Stool culture: are you getting value for money?

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Diagnostic Bacteriology

Background:

• Accurate isolation of enteric pathogens is crucial for diagnosing gastrointestinal infections.
• Various culture media are used, but their comparative efficacy and cost-effectiveness are not always well-established.
• Understanding current laboratory practices is important for optimizing diagnostic workflows.

Purpose of the Study:

• To evaluate the performance of three primary stool culture media: desoxycholate citrate agar (DCA), Hektoen enteric agar, and xylose lysine deoxycholate agar (XLD).
• To determine if a secondary primary culture medium is necessary for optimal pathogen recovery.
• To survey the stool culture practices and cost-effectiveness evaluations in 20 other laboratories.

Main Methods:

• Stool specimens were cultured on DCA, Hektoen, and XLD agar.
• Non-lactose fermenters were identified using Rapidec Z and API 10S systems.
• Shigella and Salmonella were further identified using API 20E, serology, and biochemical tests.
• A telephone survey assessed culture practices and cost-effectiveness evaluations in other labs.

Main Results:

• DCA demonstrated the highest isolation rate for enteric pathogens (97%), followed by XLD (88%) and Hektoen (76%).
• DCA successfully cultured most Shigella and missed only one Salmonella, whereas XLD and Hektoen missed more pathogens, including Yersinia enterocolitica.
• The survey revealed diverse laboratory practices with limited evidence of cost-effectiveness evaluations for stool media.

Conclusions:

• Desoxycholate citrate agar (DCA) is the superior and most cost-effective medium for primary isolation of enteric pathogens.
• Xylose lysine deoxycholate agar (XLD) and Hektoen enteric agar are not satisfactory as sole primary culture media due to lower pathogen recovery rates.