Development of Healthcare-Associated Infections: Role of the Built Environment

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Slide 1

Development of Healthcare-Associated Infections: Role of the Built Environment

James P. Steinberg, MD
Division of Infectious Diseases
Emory University School of Medicine

Slide 2

Healthcare Associated Infections

• Infections acquired while in a health care facility.
• Types:
  • Endogenous—pathogen arises from normal microbiota due to factors within the health care setting.
  • Exogenous—pathogen acquired from the health care environment.

Slide 3

Modes of Transmission of Infectious Agents Design and Built Environment Prevention Strategies

Slide 4

Chain of Transmission

• Traditional model:
  • Chain of transmission:
    • Pathogens.
    • Reservoirs/sources.
    • Mode of spread.
    • Patients.
  • "Breaking" a link of the chain can interrupt transmission.
• Linear chain model may underestimate complexity.

Image: Two lengths of chain are shown; one has a broken link.

Slide 5

Variables Influencing Transmission of Pathogens Healthcare Setting

• Patient/staff/family colonization:
  • Colonization pressure.
• Biologic properties of pathogen.
• Antibiotic pressure.
• Contaminated environment:
  • Surfaces.
  • Equipment.
  • Water sources.
• Intensity of contact.
• Duration of exposure.
• Adherence to infection control measures.

Slide 6

Low colonization pressure: poor compliance with infection control measures less likely to cause on transmission of MRSA

Image: A floor plan shows the layout of a hospital ward. Bed 1, where an MRSA infection occurred, is circled in red. Beds 9 through 12 are indicated by a bracket.

Nurse caring for beds 9-12 cleans hands 40% of time, but no cross transmission.

Slide 7

High Colonization Pressure: Small breaks in infection control measures could be enough to cause transmission

Image: A floor plan shows the layout of a hospital ward, as shown in Slide 18. The MRSA infection has spread from Bed 1 to Beds 2, 4, 6, 7, 8, 9, 10, 12, and 14 . Bed 8 is circled in red. Beds 6 through 9 are indicated by a bracket.

Nurse caring for beds 6-9 cleans hands 80% of time—but patient in bed 8 acquires MRSA.

Slide 8

Chain Of Transmission

Image: A model shows the chain of transmission of pathogens from sources inside and outside the hospital to susceptible patients who might become infected.

Slide 9

Chain Of Transmission: An Intervention Model

Image: The model showing the chain of transmission of pathogens now has notes added about opportunities for interventions to prevent infection through the built environment:

• External Source—Barriers, Filters.
• Reservoir or Source in the Hospital—Disinfect, Eliminate.
• Colonized/Infected Host—Hand hygiene, PPE (personal protective equipment), Other barriers, Isolation.

Slide 10

NIH Outbreak of Carbapenem-resistant Klebsiella pneumoniae (KPC)

• 18 patients, 11 deaths, 6 from KPC.
• Sophisticated analysis with whole-genome sequencing.
• Transmission map developed based on presumed person-to-person transmission.
• However, environmental sources uncovered.
• Outbreak strain in 6 sink drains and a ventilator.
• Despite intensive investigation, role if environment unclear.
• Environmental decontamination performed.

Snitkin et al. Science Translational Med 2012 vol 4.

Slide 11

Curtains—Prototype of Issues Relevant to Role of Environment

• Used for privacy/partitions.
• Often contaminated:
  • VRE, MRSA, C. difficile.
  • Transmission to hands occurs but is inefficient:
    • Trillis ICHE 2008;29:1174.
• Have been linked to outbreaks:
  • Acinetobacter in ICU, transmission interrupted with multiple interventions including curtain replacement:
    • Das JHI 2002;50:110.
• Role in endemic transmission unclear.

Images: Two photographs show women standing with their hands on a privacy curtain.

Slide 12

Curtains—Prototype of Issues Relevant to Role of Environment

• Cleaning recommendations don’t specify frequency:
  • HICPAC—Clean when visibly soiled.
• Newer technologies (impregnated materials) marketed:
  • Can reduce contamination.
  • No data on prevention of transmission.
• Hand hygiene can mitigate risk.
• Design strategies that eliminate need of curtains may be optimal but are they cost effective?

Images: A photograph shows a woman standing with her hand on a privacy curtain. Another photograph shows vertical blinds/vents on a window.

Slide 13

Challenges in Assessing Role of Environment in Transmission of Pathogens

• Environmental contamination common and dynamic.
• Transmission often requires humans as intermediaries can be impacted by behavior.
• Overlapping pathways of transmission exist and obfuscate role of environment.
• Most transmission events are silent:
  • Lead to colonization not infection.
• Studying transmission events and impact of environment is difficult.
• Role of the environment may be underappreciated.

Slide 14

Challenges in Assessing Role of Environment in Transmission of Pathogens

• Interventions to reduce environmental contamination (materials, cleaning methods) often measure microbial burden and not colonization/infection.
• Build/design interventions sometimes impossible to study in controlled or rigorous way.
• Given paucity of data to inform facility design decisions, cost considerations very important.
• Behavior or process changes may reduce transmission of pathogens independently from design/technologic solutions:
  • Design can influence behavior.
  • Technologic/built solutions may be easier to implement.