In the quest for persistence markers in listeria monocytogenes
Autor(a) principal: | |
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Data de Publicação: | 2022 |
Tipo de documento: | Dissertação |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10400.14/40793 |
Resumo: | Listeria monocytogenes (Lm) is an opportunisticand highly invasive foodborne bacterial pathogen. Although not life-threatening for immunocompetent individuals, Lm is deleterious among more susceptible populations. This pathogen's primary transmission route relies on contaminated foods and is often associated with ready-to-eat (RTE) products, such as soft cheeses. Even though considerable efforts are spent in removing Lm from processing facilities, due to its prevalence in the environment, this pathogen effortlessly colonizes food processing environments (FPEs), with certain strains more frequently isolated from FPEs than others, with some instances of strains continuously isolated throughout time in the same processing facility. However, no consensus has yet been reached on the causes of persistence. Some attribute it to failure in facility disinfection, while others hypothesize higher intrinsic tolerances from the persistent strains. The objective of the present work was to identify genotypic and phenotypic differences between persistent and sporadic isolates. Seventeen isolates were selected to carry out the proposed tasks, and all were subjected to growth under stressful environments with varying degrees of temperature, pH, and salinity. Moreover, infrared spectra were collected from all isolates grown at 11 and 30 ºC with two objectives: I) To develop classification models that could correctly distinguish isolates grown at both temperatures and persistent and sporadic isolates; II) To evaluate how membrane fluidity in both groups (persistent and sporadic) was affected by the exposure to lower temperatures, providing useful information on phenotypic expression of both groups. Additionally, the accessory genomes of all isolates were characterized for the presence of resistance genes associated with enhanced tolerance to adverse conditions present in FPEs. Growth under the selected stress conditions did not yield significant differences between the growth parameters of persistent and sporadic isolates. Additionally, the accessory genomes of both groups were highly heterogenous and did not contain genetic elements that could account for enhanced tolerance to unfavourable conditions commonly encountered in FPEs. Analysis of the infrared spectra of Lm isolates exposed to 30 and 11 ºC yielded promising results. PLSDA prediction models for 11 ºC correctly classified a significant portion of the isolates as persistent or sporadic, possibly implying that the FTIR technique possesses enough discriminatory power to distinguish phenotypical differences between both groups. Thus, in the author's opinion, further research needs to be conducted on the FTIR analysis of isolates grown in various stress conditions to provide reliable and accurate evidence corroborating the claim that persistence may also be attributed to phenotypic characteristics, not only to sanitation deficiencies. |
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In the quest for persistence markers in listeria monocytogenesListeria monocytogenesPersistenceFTIRStress exposureAccessory genomePersistênciaStressGenoma acessórioDomínio/Área Científica::Ciências Naturais::Ciências BiológicasListeria monocytogenes (Lm) is an opportunisticand highly invasive foodborne bacterial pathogen. Although not life-threatening for immunocompetent individuals, Lm is deleterious among more susceptible populations. This pathogen's primary transmission route relies on contaminated foods and is often associated with ready-to-eat (RTE) products, such as soft cheeses. Even though considerable efforts are spent in removing Lm from processing facilities, due to its prevalence in the environment, this pathogen effortlessly colonizes food processing environments (FPEs), with certain strains more frequently isolated from FPEs than others, with some instances of strains continuously isolated throughout time in the same processing facility. However, no consensus has yet been reached on the causes of persistence. Some attribute it to failure in facility disinfection, while others hypothesize higher intrinsic tolerances from the persistent strains. The objective of the present work was to identify genotypic and phenotypic differences between persistent and sporadic isolates. Seventeen isolates were selected to carry out the proposed tasks, and all were subjected to growth under stressful environments with varying degrees of temperature, pH, and salinity. Moreover, infrared spectra were collected from all isolates grown at 11 and 30 ºC with two objectives: I) To develop classification models that could correctly distinguish isolates grown at both temperatures and persistent and sporadic isolates; II) To evaluate how membrane fluidity in both groups (persistent and sporadic) was affected by the exposure to lower temperatures, providing useful information on