Comparison of ESwab™ and Amies Gel Swab for Transport and Recovery of Anaerobic Organisms

Introduction

Appropriate collection and transport of specimens containing anaerobic organisms is critical to maximize recovery of these organisms in the clinical laboratory. We compared the ESwab™ and walk-away specimen processor (WASP®) (Copan Diagnostics, Murrieta, CA) to standard swabs in Amies gel (AG) (BD, Franklin Lakes, NJ) for the recovery of commonly encountered anaerobic organisms. Specifically, we examined the difference in recovery rate of various anaerobic bacteria following 4, 24, and 48 h hold at either 4°C or 25°C.

Method

A saline suspension of 10e5 CFU/ml was made for 10 commonly encountered anaerobic organisms. ESwab™ and AG were used to sample each suspension and were then held at 4°C or 25°C for 4, 24, or 48 hours before being inoculated to solid media manually (AG) or by WASP® (ESwab™). Colonies were enumerated following incubation.

Conclusions

  • ESwab™ is superior to Amies gel swab for the preservation and recovery of most anaerobic organisms when held up to 48 h at 4°C.
  • Recovery of anaerobic organisms (CFU/mL) is unchanged for up to 48 h using ESwab™ if specimens are held at 4°C
  • Recovery of anaerobic organisms (CFU/mL) using either ESwab™ or Amies gel is reduced if held at 25°C for > 24 h
  • Use of ESwab™ enables automated plating when coupled with the Walk Away Specimen Processor (WASP®)