RCAAP Repository
ISBE & Cochrane Portugal Newsletter nº 161: Eficácia e segurança de terceiras doses de vacinas COVID-19
Esta Newsletter (NL) resulta de uma parceria entre o Instituto de Saúde Baseada na Evidência e a Cochrane Portugal, e tem como objectivo disponibilizar informação sobre áreas interessantes para a prática clínica, com base na melhor evidência científica. São incluídos estudos relevantes, criticamente avaliados pela sua validade, importância dos resultados e aplicabilidade prática, resumidos numa óptica de suporte à decisão. É dada prioridade a estudos de causalidade incluindo-se ainda, quando justificado, estudos qualitativos e metodológicos, assim como revisões científicas. O conteúdo da NL é da exclusiva responsabilidade do(s) seu(s) autor(es).
2025-10-28T12:10:34Z
Carneiro, António VaZ Henriques, Susana Oliveira
Correção do sorriso gengival por métodos não cirúrgicos: revisão narrativa
No summary/description provided
2025-10-28T12:21:14Z
Soares, Rafaela Sofia Lopes
Perceções dos estudantes da FMDUL sobre ensino e aprendizagem durante a pandemia COVID-19
Introdução: Devido à natureza da profissão, os estudantes de saúde oral estão expostos a doenças infeciosas como a COVID-19 e a pandemia apresenta vários desafios para as instituições de ensino de saúde oral a nível mundial. As perceções dos estudantes sobre os efeitos da pandemia na educação são um assunto importante para a contínua melhoria deste processo. Objetivos: Pretendeu-se conhecer, nos estudantes dos cursos de pré-graduação da FMDUL, 1) as medidas adotadas para a prevenção do contágio por SARS-CoV-2; 2) as perceções sobre o processo de ensino-aprendizagem à distância; 3) as perceções sobre os fatores de risco sentidos durante as aulas presenciais práticas; 4) a opinião sobre os fatores que afetaram o seu desempenho académico durante a pandemia. Materiais e Métodos: Foi realizado um estudo transversal, tendo sido aplicado um questionário via on-line aos estudantes, entre abril e maio de 2021. Foi recolhida informação sobre características sociodemográficas, atitudes de prevenção do contágio, componente social académica e perceções de aprendizagem relativas ao ensino à distância e presencial. Foi efetuada a análise descritiva de todas as variáveis. Resultados: A amostra incluiu 200 estudantes, com uma idade média de 21,8 (dp=3,8) anos. Observou-se uma frequência muito elevada de atitudes de prevenção como o uso de máscara (79,0%). Quase metade (44,0%) considerou que as aulas teóricas e teórico-práticas à distância foram um substituto válido das aulas presenciais. Dos que frequentaram momentos letivos presenciais, a maioria discordou (53,0%) que a sua saúde se encontrava em maior risco por ter aulas laboratoriais, enquanto 49,5% dos que tiveram aulas clínicas concordaram com a afirmação. A pandemia afetou negativamente o seu desempenho académico geral (58,5%), sendo relatado como principais motivos a falta de prática e a ansiedade. Conclusão: De um modo geral, a pandemia COVID-19 afetou negativamente o desempenho académico dos estudantes, trazendo diversos desafios para o ensino.
