Enterococci, Gram-positive lactic acid-producing bacteria, are ubiquitous in the gut microbiota of humans, animals, fish, reptiles, insects, and birds (García-Solache and Rice, 2019; Mwikuma et al., 2023). Enterococci, facultative anaerobes, are tolerant to various environmental circumstances, including severe pH, salt concentrations, and temperatures ranging from 10 to 45 °C (Arias and Murray, 2012).The Enterococcus genus comprises Enterococcus faecalis, faecium, hirae, mundtii, and casseliflavus(Ahmed and Baptiste, 2018).(Landete et al., 2018) observed that E. faecium and E. faecalis are the most common species that can be isolated from healthy feces which are responsible for adjacent to 80 % of all enterococcal infections. Commensal enterococci are mostly harmless in healthy hosts, however, they can cause infections in wounds, the gastrointestinal tract, urinary tract, and endocarditis in susceptible hosts (Cui et al., 2020). Enterococcus is the second most frequent reason for endocarditis and bacteremia in US hospitals and the third leading cause of UTI and blood infection in hospitalized patients in Italy (Creti et al., 2004).

The presence of Enterococcus spp. in animal and human waste products was mentioned by Lebreton et al. (2014). Enterococcus species inhabit fish, shellfish, and other aquatic animals as their ability to adapt to freshwater and marine habitats (Paganelli et al., 2017). Enterococcus spp. are an emerging fish disease that significantly impacts aquaculture worldwide (Paul et al., 2021) and causes disease known as “pop-eye” in tilapia, is a fish disease that contributes to high mortality rates in aquariums and economic losses (Anshary et al., 2014).E. faecalis may could be highly or weakly pathogenic to tilapia. Enterococcus spp. be utilized as probiotics, bio-preservatives, and evidence of fecal contamination in food or water (Ben Braiek and Smaoui, 2019). Furthermore, Enterococcus spp. is an essential evidence in human and animal antimicrobial resistance (AMR) monitoring systems (Yang et al., 2023).

Fish and its products are essential for human consumption and the aquaculture business. Aquaculture antibiotic use is linked to the progress of resistance of several bacteria, including E. faecalis (Threlfall et al., 2000). Additionally, antibiotic use in aquaculture contributes to the dissemination of antibiotic-resistant genes in the environment (Algammal et al., 2022). Fish can easily introduce multi-drug resistant (MDR) bacteria into the food chain, putting consumers' health at risk (Rana et al., 2023). The rise of MDR Enterococci, including vancomycin-resistant Enterococcus (VRE) and drug-resistant Enterococci, poses a significant public health risk (Mwikuma et al., 2023). Enterococcus spp.'s optrA gene encodes an ATP-binding cassette (ABC)-F protein that confers cross-resistance to oxazolidinones and phenicols and supports targets. There are limited therapeutic options for diseases caused by these species (Daniel et al., 2015)), and they transmit resistance genes to other bacteria (Partridge et al., 2018).). Therapeutic drugs used to treat enterococcal infections include erythromycin and tetracycline leading to the proliferation of erythromycin and tetracycline-resistant bacteria (Ahmadpoor et al., 2021). Infections caused by multidrug-resistant Enterococci have increased, making treatment challenging and increasing mortality rates (Adams et al., 2016). Enterococcus spp. is essential for acquiring, storing, and disseminating factors associated with resistance (Malik et al., 2022).

Biofilms enhance Enterococcus spp.'s AMR, existence, and host invasion, enabling them to infect. Biofilm infections from Enterococcus spp. are challenging to eliminate and can transmit antibiotic-resistance genes (Ch'ng et al., 2019). The production of enterococcal biofilms requires multiple genes, including esp, gelE, and ace (Ch'ng et al., 2019). Additionally, gelatinase activity improves survival and spread within the host, while damaging tissues and the immune system (Yang et al., 2023).

Pathogenesis in Enterococcus spp. is linked to virulence factors such as aggregation substance(asa1), collagen-binding protein (ace), enterococcal surface protein (esp, and EF3314), gelatinase (gelE), hyaluronidase (hyl), pili (pil), serine protease (sprE), cytolysin (cylA, and cylB) (Stępień-Pyśniak et al., 2019). Animal-derived products may have virulence genes that are related to those found in human infections (Gaglio et al., 2016). Moreover, Nine mobile gene clusters mediate enterococci glycopeptide resistance (Yang et al., 2023). The most frequent genotypes are vanA and vanB which are located on the same transferable plasmid among VRE in several countries (Aarestrup et al., 2000). The vanA gene is widely noticed in wastewater and drinking water biofilms. The report revealed evidence of gene transfer from wastewater to drinking water (Schwartz et al., 2003). The aac (6′)-Ie-aph(2″)-Ia gene on transposon is the primary cause of the high-level gentamicin resistant (HLGR) emergence (Rosvoll et al., 2012; Miller et al., 2014). Enterococcal β-lactamases are believed to have evolved from Staphylococci by the blaZ gene (Miller et al., 2014). Tetracycline resistance in enterococci is usually linked to the tet(M), which protects ribosomes (Roberts, 2005). Macrolide resistance is linked to the erm gene (Portillo et al., 2000). As far as we are aware, no studies have been conducted on antimicrobial resistance and virulence factors in Argyrosomus regius. Thus, we want to detect AMR, antibiotic resistance genes (ARGs), virulence-associated genes (VAGs), gelatinase activity, biofilm formation, and their association with Enterococcus isolates in fish and shrimp.