Percorrer por autor "Bandeira, Maria"
A mostrar 1 - 10 de 11
Resultados por página
Opções de ordenação
- Bacterial biofilms, antibiotic resistance and healthcare-associated infections: a dangerous connectionPublication . Bandeira, Maria; Carvalho, Patrícia; Duarte, Aida; Jordão, LuísaIn 2012, were estimated 6.7 million cases of healthcare-associated infections (HAI) either in long-term care facilities or acute-care hospitals from which result 37,000 deaths configuring a serious public health problem [1]. The etiological agents are diverse and often resistant to antimicrobial agents. One of the mechanisms responsible for the emergence of drug resistance is biofilm assembly. Biofilms are defined as thin layers of microorganisms adhering to the surface of a structure, which may be organic or inorganic, together with the polymers that they secrete [2]. They are dynamic structures which experience different stages of organization with the ageing and are linked to an increase in bacterial resistance to host defense mechanisms, antibiotics, sterilization procedures other than autoclaving, persistence in water distribution systems and other surfaces. The understanding of bacteria organization within the biofilm and the identification of differences between planktonic and sessile forms of bacteria will be a step forward to fight HAIs. Bacterial isolates were grown in adequate medium. Antibiotic susceptibility was evaluated by broth microdilution method and interpreted according to NCCLS guidelines. A similar assay was performed to evaluate biofilm susceptibility to antibiotics. Bacteria ability to assemble biofilms was assayed by the microtiter-plate test [3] being tested in both abiotic (materials present in healthcare units) and biotic (Hella cells) surfaces. The biofilm structure was assessed by scanning electron microscopy (SEM) in either backscattered electron diffraction or secondary electrons mode. The kinetic of biofilm assembly depends on bacteria growth rate, incubation temperature and medium. Furthermore, the SEM analysis of planktonic and sessile forms of the same bacteria allowed the identification of structural differences which may be involved in virulence (Fig. 1). Bacteria ability to assemble biofilms seems to be independent of the abiotic structure (Fig.2). The same is not observed in biotic surfaces. This fact suggests that biofilm assembly in vivo is dependent of bacteria tropism. The minimum inhibitory concentration (MIC) determine for bacteria organized in biofilms is higher than for their planktonic forms. The increase ranges from 2 to 200 folds and is proportional to the ability of bacteria to assemble biofilms. Further studies will be conducted in order to prevent biofilm assembly within healthcare units which will result in a decrease of HAI and emergence of antibiotic resistant bacteria.
- Bacterial biofilms, antibiotic resistance and healthcare-associated infections: a dangerous connectionPublication . Bandeira, Maria; Carvalho, Patricia Almeida; Duarte, Aida; Jordao, LuisaIn 2012, were estimated 6.7 million cases of healthcare-associated infections (HAI) either in long-term care facilities or acute-care hospitals from which result 37,000 deaths configuring a serious public health problem. The etiological agents are diverse and often resistant to antimicrobial drugs. One of the mechanisms responsible for the emergence of drug resistance is biofilm assembly. Biofilms are defined as thin layers of microorganisms adhering to the surface of a structure, which may be organic or inorganic, together with the polymers that they secrete. They are dynamic structures which experience different stages of organization with the ageing and are linked to an increase in bacterial resistance to host defense mechanisms, antibiotics, sterilization procedures other than autoclaving, persistence in water distribution systems and other surfaces. The understanding of bacteria organization within the biofilm and the identification of differences between planktonic and sessile forms of bacteria will be a step forward to fight HAIs.
