Definitions

Obtaining meaningful data on rates of nosocomial infection that can form the basis for comparisons within a hospital and, especially, among hospitals and that can also be used to monitor secular trends and document the efficacy or lack of efficacy of control measures must begin with clear, unambiguous definitions. Although there are no standardized definitions for infection at specific sites that are universally accepted by clinicians or investigators, the Centers for Disease Control and Prevention (CDC) has published definitions for the purpose of surveillance of nosocomial infection within hospitals, which most U.S. centers and an increasing number of hospitals around the world have adopted (Box 50.1).^16,17 For research purposes, more stringent definitions for specific infections will usually be necessary,¹⁸ especially for pneumonia.¹⁹

Incidence

The incidence of hospital-acquired infection is most commonly expressed as the number of infections per 100 patients hospitalized and is highest in burn units7,20 and surgical ICUs,^{5–7,20–23} with intermediate risk in medical ICUs,* and lowest risk in coronary care units.^4,7,8,20

Recognizing that the risk of nosocomial infection within ICUs is heavily influenced by the length of stay and that the length of stay ranges widely among ICUs in the same hospital and among different hospitals, the CDC has advocated the use of rates expressed per 1000 patient-days to permit more meaningful intrainstitutional and, especially, interhospital comparisons.25–27 Furthermore, recognizing the powerful influence of exposure to invasive devices on susceptibility to infection^28,29 and the great variation in use of devices among different ICUs in the same hospital and among different hospitals, the CDC has further recommended surveillance of device-associated nosocomial infections expressed as infections per 1000 device-days.²⁵ Representative rates of device-associated nosocomial infection in U.S. hospitals, which can be used for intrahospital and interhospital comparisons, are shown in Table 50.1.^25–27 In the future, device-associated infection rates will be sought in accreditation reviews by the Joint Commission on the Accreditation of Healthcare Organizations (JCAHO)³⁰ as this influential organization continues to move toward measurement of patient outcomes as the most effective way to improve patient care in the United States.

Profile and Secular Trends

Approximately 40% of endemic nosocomial infections within ICUs are catheter-related urinary tract infections, and 25% are pneumonias—most associated with endotracheal intubation and mechanical ventilatory support. Up to 10% of patients hospitalized in a medical-surgical ICU for more than 72 hours acquire a nosocomial bloodstream infection, most commonly from an intravascular device.25,31,32 Postoperative surgical site infections, Clostridium difficile infection, nosocomial sinusitis, and nosocomial meninigitis account for the remainder.^{4–8,25,33–37}

Nearly 50% of nosocomial infections in the ICU are caused by aerobic gram-negative bacilli, especially Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae, and 35% are caused by gram-positive cocci, most commonly coagulase-negative staphylococci, Staphylococcus aureus, and enterococci (Fig. 50.1).^38,39 Almost 15% are caused by Candida species.^38,39 Filamentous fungi such as Aspergillus and Zygomycetes are being increasingly encountered in patients with hematologic malignancy or those who received solid organ transplants.^40–42 Legionella species account for up to 10% of nosocomial pneumonias in centers that make efforts to diagnose Legionella infections.⁴³

The microbial profile of infections at individual sites in ICU patients is shown in Table 50.2.³⁹ There has been an unrelenting increase in nosocomial infections caused by intrinsically resistant organisms, especially P. aeruginosa, Acinetobacter species, and other resistant gram-negative bacilli; coagulase-negative staphylococci, S. aureus, enterococci; and Candida.^{31,38,39,44,45} Moreover, the incidence of infection caused by organisms with acquired resistance, especially methicillin-resistant S. aureus (MRSA); enterococci resistant to vancomycin (VRE), ampicillin, or both drugs; and gram-negative bacilli resistant to extended-spectrum β-lactams and fluoroquinolones, has increased even more sharply over the past several decades (Fig. 50.2).^39,46 The recent emergence of carbapenem-resistant K. pneumoniae has become a significant problem as there are limited therapeutic options to treat this pathogen.^39,47