2025-10-28T12:14:28Z
Castro, Raquel Andreia Ferreira Salgado de
Aplicação de um agente dessensibilizante em pacientes com hipersensibilidade dentinária e história de periodontite e em pacientes periodontalmente saudáveis
No summary/description provided
2025-10-28T12:29:12Z
Gama, Sandra Niara Spencer Soares da
Disfunção temporomandibular em praticantes de tiro com armas de caça
Resumo Objetivo: Avaliar a presença de disfunção temporomandibular (DTM) nos praticantes de tiro com armas de caça. Materiais e Métodos: Numa amostra não probabilística de 30 praticantes de tiro realizou-se um estudo observacional, transversal, do tipo analítico utilizando o questionário CPD/DTM, um questionário de treino específico e fotografias das estruturas maxilofaciais como sugerido em estudos prévios, com consentimento por escrito de todos os participantes. Para análise estatística optou-se por testes não paramétricos. Resultados: 30 atiradores, com uma média de idades de 36,93 20,28 anos sendo a maioria (27) do género masculino. Na amostra, 14 atletas praticavam tiro há mais de 10 anos e a modalidade mais praticada foi o Fosso Olímpico com 19 atletas. O zumbido nos ouvidos foi a alteração mais relatada (10) associada a atiradores de lazer, p=0,014. O som articular mais prevalente foi o estalido bilateral. Diagnosticou- se DTM do tipo II em 9 praticantes, sendo o deslocamento do disco com redução a condição mais prevalente e associado aos que praticavam há mais de 10 anos e a atiradores de Trap. Os atletas apresentaram faces clinicamente simétricas (1,82), contudo, os que praticam a modalidade de Trap, assim como os atiradores decenários revelaram uma assimetria superior com 2,61º e 2,07, respetivamente. Conclusão: Não se verificaram diferenças significativas entre ser atleta da seleção, o tipo de modalidade e a frequência da prática para o diagnóstico de DTM (p> 0,05). Mais estudos são necessários para aferir a relação deste desporto de impacto com possíveis efeitos colaterais no sistema estomatognático.
2025-10-28T12:23:14Z
Matos, Sara Catarina Valente de
A case series analysis of dental extractions’ outcome in cats with Chronic Gingivostomatitis carrying retroviral disease
This study aims to evaluate and compare the clinical outcome after dental extractions of cats with FCGS infected with feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). A retrospective case series included cats with diagnosis of FCGS, availability of detailed clinical records, full-mouth dental radiographs, and retroviral disease test results. Effectiveness of surgical treatment (EOT) was registered. Three groups were defined: control, FIV and FeLV. In this study, 111 cats were included: 60 controls, 29 FIV- and 22 FeLV-positive cats. When compared with control cases, FeLV-positive cats had significantly less proliferative stomatitis lesions, and they tended to have more lingual ulcers. Concurrently, FeLV-positive cats had significantly less tooth resorptive lesions. No other significant differences in FCGS clinical signs were found between groups. FeLV-positive cats had a significantly worse outcome after dental extractions compared to the other groups. In fact, FeLV-positive cats had 7.5 times more chances of having no improvement after dental extractions. This study concludes that the response to dental extractions in FeLV-positive cats is significantly worse, when comparing to cats that do not carry retroviral disease. Therefore, it is important to acknowledge the effect of FeLV status on the prognosis of these cats.
2025-10-28T12:13:06Z
Azevedo Lopes Da Silva, Marta Fernandes, Marta Fialho, Mónica Mestrinho, Lisa A.
Linguagem, cultura e sociedade: abordagens linguísticas
Os artigos inseridos neste volume abrangem: um trabalho sobre o papel determinante que o factor motivacional pode desempenhar no processo de aprendizagem de uma língua; uma análise de marcadores de controlo de contacto na língua portuguesa em contexto de reuniões empresariais; uma abordagem do uso de estrangeirismos em processos de comunicação relacionados com três campos de actividade distintos; uma investigação sobre várias versões de traduções técnicas de inglês para português e as implicações decorrentes da sua falta de adaptação a diferentes realidades culturais e linguísticas; e, ainda, um estudo das dificuldades de compreensão do discurso científico e tecnológico enquanto factor de exclusão.
