Sample collection

This study took place at Barnes-Jewish Hospital (BJH) in St. Louis, MO. This study was approved by the Washington University Human Research Protection Office (#202209127). High-touch surfaces were sampled at a single time point using Eswabs (Copan, Brescia, Italy) and sponge sticks (3M, St. Paul, MN) in 10 patient rooms in the medical intensive care unit (MICU) and 10 patient rooms in the surgical ICU (SICU). Stick-mounted sponges come premoistened in bags for sampling and firm pressure was applied to surfaces being sampled. Eswabs were premoistened by dipping them into molecular-grade sterile water to mimic that of the stick-mounted sponge. Surfaces were swabbed by applying firm pressure to the area being sampled and then placed back into individual vials of transport media as previously described.^{Reference Sukhum, Newcomer, Cass, Wallace, Johnson, Fine, Sax, Barlet, Burnham, Dantas and Kwon5}

In each patient room, 7 high-touch areas within individual patient rooms were chosen to conduct sampling: 1) sink and sink drain composite, 2) floor composite, 3) bathroom composite, 4) ventilator (if present) and IV pole composite, 5) visitor chair and/or bed composite, 6) ≤3 feet from the patient (bedside rail, call button, phone, and table), and 7) >3 feet from the patient (inner door handle, keyboard, and barcode scanner). Eight additional high-touch area samples from communal spaces were collected in both ICU settings: 1) visitor bathroom composite, 2) visitor sink composite, 3) floor composite, 4) chairs, table, and vending machine composite, 5) glucometer, 6) Doppler ultrasound, 7) vital signs monitor, and 8) medication dispenser. Sample sites were chosen based on previously published studies about bacterial load in specific areas of hospital rooms.^{Reference D’Souza, Potter, Wallace, Shupe, Patel, Sun, Gul, Kwon, Andleeb, Burnham and Dantas6} Each site was sampled by both the Eswab and stick-mounted sponge by the same individual. For example, the floor composite sample for the Eswab consisted of a 4-inch by 4-inch area near the patient waist area along the bed and then a second 4-inch by 4-inch area next to the IV pole. The floor composite collection was repeated for the sponge-mounted stick, using the same parameters, near but not overlapping the Eswab collection areas.

Sample processing and culture methods

Samples using stick-mounted sponges were processed as previously published in Rose et al.,^{Reference Rose, Hodges, O’Connell and Noble-Wang7} with the following modifications: stick-mounted sponges were placed into a stomacher bag with 10 mL of phosphate-buffered saline containing 0.02% Tween 80 (PBST) and processed with a stomacher (Biomaster, Seward, Bohemia, NY) for 1 minute at 265 rpm. After processing via the stomacher and settling for 5–10 minutes, specimens were transferred into 15 mL conical tubes. The samples were centrifuged at 3000 g for 15 minutes at room temperature to pellet cellular material. Supernatant was removed after centrifugation and pellets resuspended in the remaining 3 mL volume for culture.

Samples collected using Eswabs were processed by vortex mixing for 30 seconds prior to plating the specimens for culture.

All samples were cultured using 100 uL of eluate cross-streaked onto one tryptic soy agar with 5% sheep blood (BAP, Hardy Diagnostics, Santa Maria, CA) plate and two Sabouraud dextrose with chloramphenicol agar (SABC, Hardy Diagnostics, Santa Maria, CA) plates. BAP agar and one SABC agar were incubated at 35^oC and one SABC incubated at 30^oC. BAP and SABC plates were screened for yeast colonies at days 1 and 2 via colony morphology and wet mount light microscopy of colonies. The SABC was incubated for a total of 7 days and screened on days 1, 2, and 7 for yeast colonies. Yeast isolates were subcultured to SABC and incubated at 30^oC for isolation and identified using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF) performed on the Vitek MS with database V3.2 (bioMerieux, Marcy-l’ Étoile, France).