Nosocomial infections acquired in the ICU clearly differ from infections acquired in non-ICU patient care units within the same institutions. Overall rates are two to three times higher, and rates of ventilator-associated pneumonia (VAP) and primary bacteremia—most of which originate from intravascular devices—are 10 times higher. A far greater proportion of ICU-acquired infections are caused by antibiotic-resistant bacteria because the intensive antimicrobial therapy characteristic of modern-day ICUs grossly distorts patients’ microflora. Moreover, more than half of all nosocomial epidemics now occur among the 10% of hospitalized patients confined to an ICU.20,31 Finally, the risk of occupationally acquired infection among health care workers (HCWs), particularly by bloodborne viruses and herpes simplex virus (HSV), is highest among ICU personnel, as contrasted with those who work in non-ICU patient care units (see Protection of Health Care Workers in the Intensive Care Unit later).

Hospital Infection Control Programs

Beginning in the late 1960s, scattered U.S. hospitals began to establish infection control programs to conduct surveillance, to develop infection control policies, and especially to try to implement control measures more consistently.¹¹⁶ In 1976 JCAHO added to its requirements for hospital accreditation the establishment of a formal infection control program.

In the early 1970s the CDC undertook determining the effectiveness of nosocomial infection surveillance and control programs in the United States through the auspices of the Study of the Efficacy of Nosocomial Infection Control (SENIC). The goals of SENIC were to determine the extent to which infection control programs had been adopted by U.S. hospitals and to ascertain how much these programs had reduced rates of nosocomial infection. SENIC was launched by a survey of all U.S. hospitals to determine the characteristics of infection control programs and was completed in 1975-1976 by a review of more than 339,000 patient medical records in 338 randomly selected hospitals.¹¹⁷

The SENIC found that hospitals reduced their nosocomial infection rates by approximately 32% if their surveillance and infection control program included four components: (1) emphasis on both surveillance and an infection control program, (2) at least one full-time infection control practitioner for every 250 beds, (3) a trained hospital epidemiologist, and (4) surveillance of surgical wound infections with feedback of wound infection rates to practicing surgeons.¹¹⁸ However, the relative importance of each component varied for the four major types of nosocomial infections (surgical wound infections, urinary tract infections, bloodstream infections, and pneumonia).^118,119 SENIC suggests that nearly one third of all nosocomial infections are in theory preventable, whereas a 1983 survey of surveillance and control programs in a random sample of U.S. hospitals found that failure to implement all essentials of the program, particularly to have an adequate number of infection control practitioners or a trained hospital epidemiologist or to disseminate wound infection rates to surgeons, was greatly limiting the potential for prevention: U.S. hospitals were estimated to be preventing only 9% of all infections.¹²⁰

It is hoped that surveillance and control programs will continue to evolve. Prevention of nosocomial infections is a major priority of the U.S. Public Health Service,¹²¹ JCAHO,³⁰ and the Institute of Medicine.¹²² With the shift to prospective-payment reimbursement, hospitals now have a powerful financial incentive to reduce their rates of nosocomial infection,¹²³ and it can be anticipated that efforts to prevent hospital-acquired infections will assume ever greater importance.

JCAHO mandates that all hospitals have an active program for the surveillance, prevention, and control of hospital-acquired infections, which begins with an institutional infection control committee with representation from the major clinical services and hospital departments including the institution’s ICUs. The most essential members of the infection control program are the infection control practitioner(s), usually registered nurse(s), and the hospital epidemiologist, usually a physician with training in infectious diseases or microbiology, who implement the policies developed by the committee, educate hospital personnel about nosocomial infection control, and investigate suspected outbreaks (Box 50.2).

