Validation of Optimal Sample Volume/Loop/Streaking Pattern and Flexibility to Customize Solutions for Walk Away Specimen Processor (WASP®) Users

Background

Traditionally, bacteriology clinical specimens are manually streaked using swabs and/or different sizes loops. With the introduction of WASPLab® automation in the Microbiology laboratories and the requirement to use samples in liquid phase, it is important to validate automated streaked of liquid samples using 1ul, 10 ul and 30ul loops to guarantee good colonies isolation. It is important to have a flexible system to accommodate customers’ requests in terms of volume or streaking patterns for different sample types.

Objectives

1) to validate the optimal size/volume loop and streaking pattern with good colonies separation for Urine samples in UriSwab™, swab samples in ESwab™, Stool samples in FecalSwab® and Sputum samples in SLSolution™

2) to demonstrate the flexibility of WASPLab® automation to deliver customized solutions.

Materials & Methods

Spiked samples, prepared with single and mixed bacteria with high/low, equal, and low/high concentrations from 107 cfu/ml to countable dilutions. UriSwab™ samples (USP), with E. coli (EC) and S. aureus (SA), ESwab™ samples (ESP) with MRSA and S. pyogenes (SP), FecalSwab® samples (FSP) with EC and salmonella (S) and SLSolution™ samples (SSP) with P.aeruginosa (PA) and K.pneumoniae (KP). USP, ESP, FSP, and SSP samples, spiked with 3 ascending dilutions of 2 bacteria were randomly loaded on the WASP® and streaked on 3 different agar plates amongst blood, choc, UTI, MRSA II, TSA, XLD, and MacConkey. Loops, 1ul, 10ul, and 30ul, and appropriate streaking patterns selected from standard, optional and customized solutions were used to prepare dedicated WASP® protocols. Inoculated plates were incubated at 350C; plates reading and image acquisition was done at 0 time and after 16-24 hrs incubation and images were recorded on the WASPLab® server. 50 replicates were done for each sample.

Results

  • UriSwab™ samples gave the best colonies separation with the 1 ul loop with all the 20 streaking patterns tested, while the 10 ul loops gave the best colonies separation with the Single Streak type 7 streaking pattern.
  • ESwab™ samples gave the best colonies separation with the 10 ul and 30 ul loops and the 4Qtype6, 4Q type 4 and 5Q type 1 even with high bacteria loads.
  • FecalSwab® samples gave best colonies separation with the 4 quadrant type 6 pattern. SLSolution™ samples gave the best colonies separation with 4Q type 1 and 4.
  • Optimal colonies separation was found in the customized streaking pattern with modified sample deposition.

Conclusions

  • It was demonstrated that the Copan WASP® can reliably and accurately produce isolated colonies in samples with mixed concentration of bacteria according to the loop size and streaking pattern.
  • Automated WASP® seeding, and WASPLab® plates image recording system supports quality in the microbiology laboratory.
  • The results obtained in this study are stored in a library to monitor the WASP® streaking performance and to help new WASP® user select the optimal loop size and streaking patterns for their laboratory.