Yersinia ruckeri causes important economic losses for rainbow trout (Oncorhynchus mykiss) farms worldwide. This bacterial disease is likely the most common among trout in Peru; however, no commercial ...vaccine is available nationally, which is, in part, due to a lack of information on the bacterium. The aim of the current study was to characterize 29 Y. ruckeri isolates sampled from seven cage‐reared farms in the Puno Region, the focal point for aquaculture activities in Peru. For this, samples were taken from fish with clinical signs (i.e. haemorrhages, uni‐ or bilateral exophthalmia, hyphaemia and/or melanosis). Notable among our findings was the existence of both Y. ruckeri biotype 1 (9 isolates) and biotype 2 (20 isolates; negative for sorbitol and Tween 80). The isolates further differed in API profiles 5307100 (21 isolates), 1307100 (4 isolates), 1305100 (2 isolates), 1307120 (1 isolate) and 5305100 (1 isolate), with the main differences being in the tests for lysine decarboxylase, gelatine hydrolysis and D‐saccharose fermentation. Despite these differences, all isolates shared identical ERIC‐PCR and REP‐PCR profiles and belonged to the O1a serotype. Fingerprints were identical to the reference strain CECT 955 (serotype O1a). The information obtained will be used for epidemiological purposes by health authorities and for the development of a vaccine against Y. ruckeri, a prominent request made by fish farmers in Peru.
Mortalities of up to 60% farmed rainbow trout (Oncorhynchus mykiss) were recorded in six floating cages farms in the Lake Titicaca during the wet season (December to April) of 2018. Fish presented ...uni or bilateral exophthalmia, ocular hemorrhages and melanosis. Necropsy showed severe hemorrhage in swim bladder, brain, liver and muscle, splenomegaly, and gut congestion. Histology revealed retrobulbar hemorrhage with macrophage infiltration, multifocal necrosis in several tissues, meningitis, splenitis, epicarditis, and congestion. After microbiological culture in blood agar, flat and circular colonies with smooth edges and a zone of α-hemolysis were observed. The presence of Weissella ceti was confirmed through biochemical and molecular analysis (16S rRNA gene sequence analysis), without differences between Peruvian isolates. Worldwide, W. ceti isolates from rainbow trout were similar using 16S rRNA gene sequence, however, showed discrepancies between those isolates from different hosts. Finally, Koch's postulate was confirmed with experimental infections using rainbow trouts (~9 cm) infected intraperitoneally (0.1 mL of 104 CFU). After 21 days, clinical signs and lesions similar to the recorded in natural outbreaks were observed, cumulative mortality rate was 90% and bacteria was successfully recovered from both moribund and survivor fish. This is the first report and description of weissellosis caused by Weissella ceti isolated from rainbow trout cultured in Lake Titicaca, Peru and it is the first report of the primary isolation of this bacterium on TSA and TYES media instead of TSAB medium.
•This is the first report of Weissella ceti in Peru.•First report of primary isolate of this bacteria on TSA and TYES media.•Worldwide, W. ceti isolates from rainbow trout are similar using 16S rRNA gene sequence.
The global ornamental fish trade carries important risk factors for spreading pathogens between different countries and regions, not only for ornamental fish but also for cultured fish and even other ...animal species. In the current study, we reported the capacity of Aeromonas veronii and A. hydrophila isolated from ornamental fish to experimentally infect the reared Amazonian fish Colossoma macropomum. For this, those bacteria were identified, and a primary characterization was performed. Fish were inoculated with 0.1 mL of increasing concentrations of A. hydrophila or A. veronii (C1 = 1 × 102; C2 = 1.8 × 104; C3 = 2.1 × 106; C4 = 2.4 × 108 bacterial cells per mL) in the coelomic cavity. In the control group, fish received the same volume of sterile saline solution (0.9 %). Fish presented petechiae, skin suffusions, and mortality rates up to 100 % according to the inoculum concentration. Histopathologically, fish presented necrosis with karyolysis, loss of the cytoplasmic delimitation of cells of the renal tubules and hepatocytes, hemorrhage, cellular edema, and the presence of bacterial cells. The LD50–96h of A. veronii on C. macropomum was estimated at 2.4 × 106 CFU mL−1 and of A. hydrophila at 1.408 × 105 CFU mL−1. The results demonstrated that it is possible that Aeromonas species isolated from ornamental fish affect C. macropomum, causing similar clinical signs and lesions. This shows the importance of promoting risk control measures worldwide regarding the trade of ornamental fish.
