Abstract

Objectives: We investigated the contribution of extended incubation period of stool cultures to the isolation rates of Salmonella species.

Study Design: A total of 1207 stool specimens were inoculated into differential, enrichment, and selective media. The solid media (Salmonella- Shigella agar, eosin methylene blue agar), and subcultures from liquid media (selenite broth) were incubated for 24 and 48 hours.

Results: No growth was observed in 1150 cultures (95.3%) of stool specimens. Salmonella strains were isolated in 55 specimens (4.6%) and Shigella (0.2%) in two specimens. Reincubation of 1150 specimens for another 16-18 hours yielded Salmonella growth in 10 samples, all of which were isolated in selenite broth except one which was isolated in both eosin methylene blue agar and selenite broth. It was found that extending the incubation period to 48 hours resulted in a 18.2% increase in the isolation of Salmonella strains.

Conclusion: Based on our findings, we suggest that the system of extended incubation be a routine practice for stool cultures in clinical microbiology laboratories.