TDH and coinfection: Therefore, it is still unclear if tdh-negative and trh-negative clinical isolates are a rare cause of vibriosis and have novel virulence factors that warrant future study, or if these isolates are merely co-infecting alongside pathogenic isolates; and if these isolates are only involved in co-infection, do these tdh-negative and trh-negative clinical isolates have an increased ability to survive in vivo relative to their environmental counterparts?