Laboratory Medicine and Nosocomial Infections: Origins

Nosocomial infections are troublesome because they occur in people whose health is already compromised by the condition for which they were first hospitalized. The U.S. Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) has shown that about 36% of hospital-acquired infections (HAIs) are preventable through the adherence to strict guidelines by health care workers.

HAIs are frequently related to a procedure or treatment used to diagnose or treat the patient's initial illness or injury. The causative organisms can already be present in the patient's body, come from the environment, contaminated hospital equipment, health care workers, or other patients.

An infection may start in any part of the body. A localized infection is limited to a specific part of the body and has local symptoms. When a surgical wound in the abdomen becomes infected, the area around the wound becomes inflamed. A generalized infection results from microorganisms entering the bloodstream. This can cause systemic symptoms such as fever, chills, low blood pressure, or mental confusion. If sepsis, a serious, rapidly progressive, multiorgan infection develops, it can be fatal.

The most common types of HAIs are urinary tract infections (UTIs), ventilator-associated pneumonia, and surgical wound infections. The University of Michigan Health System (MI, USA) reports that the most common sources of infection in its hospital are urinary catheters, central venous (in the vein) catheters, and endotrachial tubes. Catheters going into the body allow bacteria to walk along the outside of the tube into the body where they find their way into the bloodstream. About 24% of patients with catheters develop catheter-related infections, of which 5.2% will become bloodstream infections. Death has been shown to occur in 4%-20% of catheter-related infections.

Pneumonia is the second most common type of HAI. Bacteria and other microorganisms are easily introduced into the throat by treatment procedures performed to treat respiratory illnesses. Patients with chronic obstructive lung disease (COPD or asthma) are especially susceptible to infection because of frequent and prolonged antibiotic therapy and long-term mechanical ventilation used in their treatment. The infecting microorganisms can come from contaminated equipment or the hands of health care workers as procedures are conducted such as respiratory intubation, suctioning of material from the throat and mouth, and mechanical ventilation. Once introduced through the nose and mouth, microorganisms quickly colonize the throat area. This means that they grow and form a colony, but have not yet caused an infection. Once the throat is colonized, it is easy for a patient to aspirate the microorganisms into the lungs, where the infection will be found.

Related Links:
The US Centers for Disease Control and Prevention
The University of Michigan Health System