Surveillance of nosocomial infections is the cornerstone of an effective infection control program and offers numerous potential benefits119,124: (1) It permits determination of baseline (expected) infection rates, assisting recognition of outbreaks and evaluation of new policies and control measures; (2) it identifies institutional problems that require attention, permitting focused infection control efforts and education; (3) it provides reliable data that can be disseminated to individual departments, increasing awareness and involvement of individual staff members; (4) it increases the visibility of the infection control staff on patient care units, providing an opportunity for consultation and ad hoc education; and (5) it facilitates the earliest discovery of patients with communicable infections, permitting timely institution of isolation precautions to limit spread. Because total surveillance (of all infections) is labor intensive, most hospitals now focus their surveillance efforts on infections that are associated with high morbidity (e.g., nosocomial pneumonia), that greatly increase health care costs (e.g., post–cardiac surgery sternotomy infections), that are caused by antibiotic-resistant organisms with potential for spread (e.g., MRSA, C. difficile), or that are highly preventable (e.g., intravascular device-related bloodstream infections).^119,125

The 1990s were characterized by major efforts by hospitals to apply the numerous facets of health care principles of quality improvement developed by industry. Hospital infection control programs had been working on quality improvement¹²⁶ but, influenced by JCAHO, were probably too heavily focused on process, namely, policies and procedures, rather than documenting outcome vis-à-vis reduced infection rates. Infection control programs in most U.S. hospitals are now closely allied with their institutional quality improvement departments.^126,127

Hospital infection control programs are also regulated by the Occupational Safety and Health Administration (OSHA) in terms of institutional standards and programs to protect HCWs from bloodborne pathogens¹²⁸ and tuberculosis¹²⁹; the Environmental Protection Agency¹³⁰ has also published regulations in terms of disposal and tracking of medical waste—only a small fraction of which is truly biohazardous.¹³¹

Finally, it is essential that all health care personnel working in an ICU receive training in the epidemiology and control of nosocomial infections. This may be most important for house officers in teaching hospitals, who commonly enter the ICU with only the most rudimentary knowledge of asepsis but have hands-on contact with numerous patients each day. ICU physicians and nurses must be especially familiar with their hospitals’ guidelines for the management of invasive devices, particularly intravascular catheters of all types,¹³² urinary catheters,^133,134 endotracheal tubes,¹³⁵ and tracheostomies.¹³⁵ Moreover, all physicians need to be made aware that broad-spectrum antimicrobial therapy greatly increases the risk of superinfection by antibiotic-resistant bacteria and Candida, as well as C. difficile.

Role of the Microbiology Laboratory

Accurate and timely diagnostic microbiology is as essential for nosocomial infection control as it is for the clinical management of patients’ infections. Although many infections can be diagnosed on the basis of clinical criteria alone, cultures and other laboratory tests allow infections to be diagnosed with much greater certainty, and certain infections such as bacteriuria, bacteremia, and fungal and viral infections cannot be diagnosed without cultures or other laboratory tests (see Box 50.1).^16,17 Moreover, accurate antimicrobial susceptibility testing of clinical isolates is the only means of monitoring trends in antibiotic resistance of hospital organisms.¹³⁶ Most importantly, identifying the microbial cause of nosocomial infections allows epidemiologic tracking of individual pathogens within the hospital, especially those that are commonly spread from patient to patient such as S. aureus, beta-hemolytic streptococci, enterococci, and the numerous gram-negative bacilli.

From an organizational standpoint, the institutional infection control program and clinical microbiology laboratory must have a close working relationship (see Box 50.2) to assist surveillance, which must be strongly laboratory based,^119,137 and to permit the detection and resolution of potential problems. The laboratory director or a senior member of the laboratory staff should be a permanent member of the infection control committee.

The primary role of the clinical microbiology laboratory in any infection control program is to provide up-to-date clinical microbiologic data for use in the surveillance of nosocomial infections and identification of potential outbreaks.¹³⁷ Protocols should be developed to ensure that laboratory staff immediately contact infection control personnel after the isolation of certain important pathogens such as MRSA or vancomycin-resistant enterococci (VRE) or the appearance of new resistance patterns in endemic organisms such as resistance of Klebsiella species to third-generation cephalosporins and carbapenems, or P. aeruginosa to aminoglycosides, fluoroquinolones, and carbapenems. Sifting through these data can be time consuming, and developing electronic information systems that streamline this process is essential to improving the efficiency of the infection control program. Commercial software programs that can automate this process are now available. Many of these programs automatically collate microbiologic data, provide rudimentary geographic information, and perform basic statistical analyses that can assist in the surveillance of nosocomial infections and identification of potential outbreaks.^138,139

