Other gram-negative bacteria present in potable water also can cause health-care associated infections. Clinically important, opportunistic organisms in tap water include Pseudomonas aeruginosa, Pseudomonas spp., Burkholderia cepacia, Ralstonia pickettii, Stenotrophomonas maltophilia, and Sphingomonas spp.. Immunocompromised patients are at greatest risk of developing infection. Medical conditions associated with these bacterial agents range from colonization of the respiratory and urinary tracts to deep, disseminated infections that can result in pneumonia and bloodstream bacteremia. Colonization by any of these organisms often precedes the development of infection. The use of tap water in medical care (e.g., in direct patient care, as a diluent for solutions, as a water source for medical instruments and equipment, and during the final stages of instrument disinfection) therefore presents a potential risk for exposure. Colonized patients also can serve as a source of contamination, particularly for moist environments of medical equipment (e.g., ventilators).
In addition to Legionella spp., Pseudomonas aeruginosa and Pseudomonas spp. are among the most clinically relevant, gram-negative, health-care associated pathogens identified from water. These and other gram-negative, non-fermentative bacteria have minimal nutritional requirements (i.e., these organisms can grow in distilled water) and can tolerate a variety of physical conditions. These attributes are critical to the success of these organisms as health-care associated pathogens. Measures to prevent the spread of these organisms and other waterborne, gram-negative bacteria include hand hygiene, glove use, barrier precautions, and eliminating potentially contaminated environmental reservoirs.
Two additional gram-negative bacterial pathogens that can proliferate in moist environments are Acinetobacter spp. and Enterobacter spp. Members of both genera are responsible for healthcare– associated episodes of colonization, bloodstream infections, pneumonia, and urinary tract infections among medically compromised patients, especially those in ICUs and burn therapy units.
Infections caused by Acinetobacter spp. represent a significant clinical problem. Average infection rates are higher from July through October compared with rates from November through June. Mortality rates associated with Acinetobacter bacteremia are 17%–52%, and rates as high as 71% have been reported for pneumonia caused by infection with either Acinetobacter spp. or Pseudomonas spp.Multi-drug resistance, especially in third generation cephalosporins for Enterobacter spp., contributes to increased morbidity and mortality.
Patients and health-care workers contribute significantly to the environmental contamination of surfaces and equipment with Acinetobacter spp. and Enterobacter spp., especially in intensive care areas, because of the nature of the medical equipment (e.g., ventilators) and the moisture associated with this equipment.
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