RESUMO
The aim of this study is to characterize the factors related to peptidoglycan metabolism in isogenic hVISA/VISA ST100 strains. Recently, we reported the increase in IS256 transposition in invasive hVISA ST100 clinical strains isolated from the same patient (D1 and D2) before and after vancomycin treatment and two laboratory VISA mutants (D23C9 and D2P11) selected from D2 in independent experiments. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis of peptidoglycan muropeptides showed increased proportion of monomeric muropeptides and a concomitant decrease in the proportion of tetrameric muropeptide in D2 and derived mutants when compared to the original strain D1. In addition, strain D2 and its derived mutants showed an increase in cell wall thickness with increased pbp2 gene expression. The VISA phenotype was not stable in D2P11 and showed a reduced autolysis profile. On the other hand, the mutant D23C9 differentiates from D2 and D2P11 in the autolysis profile, and pbp4 transcription profile. D2-derived mutants exhibited differences in the susceptibility to other antimicrobials. Our results highlight the possibility of selection of different VISA phenotypes from a single hVISA-ST100 genetic background.
Assuntos
Antibacterianos/farmacologia , Fenótipo , Seleção Genética , Staphylococcus aureus/genética , Resistência a Vancomicina/genética , Vancomicina/farmacologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Parede Celular/química , Parede Celular/efeitos dos fármacos , Parede Celular/metabolismo , Elementos de DNA Transponíveis/efeitos dos fármacos , Expressão Gênica , Humanos , Testes de Sensibilidade Microbiana , Mutação , Proteínas de Ligação às Penicilinas/genética , Proteínas de Ligação às Penicilinas/metabolismo , Peptidoglicano/metabolismo , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus aureus/isolamento & purificaçãoRESUMO
Background: Acinetobacter baumannii is an important etiological agent causing nosocomial infections. High level of resistance for different kind of antimicrobials has been observed, including ß-lactam antibiotics. This feature, chromosomal or plasmid encoded, has been associated to integrons harbouring antibiotic resistance gene cassettes. Aims: To investigate the presence of integrons among clinical isolates resistant to third generation cephalosporins (3GC). Material and methods: One hundred A. baumannii strains isolated from several Chilean hospitals were included in this study. Minimal inhibitory concentrations (MIC) of 3GC by an agar dilution method were carried out. Integrons class 1, 2 and 3 were investigated by colony blot hybridisation and confirmed by PCR. Results: High level of resistance to all assayed 3GC was observed. On the other hand, integrón class 2 was the most prevalent (77 percent of isolates) followed by integron class 1 (52 percent). Forty six percent of isolates hybridised with probes for both of them. However, no positive hybridisation was detected for integron class 3. Conclusions: Nevertheless, most isolates harboured one or both class of integron; there was no direct relationship between the presence of these genetic structures and the resistance to this kind of ß-lactam antibiotics
Assuntos
Humanos , Acinetobacter/genética , Resistência Microbiana a Medicamentos/genética , Resistência às Cefalosporinas/genética , Técnicas In Vitro , Acinetobacter/isolamento & purificação , Acinetobacter/efeitos dos fármacos , Acinetobacter/patogenicidade , Elementos de DNA Transponíveis/efeitos dos fármacos , Infecção Hospitalar/microbiologia , OligonucleotídeosRESUMO
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
Transposition of Tn10 in polA, recA, uvrB, mutH and uvrD mutants of Salmonella typhimurium was studied by a mating-out assay mediated by R plasmid pKM101. A decrease in transposition frequency was observed with polA, recA and uvrD mutants; uvrB and mutH mutants showed frequencies somewhat higher than control values. No effect of dimethyl sulfoxide, sodium acetate or nitrofurazone on Tn10 transposition was observed with this assay. Precise excision of Tn10 from srl202::Tn10 in these DNA-repair mutants was also studied. An increase in excision frequency of about 20 or 150 times in 2 different polA mutants, and a smaller increase, of about 2 or 15 times over control values, was detected in mutH and uvrD mutants, respectively.
Assuntos
Reparo do DNA/genética , Elementos de DNA Transponíveis/genética , DNA Bacteriano/genética , Mutação , Salmonella typhimurium/genética , Acetatos/farmacologia , Ácido Acético , Conjugação Genética , Elementos de DNA Transponíveis/efeitos dos fármacos , Dimetil Sulfóxido/farmacologia , Genes Bacterianos/genética , Nitrofurazona/farmacologia , Fatores R , Especificidade da EspécieRESUMO
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
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.