Reporting cumulative summaries of antimicrobial susceptibility data (antibiograms) is another essential responsibility of the clinical microbiology laboratory.140,141 When implemented appropriately, the timely dissemination of antibiograms helps guide the choice of empiric antimicrobials, pending the results of clinical cultures, and provides valuable data to help the infection control department monitor institutional antimicrobial resistance trends and identify potential outbreaks.¹⁴² The Clinical and Laboratory Standards Institute—formerly the National Committee for Clinical Laboratory Standards—recommends that institutional antibiograms be updated at least annually and has recently published standards for their content and format.¹⁴³ Automated electronic systems for collating and disseminating nearly real-time antibiograms along with antibiotic-use decision support exist and, when implemented properly, have been effective in improving antimicrobial utilization within the hospital setting.^144,145

Monitoring of sterilizers with spore tests, environmental sampling, and advanced microbiologic support for epidemiologic investigations are additional responsibilities expected of most clinical microbiology laboratories, although some university hospital programs have dedicated personnel within their infection control programs who perform these activities.¹³⁷

The clinical microbiology laboratory is a key resource in the investigation of a suspected outbreak. One of the first and foremost actions when a nosocomial outbreak is suspected is to immediately retrieve all available isolates of the putative epidemic pathogen for possible subtyping.¹⁴⁶ The need to move rapidly becomes apparent when it is realized that most hospital laboratories discard cultures as soon as the isolates have been fully characterized. All blood isolates should be routinely saved for at least 1 year.¹⁴⁶ Laboratory personnel must be requested to save clinical isolates of any unusual organisms that are encountered for the first time or clusters of any organism and to inform infection control personnel of the findings and availability of the isolates.

The rapid evolution of molecular microbiology has revolutionized epidemiologic investigation of nosocomial outbreaks. Molecular-based tests for the rapid diagnosis of bacterial,¹⁴⁷ viral,^78,148 and fungal¹⁴⁹ infections are now routinely available in most hospital-based and reference laboratories. Modern molecular tests can reliably detect minute numbers of organisms, allowing direct testing of clinical samples without the need for culture. In modern-day clinical virology, molecular tests based on polymerase chain reaction (PCR) for amplification of the pathogen’s DNA or RNA have supplanted tissue cultures and now allow rapid diagnosis of infections that would otherwise often not be identifiable by classic methods.

The availability of molecular subtyping systems has greatly strengthened investigations of outbreaks, as well as research on the epidemiology of nosocomial infections.150,151 The antimicrobial susceptibility pattern (antibiogram) or the detailed biochemical profile (biotype) is often useful for the initial epidemiologic subtyping of many bacteria and may be adequate for identifying an epidemic caused by an unusual pathogen. However, if an epidemic organism is a common species such as S. aureus, it can be difficult or even impossible to know with certainty that an outbreak derives from a common source using these techniques because they lack sufficient discriminatory power.¹⁵⁰

The new molecular techniques of subtyping such as plasmid profile typing by agarose gel electrophoresis or the use of restriction endonuclease digests with pulsed-field electrophoresis (DNA fingerprinting)¹⁵⁰ are now available in most infection control research laboratories but should be adaptable by many hospital laboratories. Genetic probes promise even more powerful tools for investigating outbreaks, particularly those caused by antibiotic-resistant organisms.¹⁴⁷

Although molecular-based tests offer several advantages over traditional microbiologic techniques, they are not a panacea. A number of molecular diagnostic assays (e.g., analyte specific reagents [ASRs]) marketed for clinical practice do not require approval by the U.S. Food and Drug Administration.¹⁴⁷ In the absence of published data on their accuracy and precision, the results of these tests must be interpreted with caution and should always undergo extensive inhouse validation before widespread adoption. Moreover, the exquisite sensitivity of many of these tests renders them more susceptible to false-positive results as a consequence of environmental contamination^152,153 and mandates stringent quality control practices and procedures.

