconazol em C.
parapsilosis em Portugal, associar os mecanismos moleculares dessa resistência, prever fatores de
virulência e relacionar com dados genómicos.
Neste trabalho foram analisados 148 isolados de C. parapsilosis recolhidos a partir de diversos
produtos biológicos e ambientais (N= 53 de 2003-2007; N= 95 de 2017 – 2024). A frequência de
isolados de C. parapsilosis resistentes ao fluconazol nos isolados portugueses estudados é de 8,4%
(8/95). Através de PCR convencional e sequenciação do gene erg11 verificou-se que todas as estirpes
com fenótipo resistentes apresentaram a mutação Y132F e R398I.
Com base em Whole-genome sequencing (WGS) foi possível observar mutações nos genes mdr1
e cdr1. A mutação em mdr1 (I396V) foi detetada em todos isoladosresistentes podendo estar relacionada
com a sobre-expressão deste gene. A mutação no gene cdr1 (Q935K) foi encontrada em todos os
isolados resistentes à exceção de um, desconhecendo-se o papel desta mutação. Além disso, foram
detetados eventos de deleção e aumento no número de cópias de genes, embora a função da maioria
desses genes seja incerta. Filogeneticamente, os isolados portugueses estão mais próximos dos isolados
dos EUA e Alemanha do que os de Espanha, ao contrário do esperado. Novos estudos são necessários
para compreender melhor o impacto desses eventos no fenótipo dos isolados.
Yeasts belonging to Candida genus are fungi causing superficial to deep systemic infections, which can be highly lethal. Candida parapsilosis causes infections mainly in immunocompromised patients, newborns and transplant patients. Resistance to fluconazole in C. parapsilosis has been emerging in different countries and this is a subject of great interest and concern. Considering the great importance of C. parapsilosis as an etiological agent of systemic infections associated with hospital outbreaks and the emergence of fluconazole resistance, this study aims to calculate the frequency of fluconazole resistance in C. parapsilosis in Portugal, associate the molecular mechanisms of this resistance, predict virulence factors and relate it to genomic data. This study analyzed 148 isolates of C. parapsilosis collected from different biological and environmental products (N= 53 from 2003-2007; N= 95 from 2017-2024). The frequency of C. parapsilosis isolates resistant to fluconazole in the Portuguese isolates studied was 8.4% (8/95). Conventional PCR and sequencing of the erg11 gene showed that all strains with a resistant phenotype had the Y132F and R398I mutations. Whole-genome sequencing (WGS) revealed the presence of mutations in the mdr1 and cdr1 genes. The mdr1 mutation (I396V) was observed in all resistant isolates and may be associated with the overexpression of this gene. The mutation in the cdr1 gene (Q935K) was identified in all but one of the resistant isolates, yet its precise role remains unclear. Additionally, deletions and increases in the number of copies of certain genes were observed; the functions of the majority of the genes affected by deletions remain unknown. Phylogenetically, the Portuguese isolates are more closely related to those from the USA and Germany than to those from Spain, which is contrary to expectations. Further research is required to gain a deeper understanding of the impact of these events on the phenotype of the isolates.
Yeasts belonging to Candida genus are fungi causing superficial to deep systemic infections, which can be highly lethal. Candida parapsilosis causes infections mainly in immunocompromised patients, newborns and transplant patients. Resistance to fluconazole in C. parapsilosis has been emerging in different countries and this is a subject of great interest and concern. Considering the great importance of C. parapsilosis as an etiological agent of systemic infections associated with hospital outbreaks and the emergence of fluconazole resistance, this study aims to calculate the frequency of fluconazole resistance in C. parapsilosis in Portugal, associate the molecular mechanisms of this resistance, predict virulence factors and relate it to genomic data. This study analyzed 148 isolates of C. parapsilosis collected from different biological and environmental products (N= 53 from 2003-2007; N= 95 from 2017-2024). The frequency of C. parapsilosis isolates resistant to fluconazole in the Portuguese isolates studied was 8.4% (8/95). Conventional PCR and sequencing of the erg11 gene showed that all strains with a resistant phenotype had the Y132F and R398I mutations. Whole-genome sequencing (WGS) revealed the presence of mutations in the mdr1 and cdr1 genes. The mdr1 mutation (I396V) was observed in all resistant isolates and may be associated with the overexpression of this gene. The mutation in the cdr1 gene (Q935K) was identified in all but one of the resistant isolates, yet its precise role remains unclear. Additionally, deletions and increases in the number of copies of certain genes were observed; the functions of the majority of the genes affected by deletions remain unknown. Phylogenetically, the Portuguese isolates are more closely related to those from the USA and Germany than to those from Spain, which is contrary to expectations. Further research is required to gain a deeper understanding of the impact of these events on the phenotype of the isolates.
Description
Tese de Mestrado, Biologia Humana e Ambiente, 2024, Universidade de Lisboa, Faculdade de Ciências
Keywords
Candida parapsilosis Resistência Fluconazol erg11 Sequenciação do genoma total Teses de mestrado - 2024