Nosocomial infection

From Wikipedia, the free encyclopedia

1 Epidemiology
2 Transmission
3 Predisposition to infection
- 3.1 Isolation
- 3.2 Handwashing and gloving
4 References
5 External links

Nosocomial infections are those which are a result of treatment in a hospital or hospital-like setting, but secondary to the patient's original condition. Infections are considered nosocomial if they first appear 48 hours or more after hospital admission or within 30 days after discharge. Nosocomial comes from the Greek word nosokomeion meaning hospital (nosos = disease, komeo = to take care of ). The most common nosocomial infections are of the urinary tract, and various pneumonias.

Nosocomial infections are even more alarming in the 21st century as antibiotic resistance spreads. Reasons why nosocomial infections are so common include:

Hospitals house large numbers of people who are sick and whose immune systems are often in a weakened state.
increased use of outpatient treatment means that people who are in the hospital are sicker on average.
medical staff move from patient to patient, providing a way for pathogens to spread.
many medical procedures bypass the body's natural protective barriers.
routine use of anti-microbial agents in hospitals creates selection pressure for the emergence of resistant strains.

Thorough hand washing and/or use of alcohol rubs by all medical personnel before each patient contact is one of the most effective ways to combat nosocomial infections. More careful use of anti-microbial agents, such as antibiotics, is also considered vital.

[edit] Epidemiology

In the United States, it has been estimated that as many as one hospital patient in ten acquires a nosocomial infection, or 2 million patients a year. Estimates of the annual cost range from $4.5 billion to $11 billion and up. Nosocomial infections contributed to 88,000 deaths in the U.S. in 1995. One third of nosocomial infections are considered preventable.

In France, the prevalence is 6,87%^[1], to 7,5%^[2] (some patients are infected twice) :

Urinary tract infection: 40%;
infection of the skin and mucous membrane: 10,8%;
infections of surgery site: 10,3%;
pneumopathy: 10%.

A ratio of 5 to 19% hospitalized patients are infected, and up to 30% in intensive care units. The patients must stay in the hospital 4-5 additional days. About 9,000 people die with a nosocomial infection, but about 4,200 would have not died without this infection.

In Italy, in the 2000's, about 6,7 % of hospitalized patients were infected, i.e. between 450,000 and 700,000 patients, which caused between 4,500 and 7,000 deaths.^[3]

In Switzerland, extrapolations assume about 70'000 hospitalised patients are affected by nosocomial infections (between 2 and 14% of hospitalized patients).^[4] ^[5]

[edit] Transmission

Microorganisms are transmitted in hospitals by several routes, and the same microorganism may be transmitted by more than one route. There are five main routes of transmission -- contact, droplet, airborne, common vehicle, and vectorborne.

Contact transmission, the most important and frequent mode of transmission of nosocomial infections, is divided into two subgroups: direct-contact transmission and indirect-contact transmission.
- Direct-contact transmission 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 occurs 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 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. Additionally, the improper use of saline flush syringes, vials, and bags have been implicated in disease transmission in the US, even when healthcare workers had access to gloves, disposable needles, intravenous devices, and flushes.^[6]

Airborne transmission occurs by dissemination of 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 Mycobacterium tuberculosis and the rubeola and varicella viruses.

Common vehicle transmission applies to microorganisms transmitted to the host by contaminated items such as food, water, medications, devices, and equipment.

[edit] Predisposition to infection

Factors predisposing a patient to infection can broadly be divided into four areas:

People in hospitals are usually already in a poor state of health, impairing their defense against bacteria – advanced age or premature birth along with immunodeficiency (due to drugs, illness, or IR radiation) present a general risk, while other diseases can present specific risks - for instance chronic obstructive pulmonary disease can increase chances of respiratory tract infection.

Invasive devices, for instance intubation tubes, catheters, surgical drains and tracheostomy tubes all bypass the body’s natural lines of defence against pathogens and provide an easy route for infection. Patients already colonised on admission are instantly put at greater risk when they undergo an invasive procedure.
A patient’s treatment itself can leave them vulnerable to infection – immunosuppression and antacid treatment undermine the body’s defences, while antimicrobial therapy (removing competitive flora and only leaving resistant organisms), recurrent blood transfusions.

[edit] Isolation

Isolation precautions are designed to prevent transmission of microorganisms by these routes in hospitals. Because agent and host factors are more difficult to control, interruption of transfer of microorganisms is directed primarily at transmission.

[edit] Handwashing and gloving

Handwashing frequently is called the single most important measure to reduce the risks of transmitting 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.

Although handwashing may seem like a simple measure, it is often not used or hand washing is performed incorrectly. Healthcare settings must continually remind practitioners to wash their hands thoroughly. Simple programs, for example - "Henry The Hand", can be used to help healthcare facilities prevent nosocomial infections.

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, gloves 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; the wearing of gloves in specified circumstances to reduce the risk of exposures to bloodborne pathogens is mandated by the OSHA Bloodborne Pathogens final rule. Second, gloves are worn to reduce the likelihood that 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, gloves are worn to reduce the likelihood that hands of personnel contaminated with microorganisms from a patient or a fomite can transmit these microorganisms 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, non-apparent 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.

Examples of nosocomial infections include Methicilline Resistant Staphylococcus Aureus (MRSA) and Acinetobacter Baumanni.