Architectural and Environmental Issues

The role of the inanimate environment on the transmission of nosocomial infections has been a subject of intense debate for decades. It has been shown that hospital surfaces are almost universally contaminated by potentially pathogenic bacteria such S. aureus,¹⁵⁴ enterococcus,¹⁵⁵ and gram-negative bacilli such as Acinetobacter baumanii.¹⁵⁶ Prior to the 1970s, infection control personnel routinely sampled hospital surfaces. Despite this level of surface colonization, early studies found that the inanimate environment—surfaces, walls, and even air—does not contribute materially to the occurrence of most nosocomial infections,¹⁵⁷ other than invasive infections caused by airborne Aspergillus and other filamentous fungi in seriously immunocompromised patients.^40,41

Although inanimate surfaces may rarely be involved in the direct transmission of infection to patients, more recent evidence suggests that surfaces may well play an important role in the nosocomial acquisition of pathogenic bacteria, indirectly, through contact with HCWs’ hands and equipment (see Fig. 50.3). This indirect route of infection is of particular importance in the ICU, where all patients are heavily exposed to invasive devices and have a high risk of infection. In the ICU the inanimate environment may become a reservoir for the transmission of resistant nosocomial organisms such as MRSA,^158,159 C. difficile,^83,160 VRE,^155,161 and gram-negative bacilli such as Klebsiella spp., Acinetobacter spp., and Enterobacter organisms.^162,163 Studies have shown that enhanced surface decontamination with hypochlorite-containing cleaning solutions has been necessary to terminate outbreaks caused by C. difficile ¹⁶⁴ and Acinetobacter baumanii.¹⁵⁶

Although the ICU environment cannot be made microbe free, certain organizational, architectural, and environmental issues must be addressed with the design or remodeling of an ICU. The capacity to systematically improve the care of critically ill patients and prevent nosocomial infection requires a structural foundation on which the processes of care can be optimized (i.e., make it easy for HCWs to do it right and difficult to do it wrong). Accountability for compliance with critical policies and procedures and ongoing assessment of outcomes needs to be built into the administrative structure of the ICU.

An ICU must be adequately staffed to allow the processes of care to be carried out but also assure a high level of compliance with essential infection control measures such as hand hygiene and barrier isolation. Adequate staffing cannot be overemphasized; numerous studies have found greatly increased rates of nosocomial infection when ICUs are staffed suboptimally or when staffing requirements are met with temporary personnel who are unfamiliar with ICU infection control policies and procedures.165,166 In a large nosocomial outbreak of Enterobacter cloacae infection in a neonatal ICU, Harbarth and colleagues¹⁶⁷ found that infection rates during periods of understaffing were strikingly higher than during periods with adequate levels of staffing (relative risk [RR] = 6, 95% confidence interval [CI] = 2.2 to 16.4). The effects of understaffing are likely multiple; however, erosion of basic hygienic practices with excessive patient-to-staff ratios likely explains much of this phenomenon.¹⁶⁸

Many of the published recommendations for ICU architectural design¹⁶⁹ are empiric, and evidence that they reduce rates of nosocomial infection is, by and large, lacking. Although more research is necessary before specific features of ICU design achieve a level of evidence sufficient for an evidence-based guideline, certain facets of the ICU layout deserve attention:

A variety of microorganisms including bacteria, mycobacteria, fungi, and parasites can be isolated from hospital water and have been implicated in endemic and epidemic nosocomial infections.¹⁷⁸ Many of these outbreaks were caused by bacteria typically thought of as “water” organisms such as P. aeruginosa,¹⁷⁶ Stenotrophomonas maltophilia,¹⁷⁹ and A. baumanii^16,180,181; however, the most important and epidemiologically linked hospital water pathogen is the Legionella group.¹⁸²

Nosocomial legionellosis was first described in 1979,¹⁸³ and it is estimated that up to 50% of cases of legionellosis are acquired in the health care setting,¹⁸⁴ with a mortality rate that approaches 30%.¹⁸⁵ Contamination of hospital potable water remains underappreciated despite studies showing that Legionella species can be recovered from 12% to 70% of hospital water systems,¹⁸⁶ and a number of studies in which nosocomial cases were identified only when specific diagnostic and surveillance methods were employed.^187,188 Characteristics of hospital water systems that are associated with Legionella contamination include piping systems with dead-ends that facilitate stagnation, large-volume water heaters that result in inefficient heating of hospital water, sediment buildup, water heater temperatures less than 60° C and tap water temperatures less than 50° C, maintaining water pH greater than 8 and receiving municipal water untreated with monochloramine.^189–191

