Journal of Applied Microbiology, Vol.115, No.1, 171-178, 2013
Comparative performance of contact plates, electrostatic wipes, swabs and a novel sampling device for the detection of Staphylococcus aureus on environmental surfaces
Aims To evaluate the performance of four sampling methods [contact plates, electrostatic wipes (wipe), swabs and a novel roller sampler] for recovery of Staphylococcus aureus from a stainless steel surface. Methods and Results Stainless steel test plates were inoculated with Staph.aureus, dried for 24h and sampled using each of the four methods. Samples were either incubated directly (roller, contact plate) or processed using elution and membrane filtration (swab, wipe). Performance was assessed by calculating the apparent sampling efficiency (ASE), analytical sensitivity (Sn) and percentage of replications with positive growth. The wipe demonstrated the best performance across all inoculating concentrations (ASE48h=18%; Sn48h=7CFU per 100cm2). The swab performed well when corrected for area actually sampled (ASE48h=24%; Sn48h=76CFU per 100cm2). Of the contact-based methods, the newly developed roller sampler outperformed the contact plate (roller: ASE48h=10%; Sn48h=17CFU per 100cm2; contact plate: ASE48h=0 center dot 04%; Sn48h=1412CFU per 100cm2); both contact samplers performed better at higher inoculating concentrations (6E3CFU per 100cm2 for the roller and 6E6CFU per 100cm2 for the contact plate). Overall, the electrostatic wipe produced the highest number of replications resulting in positive growth (74%24h, 91%48h). Conclusions This study demonstrates that selection of the sampling method must be carefully considered, given that different methods have varying performance. Significance and Impact of the Study This is the first study assessing static wipes for sampling and one that uses a more real-world-relevant 24-h drying time. The results help with infection control, and environmental health professionals choose better sampling methodologies.