_______________________________________________________________ Healthcare-Associated Infections
Advances in medical treatments have led to longer lives for individuals of all ages who have had organ transplantation, cancer, or infection with human immunodeficiency virus (HIV), and their compromised immune system puts them at high risk for HAI. High risk is also assigned to patients with multiple trauma or severe burns, or those who have surgery or an invasive procedure that is considered to be high risk, such as endotracheal intubation or insertion of a central venous catheter. IATROGENIC FACTORS The primary iatrogenic factors contributing to the develop- ment of HAIs are devices (nonimplanted and implanted) and invasive procedures. As noted, the four most common HAIs—catheter-associated urinary tract infection, intravascular device-related bloodstream infection, surgical site infection, and pneumonia (ventilator-associated and hospital-acquired)— are related to the use of invasive devices or invasive procedures. Nonimplanted Devices HAIs have been associated with several types of devices and equipment unique to healthcare facilities. The Spaulding classification, developed in 1968, is widely used to categorize devices according to their associated risk of infection [103]. The system includes three categories: • Critical: A device that enters normally sterile tissue or the vascular system • Semicritical: A device that comes into contact with intact mucous membranes and does not ordinarily penetrate sterile tissue • Noncritical: A device that does not ordinarily touch a patient or touches only intact skin Most HAIs can be attributed to devices in the critical and semicritical categories, including intravascular catheters, sur- gical drains, urinary catheters, and endoscopic instruments [89]. Discussion here is limited to endoscopic instruments, as infections related to the other devices are addressed in detail later. In general, the transmission of pathogens on endoscopic devices has been attributed to noncompliance with appropriate reprocessing (cleaning, disinfection, sterilization, and drying) [19; 34; 104; 105]. In particular, appropriate drying has been overlooked as an integral component of reprocessing, and guidelines have been inconsistent in recommendations on drying [106]. Bronchoscopes and gastrointestinal endoscopes are the pri- mary diagnostic scopes used in healthcare settings. Both types of devices are associated with a low risk of infection transmis- sion. Approximately 500,000 flexible bronchoscopies are done in the United States each year [19; 107]. Few studies, however, have been carried out to evaluate the risk of infection; nosoco- mial infection related to bronchoscopy is difficult to detect and is likely under-recognized and under-reported [108]. In 2003, there were two reports of multiple pseudoinfections and true infections, primarily with P. aeruginosa , associated with bron-
choscopes that had been reprocessed according to current stan- dards [109; 110]. However, in both reports, loose fittings over the valve stem for the working channel of the bronchoscope were thought to have prevented effective mechanical cleaning and disinfection [108]. Overall, the pathogens associated with bronchoscopy-related infection have been P. aeruginosa , Serratia marcescens , nontuberculous mycobacteria, and environmental fungi [108]. In 2014, the U.S. Food and Drug Administration (FDA) received 50 medical device reports that mentioned infection or device contamination associated with reprocessed flexible bronchoscopes [107]. During the course of investigat- ing these reports, the FDA identified two recurrent themes that contributed to device contamination or device-associated infection: failure to meticulously follow the manufacturer’s instructions for reprocessing (e.g., failure to perform thorough manual cleaning before high-level disinfection), and continued use of devices, despite integrity, maintenance, and mechanical issues (e.g., persistent channel kinks or bends). More studies have evaluated the risk of infection associated with gastrointestinal endoscopy, which is performed on approximately 10 to 20 million people each year [111]. The American Society for Gastrointestinal Endoscopy (ASGE) estimates that infectious organisms are transmitted in 1 of 1.8 million gastrointestinal endoscopies [104]. Furthermore, all instances of infection during endoscopy have been the result of noncompliance with established guidelines for reprocess- ing of endoscopy equipment, highlighting the importance of adhering to these recommendations [34; 111; 112; 113]. As with bronchoscopy, the pathogen with the highest rate of transmission associated with gastrointestinal endoscopy is P. aeruginosa [111; 113]. As is true for other pathogens associ- ated with endoscopy, infection with P. aeruginosa has resulted from nonadherence to reprocessing guidelines; however, this pathogen differs from the others because of its predilection for a moist environment. Many cases of infection with P. aeruginosa have been linked to the water supply to the endoscope and to failure to completely dry the endoscope channels with a 70% alcohol solution and forced air [106; 111; 113]. Salmonella species have also been associated with endoscopy, but no cases have been reported since the publication of the 1988 guidelines for standardized cleaning and disinfection of the devices [111; 113]. Infection with Helicobacter pylori has also been related to suboptimal cleaning and disinfection [111]. Low rates of hepa- titis B and C virus transmission have been reported, and most cases of infection with hepatitis C were found to be related to the inappropriate use of multiple-dose vials and/or syringes rather than to the endoscope itself [34; 111]. Noncritical devices are often overlooked by healthcare work- ers as vectors for infection. These devices include diagnostic equipment, stethoscopes, and other commonplace items. A systematic review of 23 studies found bacterial contamina- tion of 87% of sampled healthcare equipment, primarily stethoscope membranes, as well as diagnostic ultrasound equipment, otoscopes, and auriscopes [114]. The organisms
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