2025-10-28T12:20:48Z
Pedro, Emília Ribeiro Mealha, Isabel Ferro Costa, Maria Cecília Lopes da Avelar, António Silvestre, Carminda Teixeira, Madalena T. Dias Monteiro, Maria Goreti Hartnack, Vicky
Hafnia alvei Pneumonia: a rare cause of infection in a patient with COVID-19
Herein, we describe a case report of a critically ill patient, a 48-year-old man without comorbidities admitted to the hospital with a serious type 1 (hypoxemic) respiratory insufficiency and confirmed diagnosis of COVID-19. After 5 days with invasive mechanical ventilation, the patient developed a bacterial co-infection, namely a pneumonia by Hafnia alvei, requiring the last line of respiratory support: extracorporeal membrane oxygenation (ECMO). Subsequently, his clinical situation gradually stabilized, until he was discharged from the hospital on day 61, being accompanied in ambulatory consultation by the physical medicine and pulmonology department during the post-COVID-19 recovery. H. alvei is a Gram-negative bacterium that is rarely isolated from human specimens and is rarely considered to be pathogenic. However, COVID-19 disease can cause substantial organ dysfunction and can be associated with bacterial secondary infections which can favor the emergence of rare infectious diseases by uncommon microorganisms.
2025-10-28T12:20:07Z
Méndez, Lucía Ferreira, Jorge Caneiras, Catia
Correlation between hyperglycemia and glycated albumin with retinopathy of prematurity
To determine the association between hyperglycemia, glycated albumin (GlyA) and retinopathy of prematurity (ROP). Prospective study of all infants under ROP screening from March 2017 to July 2019. All demographic, clinical and laboratory data were collected. Glucose was measured at birth and every 8 h for the first week and serum GlyA was evaluated at birth, 1st, 2nd and 4th weeks after birth. Reference range for GlyA was obtained. Univariate logistic regression was used to examine risk factors for ROP followed by multivariate regression. A total of 152 infants were included in the study. Median gestational age was 30 weeks and median birth weight 1240 g. Thirty-three infants (21.7%) had ROP. Hyperglycemia was present in 24 (72.7%) infants diagnosed with any ROP versus 6 (0.05%) in those without ROP. Median GlyA at birth, 1st, 2nd and 4th and respective reference ranges were 8.50% (6.00-12.65), 8.20% (5.32-11.67), 8.00% (5.32-10.00) and 7.90% (5.30-9.00) respectively. After multivariate logistic regression, hyperglycemia but not GlyA, remained a significant risk factor for ROP overpowering the other recognized risk factors (Exp (B) 28.062, 95% CI for Exp(B) 7.881-99.924 p < 0.001). In our cohort, hyperglycemia but not GlyA, remained a significant risk factor for ROP overpowering the other recognized risk factors.
2025-10-28T12:11:58Z
Almeida, Ana C. Silva, Gabriela A. Santini, Gabriele Brízido, Margarida Correia, Miguel Coelho, Constança Borrego, Luís Miguel
Combined high-intensity interval training as an obesity-management strategy for adolescents
Effective and safe exercise protocols for obesity management in adolescents are imperative. This study aimed to analyse compliance, efficacy, and safety of combined high-intensity interval training circuit (HIIT) in the management of obesity (including overweight) in adolescents, compared to traditional training (TT). Data from 55 adolescents (47.3% girls) (TT n = 31; HIIT n = 24), aged 12-18 (mean age of 14.3 ± 1.7), with overweight and obesity (median BMI z-score of 2.95), were assessed at baseline and month 6 (Clinicaltrials.gov/NCT02941770). During the 6-month intervention, participants in both exercise groups attended two exercise sessions/week (60 min/session) along with a set of appointments with a paediatrician, nutritionist, and exercise physiologist. Forty-six participants completed the intervention (TT n = 23; HIIT n = 23). Exercise session attendance (≥80%) was significantly higher among HIIT participants (73.9 vs. 13.0%, p < .001). HIIT, but not TT, showed a significant decrease in BMI z-score (d = 0.40, p < .001), body fat mass (BFM, %) (d = 0.41, p = .001), and trunk fat mass (d = 0.56, p < .001), as well as a significant increase in muscle mass (MM, %) (d = 0.28, p = .001) between baseline and 6 months. According to generalized estimating equations, time-by-attendance interactions (instead of time-by group) were found in BMI z-score (β = 0.25, 95%CI: 0.17, 0.33), BFM (β = 2.29, 95%CI: 1.02, 3.56), trunk fat mass (β = 2.94, 95%CI: 1.70, 4.18), and MM (β = -1.16, 95%CI: -1.87, -0.45). No adverse events were reported during HIIT sessions. Although compliance may mediate the impact of an exercise protocol on health-related outcomes, HIIT showed to be safe, with higher compliance compared to TT, which may result in improved outcomes overtime.