phenotypic expression of both groups. Additionally, the accessory genomes of all isolates were characterized for the presence of resistance genes associated with enhanced tolerance to adverse conditions present in FPEs. Growth under the selected stress conditions did not yield significant differences between the growth parameters of persistent and sporadic isolates. Additionally, the accessory genomes of both groups were highly heterogenous and did not contain genetic elements that could account for enhanced tolerance to unfavourable conditions commonly encountered in FPEs. Analysis of the infrared spectra of Lm isolates exposed to 30 and 11 ºC yielded promising results. PLSDA prediction models for 11 ºC correctly classified a significant portion of the isolates as persistent or sporadic, possibly implying that the FTIR technique possesses enough discriminatory power to distinguish phenotypical differences between both groups. Thus, in the author's opinion, further research needs to be conducted on the FTIR analysis of isolates grown in various stress conditions to provide reliable and accurate evidence corroborating the claim that persistence may also be attributed to phenotypic characteristics, not only to sanitation deficiencies.Listeria monocytogenes (Lm) é um agente patogénico invasivo. Infeções por este microrganismo são particularmente danosas para as populações mais suscetíveis. É primordialmente disseminado via alimentos, estando associado a produtos prontos a comer, como os queijos. Ainda que se apliquem muitos esforços na sua remoção, devido à sua natureza ubíqua, Lm consegue colonizar com grande facilidade ambientes de processamento alimentar (FPEs). Com certas estirpes, sendo frequentemente isoladas nestes ambientes, e outras sendo isoladas esporadicamente. Apesar de não ser totalmente compreendido, alguns autores conjeturam a persistência como decorrência de falhas críticas nos planos de higienização das instalações. Enquanto outros, supõem a presença de mecanismos intrínsecos, responsáveis por este fenómeno. O presente trabalho teve como objetivo a identificação e caracterização de diferenças fenotípicas entre os dois grupos de isolados (persistente e esporádico), comparando também possíveis diferenças nos seus genomas acessórios. Para isso, selecionaram-se 17 isolados, sujeitando-os a crescer sob condições de stress com diferentes parâmetros de temperatura, pH e salinidade. Além disso, recolheram-se espetros de infravermelho (IR) para os 17 isolados crescidos a 11 e 30 ºC com dois propósitos: I) Desenvolver modelos de classificação capazes de distinguir isolados crescidos para ambas as temperaturas, bem como diferenciar entre isolados persistentes e esporádicos; II) Avaliar alterações na fluidez membranar dos dois grupos após a exposição a baixas temperaturas permitindo aferir diferenças na expressão fenotípica de ambos os grupos. Por último, o genoma acessório dos isolados foi caracterizado quanto à presença de genes de resistência que concedessem tolerância a condições adversas presentes em FPEs. Relativamente ao crescimento em condições de stress, não foram identificadas diferenças substanciais entre os parâmetros de crescimento dos isolados persistentes e esporádicos. Adicionalmente, os genomas acessórios de ambos os grupos demonstraram-se intrinsecamente heterogéneos, não contendo elementos genéticos que pudessem conferir tolerância a condições adversas. A análise dos espetros de IR de isolados de Lm expostos a 11 e 30 °C foi promissora. Os modelos de predição do PLSDA para 11 °C classificaram corretamente uma porção significativa dos isolados, evidenciando que a técnica de FTIR possuí um poder discriminatório satisfatório para a distinção de diferenças fenotípicas entre os dois grupos. Devem-se conduzir ensaios adicionais, para viabilizar a hipótese de que eventos de persistência podem ser atribuídos não apenas a deficiências na higienização, mas também a características fenotípicas intrínsecas dos isolados.Teixeira, Paula Cristina MaiaSousa, Clara Cecília SantanaFerreira, Vânia Alexandra BorgesVeritati - Repositório Institucional da Universidade Católica PortuguesaMeneses, Rui Manuel Santos2022-11-142022-102024-04-11T00:00:00Z2022-11-14T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisapplication/pdfhttp://hdl.handle.net/10400.14/40793TID:203223365enginfo:eu-repo/semantics/embargoedAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-07-12T17:46:21Zoai:repositorio.ucp.pt:10400.14/40793Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T18:33:29.164548Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
In the quest for persistence markers in listeria monocytogenes |
title |
In the quest for persistence markers in listeria monocytogenes |
spellingShingle |
In the quest for persistence markers in listeria monocytogenes Meneses, Rui Manuel Santos Listeria monocytogenes Persistence FTIR Stress exposure Accessory genome Persistência Stress Genoma acessório Domínio/Área Científica::Ciências Naturais::Ciências Biológicas |
title_short |
In the quest for persistence markers in listeria monocytogenes |
title_full |
