Preventing the transmission of antimicrobial-resistant organisms such as methicillin-resistant Staphylococcus aureus (S. aureus) and Candida auris (C. auris) is a top priority for hospital epidemiologists and infection preventionists. By adhering to contact-precaution recommendations (ie, wearing gloves and gowns), healthcare personnel (HCP) can play a major role in preventing patient-to-patient transmission. Gloves and gowns of HCP are frequently contaminated with epidemiologically important pathogens, such as S. aureus and C. auris. Several studies have used the presence of bacteria on HCP gloves and gown as a surrogate outcome for transmission studies,Reference O’Hara, Calfee and Miller1,Reference Roghmann, Johnson and Sorkin2 yet consensus is lacking regarding the best method for sampling HCP personal protective equipment. Previous studies have compared the recovery efficiency of the direct imprint of gloved hands onto agar plates and the use of cellulose sponges,Reference Lyons, Rose and Noble-Wang3 and others have studied pathogen recovery from environmental surfaces.Reference Rose, Houston and Martinez-Smith4,Reference Furin, Tran, Chan, Lyons, Noble-Wang and Rose5 However, no studies have investigated which swab type optimizes recovery of pathogens from personal protective equipment. Therefore, we sought to determine whether the E-swab or the BBL swab is most suitable for recovering Staphylococcus aureus and Candida auris from HCP gloves and gowns.
Methods
The primary comparison was between E-swabs and BBL swabs. The ESwab (Copan Diagnostics, Murrieta, CA) is a flocked swab with 1 mL liquid Amies in a plastic, screw-cap tube. The BD BBL CultureSwab (Becton Dickinson, Franklin Lakes, NJ) is a median-free system. A 10-µL aliquot of cell suspension with a concentration of 105 colony-forming units per milliliter (CFU/mL) of S. aureus or C. auris was inoculated onto a 5×5-cm square cutout of a standard latex glove. After allowing the area to dry for 2 minutes, the glove was sampled in a systematic manner with an E-swab and a BBL swab. E-swabs were then spun in a vortexer in the same transport device for 15 seconds. BBL swabs were placed in a tube containing 1 mL 0.85% saline and were spun in a vortexer for 15 seconds. Tenfold serial dilutions were performed in 1 mL 0.85% saline, and aliquots were plated onto 3 separate Sabouraud dextrose agar plates. The same procedures were performed on Ansell EY 10-214-3XL Edge 67-100 yellow polypropylene isolation gowns using both S. aureus and C. auris. After 48 hours, the average CFU per plate set were counted. For S. aureus, 20 paired samples were inoculated on gloves and 20 paired-samples were inoculated on gowns. Also, 10 paired samples were inoculated on the gloves and 10 paired samples were inoculated on the gowns for C. auris isolates selected from the Centers for Disease Control and Prevention (CDC) Antibiotic Resistance Isolate Bank C. auris panel. Using SAS version 9.4 software (SAS Institute, Cary, NC), the Wilcoxon signed-rank test was employed to compare whether the means differed between the paired samples. To further visualize the mean CFU/mL recovered on gloves and gowns from E-swabs and the BBL swabs from the triplicate plates, paired profiles for both S. aureus and C. auris were plotted.
Results
For S. aureus, the mean amount recovered from glove samples was 221 CFU/mL (SD, 339) for the E-swabs and 258 CFU/mL (SD, 328) for the BBL swabs. The Wilcoxon signed-rank test indicated that the mean CFU/mL recovered from gloves on the E-swabs was not statistically significantly different than that recovered from the BBL swab (Z = −2; P = .92). On the gown samples, the mean amounts of S. aureus recovered were 850 CFU/mL (SD, 1,119) for the E-swabs and 775 CFU/mL (SD, 969) for the BBL swabs (Z = 1; P = .99). For C. auris, the mean amounts of pathogen recovered from gloves were 176 CFU/mL (SD, 461) from the E-swabs and 270 CFU/mL (SD, 215) from the BBL swabs. Here, the Wilcoxon signed-rank test also showed that the mean CFU/mL recovered from gloves on the E-swabs was not statistically significantly different than that recovered from the BBL swab (Z = −14.5; P = .16). Finally, the mean amounts of C. auris recovered on the gowns were 722 CFU/mL (SD, 567) for the E-swabs and 739 CFU/mL (SD, 255) for the BBL swabs (Z = −5.5; P = .63). Figure 1 shows the paired profiles for E-swabs and BBL swabs that were inoculated with S. aureus for the glove (panel A) and gown samples (panel B). Each line represents a paired sample. The left end of the line indicates the mean amount of S. aureus recovered from the E-swab and the right end of the line indicates the amount recovered from the BBL swab. This procedure illustrated that in some pairs, the E-swab recovered more S. aureus, but in other pairs, the BBL swab recovered more. These plots also show that there is a fair amount of variation in how much pathogen was recovered from both swab types. Similar to the plots for S. aureus, Figure 2 shows the paired profiles for E-swab and BBL swabs that were inoculated with C. auris for the glove (panel A) and gown samples (panel B). With the exception of a single outlier, panel A suggests that the BBL swab tended to recover slightly more C. auris from glove samples, though this was not statistically significant.
Fig. 1. Paired profiles for E-swab and BBL swabs with Staphylococcus aureus. (A) Recovery from gloves. (B) Recovery from gowns.
Fig. 2. Paired profiles for E-swab and BBL swabs with Candida auris. (A) Recovery from gloves. (B) Recovery from gowns.
Discussion
To improve the quality of studies assessing the role of glove and gown contamination in the transmission of high-consequence pathogens such as S. aureus and C. auris, it is important to understand which sampling methods are most efficient. Our findings suggest that there is no difference between E-swabs and BBL swabs in the recovery of S. aureus and C. auris from personal protective equipment. Investigators may therefore consider making the decision based on budget and availability of supplies when developing their study methodologies. Although we found similar recovery of both S. aureus and C. auris for the 2 swab types studied, other sampling methods may improve recovery efficiency for other organisms. For example, 1 study found that the use of a sponge sampling method is best for recovering Clostridioides difficile from gloves.Reference Lyons, Rose and Noble-Wang3 However, sponge processing is more time-consuming for laboratory staff, and the sponges themselves can be more expensive than E-swabs or BBL swabs. Other studies have also shown that sponges may be optimal for sampling environmental items in patient rooms,Reference O’Hara, Calfee and Miller1 suggesting that the findings may not be generalizable to environmental surfaces. When sampling HCP personal protective equipment, both E-swabs and BBL swabs can be used to assess recovery of pathogens such as S. aureus and C. auris in the healthcare setting.
Acknowledgments
Financial support
This work was supported by the US Centers for Disease Control and Prevention Epicenters Program.
Conflicts of interest
All authors report no conflicts of interest relevant to this article.