2025-10-28T12:26:07Z
Videira-Silva, Antonio Hetherington-Rauth, Megan Sardinha, Luís B. Fonseca, Helena
Urban planning and residential segregation in Brazil: the failure of the “Special Zone of Social Interest” instrument in Londrina city (PR)
The objective of this analysis is linked to the discussion of urban residential segregation marked by the Brazilian urban land structure and perpetuated by urban planning instruments at the municipal level. The spatial focus of the study is the municipality of Londrina (state of Paraná/Brazil). We aimed to analyze the relationship between urban zoning and the dynamics of residential segregation, unfolding two foci: verify to what extent the objectives presented in the municipal instrument translate the objectives of the instrument at the federal level (the City Statute– CE) and the national program “My Home, My Life” aimed to provide housing to socially vulnerable populations; the second focus, aims to assess how the planning instrument—the Special Zone of Social Interest (ZEIS), contemplated in the Land Use and Occupation Law and in the Municipal Master Plan of Londrina (PDPML, 2008)—materializes in practice the objectives of promoting equity in access to housing. The results show that although the objectives defined at the federal level are transposed to the municipal level, demonstrating a theoretical coherence between the instruments, there are flaws in their implementation. The case study results show that the urban zoning of Londrina has as a guideline a segregationist territorial ordering, leading to a residential segregation of the population with low purchasing power. On the other hand, the planning instrument that could change this reality is the ZEIS that, on the contrary, reinforced social housing in the periphery, conditioning the right to the city and perpetuating the social vulnerability of disadvantaged groups, in a process common to other Brazilian cities. Such constraints make relevant the establishment of land reserves for social housing based on clear roles of a social and functional mix, reinforced by the combat of vacant spaces and the definition of minimal housing and infrastructure densities to allow urban occupation.
2025-10-28T12:16:48Z
Marques da Costa, Eduarda Antonello, Ideni Terezinha
The right time for senescence
Cellular senescence is a highly complex and programmed cellular state with diverse and, at times, conflicting physiological and pathological roles across the lifespan of an organism. Initially considered a cell culture artifact, senescence evolved from an age-related circumstance to an intricate cellular defense mechanism in response to stress, implicated in a wide spectrum of biological processes like tissue remodelling, injury and cancer. The development of new tools to study senescence in vivo paved the way to uncover its functional roles in various frameworks, which are sometimes hard to reconcile. Here, we review the functional impact of senescent cells on different organismal contexts. We provide updated insights on the role of senescent cells in tissue repair and regeneration, in which they essentially modulate the levels of fibrosis and inflammation, discussing how "time" seems to be the key maestro of their effects. Finally, we overview the current clinical research landscape to target senescent cells and contemplate its repercussions on this fast-evolving field.
