Examinando por Autor "Valenzuela, Karla"

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    In vitro genomic and proteomic evidence of a type IV pili-like structure in the fish pathogen Piscirickettsia salmonis
    (Oxford University Press, 2018-08) Śanchez, Patricio; Oliver, Cristian; Hernández, Mauricio; Cortés, Marcos; Cecilia Rauch, María; Valenzuela, Karla; Garduno, Rafael A.; Avendano-Herrera, Rubén; Yánez, Alejandro J.
    Piscirickettsia salmonis is an intracellular γ -proteobacteria and the etiological agent of piscirickettsiosis, which causes massive economic losses in the Chilean salmon industry. The type IV pili (T4P) play an important role in adherence to host cell surfaces and bacterial pathogenicity. T4P contains a variable number of components, as predicted in P. salmonis genomes. However, no studies have determined if P. salmonis possesses T4P. The aims of this investigation were to identify T4P components in the P. salmonis type strain LF-89T, evaluate respective transcript expressions, and analyze the main putative T4P proteins using bioinformatics and proteomic approaches. Two main clusters of P. salmonis T4P genes were found. Expression of the pilA gene was upregulated at 4 h post-infection (hpi), while pilQ was upregulated 4 days post-infection. At 16 hpi, pilB and pilD were strongly upregulated. The PilA amino acid sequence analysis showed a conserved N-terminal domain and sequence motifs critical for T4P biosynthesis. MudPIT analysis revealed PilA in the P. salmonis LF-89T proteome, and TEM showed pili-like filamentous structures on the P. salmonis surface. These results strongly suggest the presence of a T4P-like structure in P. salmonis. © FEMS 2018.
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    Ítem
    Resistance-nodulation-division efflux pump acrAB is modulated by florfenicol and contributes to drug resistance in the fish pathogen Piscirickettsia salmonis
    (Oxford University Press, 2016-06) Sandoval, Rodrigo; Oliver, Cristian; Valdivia, Sharin; Valenzuela, Karla; Haro, Ronie E.; Sánchez, Patricio; Olavarría, Víctor H.; Valenzuela, Paulina; Avendaño-Herrera, Rubén; Romero, Alex; Cárcamo, Juan G.; Figueroa, Jaime E.; Yáñez, Alejandro J.
    Piscirickettsia salmonis is a fastidious intracellular pathogen responsible for high mortality rates in farmed salmonids, with serious economic consequences for the Chilean aquaculture industry. Oxytetracycline and florfenicol are the most frequently used antibiotics against P. salmonis, but routine use could contribute to drug resistance. This study identified differentiated florfenicol susceptibilities in two P. salmonis strains, LF-89 and AUSTRAL-005. The less susceptible isolate, AUSTRAL-005, also showed a high ethidium bromide efflux rate, indicating a higher activity of general efflux pump genes than LF-89. The P. salmonis genome presented resistance nodulation division (RND) family members, a family containing typical multidrug resistance-related efflux pumps in Gram-negative bacteria. Additionally, efflux pump acrAB genes were overexpressed in AUSTRAL-005 following exposure to the tolerated maximal concentration of florfenicol, in contrast to LF-89. These results indicate that tolerated maximum concentrations of florfenicol can modulate RND gene expression and increase efflux pump activity. We propose that the acrAB efflux pump is essential for P. salmonis survival at critical florfenicol concentrations and for the generation of antibiotic-resistant bacterial strains.