Infection Control

Infection Control & Dust Control Management

Lawrence Environmental Group is currently working at some of the nation's preeminent hospitals to design and monitor containment systems and dust control procedures during facility renovations. At the inception of a project, the LEG team will coordinate with in-house project management and the hospital's infection control professionals, as well as architects and general contractors, to develop site-specific containment systems and task sequencing to ensure that patient areas adjacent to an active work area remain uncontaminated.

LEG can also provide experienced hygienists for daily oversight and inspections as well as a variety of testing to insure that any engineering controls in use are functioning optimally. Our ability to analyze most microbial samples within a twelve-hour window, combined with the use of direct read particle counters and manometers with data-logging, allows for a daily assessment of site conditions that is thoroughly documented.

Background

Construction-related nosocomial infections are primarily due to fungi and, to a lesser extent, bacteria. The predominant etiologic agent is Aspergillus. Since Aspergillus and Legionella species are the most frequent causes of construction-related nosocomial infection, understanding the relation between these organisms and construction and renovation activities leads to a better understanding of the need for preventive measures.

Aspergillus organisms are fungi found ubiquitously in soil, water and decaying vegetation. The fungal spores proliferate on dead organic debris and can remain viable for months in dry locations. During construction and renovation activities, spores can be dispersed on dust or dirt particles when floors, walls or ceilings are penetrated. Since Aspergillus spores are small (2.5 mm-3.5 mm) and settle very slowly (0.03 cm per second), they can remain suspended in air for prolonged periods. This increases the likelihood that they will be inhaled or will contaminate environmental surfaces.

Healthy individuals, such as healthcare workers, may become sensitized to Aspergillus but have only a minute risk of infection if exposed, whereas exposure to Aspergillus can be life-threatening and often fatal for patients who are severely immunosuppressed. It is essential that preventive measures are implemented to decrease the exposure to patients or residents to dust particles contaminated with Aspergillus spores.

Legionella is also a ubiquitous organism reservoirs in hospitals have included cooling towers, evaporative condensers, locally produced distilled water, heated potable water systems, and heating and air-conditioning systems. During construction and renovation projects, water systems are often disrupted, and the potable water can become contaminated with Legionella when the water supply is restored. Contamination may be related to massive descaling in the water pipes as they are repressurized or to the introduction of contaminated soil into the plumbing system(32). Legionella can then proliferate in the facility's water supply if certain conditions exist, such as sediment in hot water tanks, low hot-water temperatures at faucets, and water systems that are prone to stagnation. In addition, soil and dust containing dormant forms of Legionella can become airborne during soil excavation and can subsequently contaminate cooling towers or be inhaled by susceptible patients. The occurrence of a nosocomial infection caused by Legionella depends on the resistance of the host, exposure of the host to a contaminated source, and the degree of contamination of the source. Patients receiving high dose steroids are at particular risk. Legionnaires' disease is thought to be acquired by inhalation of aerosols contaminated with Legionella from the water supply. Legionnaires' disease can be difficult to diagnose if not suspected because specialized laboratory methods and culture media are required(82). Thus, preventive measures to decrease the transmission of Legionella should be implemented when construction or renovation activities that disrupt some of the healthcare facility's water supply are planned.

2.Source of the Micro-organism Causing Infection in Construction Settings

Biological sources causing infection in construction settings include mold, dust or soil contaminated with fungal spores or bacteria. Contaminated mold or dust particles can be present above false ceilings, or within fibrous insulating material, roller-blind casings and fire-proofing material. Outbreaks have been related to a hospital's plumbing or ventilation system.

As this review illustrates, a variety of sources of infection exist in healthcare facilities during construction and renovation activities. When such activities are being planned, healthcare personnel and other professionals involved must consider potential sources of highly concentrated micro-organisms that may cause nosocomial infections.

3. Risk Factors for Construction-Related Nosocomial Infections

A. Exposure to Construction

Any patients exposed to healthcare facility construction activities or soil excavation may be at increased risk of acquiring a construction-related nosocomial infection. The importance of decreasing the exposure to patients during construction activities or soil excavation is well documented.

B. Patient Characteristics

Certain patients are at increased risk of construction-related nosocomial infections because of underlying medical conditions. Comorbidity is one of the best predictors of the development of invasive Aspergillosis or Legionnaires' disease.

Immunosuppressed patients are at greatest risk of acquiring a nosocomial fungal infection or Legionellosis. This includes patients who have undergone bone marrow or solid organ transplantation, oncology patients who are receiving chemotherapy, patients receiving dialysis, and patients taking immunosuppressive medication, including steroids. Such high risk individuals may receive care in healthcare facilities across the continuum of care, e.g. oncology patients in ambulatory units; thus there is a need for a risk assessment prior to construction and renovation activities wherever healthcare is provided.

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