2025-10-28T12:27:41Z
Paramos-de-Carvalho, Diogo Jacinto, Antonio Saúde, Leonor
A systematic review of clinical practice guidelines for the diagnosis and management of Bronchiolitis
Background: Bronchiolitis is the leading cause of hospital admission for respiratory disease among infants aged <1 year. Clinical practice guidelines can benefit patients by reducing the performance of unnecessary tests, hospital admissions, and treatment with lack of a supportive evidence base. This review aimed to identify current clinical practice guidelines worldwide, appraise their methodological quality, and discuss variability across guidelines for the diagnosis and management of bronchiolitis. Methods: A systematic literature review of electronic databases EMBASE, Global Health, and Medline was performed. Manual searches of the gray literature, national pediatric society websites, and guideline-focused databases were performed, and select international experts were contacted to identify additional guidelines. The Appraisal of Guidelines for Research and Evaluation assessment tool was used by 2 independent reviewers to appraise each guideline. Results: Thirty-two clinical practice guidelines met the selection criteria. Quality assessment revealed significant shortcomings in a number of guidelines, including lack of systematic processes in formulating guidelines, failure to state conflicts of interest, and lack of consultation with families of affected children. There was widespread agreement about a number of aspects, such as avoidance of the use of unnecessary diagnostic tests, risk factors for severe disease, indicators for hospital admission, discharge criteria, and nosocomial infection control. However, there was variability, even within areas of consensus, over specific recommendations, such as variable thresholds for oxygen therapy. Guidelines showed significant variability in recommendations for the pharmacological management of bronchiolitis, with conflicting recommendations over whether use of nebulized epinephrine, hypertonic saline, or bronchodilators should be routinely trialled. Conclusions: Future guidelines should aim to be compliant with international standards for clinical guidelines to improve their quality and clarity and to promote their adoption into practice. Variable recommendations between guidelines may reflect the evolving evidence base for bronchiolitis management, and platforms should be created to understand this variability and promote evidence-based recommendations.
2025-10-28T12:24:46Z
Kirolos, Amir Manti, Sara Blacow, Rachel Tse, Gabriel Wilson, Thomas Lister, Martin Cunningham, Steve Campbell, Alasdair Nair, Harish Reeves, Rachel M Fernandes, Ricardo M. Campbell, Harry Douglas, Anne Meijer, Adam Fischer, Thea Kølsen Heikkinen, Terho Giaquinto, Carlo Knirsch, Charles Stoszek, Sonia Leach, Amanda Demont, Clarisse Gallichan, Scott Aerssens, Jeroen Beutels, Philippe Bont, Louis Pollard, Andrew Openshaw, Peter Hackett, Judy Rosen, Brian Molero, Eva
Escola em meio rural e medidas de concentração escolar: o caso da zona geográfica do Pinhal Interior Sul, Portugal (início do século XXI)
O artigo procura analisar o impacto que o encerramento de escolas unitárias e as medidas de concentração associadas (construção de centros escolares) tiveram numa zona geográfica de Portugal Continental – o Pinhal Interior Sul (PIS), território de baixa densidade e rural –, no início do século XXI. O objetivo, mobilizando um conjunto de fontes estatísticas (demográficas e educacionais) e, também, recorrendo às cartas educativas dos municípios, foi o de perceber se esse processo obedeceu a razões sociais, económicas e pedagógicas fundadas na ideia de desenvolvimento rural numa perspetiva integrada. No fundo, que visão de desenvolvimento foi difundida? Aquilo que se conclui é que não só não se inverteu o recuo do mundo rural (intensificou-se, aliás) como a tipologia centro escolar parece não ter aumentado a capacidade pedagógica das escolas.
Structural and biophysical insights into the mode of covalent binding of rationally designed potent BMX inhibitors
The bone marrow tyrosine kinase in chromosome X (BMX) is pursued as a drug target because of its role in various pathophysiological processes. We designed BMX covalent inhibitors with single-digit nanomolar potency with unexploited topological pharmacophore patterns. Importantly, we reveal the first X-ray crystal structure of covalently inhibited BMX at Cys496, which displays key interactions with Lys445, responsible for hampering ATP catalysis and the DFG-out-like motif, typical of an inactive conformation. Molecular dynamic simulations also showed this interaction for two ligand/BMX complexes. Kinome selectivity profiling showed that the most potent compound is the strongest binder, displays intracellular target engagement in BMX-transfected cells with two-digit nanomolar inhibitory potency, and leads to BMX degradation PC3 in cells. The new inhibitors displayed anti-proliferative effects in androgen-receptor positive prostate cancer cells that where further increased when combined with known inhibitors of related signaling pathways, such as PI3K, AKT and Androgen Receptor. We expect these findings to guide development of new selective BMX therapeutic approaches.
