出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/02/04 20:13:09」(JST)
| Nosocomial infection | |
|---|---|
| Classification and external resources | |
Contaminated surfaces increase cross-transmission |
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| ICD-10 | Y95 |
| eMedicine | article/967022 |
| Look up nosocomial in Wiktionary, the free dictionary. |
A hospital-acquired infection, also known as a HAI or in medical literature as a nosocomial infection, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff. Such infections include fungal and bacterial infections and are aggravated by the reduced resistance of individual patients.[1][dead link]
In the United States, the Centers for Disease Control and Prevention estimated roughly 1.7 million hospital-associated infections, from all types of microorganisms, including bacteria, combined, cause or contribute to 99,000 deaths each year.[2] In Europe, where hospital surveys have been conducted, the category of Gram-negative infections are estimated to account for two-thirds of the 25,000 deaths each year. Nosocomial infections can cause severe pneumonia and infections of the urinary tract, bloodstream and other parts of the body. Many types are difficult to attack with antibiotics, and antibiotic resistance is spreading to Gram-negative bacteria that can infect people outside the hospital.[2]
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| This paragraph needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2012) |
Nosocomial infections are commonly transmitted when hospital officials become complacent and personnel do not practice correct hygiene regularly. Also, increased use of outpatient treatment in recent decades means that a greater percentage of people who are hospitalized today are likely to be seriously ill with more weakened immune systems than in the past. Moreover, some medical procedures bypass the body's natural protective barriers. Since medical staff move from patient to patient, the staff themselves serve as a means for spreading pathogens. Essentially, the staff act as vectors.
Among the categories of bacteria most known to infect patients are the category MRSA (resistant strain of S. aureus), member of Gram-positive bacteria and Acinetobacter (A. baumannii), which is Gram-negative. While antibiotic drugs to treat diseases caused by Gram-positive MRSA are available, few effective drugs are available for Acinetobacter. Acinetobacter bacteria are evolving and becoming immune to existing antibiotics, so in many cases, polymyxin-type antibacterials need to be used. "In many respects it’s far worse than MRSA," said a specialist at Case Western Reserve University.[2]
Another growing disease, especially prevalent in New York City hospitals, is the drug-resistant, Gram-negative Klebsiella pneumoniae. An estimated more than 20% of the Klebsiella infections in Brooklyn hospitals "are now resistant to virtually all modern antibiotics, and those supergerms are now spreading worldwide.[2]
The bacteria, classified as Gram-negative because of their reaction to the Gram stain test, can cause severe pneumonia and infections of the urinary tract, bloodstream, and other parts of the body. Their cell structures make them more difficult to attack with antibiotics than Gram-positive organisms like MRSA. In some cases, antibiotic resistance is spreading to Gram-negative bacteria that can infect people outside the hospital. "For Gram-positives we need better drugs; for Gram-negatives we need any drugs," said Dr. Brad Spellberg, an infectious-disease specialist at Harbor-UCLA Medical Center, and the author of Rising Plague, a book about drug-resistant pathogens.[2]
One-third of nosocomial infections are considered preventable. The CDC estimates 2 million people in the United States are infected annually by hospital-acquired infections, resulting in 20,000 deaths.[3] The most common nosocomial infections are of the urinary tract, surgical site and various pneumonias.[4]
The methods used differ from country to country (definitions used, type of nosocomial infections covered, health units surveyed, inclusion or exclusion of imported infections, etc.), so the international comparisons of nosocomial infection rates should be made with the utmost care.
The Centers for Disease Control and Prevention (CDC) estimated roughly 1.7 million hospital-associated infections, from all types of bacteria combined, cause or contribute to 99,000 deaths each year.[5] Other estimates indicate 10%, or 2 million, patients a year become infected, with the annual cost ranging from $4.5 billion to $11 billion. In the USA, the most frequent type of infection hospitalwide is urinary tract infection (36%), followed by surgical site infection (20%), and bloodstream infection and pneumonia (both 11%).[2]
Estimates ranged from 6.7% in 1990 to 7.4% (patients may have several infections).[6] At national level, prevalence among patients in health care facilities was 6.7% in 1996,[7] 5.9% in 2001[8] and 5.0% in 2006.[9] The rates for nosocomial infections were 7.6% in 1996, 6.4% in 2001 and 5.4% in 2006.
