Infection Control & Hospital Epidemiology
with MRSA colonization or infection are placed in contact precau- tions.A commercial bleach product is used for postdischarge clean- ing of all patient rooms. Daily cleaning is performed in MRSA isolation rooms only if surfaces are visibly soiled.
Participants and procedures
The study protocol was approved by the facility’s institutional review board. Between February 1, 2016, and June 30, 2017, we conducted an observational cohort study of hospitalized patients in contact precautions for MRSA colonization or infection. BBL culture swabs (Becton Dickinson, Cockeysville, MD) were used to sample the anterior nares, chest and abdomen, hands, and any open wounds. Initial studies demonstrated that shedding of MRSA was rare for patients in isolation for prior detection of MRSA but with negative current nasal and wound cultures. Therefore, we examined the frequency and distribution of shed- ding of MRSA during medical and nonmedical procedures in the subset of patients with positive anterior nares and/or wound cultures. Nonmedical procedures included bathing, eating meals, bedding change, and transfer from bed to chair or to a gurney. Medical procedures included wound care, respiratory therapy, physical therapy, medication administration, ostomy change, and ultrasound testing. Prior to the procedures, high-touch environmental surfaces in
the room were cleaned and disinfected with a commercial 1-step cleaner and disinfectant containing 30% ethanol and allowed to air dry for at least 5 minutes. For the first 30 procedures, cultures were obtained to ensure that no MRSA was recovered after clean- ing. Research staff observed the procedures and recorded informa- tion regarding contact between environmental surfaces in the room and personnel, patients, and portable equipment used for the procedures. After completion of the procedures, replicate organ- ism detection and counting (RODAC) plates containing BBL CHROMagar with cefoxitin 6 μg/mL were used to sample a stand- ardized group of high-touch environmental surfaces; separate plates were used to sample surfaces ≤0.9 m (eg, bed rails, bedside tables, call button, telephone, vital signs equipment) and >0.9 m (eg, chair, door knob, closet, night stand) from the patient. The RODAC plates were applied to 3 separate areas on each sampled surface. In addition to the standardized culture sites, we sampled additional surfaces in the room or bathroom that were observed to be contacted by the personnel performing the procedures and port- able equipment used during the procedures. To assess shedding in the absence of procedures, we cleaned and disinfected the high- touch surfaces at a time when the patient was in the room but no procedures or activities were scheduled and collected were cul- tures after 1 hour. A medical record review was conducted to obtain informa-
tion on demographics, medical conditions, wounds, antibiotics, chlorhexidine bathing, mobility, devices (central venous catheters and urinary catheters), fecal incontinence or diarrhea, and ward. Antibiotics were classified as anti-MRSA agents if they are commonly used to treat MRSA infections (eg, vancomycin, line- zolid, daptomycin, ceftaroline, doxycycline, and trimethoprim/ sulfamethoxazole).11
Microbiology and molecular typing
Swabs were plated on BBL CHROMagar containing cefoxitin 6 μg/mL for isolation of MRSA. Colonies consistent with S. aureus on RODAC or CHROMagar plates were tested for coagulase
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production using a Staphaurex kit (Remel, Lenexa, KS). The number of MRSA colony-forming units (CFUs) per swab were counted. For a subset of 40 patients, spa typing of nasal isolates as well as selected skin, wound, and environmental isolates was performed according to previously described methods.12 For individual patients, skin and environmental isolates were considered concordant with nares isolates if the same spa type was present.13
Statistical analysis
Procedures with and without shedding were aggregated within patients. Patients were classified as having no shedding if all envi- ronmental cultures were negative for all procedures performed. Patients were classified as shedding if 1 or more environmental cultures were positive during 1 ormore procedures.Weperformed χ2 tests to identify patient-level factors associated with environ- mental shedding of MRSA and to compare the frequencies of shedding for different procedures. For participants classified as shedding with data available from3 ormore procedures, we assessed characteristics of the subset with positive cultures for >50% of procedures. Data were analyzed using R version 3.5.0 software (The R Foundation for Statistical Computing, Vienna, Austria).
Results
Figure 1 shows a flow diagram for the study participants. Of 86 MRSA colonized patients eligible for enrollment, 75 (87%) partici- pated in the study. Of the 75 participants, 55 (73%) had positive nares and/or wound cultures forMRSA, and 18 (24%) had negative nares and wound cultures and negative skin cultures, whereas 2 (3%) had negative nares and wound cultures but positive skin cultures (ie, 1 had MRSA on the chest/abdomen and the other had MRSA on the chest/abdomen and on hands). The mean den- sity of nasal MRSA was 1.4 log10colony-forming units per swab (range, 0.3–4). Of the 52 patients with positive nares and/or wound MRSA cultures and at least 1 procedure or care activity assessed, 23 (44%) had positive chest/abdomen cultures and 25 (48%) had positive hand cultures. Figure 2 shows the frequency of environmental shedding
of MRSA associated with procedures for the 52 patients with MRSA in nares and/or wounds. All 30 of the pre-procedure cultures collected after cleaning of the surfaces were negative for MRSA. Of the 52 patients, 29 patients (56%) shed MRSA to the environment during 1 or more procedures. For these 29 patients, environmental shedding of MRSA was detected on 1 or more of the standard surfaces sampled in 59 of 138 (43%) procedures versus 8 of 83 (10%) sets of cultures collected in the absence of a procedure (P < .001). During procedures, shed- ding was detected significantly more often on the sites ≤0.9 m versus >0.9 m from the patient (52 of 138, 38% vs 25 of 138, 18%; P < .001). The procedures associated with the highest fre- quency of contamination included both medical (ie, physical/ occupational therapy, respiratory therapy, and wound care) and nonmedical procedures (ie, bathing and changing bedding). There were no statistically significant differences in the frequen- cies of shedding for different
proceduretypes.Inadditionto the standardized sites, contamination occurred frequently on other surfaces that were observed to be contacted by personnel (12 of 38, 32% positive) and on portable equipment used for pro- cedures (25 of 101, 25%). The median number of colonies recov- ered from contaminated sites was 4 (range, 1–253).
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