Infection Control Today - 10/2002: Environmental Services

Infectious Reservoirs in the Physical Plant

By Kathy Dix

Microorganisms seem to take every opportunity to hide, and your facility isfull of crevices where they can go underground. There are other places besidesnooks and crannies where they take up residence -- namely inside your physicalplant. Airborne and waterborne organisms can make themselves at home in yourfacility's heating and cooling system or in your ventilation system. They areperfectly capable of loitering in forgotten reservoirs of water or in intake andexhaust ducts.

But many outbreaks of nosocomial infections could be controlled just byawareness of the potential source of such infections and preventing their growthin those sources.¹

Certain areas of the hospital are particularly in need of good waterborne andairborne infection control. These areas include operating rooms, specialprocedure rooms, delivery rooms, airborne communicable disease isolation rooms,protective isolation rooms, laboratories and sterile supply rooms.²

Airborne Microorganisms

Indoor air quality is a definite environmental health problem, according tothe Environmental Protection Agency (EPA). And although most people may not bebothered by normal levels of fungus or other "natural" irritants inthe air, immunocompromised patients or people with severe allergies could be atserious risk from even naturally-occurring airborne microorganisms. However,airborne contaminants can be controlled with properly maintained pressurerelationships, air exchanges, filtration systems, local exhaust and dilutionventilation.²

These recommendations are intended to control not only fungi, viruses andbacteria, but also biological agents, gases, fumes and dust. However, controlnecessitates clean filtration systems, correct balances and filter efficiencies.Preventative maintenance, surveillance surveys and environmental rounds shouldbe part of the regularly scheduled infection control procedures.

Accurate records should be kept of these procedures, and of the solutions toany problems that arise during regular maintenance. Copies of these recordsshould be kept by infection control personnel as well as facility managers andleadership.

Waterborne Microorganisms

You should pay particular attention to these water systems, which may be goodsources of pathogens: cooling towers, aerosolizing systems and domestic hotwater.

The growth of Legionella pneumophila, for example, can be intensified bywater stagnation and sediment buildup -- which can be caused by alterations inthe plumbing of intricate distribution systems found in some hospital hot-watersystems. Proper maintenance could remove or at least control the sedimentaccumulation.¹

Cooling towers spray water onto a packing material through which there is acountercurrent flow of air -- easily producing fine droplets of water. Suchtowers are often the source of outbreaks and should thus be cleaned anddisinfected on a regular basis.

According to the American Society of Heating, Refrigerating andAir-Conditioning Engineers, Inc. (ASHRAE), to avoid Legionellosis specifically,avoid piping that is capped and has no flow (dead legs); keep water temperaturesbelow 25 degrees Centigrade and above 55 degrees C; apply biocidesappropriately; and limit available niches for microbiata.³

ASHRAE specifies, "More emphasis should be placed on clean equipment inexcellent repair than on periodic testing with concurrent system neglect,"and stresses that periodic or routine monitoring is never effective if donewithout adequate maintenance.

To curtail colonization and multiplication of bacteria in water systems,water should be circulated and not allowed to stagnate. Inspection, cleaning anddisinfecting should be part of the regular maintenance schedule for storagetanks and calorifiers. Remove "dead legs" from plumbing systems, avoidwashers and gaskets made of natural rubber, replace heavily-scaled faucets andshowerheads (which can distribute contaminated water droplets) and avoid shockabsorbers and pipe materials that are not copper or plastic.^{1, 3}

Fungi can breed in the drain pan under cooling coils or in the cooling coilsthemselves. Water pans for humidifiers are also a potential site. Although HEPAfilters are a reasonable means of filtering out organisms from the air webreathe, they should be tightly installed and well-maintained -- and they shouldbe monitored to ensure the filters themselves do not harbor fungus growth.⁴

Ductwork is also a possible hiding place for moisture and microorganisms.Clean ductwork with a disinfectant after inspecting it for fungus. Insulationcan also harbor moisture and fungus.

But fungi don't necessarily need moisture to get into your facility. If wateris not available, they can reduce to spore form and become even easier totransmit by air.

JCAHO Recommendations

The Joint Commission on the Accreditation of Healthcare Organizations (JCAHO)recommends that at least once a year, facilities choose one high-risk processand assess the risk and how a failure of the system can occur. Three steps areinvolved in this risk assessment: failure mode, effect on other components orsystems, and criticality analysis.²

One proactive risk reduction activity might be to study the safety of thehospital's water system. Staff members from multiple departments -- engineering,maintenance, infection control and clinical areas -- could identify any ways inwhich the water system could fail, and how notice of those failures could berelayed to the hospital.

The facility would then assess how the users would be affected, how often thefailure might occur, how severe the failure's effect would be, and whether itcould be discovered before adverse effects arose.

Some other potential reservoirs include fireproofing material, damp wood, andbird droppings in air ducts. Aspergillus sp. has been found in these sites.⁵