In 2006, the most common infection sites were urinary tract infections (30,3%), pneumopathy (14,7%), infections of surgery site (14,2%). Infections of the skin and mucous membrane (10,2%), other respiratory infections (6,8%) and bacterial infections / blood poisoning (6,4%).[10] The rates among adult patients in intensive care were 13,5% in 2004, 14,6% in 2005, 14,1% in 2006 and 14.4% in 2007.[11]
Nosocomial infections are estimated to make patients stay in the hospital four to five additional days. Around 2004-2005, about 9,000 people died each year with a nosocomial infection, of which about 4,200 would have survived without this infection.[12]
Since 2000, estimates show about a 6.7% infection rate, i.e. between 450,000 and 700,000 patients, which caused between 4,500 and 7,000 deaths.[13] A survey in Lombardy gave a rate of 4.9% of patients in 2000.[14]
Estimates show a 10% infection rate,[15] with 8.2% estimated in 2006.[16]
Estimates range between 2 and 14%.[17] A national survey gave a rate of 7.2% in 2004.[18]
Rate were estimated at 8.5% of patients in 2005.[19]
The drug-resistant Gram-negative bacteria, for the most part, threaten only hospitalized patients whose immune systems are weak. They can survive for a long time on surfaces in the hospital and enter the body through wounds, catheters, and ventilators.[2]
| Route | Description |
|---|---|
| Contact transmission | The most important and frequent mode of transmission of nosocomial infections is by direct contact. |
| Droplet transmission | Transmission occurs when droplets containing microbes from the infected person are propelled a short distance through the air and deposited on the host's body; droplets are generated from the source person mainly by coughing, sneezing, and talking, and during the performance of certain procedures, such as bronchoscopy. |
| Airborne transmission | Dissemination can be either airborne droplet nuclei (small-particle residue {5 µm or smaller in size} of evaporated droplets containing microorganisms that remain suspended in the air for long periods of time) or dust particles containing the infectious agent. Microorganisms carried in this manner can be dispersed widely by air currents and may become inhaled by a susceptible host within the same room or over a longer distance from the source patient, depending on environmental factors; therefore, special air-handling and ventilation are required to prevent airborne transmission. Microorganisms transmitted by airborne transmission include Legionella, Mycobacterium tuberculosis and the rubeola and varicella viruses. |
| Common vehicle transmission | This applies to microorganisms transmitted to the host by contaminated items, such as food, water, medications, devices, and equipment. |
| Vector borne transmission | This occurs when vectors such as mosquitoes, flies, rats, and other vermin transmit microorganisms. |
Contact transmission is divided into two subgroups: direct-contact transmission and indirect-contact transmission.
| Route | Description |
|---|---|
| Direct-contact transmission | This involves a direct body surface-to-body surface contact and physical transfer of microorganisms between a susceptible host and an infected or colonized person, such as when a person turns a patient, gives a patient a bath, or performs other patient-care activities that require direct personal contact. Direct-contact transmission also can occur between two patients, with one serving as the source of the infectious microorganisms and the other as a susceptible host. |
| Indirect-contact transmission | This involves contact of a susceptible host with a contaminated intermediate object, usually inanimate, such as contaminated instruments, needles, or dressings, or contaminated gloves that are not changed between patients. In addition, the improper use of saline flush syringes, vials, and bags has been implicated in disease transmission in the US, even when healthcare workers had access to gloves, disposable needles, intravenous devices, and flushes.[20] |
Factors predisposing a patient to infection can broadly be divided into three areas:
Hospitals have sanitation protocols regarding uniforms, equipment sterilization, washing, and other preventive measures. Thorough hand washing and/or use of alcohol rubs by all medical personnel before and after each patient contact is one of the most effective ways to combat nosocomial infections.[21] More careful use of antimicrobial agents, such as antibiotics, is also considered vital.[22]
Despite sanitation protocol, patients cannot be entirely isolated from infectious agents. Furthermore, patients are often prescribed antibiotics and other antimicrobial drugs to help treat illness; this may increase the selection pressure for the emergence of resistant strains.
Sterilization goes further than just sanitizing. It kills all microorganisms on equipment and surfaces through exposure to chemicals, ionizing radiation, dry heat, or steam under pressure.
Isolation precautions are designed to prevent transmission of microorganisms by common routes in hospitals. Because agent and host factors are more difficult to control, interruption of transfer of microorganisms is directed primarily at transmission.
