Streptococcus agalactiae associado à meningoencefalite e infecção sistêmica em tilápia-do-nilo (Oreochromis niloticus) no Brasil

Establishment of an astrocyte-like cell line from the brain of tilapia (Oreochromis niloticus) for virus pathogenesis and a vitro model of the blood-brain barrier

A new cell line was established from the brain of a cultured fish, tilapia (Oreochromis niloticus), designated as TA-02 (Tilapia Astrocyte clone 02 cell line). The TA-02 cells are grown for 300 days in an L-15 medium supplemented with 10% fetal bovine serum (FBS). This cell line showed excellent proliferative capacity and expressed various neuroglial cell markers, including SOX2, SOX10, Hes1, Notch1, Occludin, E-cadherin, and GFAP. In addition, TA-02 cells were susceptible to Tilapia Lake Virus (TiLV) as demonstrated by the presence of a severe cytopathic effect (CPE), virus particle in a transmission electron microscope (TEM), and PCR positive signal. Bacterial cytotoxicity studies showed that Streptococcus agalactiae was toxic to TA-02 cells. When co-culture with trans-well, TA-02 exhibited prominent barrier properties, manifested by tight intercellular junctions and increased trans-endothelial electrical resistance (TEER). In addition, the barrier is effective against Escherichia coli (non-meningitis pathogenic bacteria). In contrast, S. agalactiae (meningitis pathogenic bacteria) can pass through the membrane comprising the cells in the trans-well insert. The newly established TA-02 cell line provided a valuable tool for virus pathogenesis and a vitro model of the fish blood-brain barrier.

Antimicrobials and resistant bacteria in global fish farming and the possible risk for public health

ABSTRACT: The use of antimicrobials in fish farming is a reflection of the fast aquaculture development worldwide. The intensification of aquaculture to achieve market demands could lead to an increase in infectious diseases by pathogenic bacteria. Consequently, antimicrobials act as controls for emerging infectious diseases, but their use must follow the rules and regulations of the country where the activity is performed. Although the regulations impose limits to the use of antimicrobials in fish farming, many studies show that resistant bacteria are isolated from this system. The selection of resistant bacteria is not limited only to the use of antimicrobials, but also to co-selection of resistance genes or even with cross-resistance processes. Resistant bacteria from fish farming are a serious concern because they can be acquired by humans with handling or food chain, which may represent a public health problem. In the present review, we present an overview of antimicrobials use in aquaculture, the antimicrobial resistance and the impact of antimicrobial and bacterial resistance from a public health perspective.