Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 3 de 3
Filtrar
Mais filtros










Filtros aplicados
Base de dados
Intervalo de ano de publicação
1.
Int. microbiol ; 27(1): 277-290, Feb. 2024. ilus, graf
Artigo em Inglês | IBECS | ID: ibc-230260

RESUMO

Background: Polymyxin B is considered a last-line therapeutic option against multidrug-resistant gram-negative bacteria, especially in COVID-19 coinfections or other serious infections. However, the risk of antimicrobial resistance and its spread to the environment should be brought to the forefront. Methods: Pandoraea pnomenusa M202 was isolated under selection with 8 mg/L polymyxin B from hospital sewage and then was sequenced by the PacBio RS II and Illumina HiSeq 4000 platforms. Mating experiments were performed to evaluate the transfer of the major facilitator superfamily (MFS) transporter in genomic islands (GIs) to Escherichia coli 25DN. The recombinant E. coli strain Mrc-3 harboring MFS transporter encoding gene FKQ53_RS21695 was also constructed. The influence of efflux pump inhibitors (EPIs) on MICs was determined. The mechanism of polymyxin B excretion mediated by FKQ53_RS21695 was investigated by Discovery Studio 2.0 based on homology modeling. Results: The MIC of polymyxin B for the multidrug-resistant bacterial strain P. pnomenusa M202, isolated from hospital sewage, was 96 mg/L. GI-M202a, harboring an MFS transporter-encoding gene and conjugative transfer protein-encoding genes of the type IV secretion system, was identified in P. pnomenusa M202. The mating experiment between M202 and E. coli 25DN reflected the transferability of polymyxin B resistance via GI-M202a. EPI and heterogeneous expression assays also suggested that the MFS transporter gene FKQ53_RS21695 in GI-M202a was responsible for polymyxin B resistance. Molecular docking revealed that the polymyxin B fatty acyl group inserts into the hydrophobic region of the transmembrane core with Pi-alkyl and unfavorable bump interactions, and then polymyxin B rotates around Tyr43 to externally display the peptide group during the efflux process, accompanied by an inward-to-outward conformational change in the MFS transporter...(AU)


Assuntos
Humanos , Polimixina B , Simulação de Acoplamento Molecular , Proteínas de Membrana Transportadoras , Ilhas Genômicas , Antibacterianos , Escherichia coli/genética , Microbiologia , Técnicas Microbiológicas , Águas Residuárias , Testes de Sensibilidade Microbiana
2.
Int. microbiol ; 25(1): 111-122, Ene. 2022. ilus, graf
Artigo em Inglês | IBECS | ID: ibc-216016

RESUMO

In current times, the opportunistic pathogen Morganella morganii is increasingly becoming a cause of urinary tract infections. The condition has been further complicated by the multiple drug resistance of most isolates. Swimming motility plays an important role in the development of urinary tract infections, allowing bacteria to colonize the upper urinary tract. We determined the differences between the growth, swimming motility, and biofilm formation of two M. morganii strains MM 1 and MM 190 isolated from the urine of patients who had community-acquired urinary tract infections. MM 190 showed a lower growth rate but better-formed biofilms in comparison to MM 1. In addition, MM 190 possessed autoaggregation abilities. It was found that a high temperature (37 °C) inhibits the flagellation of strains and makes MM 190 less motile. At the same time, the MM 1 strain maintained its rate of motility at this temperature. We demonstrated that urea at a concentration of 1.5% suppresses the growth and swimming motility of both strains. Genome analysis showed that MM 1 has a 17.7-kb-long insertion in flagellar regulon between fliE and glycosyltransferase genes, which was not identified in corresponding loci of MM 190 and 9 other M. morganii strains with whole genomes. Both strains carry two genes encoding flagellin, which may indicate flagellar antigen phase variation. However, the fliC2 genes have only 91% identity to each other and exhibit some variability in the regulatory region. We assume that all these differences influence the swimming motility of the strains.(AU)


Assuntos
Humanos , Ilhas Genômicas , Virulência , Fatores de Virulência , Morganella morganii , Microbiologia
3.
Inmunología (1987) ; 24(4): 355-361, oct.-dic. 2005. ilus
Artigo em En | IBECS | ID: ibc-044286

RESUMO

Las Células Dendríticas (DCs) son células presentadoras deantígeno profesionales, capaces de reconocer y degradar antígenosbacterianos que son presentados a linfocitos T vírgenes paraasí iniciar la respuesta inmune específica contra los antígenos derivadosde patógenos. Por esta razón, algunos microorganismospatógenos han adquirido mecanismos de virulencia que interfierencon la función de la DC y evitan la activación de la respuestainmune específica. Salmonella entericaserovar Typhimurium, elagente causal en el ratón de una enfermedad similar a fiebre tifoidea,es capaz de escapar de la presentación de antígenos mediadapor la DC al evitar su degradación lisosomal. Esta capacidadvirulenta de Salmonellarequiere la expresión funcional de un Sistemade Secreción de Tipo III (TTSS) y de otras proteínas de virulenciacodificadas por la Isla de Patogenicidad 2 (SPI-2). En estarevisión discutimos estudios recientes que han demostrado queel impedimento de la función de la DC, debido a la actividad delos productos génicos de la SPI-2 y a la evasión de la fusión fagosoma-lisosoma, es crucial para la patogénesis de Salmonella


Dendritic cells (DCs) are professional antigen presenting cellswith the ability to recognize and degrade bacterial antigens, whichare presented to naïve T cells to initiate the adaptive immune responseagainst pathogen-derived antigens. For this reason, somebacterial pathogens have acquired virulence mechanisms thatinterfere with DC function and avoid the adaptive immune responseactivation. Salmonella entericaserovar Typhimurium, thecausative agent of typhoid-like disease in the mouse, is able toescape from DC-mediated antigen presentation by avoiding lysosomaldegradation. This feature of virulent Salmonellarequiresthe functional expression of the Type Three Secretion System(TTSS) and other virulence proteins encoded within the SalmonellaPathogenicity Island 2 (SPI-2). In this review we discuss recentstudies showing that impairment of DC function by the activityof SPI-2 gene products and the avoidance of phagosome-lysosomefusion in these cells are crucial for Salmonellapathogenesis


Assuntos
Ratos , Animais , Salmonella enterica/imunologia , Células Dendríticas/imunologia , Ilhas Genômicas/imunologia , Salmonella enterica/patogenicidade , Lisossomos/imunologia , Fagossomos/imunologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...