black bacterial colonies of salmonella species on salmonella shigella agar (ss agar, selective and differential medium) plate on

abstract agar background bacteria bacterial black closeup colony culture dark diarrhea differential disease dish enteric enteritidis fever food grow identification infection isolated laboratory line macro medical medium microbiology organism pathogen petri plate poisoning research salmonella salmonellosis selective shigella species strain streak test top toxic transparent typhi typhoid view virulence white