[Bacteriological sampling of surfaces: importance of the step of enrichment and the choice of the culture media]. / Prélèvements bactériologiques des surfaces: importance de l'étape d'enrichissement et du choix des milieux de culture.

This study tested the efficiency of four different procedures for isolating bacteria found on hospital surfaces. The techniques studied use both rich and poor media with or without enrichment in nutritive broth. The sampling of surfaces in hospital care departments was carried out using a dampened sterile flue brush. Bacteria samples were then placed on TCSA agar plates (method 1) and blood agar plates (GS) (method 2) before immersion in a nutritive broth for enrichment. The following day, the broth was used to produce two new media: TCSA (method 3) and GS (method 4). For each sample, we established the global amount of different bacterial species isolated by all 4 methods combined. These values were then used as a reference to evaluate the efficiency of each technique. 360 smears were carried out, and a total of 718 bacterial strains were isolated. Methods 1 and 2 (without enrichment) permitted the isolation of 10.86 and 13.37% respectively of the total number of strains. Methods 3 and 4, with preliminary enrichment, made it possible to isolate 69.08% of bacterial strains on TCSA medium and 90.53% on GS medium. The combination of the enrichment stage and an enriched culture medium lead to an excellent output that highlights and identifies bacteria isolated from samples taken from hospital surfaces.