A hospital-acquired infection (HAI), also known as a nosocomial infection (from Greek nosokomeîon "hospital, infirmary", from nósos "disease" + koméō "to tend, care for", with locative suffix -eîon), is an infection that is acquired in a hospital or other healthcare facility. To encompass both hospital and non-hospital settings, it is sometimes instead called a healthcare-associated infection. Such an infection can be acquired in a hospital, nursing home, rehabilitation facility, outpatient clinic, diagnostic laboratory or other clinical settings. The term nosocomial infection is used when there is a lack of evidence that the infection was present when the patient entered the healthcare setting, thus meaning it was acquired or became problematic post-admission.
A number of dynamic processes can bring contamination into operating rooms and other areas within nosocomial settings. Infection is spread to the susceptible patient in the clinical setting by various means. Healthcare staff also spread infection, as can contaminated equipment, bed linens, or air droplets. The infection can originate from the outside environment, another infected patient, staff that may be infected, or—in some cases—the source of infection cannot be determined. In some cases the microorganism originates from the patient's own skin microbiota, becoming opportunistic after surgery or other procedures that compromise the protective skin barrier or immune system. Though the patient may have contracted the infection from their own skin, the infection is still considered nosocomial since it develops in the health care setting.
Effects
During 2002 in the United States, the Centers for Disease Control and Prevention estimated that roughly 1.7 million healthcare-associated infections occurred, from all types of microorganisms, including bacteria and fungi; such infections caused or contributed to an estimated 99,000 deaths. 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 HAI-related deaths each year. Nosocomial infections can cause severe pneumonia and infections of the urinary tract, bloodstream and other parts of the body. Many types display antimicrobial resistance, which can complicate treatment.
In the UK about 300,000 patients were affected in 2017, and this was estimated to cost the NHS about £1 billion a year.
Types
Hospital-acquired pneumonia Ventilator-associated pneumonia Urinary tract infection Gastroenteritis Puerperal fever Central line-associated blood stream infection
Organisms
Staphylococcus aureus Methicillin-resistant Staphylococcus aureus Candida albicans Pseudomonas aeruginosa Acinetobacter baumannii Stenotrophomonas maltophilia Clostridioides difficile Escherichia coli Tuberculosis Vancomycin-resistant Enterococcus Legionnaires' disease
Cause
Transmission In-dwelling catheters have been identified with hospital-acquired infections. To deal with this complication, procedures are used, called intravascular antimicrobial lock therapy, that can reduce infections that are unexposed to blood-borne antibiotics. Introducing antibiotics, including ethanol, into the catheter (without flushing it into the bloodstream) reduces the formation of biofilms. +Main routes of transmissionRouteDescriptionContact transmissionThe most important and frequent mode of transmission of nosocomial infections is by direct contact.Droplet transmissionTransmission occurs when droplets containing microbes from the infected person are propelled a short distance through the air and deposited on the patient'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 transmissionDissemination 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 transmissionThis applies to microorganisms transmitted to the host by contaminated fomite items, such as food, water, medications, devices, and equipment.Vector borne transmissionThis 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. +Routes of contact transmissionRouteDescriptionDirect-contact transmissionThis 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 transmissionThis 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.
Patient susceptibility Alongside reducing vectors for transmission, patient susceptibility to hospital-acquired infections needs to be considered. Factors which render patients at greater risk of infections include:
Receipt of immunosuppressive medications such as glucocorticoids or immunosuppressive drugs as part of treatments for cancer, organ transplantation or autoimmune diseases Impaired immunity due to diseases such as haematological malignancy, primary immunodeficiency, HIV/AIDS or critical illness, including severe COVID-19 Presence of indwelling devices which breach natural defences, including endotracheal tubes, central venous catheters and urinary catheters. The use of antibiotics does not, itself, increase risk of hospital-acquired infections, but does contribute to the prevalence of antimicrobial resistant organisms amongst patients with hospital-acquired infections
Device-associated infections Given the association between invasive devices and hospital-acquired infections, specific terms are used to delineate such infections to allow for monitoring and prevention. Noted device-associated infections include ventilator-associated pneumonia, catheter-associated blood stream infections, catheter-associated urinary tract infections and device-associated ventriculitis. Surveillance for these infections is commonly undertaken and reported by bodies such as the European Centre for Disease Prevention and Control and Centers for Disease Control and Prevention.
Prevention
Controlling nosocomial infection is to 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, whereas for nosocomial rotavirus infection, a hand hygiene protocol has to be enforced.
To reduce the number of hospital-acquired infections, the state of Maryland implemented the Maryland Hospital-Acquired Conditions Program that provides financial rewards and penalties for individual hospitals. An adaptation of the Centers for Medicare & Medicaid Services payment policy causes poor-performing hospitals to lose up to 3% of their inpatient revenues, whereas hospitals that are able to decrease hospital-acquired infections can earn up to 3% in rewards. During the program's first two years, complication rates fell by 15.26% across all hospital-acquired conditions tracked by the state (including those not covered by the program), from a risk-adjusted complication rate of 2.38 per 1,000 people in 2009 to a rate of 2.02 in 2011. The 15.26% decline translates into more than $100 million in cost savings for the health care system in Maryland, with the largest savings coming from avoidance of urinary tract infections, sepsis and other severe infections, and pneumonia and other lung infections. If similar results could be achieved nationwide, the Medicare program would save an estimated $1.3 billion over two years, while the US healthcare system as a whole would save $5.3 billion.
Sanitation Hospitals have sanitation protocols regarding uniforms, equipment sterilization, washing, and other preventive measures. Thorough hand washing and 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. More careful use of antimicrobial agents, such as antibiotics, is also considered vital. As many hospital-acquired infections caused by bacteria such as methicillin-resistant Staphylococcus aureus, methicillin-susceptible Staphylococcus aureus, and Clostridioides difficile are caused by a breach of these protocols, it is common that affected patients make medical negligence claims against the hospital in question.
Sanitizing surfaces is part of control measures to reduce nosocomial infections in healthcare environments. Modern sanitizing methods such as non-flammable alcohol vapor in carbon dioxide systems have been effective against gastroenteritis, methicillin-resistant Staphylococcus aureus, and influenza agents. The 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 Clostridioides difficile, whereas alcohol is ineffective. Ultraviolet cleaning devices may also be used to disinfect the rooms of patients infected with Clostridioides difficile or methicillin-resistant Staphylococcus aureus after discharge.
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 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
Isolation is the implementation of isolating precautions designed to prevent transmission of microorganisms by common routes in hospitals. (See Universal precautions and Transmission-based precautions.) Because agent and host factors are more difficult to control, interruption of transfer of microorganisms is directed primarily at transmission for example isolation of infectious cases in special hospitals and isolation of patient with infected wounds in special rooms also isolation of joint transplantation patients on specific rooms.
Handwashing