RESUMO
Analysis of a clinical isolate of Acinetobacter baumannii showed that this bacterium was able to grow under iron-limiting conditions, using chemically defined growth media containing different iron chelators such as human transferrin, ethylenediaminedi-(o-hydroxyphenyl)acetic acid, nitrilotriacetic acid, and 2,2'-bipyridyl. This iron uptake-proficient phenotype was due to the synthesis and secretion of a catechol-type siderophore compound. Utilization bioassays using the Salmonella typhimurium iron uptake mutants enb-1 and enb-7 proved that this siderophore is different from enterobactin. This catechol siderophore was partially purified from culture supernatants by adsorption chromatography using an XAD-7 resin. The purified component exhibited a chromatographic behavior and a UV-visible light absorption spectrum different from those of 2,3-dihydroxybenzoic acid and other bacterial catechol siderophores. Furthermore, the siderophore activity of this extracellular catechol was confirmed by its ability to stimulate energy-dependent uptake of 55Fe(III) as well as to promote the growth of A. baumannii bacterial cells under iron-deficient conditions imposed by 60 microM human transferrin. Polyacrylamide gel electrophoresis analysis showed the presence of iron-regulated proteins in both inner and outer membranes of this clinical isolate of A. baumannii. Some of these membrane proteins may be involved in the recognition and internalization of the iron-siderophore complexes.
Assuntos
Acinetobacter calcoaceticus/metabolismo , Ferro/metabolismo , Sideróforos/metabolismo , Transporte Biológico , Catecóis/isolamento & purificação , Catecóis/metabolismo , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Ferro/farmacologia , Proteínas de Membrana/biossíntese , Proteínas de Membrana/efeitos dos fármacos , Sideróforos/química , Sideróforos/isolamento & purificação , Transferrina/metabolismoRESUMO
Se analizó el contenido plasmídico de una serie de cepas de Klebsiella pneumoniae resistentes a amikacina y otros antibióticos. Estas cepas se identificaron como causantes de epidemias intrahospitalares en unidades pediátricas situadas en distintas localidades geográficas de Argentina. En todos los casos se encontraron plásmidos que poseían determinantes genéticos para resistencia a amikacina. Mediante análisis realizados con cortes con enzimas de restricción e hibridizaciones se determinó la presencia de elementos transponibles relacionados a Tn 1331 en todos las cepas estudiadas. Estos resultados indican que la transposición de estos elementos ha jugado un papel importante en el proceso de diseminación de la resistencia a la amikacina en el género Klebsiella (y probablemente en otras bacterias gram negativas) en Argentina (AU)
Assuntos
Klebsiella pneumoniae/genética , Amicacina/farmacologia , Fatores R/genética , Resistência Microbiana a Medicamentos/genética , Elementos de DNA Transponíveis/efeitos dos fármacos , Argentina , Fatores R/efeitos dos fármacos , Mapeamento CromossômicoRESUMO
Se analizó el contenido plasmídico de una serie de cepas de Klebsiella pneumoniae resistentes a amikacina y otros antibióticos. Estas cepas se identificaron como causantes de epidemias intrahospitalares en unidades pediátricas situadas en distintas localidades geográficas de Argentina. En todos los casos se encontraron plásmidos que poseían determinantes genéticos para resistencia a amikacina. Mediante análisis realizados con cortes con enzimas de restricción e hibridizaciones se determinó la presencia de elementos transponibles relacionados a Tn 1331 en todos las cepas estudiadas. Estos resultados indican que la transposición de estos elementos ha jugado un papel importante en el proceso de diseminación de la resistencia a la amikacina en el género Klebsiella (y probablemente en otras bacterias gram negativas) en Argentina
Assuntos
Amicacina/farmacologia , Klebsiella pneumoniae/genética , Fatores R/genética , Argentina , Mapeamento Cromossômico , Elementos de DNA Transponíveis/efeitos dos fármacos , Resistência Microbiana a Medicamentos/genética , Fatores R/efeitos dos fármacosRESUMO
Plasmids isolated from Klebsiella pneumoniae strains that caused outbreaks in pediatric units in various geographical regions of Argentina harbored genetic determinants for resistance to amikacin. By using restriction endonuclease and Southern blot hybridization analysis it was determined that all of the strains carried plasmids with Tn1331-related elements indicating that transposition of these elements may have played an important role in the dissemination process of resistance to amikacin.
Assuntos
Amicacina/farmacologia , Klebsiella pneumoniae/genética , Fatores R/genética , Argentina , Mapeamento Cromossômico , Elementos de DNA Transponíveis/efeitos dos fármacos , Resistência Microbiana a Medicamentos/genética , Fatores R/efeitos dos fármacosRESUMO
Plasmids isolated from Klebsiella pneumoniae strains that caused outbreaks in pediatric units in various geographical regions of Argentina harbored genetic determinants for resistance to amikacin. By using restriction endonuclease and Southern blot hybridization analysis it was determined that all of the strains carried plasmids with Tn1331-related elements indicating that transposition of these elements may have played an important role in the dissemination process of resistance to amikacin.
RESUMO
A multiresistant Klebsiella pneumoniae strain isolated from neonates in Mendoza, Argentina, harbored a 48-kilobase-pair (kbp) plasmid, pMET1, with genetic determinants for resistance to amikacin and also ampicillin, kanamycin, streptomycin, and tobramycin. This plasmid was compared with pJHCMW1, a previously isolated 11-kbp plasmid carrying transposon Tn1331, which encodes resistance to amikacin, as well as ampicillin, kanamycin, streptomycin, and tobramycin, and which was originally present in a K. pneumoniae strain that caused an outbreak in a hospital in Buenos Aires, Argentina. The comparison demonstrated that the replication regions of the two plasmids are unrelated. However, in pMET1 an 11-kbp transposition element, Tn1331.2, was identified; it was closely related to Tn1331, with the difference that a 3-kbp BamHI DNA fragment carrying the aminoglycoside resistance genes was duplicated in tandem.
Assuntos
Amicacina/farmacologia , Elementos de DNA Transponíveis/efeitos dos fármacos , Klebsiella pneumoniae/efeitos dos fármacos , Southern Blotting , Clonagem Molecular , Resistência Microbiana a Medicamentos , Testes de Sensibilidade Microbiana , Plasmídeos , Mapeamento por RestriçãoRESUMO
A lipid-bound oligosaccharide was isolated from pea (Pisum sativum) cotyledons incubated with [(14)C]mannose. The oligosaccharide moiety appeared to be identical with the one obtained from rat liver, known to contain three glucoses, nine mannoses, and two N-acetylglucosamines, and to be involved in protein glycosylation.Enzymes obtained from soya (Glycine max) roots and developing pea cotyledons were found to catalyze the transfer of oligosaccharide from the lipid intermediate to endogenous protein. The enzymes require Mn(2+) and detergent for activity. Evidence is presented indicating that the lipid-bound oligosaccharide with three glucoses is transferred faster than that with less. Some of the peripheral mannoses could be removed without affecting the rate of transfer.The protein-bound oligosaccharide, formed by incubation of whole cotyledons or by transfer with the enzyme preparation, could be released by protease and endo-beta-N-acetylglucosaminidase treatment, as expected for an asparagine-bound high mannose oligosaccharide.