2025-10-28T12:21:27Z
Seixas, João D. Sousa, Bárbara B. Marques, Marta C. Guerreiro, Ana Traquete, Rui Rodrigues, Tiago Albuquerque, Inês S. Sousa, Marcos F. Q. Lemos, Ana R. Sousa, Pedro M. F. Bandeiras, Tiago M. Wu, Di Doyle, Shelby K. Robinson, Carol V. Koehler, Angela N. Corzana, Francisco Matias, Pedro M. Bernardes, Gonçalo J. L.
Modulation of neuromuscular transmission using transcutaneous direct currents: an exploratory study
Objective: To assess the in vivo long-lasting effects on neuromuscular transmission using transcutaneous stimulation with anodal and cathodal direct currents applied over the end-plate region (epDCS). Methods: An active DCS electrode was placed over the end-plate region of both abductor pollicis brevis and first dorsal interosseous muscles, with a reference electrode located on the forearm. Cathodal or anodal currents were applied (2.5mA during 15min). Repetitive nerve stimulation of the median and ulnar nerves at the wrist was performed before and after DCS: protocol A - 500 stimuli at 3Hz; protocol B - 30 stimuli at 30Hz. For both muscles, we measured changes in amplitude and area between the first and 4th compound muscle action potential (CMAP) and between the first and 500th CMAP (protocol A); and the change in amplitude and area between the first and 30th CMAP (protocol B). Results: Anodal current did not change any measurement. Using cathodal epDCS and median nerve testing, there was a larger increase in CMAP amplitude (p=0.046) and a smaller decrease in area (p=0.008) between the first and 30th response (protocol B). Using cathodal epDCS and ulnar nerve testing, there was a possible significant smaller amplitude decrease of the CMAP measured, between the first and fourth response (protocol A). Conclusions: Cathodal transcutaneous direct currents over the end-plate may modulate end-plate function by increasing the release of quanta of acetylcholine (Ach) and/or the number of Ach receptors available. Future studies should address this topic.
2025-10-28T12:25:26Z
Caetano, Andre Carvalho, Mamede
Emotional lability at disease onset is an independent prognostic factor of faster disease progression in Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS) is a fast progressing neurodegenerative disease leading to quadriplegia, anarthria and respiratory insufficiency. A large variety of phenotypes and disability progression requires individually tailored management. Identification of predictors of poor prognosis may not only improve management, but also allow for more precise patients' stratification for clinical trials or research studies. The aim of the study was to investigate the influence of emotional lability present at disease onset on ALS progression by exploring its direct impact on the decay of the ALS Functional Rating Scale-Revised (ALSFRS-R). The study was performed in a group of 1145 patients from Germany, Poland, Portugal and Turkey between 2014 and 2018. The analysis showed that the presence of emotional lability at ALS onset was linked to a faster decline of ALSFRS-R (0.70 vs 0.50, p<0.0001), in case of either bulbar (0.80 vs 0.65, p<0.05) or limb disease onset (0.59 vs 0.46, p <0.01). It was most prominent in the bulbar subscore of ALSFRS-R. A multiple regression analysis showed a direct influence of emotional lability at ALS onset on disease progression, regardless of age, gender, site of onset, weight loss, cognitive impairment and diagnosis delay (β=0.071; p=0.019). It can therefore be concluded that the presence of emotional lability at the disease onset is an independent factor of faster disease progression in ALS.
