Hospital room.

Viable bacterial communities on hospital window components in patient rooms.

The microbial community found in buildings is primarily a reflection of the occupants, and in the case of hospitals, the microbiota may be sourced from patients, staff, or visitors. In addition to leaving microbiota behind, occupants may pick up microorganisms from building surfaces. Most of the time, this continuous exchange of microorganisms between a person and their surroundings is unremarkable and does not raise concerns. But in a hospital setting with immunocompromised patients, these microbial reservoirs may pose a risk.  Window glass, sills, and the surfaces around windows are often forgotten during hospital disinfection protocols, and the microbial communities found there have not previously been examined.

In a 2019 collaboration between the Biology and the Built Environment Center at the University of Oregon and the Oregon Health & Sciences University, we sampled various window surfaces from patient rooms in a hospital ward. We characterized the viable bacterial community located on these surfaces, and investigated the association of relative light exposure of the surface (in direct light or not), the cardinal direction of the room (and roughly the amount of total light exposure in a day), and proximity of the patient room to the nurses’ station (which has higher occupancy and traffic).

Figure 1. Floor plan and rendering of a typical patient room at the Oregon Health and Science University hospital. (a) Floor plan of the 13th floor of Kohler Pavilion (13K) at Oregon Health and Science University (OHSU). Red shading indicates the rooms that were sampled between 10:00 a.m. and 11:00 a.m. on June 7, 2019 (b) Digital rendering of a typical patient room on OHSU (13K) with the sampling locations indicated by the numbers. The sampled locations were (1) window glass surface, (2) the window frame surface facing into the room at the sill, (3) glazing-side of the window frame at the sill, (4) window-side of the curtain, (5) patient-side of the curtain and, (6) wood-covered air return grille.

This paper is the first first-authored research paper from a former undergraduate mentee of mine at the University of Oregon; Patrick Horve.


Horve, P.F., Dietz, L., Ishaq, S.L., Kline, J., Fretz, M., Van Den Wymelenberg, K. 2020. Viable bacterial communities on hospital window components in patient rooms. PeerJ 8: e9580.

Abstract

Previous studies demonstrate an exchange of bacteria between hospital room surfaces and patients, and a reduction in survival of microorganisms in dust inside buildings from sunlight exposure. While the transmission of microorganisms between humans and their local environment is a continuous exchange which generally does not raise cause for alarm, in a hospital setting with immunocompromised patients, these building-source microbial reservoirs may pose a risk.  Window glass is often neglected during hospital disinfection protocols, and the microbial communities found there have not previously been examined. This pilot study examined whether living bacterial communities, and specifically the pathogens Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridioides difficile (C. difficile), were present on window components of exterior-facing windows inside patient rooms, and whether relative light exposure (direct or indirect) was associated with changes in bacterial communities on those hospital surfaces. Environmental samples were collected from 30 patient rooms from a single ward at Oregon Health & Science University (OHSU) in Portland, Oregon, USA. Sampling locations within each room included the window glass surface, both sides of the window curtain, two surfaces of the window frame, and the air return grille. Viable bacterial abundances were quantified using qPCR, and community composition was assessed using Illumina MiSeq sequencing of the 16S rRNA gene V3/V4 region. Viable bacteria occupied all sampled locations but was not associated with a specific hospital surface or relative sunlight exposure. Bacterial communities were similar between window glass and the rest of the room, but had significantly lower Shannon Diversity, theorized to be related to low nutrient density and resistance to bacterial attachment of glass compared to other surface materials. Rooms with windows that were facing west demonstrated a higher abundance of viable bacteria than those facing other directions, potentially because at the time of sampling (morning) west-facing rooms had not yet been exposed to sunlight that day.  Viable C. difficile was not detected and viable MRSA was detected at very low abundance. Bacterial abundance was negatively correlated with distance from the central staff area containing the break room and nursing station. In the present study, it can be assumed that there is more human traffic in the center of the ward, and is likely responsible for the observed gradient of total abundance in rooms along the ward, as healthcare staff both deposit more bacteria during activities and affect microbial transit indoors. Overall, hospital window components possess similar microbial communities to other previously identified room locations known to act as reservoirs for microbial agents of hospital-associated infections.

Featured Image Credit: catinsyrup, iStock

Vinyl flooring materials inside petri dishes and seeded with house dust for experimentation

Accumulation of di-2-ethylhexyl phthalate from polyvinyl chloride flooring into settled house dust and the effect on the bacterial community.

The chemistry that happens indoors is relevant to human health due to the proximity to human occupants, and risk for exposure because of long periods spent indoors. There is a lot of diversity in chemical compounds present in the built environment, emission from materials, chemical interactions (e.g., adsorption, absorption) with materials, and local environmental conditions such as ventilation rate and temperature, all of which can alter chemical reactivity. This complexity makes it difficult to understand how indoor chemistry affects biological life.

Di-2-ethylhexyl phthalate (DEHP), a known endocrine-disrupting chemical, DEHP has been associated with increased reports of children’s asthma during warmer seasons, and its byproducts or metabolites can likewise be hazardous to human health. DEHP is commonly used in consumer goods and building materials, especially vinyl floor. It becomes a concern when it leaches from these materials into dust, water, or soil, as it can then be inhaled, absorbed, or ingested by building occupants. DEHP concentration is significantly higher in settled (i.e., surface) dust in homes with polyvinyl flooring. It is also found in HVAC filters, indicating that DEHP in dust easily moves from the floor to the air.

Little research has been done to elucidate the relationships between phthalate composition and the effects on microbial communities in dust. This pilot study investigated whether dust which accumulated DEHP emitted from polyvinyl chloride flooring would affect the bacterial communities in dust gathered from homes.

This was the first first-authored research paper by former undergraduate mentees of mine at the University of Oregon; Samantha Velazquez and Susie Nunez.


Velazquez, S., Bi, C., Kline, J., Nunez, S., Corsi, R., Xu, Y., Ishaq, S.L. 2019. Accumulation of di-2-ethylhexyl phthalate from polyvinyl chloride flooring into settled house dust and the effect on the bacterial community. PeerJ 7:e8147. Impact 2.353. Article.

Abstract

Di-2-ethylhexyl phthalate (DEHP) is a plasticizer used in consumer products and building materials, including polyvinyl chloride flooring material. DEHP adsorbs from material and leaches into soil, water, or dust, and presents an exposure risk to building occupants by inhalation, ingestion, or absorption.  A number of bacterial isolates are demonstrated to degrade DEHP in culture, but bacteria may be susceptible to it as well, thus this study examined the relation of DEHP to bacterial communities in dust.  Polyvinyl chloride flooring was seeded with homogenized house dust and incubated for up to 14 days, and bacterial communities in dust were identified at days 1, 7, and 14 using the V3-V4 regions of the bacterial 16S rRNA gene.  DEHP concentration in dust increased over time, as expected, and bacterial richness and Shannon diversity were negatively correlated with DEHP concentration.  Some sequence variants of Bacillus, Corynebacterium jeddahense, Streptococcus, and Peptoniphilus were relatively more abundant at low concentrations of DEHP, while some Sphingomonas, Chryseobacterium, and a member of the Enterobacteriaceae family were relatively more abundant at higher concentrations.  The built environment is known to host lower microbial diversity and biomass than natural environments, and DEHP or other chemicals indoors may contribute to this paucity.

Featured Image: Examples of seeded dust on the vinyl flooring materials. Image courtesy of Dr. Chenyang Bi.