Storage of stools specimens and of Mueller-Kauffmann enrichment broths during week-ends does not hinder the isolation of Salmonella strains

Abstract

Technicians are fewer in the laboratory during week-ends. Therefore, following the day of arrival, stools submitted for isolation of Salmonella are either processed immediately or stored at +4 degrees C. The same difference exists for Mueller-Kauffmann enrichment broths (MK): either immediately plated, or stored at room temperature at the end of their overnight incubation when it occurs on saturday morning. Prevalences of Salmonella in 5548 stools of human origin were compared following their day of arrival in the week. Results showed that the storage of stools at +4 degrees C during the week-ends yields a higher rate of isolation of Salmonella though the difference is not significant (prevalence 2.6% for stored stools, versus 2.1%), but significantly improves the isolation of Salmonella from their MK enrichment (4.3% vs 2.6%, p < 0.01), and that storage of overnight incubated MK at room temperature for the week-end also improves significantly the isolation of Salmonella (5.0% vs 2.6%, p < 0.001).