Originally written for SCG Innovation Institute.
The term nosocomial infection refers to any infection which is acquired by a patient after a hospital stay, or in another health care related facility. It is estimated by the Centres for Disease Control and Prevention (CDC) that between 5-15% of patients acquire a form of nosocomial infection every year. Around 20,000 people die yearly from this.
There are several factors which influence the onset of these infections. The three major factors are microorganisms in the hospital environment, the compromised status of the host and the chain of transmission. Generally, more than one factor must be present for infection to occur. The four most common types of nosocomial infection are:
- Urinary Tract Infection, which accounts for approximately 50 percent of the total number of nosocomial infections and are typically caused or related to urinary catheterization,
- Surgical wound infection, which accounts for approximately 25 percent of infections and have a higher incidence rate in certain surgeries such as amputations and colon surgery,
- Lower respiratory tract infection, which accounts for approximately 12 percent of infections and have the highest mortality rates. Nosocomial pneumonias are typically caused by or related to respiratory devices which either aid breathing or administer medications,
- And finally, Bacteremias, which account for approximately 6 percent of infections. Intravenous catheterization is thought to cause infections which occur in the bloodstream, particularly when the infection is caused by fungi or bacteria.
While hospitals make every effort to minimize or control the growth of microbes in hospital settings, the hospital environment is an extreme reservoir for a large number and types of pathogenic microbes. These microbes are opportunistic and can present a large danger to patients who are ill. Additionally, the microbes can become resistant to any antimicrobial drugs which are being used in that hospital setting. When disease, trauma or surgery weaken the patient’s natural immune defences, the resulting secondary infections can be extremely difficult to treat.
The two main conditions which can compromise a host (patient suffering infection by a specific pathogen) are a suppressed immune system and broken skin or mucous membranes. Surgical wounds, burns, injections, invasive diagnostic procedures, trauma, intravenous therapy and urinary catheters are examples of cases where the skin or mucous membranes would be broken, providing an ample opportunity for microbes to infect the patient. Burns victims in particular are at risk to developing infection as their skin is no longer an effective barrier against microbes.
T lymphocytes and B lymphocytes (white blood cells) are another defence against microorganisms in healthy individuals. However there are a variety of drugs, therapies and conditions typically found in hospital settings which can adversely affect the production and action of these cells, which then leaves the patient more susceptible to risk of infection.
The chain of transmission is the final major factor in nosocomial infections forming. The main routes of transmission are direct contact transmission which occurs from hospital staff to patient, then patient to patient, and indirect contact transmission which occurs via airborne transmission.
Control measures to prevent nosocomial infections vary from one hospital to another, but with the implementation of certain procedures the risk of patients developing these infections can be greatly reduced.