ABSTRACT
This study aimed to identify and characterize isolates of Francisella salimarina associated with an outbreak on a marine fish farm in Brazil and to analyse their genetic variability and antimicrobial susceptibility. In 2021, diseased cobias (Rachycentron canadum, n = 10) and dusky groupers (Epinephelus marginatus, n = 10) were sampled and subjected to bacteriological and pathological examinations. The isolates obtained were morphologically and biochemically characterized and identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) and 16S rRNA gene sequencing. The genetic diversity of these isolates was analysed using repetitive extragenic palindromic-polymerase chain reaction (REP-PCR). Antimicrobial susceptibility was assessed using the disk diffusion technique. Macroscopically, the fish presented skin ulcerations, ocular lesions, hepatomegaly and splenomegaly. A pleomorphic, gram-negative, catalase- and oxidase-positive bacterium was isolated from seven cobias and two groupers. The 16S rRNA gene sequences showed >99% coverage and identity with other deposited sequences of F. salimarina. The results of the biochemical analysis corresponded to these bacterial species. Histologically, granulomas were observed in the spleen, liver and heart of the cobias (n = 6), and necrotizing and fibrinous dermatitis and myositis were identified in some groupers (n = 2). The isolates exhibited the same banding pattern when REP-PCR was performed, indicating that they were clonally related. Finally, the antibiogram test, no inhibition halo was observed for amoxicillin and trimethoprim-sulfamethoxazole. To our knowledge, this is the first report of F. salimarina infection in cobias and dusky groupers.
ABSTRACT
This work investigated the occurrence of Perkinsus sp. in clam Anomalocardia brasiliana, oyster Crassostrea sp. and mussel Mytella falcata from the Jaguaribe River estuary, northeastern Brazil. The collection of clam (N = 300), oysters (N = 300) and mussels (N = 300) were carried out in the estuary of the Jaguaribe River, Ceará, in March and April (rainy season) and October (dry season) in 2017. The mollusks were measured in their major axis, open, and had their tissues submitted to tissue incubation techniques in Ray's fluid thioglycollate medium (RFTM), histology, real-time polymerase chain reaction (qPCR), PCR and sequencing. The RFTM assays showed Perkinsus sp. infecting the three mollusks investigated. The prevalence of infected clams was 1.33% in both sampling periods, oysters ranged from 2.66 (rainy season) to 8% (dry period), and mussels from 0% (dry period) to 51.33% (rainy season). The intensity of infection was very light to light in clams, very soft to severe in oysters and very soft to moderate in mussels. Histological analyses showed cells of Perkinsus sp. infecting the gills and connective tissue around the digestive gland of some individuals. The qPCR generated amplicons in all positive samples in RFTM, confirming the presence of Perkinsus sp., while the sequencing evidenced high similarity (99%) with the species P. beihaiensis. In conclusion, the results obtained contribute to increasing knowledge about the occurrence of Perkinsus sp. in bivalve mollusks from northeastern Brazil.(AU)
Foi investigada a ocorrência da infecção pelo protozoário Perkinsus sp. em berbigões Anomalocardia brasiliana, ostras Crassostrea sp. e mexilhões Mytella falcata do estuário do Rio Jaguaribe, Nordeste do Brasil. As colheitas dos berbigões (N = 300), ostras (N = 300) e mexilhões (N = 300) foram realizadas no estuário do Rio Jaguaribe, Ceará, nos meses de março e abril (período chuvoso) e outubro (período seco) de 2017. Os moluscos foram medidos em seu maior eixo, abertos e os seus tecidos foram submetidos às técnicas de incubação de tecidos em meio fluido de tioglicolato de Ray (RFTM), histologia, reação em cadeia da polimerase em tempo real (qPCR), PCR e sequenciamento. Os ensaios de RFTM evidenciaram Perkinsus sp. infectando os três moluscos investigados. A prevalência de berbigões infectados foi de 1,33% em ambos os períodos de amostragem, a de ostras variou de 2,66 (período chuvoso) a 8% (período seco) e a de mexilhões de 0% (período seco) a 51,33% (período chuvoso). A intensidade de infecção apresentou-se muito leve a leve em berbigões, muito leve à severa nas ostras e muito leve à moderada nos mexilhões. As análises histológicas mostraram células de Perkinsus sp. infectando as brânquias e tecido conjuntivo em torno da glândula digestiva de alguns indivíduos. A qPCR gerou amplicons em todas as amostras positivas em RFTM, confirmando a presença de Perkinsus sp., enquanto o sequenciamento mostrou alta similaridade (99%) com a espécie P. beihaiensis. Em conclusão, os resultados do presente estudo contribuem para ampliar o conhecimento sobre a ocorrência de Perkinsus sp. em moluscos bivalves do Nordeste do Brasil.(AU)