- Bacterial biofilms: a story of persistence and invasionPublication . Sousa, Sara; Bandeira, Maria; Carvalho, Patricia ALmeida; Duarte, Aida; Jordão, LuísaBiofilms are described as colonies of microorganisms that are attached to each other and to a surface, in an irreversible mode. These structures are virtualy everywhere: natural and humanized environments, as well as within living beings (humans and animals). For a long time biofilms where regarded as a bacterial survival strategie. Nowadays, in the industrialized world, the impact of acute bacterial infections caused by rapidly proliferating planktonic cells have gradually decreased in comparison to chronic infections owing to environmental organisms growing as biofilms. The major concern in this field is the healthcare-associated infections (HAIs). In 2012, HAIs estimated cases reached 6.7 million either in long-term care facilities or acute-care hospitals from which result 37,000 deaths configuring a serious public health problem [1]. The etiological agents are diverse being often resistant to antimicrobials and able to assemble biofilms both in abiotic and biotic surfaces. Here we evaluated the ability of different bacteria to assemble biofilms on a model surface and materials mimicking surfaces present either on healthcare units or medical devices. All bacteria were able to assemble biofilmls although following different kinetics and exhibiting different structural features assessed by electron microscopy. Additionally a link was established between bacteria ability to assemble biofilms and increased antibiotic resistance [2]. 1. ECDC Europe; (2012), Annual epidemiological report 2011 2. Bandeira M; (2014), Pathogens (doi:10.3390/pathogens3030720)
- Biofilmes, micobactérias não tuberculosas e infeçãoPublication . Bandeira, Maria; Wenner, Sigurd; Ferreira, Magda; Carvalho, Patricia Almeida; Jordão, LuísaAs micobactérias não tuberculosas (MNTs) são agentes infeciosos emergentes responsáveis por infeções diversas, nomeadamente infeções associadas aos cuidados de saúde. Neste trabalho foi avaliada a capacidade de formação de biofilmes por duas MNTs (M. smegmatis e M. chelonae). Os biofilmes foram caracterizados utilizando microscopia eletrónica e a eficácia de diversos desinfetantes foi avaliada contra MNTs recuperadas de biofilmes. Os resultados obtidos demonstram que as MNTs são capazes de formar biofilmes em materiais presentes em ambiente hospitalar e de resistir à ação de diversos desinfetantes.
- Exploring a link between healthcare associated infections, biofilms and antimicrobial resistancePublication . Bandeira, Maria; Borges, Vítor; Nascimento, Maria; Duarte, Aida; Gomes, Joao Paulo; Jordão, LuísaHAIs are a major public health problem affecting 4 million patients per year in Europe. Here we present results of a retrospective study in wich the ability of K. pneumoniae isolates (collected during a period of 31 years) to assemble biofilms was evaluated; and an ongoing study of multispecies biofilms. In the first study, we found major differences in biofilm assembly kinetics, extracellular polymeric substances (EPS) content, which were further corroborated by in-depth EPS composition analysis. WGS analysis revealed a high nucleotide similarity within the core-genome, but relevant differences in the accessory genome that may account for the detected biofilm phenotypic dissimilarities, such as genes already associated with biofilm formation in other pathogenic bacteria (e.g., genes coding haemogglutinins and haemolysins). These data reinforce that the research efforts to defeat bacterial biofilms should take into account that their dynamics may be contingent on the medical devices-associated materials. The second study is ongoing and we aim at understanding the basis of multispecies biofilm assembly on different surfaces. Bacterial and fungi isolates have been used as models and until now all results suggest that the two microorganisms play different roles on biofilm onset.
- Exploring Dangerous Connections between Klebsiella pneumoniae Biofilms and Healthcare-Associated InfectionsPublication . Bandeira, Maria; Carvalho, Patricia Almeida; Duarte, Aida; Jordão, LuísaHealthcare-associated infections (HAI) are a huge public health concern, particularly when the etiological agents are multidrug resistant. The ability of bacteria to develop biofilm is a helpful skill, both to persist within hospital units and to increase antibiotic resistance. Although the links between antibiotic resistance, biofilms assembly and HAI are consensual, little is known about biofilms. Here, electron microscopy was adopted as a tool to investigate biofilm structures associated with increased antibiotic resistance. The K. pneumoniae strains investigated are able to assemble biofilms, albeit with different kinetics. The biofilm structure and the relative area fractions of bacteria and extracellular matrix depend on the particular strain, as well as the minimal inhibitory concentration (MIC) for the antibiotics. Increased values were found for bacteria organized in biofilms when compared to the respective planktonic forms, except for isolates Kp45 and Kp2948, the MIC values for which remained unchanged for fosfomycin. Altogether, these results showed that the emergence of antimicrobial resistance among bacteria responsible for HAI is a multifactorial phenomenon dependent on antibiotics and on bacteria/biofilm features.
- Exploring dangerous connections between Klebsiella pneumoniae biofilms and healthcare-associated infectionsPublication . Bandeira, Maria; Carvalho, Patricia Almeida; Duarte, Aida; Jordão, LuísaHealthcare-associated infections (HAI) are a huge public health concern,particularly when the etiological agents are multidrug resistant. The ability of bacteria to develop biofilm is a helpful skill, both to persist within hospital units and to increase antibiotic resistance. Although the links between antibiotic resistance, biofilms assembly and HAI are consensual, little is known about biofilms. Here, electron microscopy was adopted as a tool to investigate biofilm structures associated with increased antibiotic resistance. The K. pneumoniae strains investigated are able to assemble biofilms, albeit with different kinetics. The biofilm structure and the relative area fractions of bacteria and extracellular matrix depend on the particular strain, as well as the minimal inhibitory concentration (MIC) for the antibiotics. Increased values were found for bacteria organized in biofilms when compared to the respective planktonic forms, except for isolates Kp45 and Kp2948, the MIC values for which remained unchanged for fosfomycin. Altogether, these results showed that the emergence of antimicrobial resistance among bacteria responsible for HAI is a multifactorial phenomenon dependent on antibiotics and on bacteria/biofilm features.
