Cross Infection

Definition

Cross infection is the physical movement or transfer of harmful bacteria from one person, object, or place to another, or from one part of the body to another (such as touching a staph-infected hand to the eye). When this cross infection occurs in a hospital or long-term care facility it is called a nosocomial infection. Community-acquired infections are those contracted anywhere except a hospital or long-term care facility.

Description

Cross infection accounts for half of all major complications of hospitalization; the rest are medication errors, patient falls, and other noninfectious events. In American hospitals, cross infection affects between 5-10% of patients at a cost in excess of $4.5 billion. Further, with the advent of HMOs and incentives for outpatient care, hospitals now have a concentrated population of seriously ill patients, and an even greater risk of cross infection.

On one hand, trends toward same-day surgery, shorter hospital stays, and less-invasive surgical techniques will limit patients' exposure to hospital pathogens and invasive devices. On the other, long-term inpatients are likely to be older and sicker, requiring the use of invasive devices in treatment or management of their illness. This places them at increased risk of cross infection, a risk that is higher for public and larger hospitals and teaching institutions.

Statistics show that about 35 million patients are admitted to 7,000 acute-care institutions in the United States each year. This means that 1.75 million to 3.5 million patients are infected yearly in the United States. If 10% of all cross infections involve the bloodstream, then 175,000 to 350,000 patients acquire these life-threatening septicemic infections each year.

Causes and symptoms

Cross infections are caused by bacteria, viruses, fungi, or parasites that may already be present in the patient's body, or they may come from the environment, contaminated hospital equipment, health care workers, visitors, or other patients. A localized infection is limited to a specific part of the body and has local symptoms. An infected surgical site, for example, would exhibit an area that is red, hot, and painful. A generalized infection that enters the bloodstream causes general systemic symptoms such as fever, chills, low blood pressure, boils all over the body, or mental confusion.

Cross infections can occur from surgical procedures, catheters placed in the urinary tract, intravenous fluid sites, or when moisture droplets from the nose or mouth are inhaled into the lungs. The most common cause of cross infection is the failure of health care workers to wash their hands after taking off latex gloves or before donning a new pair. The most frequent types of cross infections occurring in facilities are urinary tract infections (UTIs), pneumonia, surgical site infections (SSIs), and blood stream infections (BSIs).

While all patients within a health care facility are vulnerable to cross infection, some patients are at greater risk than others because certain risk factors alter their susceptibility to infection. Intrinsic risk factors are those present in the patient and include age (the very young or the elderly), presence of chronic disease, or a compromised immune system. Extrinsic risk factors are types of interventions performed within the health care facility and the mix of patients present.

Fever is often the first sign of infection; other symptoms include rapid breathing, mental confusion, low blood pressure, reduced urine output, painful joints and muscles, and a high white blood cell count. If there is a skin break it may be red and swollen. Patients with a UTI may have pain when urinating along with cloudy or bloody urine. Symptoms of pneumonia include difficulty breathing, chronic deep coughing, and reluctance to lie flat because it makes breathing difficult. A localized infection causes swelling, redness, and tenderness at the site of infection.

Common cross infections

URINARY TRACT INFECTIONS. Urinary tract infections (UTIs), the most common type of cross infections, usually occur after catheterization, the placement of a catheter through the urethra into the bladder. This procedure is done to empty urine from the bladder, relieve pressure in the bladder, measure urine in the bladder, put medicine into the bladder, or for other medical reasons. While there can be bacteria in or around the urethra, a healthy urinary bladder is sterile: it does not normally have any bacteria or other microorganisms in it. When a catheter is inserted, bacteria can be picked up from the urethra and carried into the bladder unless both the area and equipment are properly prepared; once in the bladder, bacteria can multiply. Infections can also arise if health care personnel fail to follow proper sterile technique when emptying the collection bag. Bacteria from the intestinal tract are the most common cause of UTIs, although fungi called Candida albicans are often implicated. Although UTIs are common, they are generally the least severe and least costly type of cross infection.