•Aeromonas species from ornamental fish can infect Colossoma macropomum, the most produced Amazonian fish species.•The mortality rate can reach up to 100 % when C. macropomum is experimentally infected with A. hydrophila or A. veronii.•Ornamental fish trade is a major risk factor for disease transmission in aquaculture.
Vibrio alginolyticus está asociado a enfermedades en acuicultura. El uso indiscriminado de antibióticos ha conllevado a la búsqueda de alternativas en el tratamiento de enfermedades bacterianas, ...entre ellas la aplicación de bacteriófagos, los cuales infectan y destruyen selectivamente bacterias. En ese sentido, en este trabajo se aisló un bacteriófago altamente lítico a V. alginolyticus el cual fue denominado Va1, con el objetivo de evaluar los parámetros físicos químicos en los cuales es viable. Para esto, se evaluó al bacteriófago Va1 en diferentes condiciones de pH, temperatura, cloroformo. El fago Va1 presenta mayores títulos a 20 y 30 °C y pH de 5 a 8 disminuyendo su viabilidad a partir de 40 °C y en unidades de pH menores de 5. La exposición al cloroformo redujo la viabilidad del fago Va1 en un 25%. A partir de la curva de un paso se determinó que el periodo de latencia y el tamaño de la explosión fueron de 20 minutos y 192 UFP/centro infectivo respectivamente. Al microscopio electrónico de transmisión el fago Va1 evidencio una cabeza icosaedrica y una cola no contráctil, características propias de la familia Podoviridae. En conclusión, el fago Va1 presenta características potenciales para su uso en fagoterapia.
Vibrioalginolyticus is associated with diseases in aquaculture. The misuse of antibiotics has led to the search for alternatives in the treatment of bacterial diseases, among them the application of ...bacteriophages that infect and destroy bacteria selectively. In this way, a highly lytic V. alginolyticus bacteriophage, termed Va1, was isolated, with the aim to evaluate its physical chemical parameters. For this purpose, different temperature, pH, chloroform exposure and host range conditions were evaluated. The temperature stability of phage Va1 showed higher titers at 20 and 30 °C decreasing from 40 °C. With respect to pH, the highest titers for the bac-teriophage were between 5 and 8, and chloroform exposure reduced viability of the Va1 phage by 25%. The one-step curve determined that the latency period and the burst size were 20 minutes and 192 PFU / infective center respectively. Under the transmission electron microscope, the Va1 phage showed an icosahedral head and a non-contractile tail, belonging to the Podoviridae family. In conclusion, Va1 phage presents potential characteristics for use in phage therapy
Evalúa la eficacia de la fagoterapia para reducir la mortalidad en Artemia franciscana causada por una infección inducida con la cepa de Vibrio alginolyticus. Desarrolla las infecciones ...experimentales en recipientes con 100 ml de agua de mar estéril suplementada con peptona a una densidad de 100 nauplios por ml. Se toma como LD50, la dosis de inóculo bacteriano que causó el 50% de muerte de nauplios de Artemia franciscana a las 48 horas y realiza la cinética de infección de Vibrio alginolyticus para evaluar cómo disminuye la tasa de supervivencia en el cultivo experimental. Para evaluar la eficacia de la fagoterapia del fago Va1 se inoculan diferentes dosis del bacteriófago para determinar cuál de ellas es más efectiva y se trabaja con esta dosis para determinar en qué tiempo de comenzada la infección se debe inocular el bacteriófago para obtener una mayor supervivencia de los nauplios. Demuestra que el fago Va1 es efectivo para aumentar la supervivencia, una sola dosis de 400µl con un título de 8.108 UFP/mL al comienzo de la infección es suficiente para eliminar la infección inducida con Vibrio alginolyticus. El tiempo de aplicación del bacteriófago no puede exceder las 15 horas post infección, ya que dentro de este intervalo de tiempo el índice de supervivencia se encuentra entre 75 y 97%, resultados que muestran diferencias significativas con respecto al control. Concluye que el uso de bacteriófagos como tratamiento contra vibriosis utilizando a Artemia franciscana como modelo biológico es efectivo para la prevención y control de Vibrio alginolyticus.
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