In the quest for persistence markers in listeria monocytogenes |
title_fullStr |
In the quest for persistence markers in listeria monocytogenes |
title_full_unstemmed |
In the quest for persistence markers in listeria monocytogenes |
title_sort |
In the quest for persistence markers in listeria monocytogenes |
author |
Meneses, Rui Manuel Santos |
author_facet |
Meneses, Rui Manuel Santos |
author_role |
author |
dc.contributor.none.fl_str_mv |
Teixeira, Paula Cristina Maia Sousa, Clara Cecília Santana Ferreira, Vânia Alexandra Borges Veritati - Repositório Institucional da Universidade Católica Portuguesa |
dc.contributor.author.fl_str_mv |
Meneses, Rui Manuel Santos |
dc.subject.por.fl_str_mv |
Listeria monocytogenes Persistence FTIR Stress exposure Accessory genome Persistência Stress Genoma acessório Domínio/Área Científica::Ciências Naturais::Ciências Biológicas |
topic |
Listeria monocytogenes Persistence FTIR Stress exposure Accessory genome Persistência Stress Genoma acessório Domínio/Área Científica::Ciências Naturais::Ciências Biológicas |
description |
Listeria monocytogenes (Lm) is an opportunisticand highly invasive foodborne bacterial pathogen. Although not life-threatening for immunocompetent individuals, Lm is deleterious among more susceptible populations. This pathogen's primary transmission route relies on contaminated foods and is often associated with ready-to-eat (RTE) products, such as soft cheeses. Even though considerable efforts are spent in removing Lm from processing facilities, due to its prevalence in the environment, this pathogen effortlessly colonizes food processing environments (FPEs), with certain strains more frequently isolated from FPEs than others, with some instances of strains continuously isolated throughout time in the same processing facility. However, no consensus has yet been reached on the causes of persistence. Some attribute it to failure in facility disinfection, while others hypothesize higher intrinsic tolerances from the persistent strains. The objective of the present work was to identify genotypic and phenotypic differences between persistent and sporadic isolates. Seventeen isolates were selected to carry out the proposed tasks, and all were subjected to growth under stressful environments with varying degrees of temperature, pH, and salinity. Moreover, infrared spectra were collected from all isolates grown at 11 and 30 ºC with two objectives: I) To develop classification models that could correctly distinguish isolates grown at both temperatures and persistent and sporadic isolates; II) To evaluate how membrane fluidity in both groups (persistent and sporadic) was affected by the exposure to lower temperatures, providing useful information on phenotypic expression of both groups. Additionally, the accessory genomes of all isolates were characterized for the presence of resistance genes associated with enhanced tolerance to adverse conditions present in FPEs. Growth under the selected stress conditions did not yield significant differences between the growth parameters of persistent and sporadic isolates. Additionally, the accessory genomes of both groups were highly heterogenous and did not contain genetic elements that could account for enhanced tolerance to unfavourable conditions commonly encountered in FPEs. Analysis of the infrared spectra of Lm isolates exposed to 30 and 11 ºC yielded promising results. PLSDA prediction models for 11 ºC correctly classified a significant portion of the isolates as persistent or sporadic, possibly implying that the FTIR technique possesses enough discriminatory power to distinguish phenotypical differences between both groups. Thus, in the author's opinion, further research needs to be conducted on the FTIR analysis of isolates grown in various stress conditions to provide reliable and accurate evidence corroborating the claim that persistence may also be attributed to phenotypic characteristics, not only to sanitation deficiencies. |
publishDate |
2022 |
dc.date.none.fl_str_mv |
2022-11-14 2022-10 2022-11-14T00:00:00Z 2024-04-11T00:00:00Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/masterThesis |
format |
masterThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10400.14/40793 TID:203223365 |
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http://hdl.handle.net/10400.14/40793 |
identifier_str_mv |
TID:203223365 |
dc.language.iso.fl_str_mv |
eng |
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eng |
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info:eu-repo/semantics/embargoedAccess |
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embargoedAccess |
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application/pdf |
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reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
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Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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RCAAP |
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RCAAP |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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