2025-10-28T12:23:53Z
Kuźma-Kozakiewicz, Magdalena Uysal, Hilmi Steinbach, Robert Rödiger, Annekathrin Petri, Susanne Grosskreutz, Julian Gromicho, Marta Carvalho, Mamede Nieporęcki, Krzysztof Szacka, Katarzyna Barć, Krzysztof
A Palavra e a Imagem
Num quadro teórico-crítico, influenciado por teorias contemporâneas de classe, género e etnia, vamos considerar os confrontos entre culturas, materializados em diversas práticas discursivas e visuais, que estudaremos transdisciplinarmente, numa perspectiva formal e como documentos. São exemplos das referidas práticas, por um lado, a escrita jornalística, que as novas tecnologias estão a desenvolver exponencialmente, a ensaística, o conto, o relato de viagem e biográfico, o romance, o poema, o drama e, por outro lado, as múltiplas imagens em suporte digital, o design, a fotografia, o vídeo, o cinema, a arquitectura, a gravura. Os ensaios publicados avaliam os estudos da palavra, ou da imagem visual, ou das formas diferentes como elas interagem, em relação a temas cronologicamente localizados entre o século XVIII e o século XXI.
2025-10-28T12:19:09Z
Sousa, Alcinda Pinheiro de, 1952- Correia, Alda Maria, 1957- Malafaia, Maria Teresa, 1951-
Prognostic factors for patients treated with abiraterone
Aim: To evaluate prostate-specific antigen response (PSAr) defined as a ≥50% decrease in PSA concentration from the pretreatment value, as a prognostic factor in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate (AA). Methods: Retrospective evaluation of patients with mCRPC treated with AA. Results: 124 patients were identified. Median overall survival and progression-free survival for patients achieving PSAr versus patients without PSAr were 29.3 versus 9.7 months and 17.0 versus 5.2 months, respectively. Multivariate analysis confirmed that PSAr correlated with better overall survival (hazard ratio: 0.19; 95% CI: 0.10-0.38; p < 0.001) and progression-free survival (hazard ratio: 0.24; 95% CI: 0.14-0.41; p < 0.001). Conclusion: PSAr can be utilized as prognostic and predictive factors in mCRPC patients treated with AA.
2025-10-28T12:29:12Z
Alvim, Cecilia Mansinho, André Paiva, Rita S. Brás, Raquel Semedo, Patrícia M. Lobo-Martins, Soraia da Ponte, Carolina B. Macedo, Daniela Ribeiro, Maria Leonor dos Reis, José P Fernandes, Isabel Costa, Luis
Harmful behaviour through plasmid transfer: a successful evolutionary strategy of bacteria harbouring conjugative plasmids
Conjugative plasmids are extrachromosomal mobile genetic elements pervasive among bacteria. Plasmids' acquisition often lowers cells' growth rate, so their ubiquity has been a matter of debate. Chromosomes occasionally mutate, rendering plasmids cost-free. However, these compensatory mutations typically take hundreds of generations to appear after plasmid arrival. By then, it could be too late to compete with fast-growing plasmid-free cells successfully. Moreover, arriving plasmids would have to wait hundreds of generations for compensatory mutations to appear in the chromosome of their new host. We hypothesize that plasmid-donor cells may use the plasmid as a ‘weapon’ to compete with plasmid-free cells, particularly in structured environments. Cells already adapted to plasmids may increase their inclusive fitness through plasmid transfer to impose a cost to nearby plasmid-free cells and increase the replication opportunities of nearby relatives. A mathematical model suggests conditions under which the proposed hypothesis works, and computer simulations tested the long-term plasmid maintenance. Our hypothesis explains the maintenance of conjugative plasmids not coding for beneficial genes. This article is part of the theme issue ‘The secret lives of microbial mobile genetic elements’.
2025-10-28T12:13:20Z
Domingues, Célia P. F. Rebelo, João S. Monteiro, Francisca Nogueira, Teresa Dionisio, Francisco