_______________________________________________________________ Healthcare-Associated Infections
ENVIRONMENTAL SOURCES OF PATHOGENS IN THE HEALTHCARE SETTING
Source
Bacteria
Viruses
Fungi
Aspergillus
Air
Gram-positive cocci (originating from skin) Tuberculosis
Varicella zoster (chickenpox) Influenza
Aspergillus Exophiala jeanselmei
Water (tap and bath)
Gram-negative bacteria ( Pseudomonas aeruginosa , Aeromonas hydrophilia , Burkholderia cepacia , Stenotrophomonas maltophilia , Serratia marcescens , Flavobacterium meningosepticum , Acinetobacter calcoaceticus , and Legionella pneumophila ) Mycobacteria ( Mycobacterium xenopi , Mycobacterium chelonae , or Mycobacterium avium-intracellularae )
Molluscum contagiosum Human papillomavirus (bath water) Noroviruses
Source: [18; 87; 88]
Table 4
air is Aspergillus , which is carried through dust particles, can survive for long periods, and is easily inhaled [90]. Under normal circumstances, the level of contamination with this airborne fungus’ spores is not high enough to cause disease in otherwise healthy individuals. However, in the healthcare setting, the fungus causes respiratory infection, primarily pneumonia, in susceptible hosts. The prevalence of infection with Aspergillus within a health- care setting has been strongly associated with Aspergillus spore counts. Consequently, air conditioning systems with high- efficiency particulate air (HEPA) filters are needed to minimize contamination [91]. HEPA filters are especially needed to pre- vent infection with Aspergillus in patients at high risk for infec- tion due to a suppressed immune system [92]. In one study, the risk of transplant-related mortality and overall mortality in the first 100 days after transplantation were significantly lower among patients treated in rooms with HEPA and/or laminar flow units than among patients treated in conventional isola- tion units [93]. In these units, the air exchange rate should be high (more than 15 exchanges per hour), rooms should be tightly sealed, and the air pressure in the rooms should be positive in relation to the hallway [91; 94; 95]. HEPA filters are also used in the hoods in microbiology laboratories and pharmacies, laminar flow units in ICUs, and unidirectional flow units in operating room suites [18]. Air in the Operating Room Maintaining a high quality of air in operating rooms is an essential factor in preventing postoperative infection. The number and movement of staff within the operating room create the primary sources of airborne bacteria. Other fac- tors influencing airborne contamination include the type of surgery, the rate of air exchange, the initial quality of the air, the quality of the staff clothing and cleaning processes, and the level of compliance with infection control practices [18].
The CDC makes several suggestions about ventilation in the operating room in its guidelines for prevention of surgical site infections [31]. The Level I recommendations include: • Maintain positive-pressure ventilation in the operating room with respect to the corridors and adjacent areas. • Maintain a minimum of 15 air changes per hour, of which at least three should be fresh air. • Filter all air, recirculated and fresh, through the appropriate filters per recommendations of the American Institute of Architects. • Introduce all air at the ceiling and exhaust near the floor. • Do not use ultraviolet radiation in the operating room to prevent surgical site infection. • Keep operating room doors closed except as needed for passage of equipment, personnel, and the patient. Air During Construction Special care must be taken to protect patients during repair or renovation of a healthcare facility, as construction work can facilitate the spread of airborne organisms such as Aspergillus species [18]. Some construction issues that contribute to the spread of infection include water-damaged building materials, disruption of duct work, open windows, and improper setting of fans or installation of filters [96]. The Joint Commission requires an inspection process for construction on a facility, and a risk assessment is part of that process [96]. Risk factors to consider include the patient population, the extent and duration of the project, the impact of the project on mechanical systems, and whether space with construction will be occupied [96]. A representative from a facility’s infection control program should review any plans for construction to ensure that barriers are used as appropri- ate and patients, especially those with compromised immune systems, are moved to an area away from construction [89].
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