Comparison of rectal swabs with fecal cultures for detection of Salmonella typhimurium in adult volunteers

Rectal swabs are generally considered less sensitive than fecal culture, but there are no data directly comparing human rectal swabs with fecal samples for detection of Salmonella. A phase I clinical study of a live oral attenuated Salmonella typhimurium vaccine strain in volunteers receiving a large known inoculum provided the opportunity to compare concurrent rectal swab and fecal cultures. Of 155 paired samples from 9 volunteers, 65 (42%) were culture positive: 35 (54%) by both methods, 20 (31%) by fecal culture only, and 10 (15%) by swab only. When compared with fecal culture, rectal swabs were 64% sensitive and 90% specific. Rectal swabs are of moderate diagnostic utility for detection of Salmonella and may be useful when collection of fecal samples is impractical.