Handwashing frequently is called the single most important measure to reduce the risks of transmitting skin microorganisms from one person to another or from one site to another on the same patient. Washing hands as promptly and thoroughly as possible between patient contacts and after contact with blood, body fluids, secretions, excretions, and equipment or articles contaminated by them is an important component of infection control and isolation precautions. The spread of nosocomial infections, among immunocompromised patients is connected with health care workers' hand contamination in almost 40% of cases, and is a challenging problem in the modern hospitals. The best way for workers to overcome this problem is conducting correct hand-hygiene procedures; this is why the WHO launched in 2005 the GLOBAL Patient Safety Challenge.[23] Two categories of micro-organisms can be present on health care workers' hands: transient flora and resident flora. The first is represented by the micro-organisms taken by workers from the environment, and the bacteria in it are capable of surviving on the human skin and sometimes to grow. The second group is represented by the permanent micro-organisms living on the skin surface (on the stratum corneum or immediately under it). They are capable of surviving on the human skin and to grow freely on it. They have low pathogenicity and infection rate, and they create a kind of protection from the colonization from other more pathogenic bacteria. The skin of workers is colonized by 3.9 x 104 – 4.6 x 106 cfu/cm2. The microbes comprising the resident flora are: Staphylococcus epidermidis, S. hominis, and Microccocus, Propionibacterium, Corynebacterium, Dermobacterium, and Pitosporum spp., while in the transitional could be found S. aureus, and Klebsiella pneumoniae, and Acinetobacter, Enterobacter and Candida spp. The goal of hand hygiene is to eliminate the transient flora with a careful and proper performance of hand washing, using different kinds of soap, (normal and antiseptic), and alcohol-based gels. The main problems found in the practice of hand hygiene is connected with the lack of available sinks and time-consuming performance of hand washing. An easy way to resolve this problem could be the use of alcohol-based hand rubs, because of faster application compared to correct hand washing.[24]
Although handwashing may seem like a simple process, it is often performed incorrectly. Healthcare settings must continuously remind practitioners and visitors on the proper procedure to comply with responsible handwashing. Simple programs such as Henry the Hand, and the use of handwashing signals can assist healthcare facilities in the prevention of nosocomial infections.
All visitors must follow the same procedures as hospital staff to adequately control the spread of infections. Visitors and healthcare personnel are equally to blame in transmitting infections.[citation needed] Moreover, multidrug-resistant infections can leave the hospital and become part of the community flora if steps are not taken to stop this transmission.
In addition to handwashing, gloves play an important role in reducing the risks of transmission of microorganisms. Gloves are worn for three important reasons in hospitals. First, they are worn to provide a protective barrier and to prevent gross contamination of the hands when touching blood, body fluids, secretions, excretions, mucous membranes, and nonintact skin. In the USA, the Occupational Safety and Health Administration has mandated wearing gloves to reduce the risk of bloodborne pathogen infections.[25] Second, gloves are worn to reduce the likelihood microorganisms present on the hands of personnel will be transmitted to patients during invasive or other patient-care procedures that involve touching a patient's mucous membranes and nonintact skin. Third, they are worn to reduce the likelihood the hands of personnel contaminated with micro-organisms from a patient or a fomite can be transmitted to another patient. In this situation, gloves must be changed between patient contacts, and hands should be washed after gloves are removed.
Wearing gloves does not replace the need for handwashing, because gloves may have small, inapparent defects or may be torn during use, and hands can become contaminated during removal of gloves. Failure to change gloves between patient contacts is an infection control hazard.
Sanitizing surfaces is an often overlooked, yet crucial, component of breaking the cycle of infection in health care environments. Modern sanitizing methods such as NAV-CO2 have been effective against gastroenteritis, MRSA, and influenza agents. Use of hydrogen peroxide vapor has been clinically proven to reduce infection rates and risk of acquisition. Hydrogen peroxide is effective against endospore-forming bacteria, such as Clostridium difficile, where alcohol has been shown to be ineffective.[26]
Micro-organisms are known to survive on inanimate ‘touch’ surfaces for extended periods of time.[27] This can be especially troublesome in hospital environments where patients with immunodeficiencies are at enhanced risk for contracting nosocomial infections.