Despite the ubiquity of water systems colonized with Legionella species and studies demonstrating a correlation between the level of colonization and risk of infection, the CDC does not recommend routine surveillance of hospital water systems,¹⁸⁴ although this stance is controversial.¹⁸⁶ Researchers from Pittsburgh, Pennsylvania, and the Allegheny County Health Department have recommended a more proactive stepwise approach that involves initial surveillance of hospital water for Legionella contamination, regardless of the presence or absence of institutional nosocomial legionellosis, followed by continued surveillance based on the level of water contamination found or the presence of institutional legionellosis.¹⁸⁶

Legionella species are resistant to chlorine and heat, making it challenging to eradicate them from contaminated hospital water systems.¹⁹¹ Attempts to hyperchlorinate hospital water have been partially successful if chlorine levels are continuously maintained between 2 and 6 parts per million at all times but produce rapidly accelerated corrosion of water pipes and are expensive.¹⁹² Thermal eradication is feasible, using a “heat-and-flush” method to raise water tank temperatures to greater than 70° C and distal water sites to greater than 60° C for short periods of time.¹⁹³ Although effective, superheating is labor intensive and there is the constant fear that patients or health care personnel may sustain scald injuries if they wash or shower with tap water during a flushing period. The use of technologies such as instantaneous steam heat for incoming water¹⁹³ and ultraviolet light¹⁹⁴ are technically feasible with newer hospital water systems but may be incompatible with older hospital water systems.

Perhaps the most attractive, effective, safe, and cost-efficient method for Legionella eradication may be the use of continuous copper-silver ionization systems to sterilize hospital water systems. These systems have been well studied over the past decade and have proved to be highly effective for reliably eradicating Legionella contamination of hospital water and, most importantly, for eliminating nosocomial legionellosis in institutions when other interventions have failed.¹⁹⁵ In our own institution (Maki DG), two clusters of nosocomial legionellosis prompted a retrospective review that identified 10 cases over an 11-year period. Surveillance of the hospital water system found that 75% of all samples contained low levels of L. pneumophila, which were shown to be clonally related to the 10 cases of nosocomial legionellosis. Installation of a continuous copper-silver ionization system led to complete eradication of Legionella from water samples, and no further cases of nosocomial legionellosis have been identified at our institution since 1995, among 255,000 patients hospitalized.

Reliable Sterilization Procedures, Chemical Disinfectants, and Antiseptics

Reliable sterilization, disinfection, and antisepsis embrace virtually all measures aimed at prevention of nosocomial infection. Critical objects, which are introduced directly into the bloodstream or into other normally sterile areas of the body, such as surgical instruments, cardiac catheters, and implanted devices, must be reliably sterile and sterilized with steam, gas, hydrogen peroxide gas, or chemical sterilization. Semicritical items, which come into contact with intact mucous membranes, such as fiberoptic endoscopes, endotracheal tubes, or ventilator circuit tubing, can be decontaminated between patients by pasteurization or the use of high-level chemical disinfection with glutaraldehyde, peracetic acid, hydrogen peroxide, ethyl alcohol, or hypochlorite. Noncritical items, which normally come into contact only with intact skin, such as blood pressure cuffs or electrocardiograph electrodes, require hygienic cleansing or low-level disinfection with an iodophor, hypochlorite, quaternary ammonium or phenolic disinfectants, or alcohol.196,197 The lone exception to this classification scheme is devices that pose a risk of transmitting prion-related diseases, including Creutzfeldt-Jakob disease (CJD) and variant CJD (vCJD).^198,199 Prions are not readily inactivated by conventional disinfection and sterilization procedures.^196,199 As a result, devices that pose a risk for transmission of prion-related diseases should undergo special sterilization procedures after cleaning that involve sodium hydroxide followed by low-temperature autoclaving (121° C) or high-temperature autoclaving (132° C for 1 hour or 134° C for ≥18 minutes).^197,199 Despite concerns that procedures involving semicritical items such as endoscopes and bronchoscopes may pose a risk for transmission of prion-related infections, there has not been a single report of CJD or vCJD associated with these devices. As a result, current guidelines recommend that only critical items and semicritical items that have come in contact with neurologic tissue (e.g., brain [including dura mater], spinal cord, eye, and pituitary tissue) should undergo special prion inactivation sterilization procedures.^197,199,200