- Hospital acquired infections: Biofilm assembly and increased antibiotic resistance of microorganismsPublication . Bandeira, Maria; Martins, Raúl Daniel Carneiro Lavado; Jordão, Luísa[ENG] Healthcare-associated infections (HAI) are a public health threat. The etiological agents responsible for these infections are diverse and, in the case of bacteria, often resistant to antibiotics. Bacteria are able to assemble biofilm persisting in healthcare units, becoming more resistant to antibiotic and being responsible for HAIs onset and spread. Bacteria isolated from samples collected in hospitals fulfilling the criteria of HAI were used. The selected bacteria comprise classical (Klebsiella pneumoniae) and emergent agents of HAI (Nontuberculous mycobacteria: NTM). The bacterial ability to assemble biofilm on cell culture plates was evaluated by the microtiter plate test. The structural features of bacteria (planktonic and biofilms)were accessed using scanning electron microscopy (SEM). Biofilms assembled on the model surface(cell culture plate) and on abiotic surfaces present in healthcare units (e.g. silicon) were characterized. For K. pneumoniae strains the ability to assemble biofilms on biotic surfaces (HeLa cells) was also evaluated. The SEM analysis allowed the identification of differences between planktonic and sessile bacteria that can be related to increased virulence. The results showed that biofilm assembly depends on bacteria and abiotic surface. On biotic surfaces, the biofilm assembly is dependent on tropism relations between bacteria and the host. For NTM biofilm was possible to identify factors involved in biofilm assembly: sliding and membrane charges. In the case of K.pneumoniae this relation was not establish. Nevertheless, it was possible to establish a link between the ability to assemble biofilm and increased antibiotic resistance. Altogether these data revealed a relation between biofilm assembly,antibiotic resistance and spread of HAIs.
- Insights on Klebsiella pneumoniae Biofilms Assembled on Different Surfaces Using Phenotypic and Genotypic ApproachesPublication . Bandeira, Maria; Borges, Vítor; Gomes, João Paulo; Duarte, Aida; Jordao, LuisaKlebsiella pneumoniae is a prominent etiological agent of healthcare associated infections (HAIs). In this context, multidrug-resistant and biofilm-producing bacteria are of special public health concern due to the difficulties associated with treatment of human infections and eradication from hospital environments. Here, in order to study the impact of medical devices-associated materials on the biofilm dynamics, we performed biofilm phenotypic analyses through a classic and a new scanning electron microscopy (SEM) technique for three multidrug-resistant K. pneumoniae isolates growing on polystyrene and silicone. We also applied whole-genome sequencing (WGS) to search for genetic clues underlying biofilm phenotypic differences. We found major differences in the extracellular polymeric substances (EPS) content among the three strains, which were further corroborated by in-depth EPS composition analysis. WGS analysis revealed a high nucleotide similarity within the core-genome, but relevant differences in the accessory genome that may account for the detected biofilm phenotypic dissimilarities, such as genes already associated with biofilm formation in other pathogenic bacteria (e.g., genes coding haemogglutinins and haemolysins). These data reinforce that the research efforts to defeat bacterial biofilms should take into account that their dynamics may be contingent on the medical devices-associated materials.
- Nontuberculous mycobacteria pathogenesis and biofilm assemblyPublication . Sousa, Sara; Bandeira, Maria; Carvalho, Patricia Almeida; Duarte, Aida; Jordão, LuísaNontuberculous mycobacteria (NTM) are emergent pathogens whose importance in human health has been gaining relevance after being recognized as etiological agents of opportunist infections in HIV patients. Currently, NTM are recognized as etiological agents of several respiratory and extrarespiratory infections of immune-competent individuals. The environmental nature of NTM together with the ability to assemble biofilms on different surfaces plays a key role on their pathogenesis. In the present work the ability of three fast-growing NTM (M. smegmatis, M. fortuitum and M. chelonae) to persist within a model of human alveolar macrophages was evaluated. Most often human infections with NTM occur by contact with the environment. Biofilms can work as environmental reservoirs. For this reason, it was decided to evaluate the ability of NTM to assemble biofilms on different surfaces. Scanning electron microscopy was used to elucidate the biofilm structure. The ability to assemble biofilms was connected with the ability to spread on solid media known as sliding. Biofilm assembly and intracellular persistence seems to be ruled by different mechanisms.