Chromogenic media for the detection of Salmonella enterica serovar Paratyphi A in human stool samples: evaluation in a reference setting

This study evaluated the detection ofSalmonella Paratyphi A in stool samples usingSalmonella chromogenic media compared to a conventional medium. Four chromogenic media, COMPASSSalmonella agar (Biokar Diagnostics, Beauvais, France), BBL ™ CHROMagar™Salmonella (BD Diagnostics, Erembodegem-Aalst, Belgium),Brilliance ™ Salmonella agar (Oxoid Ltd., Basingstoke, UK) andSalmonella PLUS CHROMagar ™ (CHROMagar, Paris, France), were compared to conventionalSalmonella-Shigella agar (Oxoid Ltd.). The colony morphology of 29 freshly grown stock isolates (Salmonella and competing organisms) was assessed. The limit of detection (LOD) was also determined using saline and stool suspensions. Finally, recognizability ofSalmonella Paratyphi A isolates was assessed using 20 human stool samples spiked with different concentrations ofSalmonella Paratyphi A. AllSalmonella Paratyphi A isolates demonstrated detectable growth with typical purple-coloured colonies that could be clearly differentiated from competing organisms on all four chromogenic media. The LOD forSalmonella Paratyphi A was 103 colony-forming units (CFU)/ml for all media, except for Brilliance agar (105 CFU/ml of stool).Salmonella Paratyphi A was easy to differentiate from competing organisms in the spiked stool samples. Colony yields improved when an enrichment step (Selenite-F broth (BD Diagnostics, Erembodegem-Aalst, Belgium)) and prolonged incubation for 48  h were performed. Chromogenic media demonstrated good specific...
Source: European Journal of Clinical Microbiology and Infectious Diseases - Category: Microbiology Source Type: research