Epidemiology

Nosocomial Infections

Nosocomial, or health care–acquired, infections can be exogenous (external) or endogenous (patient's microbiota).

People can acquire infections from particular settings. An infection acquired while in a hospital or health care setting is considered nosocomial. A nosocomial infection, or health care–acquired infection, can arise from exogenous (external) or endogenous (patient's microbiota) sources. The intensive care unit (ICU) is the most common ward within a hospital to acquire these infections and 1 in 10 people admitted to a hospital will contract a nosocomial infection. In order to be considered nosocomial, certain criteria must be met. The infection must occur within 48 hours of hospital admission, up to three days after discharge, or up to 30 days postsurgery, and the infection must not be present before the patient is admitted to the health care facility.

Health care–associated infections may be caused by one or a combination of factors unique to the hospital: the microorganisms in the environment of the hospital, a weakened or compromised host, and/or the chain of transmission of the hospital. The Centers for Disease Control (CDC) approximates that on a given day, 1 in 25 hospitalized patients has a nosocomial infection, and the mortality rate of nosocomial infections is 10%. The most common cause of nosocomial infections are catheters because they are foreign objects placed directly into the body. In fact, 80% of urinary tract nosocomial infections are because of catheterization.

Common types of health care–acquired infections include ventilator-associated pneumonia (pathogens enter the ventilator, or breathing machine, and then gain entry to the lungs), gastrointestinal infections, urinary tract infections (caused by indwelling, or long-term use, urinary catheters that provide a portal of entry), surgical wound infections, and central-line–associated blood infections. A central line is an intravenous catheter that delivers fluids to a major blood vessel near the center of the body. Unsterile fields, such as areas that have become contaminated with pathogens, can also pass on infections. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant and dangerous nosocomial infection because the pathogen is resistant to antibiotic treatment. Risk factors for MRSA infection include recent or current hospitalization, long-term antibiotic use, and nursing-home living.

Types of Nosocomial Infections

Organism Infection Method of Transmission
Klebsiella pneumoniae Pneumonia Ventilator-associated
Pseudomonas aeruginosa Pneumonia Ventilator-associated
Escherichia coli Gastrointestinal infection
Urinary tract infection
Unwashed hands
Indwelling urinary catheters
Clostridium difficile Gastrointestinal infection Unwashed hands
Unsanitized medical equipment
Candida species Urinary tract infection
Blood infection
Indwelling urinary catheters
Central line
Methicillin-resistant Staphylococcus aureus Blood infection
Pneumonia
Surgical site
Central line
Ventilator-associated
Surgical instruments
Unsterile field

Nosocomial, or hospital-acquired infections, are the result of a combination of factors including weakened or compromised hosts in an environment rife with microorganisms. The most common cause of these infections is in-dwelling catheters.

Preventing nosocomial infections is a high priority for hospitals. There are certain isolation precautions for hospitals to prevent diseases. This includes educating staff members about basic control measures and using isolation rooms for those patients who need them. Education of staff members can decrease the risk of nosocomial infections by up to 70%. The single most important way to prevent the spread of infections through a hospital is handwashing and alcohol sanitizers. Staff, patients, and visitors should all be thoroughly washing and sanitizing their hands, particularly when leaving a room. During catheterization, ventilation, or surgery, ensuring a sterile field, or an area free of microorganisms, is critical to prevent infection of the treatment area. If the disease is contagious, isolation, or separation and confinement, of the patient who is felt to be harboring the infection may be required to prevent spread of the infection.