Chanu Rhee and Michael Klompas
Emergency and intensive care department health care providers often encounter patients with suspected or confirmed infections due to transmissible organisms. Isolation of patients who are infected or colonized with selected high-risk organisms is a cost-effective means of reducing rates of nosocomial infection and is a core component of infection control programs.1,2 Isolation and precaution guidelines were first issued in 1970 by the Centers for Disease Control and were last updated in 2007.3 A basic understanding of infection control terminology and practice is an essential skill for the emergency physician caring for critically ill patients.
In addition to standard precautions, which are recommended in the care of all hospitalized patients, there are three isolation categories—contact, droplet, and airborne spread—that reflect the major modes of transmission of microorganisms in health care settings. This chapter summarizes the key components and indications for each type of isolation precaution. We also include an overview of empiric isolation precautions for common clinical syndromes for use when the pathogen is unknown.
Standard precautions are recommended in the care of all hospitalized patients, in order to reduce the risk of transmission of infectious agents between patients and health care workers. Standard precautions include the following:
Hand hygiene is the single most important measure for reducing transmission of microorganisms.4 Hand cleansing with alcohol-containing disinfectants is more efficient than hand washing with soap and water. Note, however, that alcohol-based disinfectants are not effective against Clostridium difficile spores.5,6
Contact precautions prevent transmission of infectious agents, which may colonize patients' skin, wounds, and mucous membranes, as well as the inanimate environment. Contact precautions are applied to patients with multidrug-resistant bacteria (such as methicillin-resistant Staphylococcus aureus [MRSA], vancomycin-resistant Enterococcus [VRE], and some Gram negatives), diarrheal illnesses, draining wounds or abscesses, selected respiratory pathogens, and vesicular rashes (Table 63.1). Contact precautions are necessary every time a provider enters a patient room, regardless of whether or not he or she plans to touch the patient, since inanimate objects in the patient's environment are as likely to harbor pathogens as the patient himself.
TABLE 63.1 Indications for Contact Precautions
Contact precautions include the following steps:
There is some controversy regarding the use of contact precautions for drug-resistant pathogens like MRSA and VRE. Health care workers spend less time in the rooms of patients on contact precautions, compared to those on standard precautions, and this may impair the quality of care.7 In addition, a recent cluster-randomized trial involving multiple ICUs compared an intervention of enhanced surveillance for MRSA and VRE (through serial nasal and stool/perianal cultures) to standard care.8 Despite increased use of contact precautions in the intervention group (due to more patients being identified as being colonized with MRSA or VRE), there was no significant change in incidence rates of ICU infection or colonization with those pathogens. The study, however, was confounded by long turnaround times for screening results and suboptimal compliance with hand hygiene and contact precautions. On the other hand, implementation of a multifaceted MRSA “prevention bundle” that included contact precautions as well as universal surveillance, culture change, and emphasis on hand hygiene was associated with a significant decline in healthcare-associated MRSA infections at Veterans Affairs hospitals across the country.9
Emerging data suggest that an alternate strategy involving universal decolonization of all critically ill patients with nasal mupirocin and chlorhexidine baths is superior to screening and isolation or targeted decolonization (i.e., screening, isolation, and decolonization of MRSA carriers) in reducing the presence of MRSA and rates of all bloodstream infections.10 For now, however, practitioners are advised to refer to their local institution's policies.
