Piscirickettsia salmonis is the etiological agent of piscirickettsiosis, a severe disease causing high mortalities in salmonids. This bacterium has been previously identified and isolated in all cultivated salmonids in Chile and worldwide, including Salmo salar, Oncorhynchus kisutch, and O. mykiss, in addition to being found in non-salmonid species such as Dicentrarchus labrax and Atractoscion nobilis. In this study, the 16S rRNA gene and intergenic spacer ITS-1 of P. salmonis were amplified by PCR from DNA samples extracted from the native Chilean fish species Eleginops maclovinus, Odontesthes regia, Sebastes capensis, and Salilota australis. Analysis of the 16S rRNA sequences from O. regia demonstrated a close phylogenetic relationship with the 16S rRNA gene in the Chilean EM-90 strain. The 16S rRNA sequences from E. maclovinus, S. capensis, and S. australis were related to the Chilean LF-89 sequence and Scottish strains. To confirm these findings, analysis of P. salmonis ITS-1 sequences obtained from the 4 sampled native species demonstrated a high degree of identity and a close phylogenetic relationship with Chilean P. salmonis sequences, including LF-89 and EM-90. These results suggest a strong relationship between the nucleotide sequences from the 16S rRNA and ITS-1 genes amplified from native fish with those sequences described in the first P. salmonis strains to be identified and isolated in Chile.KEY WORDS: 16S gene · ITS-1 · rDNA sequences · Piscirickettsiosis · Native fish · SalmonidsResale or republication not permitted without written consent of the publisher

This paper presents a validated protocol, using a novel, specifically formulated medium, to perform broth microdilution antimicrobial susceptibility assays of the salmonid bacterial pathogen Piscirickettsia salmonis. The minimum inhibitory concentrations (MIC) for florfenicol and oxytetracycline against 58 P. salmonis isolates recovered from various outbreaks occurred in Chilean salmonid farms were determined using this protocol. Normalized resistance interpretation (NRI) analysis was applied to these data to calculate appropriate protocol-specific epidemiological cut-off values. These cut-off values allow the isolates to be categorized as either fully susceptible wild type (WT) members of this species, or as manifesting reduced susceptibility non-wild type (NWT). The distribution of MIC values of florfenicol was bimodal and the distribution of the normalized values for the putative WT observation had a standard deviation of 0.896 log2 μg mL-1. This analysis calculated a cut-off value of ≤0.25 μg mL-1 and categorized 33 (56%) of the isolates as manifesting reduced susceptibility to florfenicol. For the oxytetracycline MIC data the NRI analysis also treated the distribution as bimodal. The distribution of the normalized values for the putative WT observation had a standard deviation of 0.951 log2 μg mL-1. This analysis gave a cut-off value of ≤0.5 μg mL-1 and categorized five isolates (9%) as manifesting reduced susceptibility to oxytetracycline. The susceptibility testing protocol developed in this study was capable of generating MIC data from all the isolates tested. On the basis of the precision of the data it generated, and the degree of separation of values for WT and NWT it achieved, it is argued that this protocol has the performance characteristics necessary for it to be considered as a standard protocol.

The winemaking sector needs to ensure the microbiological quality of its products to guarantee acceptance and wide commercialization. There are treatments such as high pressure homogenization (HPH) that, apparently, do not affect the final nutritional and sensory food properties. This study is presented to evaluate possibilities of utilizing HPH treatments to reduce the indigenous flora accompanying wine musts, as well as their effects on the fermentative process, oenological parameters, color, aroma, and taste properties. Two different must varieties were used: a white must (Parellada variety) and a red one (Trepat variety). Results showed that the use of HPH at 200 MPa is capable of reducing the microbial load of musts. Residual populations of total bacteria were detected, but neither fungi, nor yeasts, nor lactic acid bacteria were detected after the treatment in either musts. Furthermore, as a result of the decrease of the wild microbiota of the musts, the implantation of the selected yeast for alcoholic fermentation was improved. Sensory assessments of the must and wines showed that there were no significant changes caused by the treatment.

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