Largemouth bass is becoming increasingly prevalent in aquaculture, particularly for U.S. recreational fisheries and as a food fish in other countries. As the demand for intensive largemouth bass aquaculture increases, the presence of emerging bacterial pathogens has also amplified in tandem. One of these is Edwardsiella piscicida (Ep), which has been isolated from clinical disease cases in various hosts and geographic regions. In this study, a pilot virulence assessment was conducted using seven Ep isolates from clinical disease cases across the U.S. Juvenile largemouth bass (16g) were challenged with two highly virulent isolates selected from the pilot, R18-43 and D16-038. Each of the isolates was administered via intracoelomic injection at two doses (R18-43: 1.55x105 and 7.55x105 CFU fish-1; D16-038: 2.23x105 and 6.95x105 CFU fish-1). Cumulative percent mortality (CPM) for isolates R18 and D16 at the high doses were 93.3% and 76.67%, respectively, while the low doses were 63.3% and 43.3%. Following the Ep virulence analysis, an investigation of a co-infection challenge involving Ep (R18-43) and F. columnare (Fc; ARS-LMB-23-5), a prominent pathogen present in intensive warmwater aquaculture, was conducted. Juvenile largemouth bass received a full dose and a half-dose of each pathogen in a mono-infection as well as in a coinfection. Although no significant differences were observed in endpoint mortality (Figure 1), a trend of increased virulence was noted in the presence of coinfection compared to pathogens challenged individually. Significant survival differences were observed via the Mantel-Cox log-rank test, reinforcing the trends noted in the endpoint mortality results. The findings from this work will help identify dynamic bacterial coinfections and provide insight into potential treatment options.