Stock Photo: SALMONELLA TYPHI. SALMONELLA TYPHI Scanning electron micrograph view of the cuticular surface of Schistosoma mansoni, a trematode parasite, shown with attached Salmonella typhi, a gram-negative, flagellated, facultatively anaerobic rod prokarote that causes typhoid fever, mag. 11,000x (at 24 x 36mm). Both are pathogenic in humans.