Droplet precautions prevent transmission of pathogens spread through respiratory secretions. These pathogens are predominantly viral, but include notable bacterial pathogens such as Neisseria meningitidis, Haemophilus influenzae type B, invasive group A streptococcal infections, and diphtheria (Table 63.2). Droplets are particles of respiratory secretions with mean diameter of larger than 5 μm. They remain suspended in the air only for limited periods and so are generally infectious over short distances (typically less than 3 feet). Unlike airborne pathogens, droplets do not require special air handling and ventilation to prevent transmission. Note that some organisms, such as respiratory viruses, can be transmitted by both droplets and direct patient contact; these require both droplet and contact precautions. Droplet precautions entail the following:
TABLE 63.2 Indications for Droplet Precautions
For influenza, studies have specifically compared the use of N95 respirators to standard masks and have found no difference in rates of transmission.11,12
Airborne precautions prevent transmission of pathogen-laden droplets that can remain suspended in the air for prolonged periods. Airborne droplet nuclei are particles of respiratory secretions with mean diameter of 1 to 5 μm. In contrast to contact and droplet precautions, the list of pathogens that require airborne precautions is short: suspected or confirmed tuberculosis, measles, varicella–zoster, smallpox, and severe acute respiratory syndrome (SARS). In addition, a novel coronavirus (now designated as the Middle East respiratory syndrome coronavirus, or MERS-CoV) has recently emerged that, similar to SARS, can cause severe lower respiratory tract infection. While the exact nature of exposure causing infection in the MERS-CoV is not known at this time, human-to-human transmission has been observed, including health care–associated clusters of infection. Clinicians should suspect MERS-CoV in patients (or their close contacts) who developed fever and an acute lower respiratory illness within 14 days after traveling from countries in areas involved in the outbreak (which currently includes countries in the Arabian Peninsula). Currently, the recommended infection control policy is the same as that for SARS and includes both airborne and standard precautions.13 Airborne precautions entail the following:
Tuberculosis is the most important pathogen requiring airborne precautions, and it should be suspected in any patient with fever, cough, and upper lobe infiltrate. The threshold for airborne isolation should be very low in patients with HIV/AIDS presenting with fever and a pulmonary infiltrate, especially as they are much more likely to have an atypical appearance on chest radiography. Note that although guidelines recommend discontinuation of airborne precautions once patients are smear negative on three consecutive samples, transmission can still occur in these situations (although at a much lower rate) (Tables 63.3 and 63.4).14
TABLE 63.3 Indications for Airborne Precautions
TABLE 63.4 Common Clinical Syndromes That Warrant Empiric Precautions
1.Haley RW, Culver DH, White JW, et al. The efficacy of infection surveillance and control programs in preventing nosocomial infections in US hospitals. Am J Epidemiol. 1985;121(2):182.
2.Kaye KS, Engemann JJ, Fulmer EM, et al. Favorable impact of an infection control network on nosocomial infection rates in community hospitals. Infect Control Hosp Epidemiol. 2006;27(3):228.
3.Siegel JD, Rhinehart E, Jackson M, et al.; Healthcare Infection Control Practices Advisory Committee. 2007. Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings. http://www.cdc.gov/ncidod/dhqp/pdf/isolation2007.pdf
4.Pittet D, Allegranzi B, Sax H, et al.; WHO Global Patient Safety Challenge, World Alliance for Patient Safety. Evidence-based model for hand transmission during patient care and the role of improved practices. Lancet Infect Dis. 2006;6(10):641.
5.Jabbar U, Leischner J, Kasper D, et al. Effectiveness of alcohol-based hand rubs for removal of Clostridium difficile spores from hands. Infect Control Hosp Epidemiol. 2010;31(6):565.
6.Oughton MT, Loo VG, Dendukuri N, et al. Hand hygiene with soap and water is superior to alcohol rub and antiseptic wipes for removal of Clostridium difficile. Infect Control Hosp Epidemiol. 2009;30(10):939.
7.Morgan DJ, Pineles L, Shardell M, et al. The effect of contact precautions on healthcare worker activity in acute care hospitals. Infect Control Hosp Epidemiol. 2013;34(1):69–73.
8.Huskins CW, Huckabee CM, O'Grady NP, et al.; for the STAR*ICU Investigators. Intervention to reduce transmission of resistant bacteria in intensive care. N Engl J Med. 2011;364:1407–1418.
9.Jain R, Kralovic SM, Evans ME, et al. Veterans Affairs initiative to prevent methicillin-resistant Staphylococcus aureus infections. N Engl J Med. 2011;364(15):1419.
10.Huang SS, Septimus E, Kleinman K, et al. Targeted versus universal decolonization to prevent ICU infection. N Engl J Med. 2013;368(24):2255–2265.
11.Loeb M, Dafoe N, Mahony J, et al. Surgical mask vs N95 respiratory for preventing influenza among health care workers: a randomized trial. JAMA. 2009;302(17):1865.
12.Johnson DF, Druce JD, Birch C, et al. A quantitative assessment of the efficacy of surgical and N95 masks to filter influenza virus in patients with acute influenza infection. Clin Infect Dis. 2009;49(2):275.
13.CDC. Interim Infection Prevention and Control Recommendations for Hospitalized Patients with Middle East Respiratory Syndrome Coronavirus (MERS-CoV). June 2013. Retrieved from http://www.cdc.gov/coronavirus/mers/interim-recommendations-patients-2013.html
14.Tostmann A, Kik SV, Kalisvaart NA, et al. Tuberculosis transmission by patients with smear-negative pulmonary tuberculosis in a large cohort in the Netherlands. Clin Infect Dis. 2008;47(9):1135.