Touch surfaces commonly found in hospital rooms, such as bed rails, call buttons, touch plates, chairs, door handles, light switches, grab rails, intravenous poles, dispensers (alcohol gel, paper towel, soap), dressing trolleys, and counter and table tops are known to be contaminated with Staphylococcus, MRSA (one of the most virulent strains of antibiotic-resistant bacteria) and vancomycin-resistant Enterococcus (VRE).[28] Objects in closest proximity to patients have the highest levels of MRSA and VRE. This is why touch surfaces in hospital rooms can serve as sources, or reservoirs, for the spread of bacteria from the hands of healthcare workers and visitors to patients.
Copper alloy surfaces have intrinsic properties to destroy a wide range of micro-organisms. In the interest of protecting public health, especially in heathcare environments with their susceptible patient populations, an abundance of peer-reviewed antimicrobial efficacy studies have been and continue to be conducted around the world regarding copper’s efficacy to destroy E. coli O157:H7, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi.[29]
Much of this antimicrobial efficacy work has been or is currently being conducted at the University of Southampton and Northumbria University (United Kingdom), University of Stellenbosch (South Africa), Panjab University (India), University of Chile (Chile), Kitasato University (Japan), the Instituto do Mar[30] and University of Coimbra (Portugal), and the University of Nebraska and Arizona State University (USA). See Antimicrobial copper-alloy touch surfaces#Clinical trials of antimicrobial copper alloy touch surfaces in healthcare facilities for a summary of antimicrobial copper touch surface clinical trials.
In 2007, U.S. Department of Defense’s Telemedicine and Advanced Technologies Research Center began to study the antimicrobial properties of copper alloys in a multisite clinical hospital trial conducted at the Memorial Sloan-Kettering Cancer Center (New York City), the Medical University of South Carolina, and the Ralph H. Johnson VA Medical Center (South Carolina).[31] Commonly touched items, such as bed rails, over-the-bed tray tables, chair arms, nurse's call buttons, IV poles, etc. were retrofitted with antimicrobial copper alloys in certain patient rooms (i.e., the “coppered” rooms) in the intensive care units (ICUs). Early results disclosed in 2011 indicated the coppered rooms demonstrated a 97% reduction in surface pathogens versus the control rooms. This reduction is the same level achieved by “terminal” cleaning regimens conducted after patients vacated their rooms. Furthermore, of critical importance to health care professionals, the preliminary results indicated the patients in the coppered ICUs had a 40.4% lower risk of contracting a hospital-acquired infection versus patients in the control ICUs.[32][33][34] The US Department of Defense investigation contract, which is ongoing, will also evaluate the effectiveness of copper alloy touch surfaces to prevent the transfer of microbes to patients and the transfer of microbes from patients to touch surfaces, as well as the potential efficacy of copper alloy-based components to improve indoor air quality.
In the US, the Environmental Protection Agency (EPA) regulates the registration of antimicrobial products. After extensive antimicrobial testing according to the agency’s stringent test protocols, 355 copper alloys, including many brasses, were found to kill more than 99.9% of MRSA, E. coli O157:H7, Pseudomonas aeruginosa, S. aureus, Enterobacter aerogenes, and VRE within two hours of contact.[35][36] Normal tarnishing was found to not impair antimicrobial effectiveness.
On February 29, 2008, the EPA granted its first registrations of five different groups of copper alloys as “antimicrobial materials” with public health benefits.[37] The registrations granted antimicrobial copper as "a supplement to and not a substitute for standard infection control practices." Subsequent registration approvals of additional copper alloys have been granted. The results of the EPA-supervised antimicrobial studies, demonstrating copper's strong antimicrobial efficacies across a wide range of alloys, have been published.[38] These copper alloys are the only solid surface materials to be granted “antimicrobial public health claims” status by EPA.
The EPA registrations state laboratory testing has shown, when cleaned regularly:
The registrations state, “antimicrobial copper alloys may be used in hospitals, other healthcare facilities, and various public, commercial and residential buildings.”
Wearing an apron during patient care reduces the risk of infection.[citation needed] The apron should either be disposable or be used only when caring for a specific patient.
| This section requires expansion. (December 2009) |
The most effective technique for controlling nosocomial infection is to strategically implement QA/QC measures to the health care sectors, and evidence-based management can be a feasible approach. For those with ventilator-associated or hospital-acquired pneumonia, controlling and monitoring hospital indoor air quality needs to be on agenda in management,[39] whereas for nosocomial rotavirus infection, a hand hygiene protocol has to be enforced.[40][41][42] Other areas needing management include ambulance transport.[citation needed]
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| リンク元 | 「医療関連感染」 |
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