Numerous epidemics of gram-negative infection have been described in association with respiratory therapy equipment,97,98 diagnostic equipment such as bronchoscopes and endoscopes,^98,102–104 and solutions used for cutaneous antisepsis.^201,202 Most of these outbreaks were traced to improper procedures or malfunction of automated systems used for the disinfection and sterilization of medical devices, although a number of epidemics in years past arose as a result of extrinsic contamination of solutions used for cutaneous antisepsis.^201,202 For these reasons, the importance of strict adherence to recommended policies and procedures for cleaning and reprocessing medical equipment used in the ICU cannot be overemphasized.

Endoscopes and bronchoscopes are essential diagnostic and therapeutic instruments in the ICU. Although most postendoscopy nosocomial infections are caused by inoculation of colonizing mucosal flora into normally sterile, vulnerable anatomic sites during the procedure, numerous epidemics have been traced to contaminated endoscopes.98,102–104 Following use for bronchoscopy, endoscopes are typically contaminated with 6×10⁴ colony-forming units per milliliter (CFUs/mL).²⁰³ All endoscopes are considered semicritical medical devices by the Spaulding classification and therefore require high-level disinfection following use.²⁰⁰ In order to ensure their safe use, flexible endoscopes should be reprocessed with the following procedures: (1) physical cleaning to reduce microbial bioburden and remove organic debris; (2) high-level disinfection—glutaraldehyde and automated chemical sterilizing systems that use peracetic acid are most commonly used in the United States—with adequate contact time between the disinfectant and device surface; (3) following disinfection, rinsing with sterile or filtered tap water to remove disinfectant residue; (4) flushing of all channels with 70% to 90% ethyl or isopropyl alcohol; and (5) drying with forced air.²⁰⁰ Devices used with endoscopes that violate mucosal barriers, such as biopsy forceps, need to be reprocessed as critical medical items with full sterilization.²⁰⁰ Other devices used in the delivery of respiratory care are also considered semicritical under the Spaulding classification and therefore should be reprocessed in a manner similar to endoscopes prior to reuse.¹³⁵

Iodophors (e.g., 10% povidone-iodine), until recently, have been the most common agents used for cutaneous disinfection in North America. However, a large, prospective, randomized trial of cutaneous antiseptics used for drawing blood cultures showed that chlorhexidine was superior to 10% povidone-iodine and was associated with a more than twofold reduced rate of contaminated blood cultures (odds ratio [OR] = 0.40, 95% CI 0.21 to 0.75, p = 0.004).²⁰⁴ Moreover, a meta-analysis examining the impact of different cutaneous antiseptic agents found that chlorhexidine was superior to povidone-iodine for both the prevention of intravascular catheter colonization and catheter-related bloodstream infection.²⁰⁵ On the basis of these and other recent studies,^206,207 chlorhexidine-containing solutions are the preferred cutaneous antiseptics for insertion of intravascular devices in the ICU.¹³² Whatever agent is used, it is essential that it be applied with vigorous scrubbing for a minimum of 1 minute to allow adequate time for germicidal activity.

Hand Hygiene

The major reservoir of nosocomial infection in the ICU is infected or colonized patients, and the major mode of spread of most nosocomial bacterial pathogens, many viruses, and even Candida from patient to patient is by transient carriage on the hands of medical personnel (see Fig. 50.3). Studies of hand carriage of nosocomial pathogens by ICU personnel, using a simple rinse technique to quantify the transient flora,²⁰⁸ have shown that, on average, approximately 60,000 CFUs (or 4.6 logs) are recovered from the hands of ICU personnel randomly sampled (Table 50.4). Nearly half of persons cultured at any point in time will be found to be carrying gram-negative bacilli, and 10% will be carrying S. aureus.