Examinando por Autor "Ortega, Cesar"

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    Detection and virulence of Lactococcus garvieae and L. petauri from four lakes in southern California
    (John Wiley and Sons Inc, 2023-09) Abraham, Taylor; Yazdi, Zeinab; Littman, Eric; Shahin, Khalid; Heckman, Taylor I.; Quijano Cardé, Eva Marie; Nguyen, Diem Thu; Hu, Ruixue; Adkison, Mark; Veek, Tresa; Mukkatira, Kavery; Richey, Christine; Kwak, Kevin; Mohammed, Haitham H.; Ortega, Cesar; Avendaño-Herrera, Ruben; Keleher, William; LePage, Véronique; Gardner, Ian; Welch, Timothy J.; Soto, Esteban
    Objective: The first objective of the study aimed to detect the presence of Lactococcus petauri, L. garvieae, and L. formosensis in fish (n = 359) and environmental (n = 161) samples from four lakes near an affected fish farm in California during an outbreak in 2020. The second objective was to compare the virulence of the Lactococcus spp. in Rainbow Trout Oncorhynchus mykiss and Largemouth Bass Micropterus salmoides. Methods: Standard bacterial culture methods were used to isolate Lactococcus spp. from brain and posterior kidney of sampled fish from the four lakes. Quantitative PCR (qPCR) was utilized to detect Lactococcus spp. DNA in fish tissues and environmental samples from the four lakes. Laboratory controlled challenges were conducted by injecting fish intracoelomically with representative isolates of L. petauri (n = 17), L. garvieae (n = 2), or L. formosensis (n = 4), and monitored for 14 days postchallenge (dpc). Result: Lactococcus garvieae was isolated from the brains of two Largemouth Bass in one of the lakes. Lactococcus spp. were detected in 14 fish (8 Bluegills Lepomis macrochirus and 6 Largemouth Bass) from 3 out of the 4 lakes using a qPCR assay. Of the collected environmental samples, all 4 lakes tested positive for Lactococcus spp. in the soil samples, while 2 of the 4 lakes tested positive in the water samples through qPCR. Challenged Largemouth Bass did not show any signs of infection postinjection throughout the challenge period. Rainbow Trout infected with L. petauri showed clinical signs within 3 dpc and presented a significantly higher cumulative mortality (62.4%; p < 0.0001) at 14 dpc when compared to L. garvieae (0%) and L. formosensis (7.5%) treatments. Conclusion: The study suggests that qPCR can be used for environmental DNA monitoring of Lactococcus spp. and demonstrates virulence diversity between the etiological agents of piscine lactococcosis. © 2023 The Authors. Journal of Aquatic Animal Health published by Wiley Periodicals LLC on behalf of American Fisheries Society.
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    First identification and characterization of lactococcus garvieae isolated from rainbow trout (Oncorhynchus mykiss) cultured in México
    (Animals, 2020-09-15) Ortega, Cesar; Irgang, Rute; Valladares-Carranza, Benjamín; Collarte, Constanza; Avendaño-Herrera, Ruben
    Lactococcosis is a hyperacute hemorrhagic septicemia disease caused by Lactococcus garvieae, which is an emerging pathogen in global fish farming. Between 2016 and 2018, rainbow trout (Oncorhynchus mykiss) from five farms that presented outbreaks were sampled as part of a Mexican surveillance program for the detection of fish diseases. Fourteen L. garvieae isolates were recovered from sampled fish, as confirmed by biochemical tests, 16S rRNA gene sequencing, and clinical and histological insights. The biochemical and protein profiles of the isolates obtained were homogeneous. Repetitive extragenic palindromic—(REP)—and enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) analyses established weak genetic heterogeneity. Rainbow trout challenged with two of the isolates used at different bacterial concentrations (10−2 and 10−4 CFU/mL) showed melanosis, and hemorrhages were observed in the fins, liver, kidney, and spleen. Isolates were obtained from all of the organs sampled, including from surviving fish, as either pure or mixed cultures. The present study is the first to confirm the presence of L. garvieae as the agent of severe lactococcosis outbreaks in the two primary Mexican states for trout farming.
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    First identification of Francisella noatunensis subsp. orientalis causing mortality in mexican tilapia oreochromis spp
    (Inter-Research, 2016-08) Ortega, Cesar; Mancera, Gerardo; Enríquez, Ricardo; Vargas, Augusto; Martínez, Simón; Fajardo, Raúl; Avendaño-Herrera, Rubén; Navarrete, María José; Romero, Alex
    Francisellosis, an emerging disease in tilapia Oreochromis spp., is caused by the fac ultative, intracellular bacterium Francisella noatunensis subsp. orientalis, which is present in var ious countries where tilapia farming is commercially important. We confirmed the presence of francisellosis in Mexican tilapia cultures in association with an outbreak during the second semes ter of 2012. Broodstock fish presented a mortality rate of approximately 40%, and disease was characterized by histologically classified granulomas, or whitish nodules, in different organs, mainly the spleen and kidney. Through DNA obtained from infected tissue and pure cultures in a cysteine heart medium supplemented with hemoglobin, F. noatunensis subsp. orientalis was ini tially confirmed through the amplification and analysis of the 16S rRNA gene and the internal transcribed spacer region. Phylogenetic analysis of these genes demonstrated close similarity with previously reported F. noatunensis subsp. orientalis sequences obtained from infected tilapia from various countries. The identification of this subspecies as the causative agent of the outbreak was confirmed using the iglC gene as a target sequence, which showed 99.5% identity to 2 F. noatunen sis subsp. orientalis strains (Ethime-1 and Toba04). These findings represent the first documented occurrence of francisellosis in Mexican tilapia cultures, which highlights the importance of estab lishing preventative measures to minimize the spread of this disease within the Mexican aqua - culture industry.