PNEUMONIA. Nosocomial pneumonia is the second most common type of cross infection; it is defined as an infection of the lungs that develops 48 or more hours after admittance. (Any infection that occurs within the first two days after admission is presumed to have come in with the patient.) Patients requiring invasive respiratory therapy may have infection rates seven to 21 times higher than those who do not need artificial ventilation. These infections occur because bacteria and other microorganisms are easily introduced into the throat by procedures such as respiratory intubation, suctioning of material from the throat and mouth, tracheostomy, and mechanical ventilation. The microorganisms can come from contaminated equipment, the hands of health care workers, or, depending on the physical health of the patient, from the patient's own bacteria. The introduced microorganisms quickly colonize the throat area, but do not yet cause an infection. Once the throat is colonized, it is easy for a patient to inhale the microorganisms into the lungs; most nosocomial pneumonia develops within two days of the infecting procedure. This is especially true for patients who cannot cough or gag very well. The occurrence of pneumonia can prolong a hospital stay by at least three or four days at considerable cost.

SURGICAL SITE INFECTIONS. Since surgery is a direct invasion of the patient's body, the natural barrier of the skin is broken, giving bacteria entrance into the normally sterile interior of the body. Surgical site infections (SSIs) can be acquired from contaminated surgical equipment, health care workers who use improper technique to change bandages postoperatively, intubations, and a depressed immune system that permits the body's natural bacteria to colonize. Other wounds from trauma, burns, and ulcers can also become infected for similar reasons.

BLOOD STREAM INFECTIONS. Many patients in health care facilities need an intravenous (IV) catheter placed in a vein for the infusion of fluids for hydration, medications, and/or nutrients. This can cause blood stream infections (BSIs) by transmission from the surroundings, contaminated equipment, or health care workers' hands via the site of catheter insertion. A local infection can develop in the skin around the catheter, or more seriously, bacteria can enter the bloodstream through the vein and cause a generalized infection. The longer a catheter is in place, the greater the risk of infection. BSIs are the most severe of the cross infections, resulting in the most deaths, greatest prolongation of stay, and highest cost. Other procedures that put patients at risk for cross infections are gastrointestinal procedures, obstetric procedures, and kidney or peritoneal dialysis.

Diagnosis

An infection is suspected any time a hospitalized or home health care patient develops a fever that cannot be explained by a known illness. Some patients, however, especially the elderly, may not develop a fever. In these patients, the first signs of infection may be rapid breathing, pale clammy skin, or mental confusion.

Diagnosis of a cross infection is based on:

• signs and symptoms of the infection
• examination of wounds and catheter entry sites
• review of procedures that might have led to infection
• laboratory test results, including blood studies, urinalysis, and culture of any suspicious wound sites

A complete physical examination is conducted by the physician, nurse practitioner, or registered nurse caring for the individual in order to determine if an infection is present. Wounds and catheter insertion sites are examined for redness, swelling, the presence of pus, an abscess, or any area of exaggerated tenderness that might indicate an abcess. The registered nurse reports findings to the physician or nurse practitioner who reviews the patient's record of procedures performed to determine if any posed a risk for infection.

Medical technicians perform laboratory tests ordered by the physician or nurse practitioner to look for signs of infection. A complete blood count reveals the white blood cell count, a measure of macrophages whose increasing numbers indicate infection. White blood cells, blood, or "casts" (mineral crystals) may be present in the urine with a UTI as well. Cultures of blood, urine, sputum, other body fluids, or tissue are examined for infectious microorganisms, which must be identified to provide proper treatment. These cultures are obtained by taking a swab of an area or a sample of fluid, blood, or tissue and placing it in a special sterile medium that promotes bacterial growth. Other tests can be done on blood and body fluids to find and identify bacteria, fungi, viruses, or other microorganisms responsible for the infection. If a patient has symptoms suggestive of pneumonia, a chest x ray is done to look for infiltrates—white blood cells and other inflammatory substances in the lung tissue.

Treatment

Upon identification of the infection, the patient is treated with antibiotics or other medications that destroy the responsible organism. Although many different antibiotics are available, bacteria strains resistant to specific antibiotics have become increasingly prevalent. In one 1998 U.S. report, only 56% of pneumococcal strains of bacteria were still sensitive to penicillin while 16% were highly resistant. At the present time, resistance is highest to penicillin, but resistance to other antibiotics such as cephalosporins, tetracyclines, and erythromycin is also rapidly increasing. Fortunately, most pneumococci are still sensitive to vancomycin, but an increasing number of vancomycin-resistant bacteria have been reported. Newer groups, called fluoroquinolones, are being used to treat resistant bacteria, as are imipenem/cilastatin (Primaxin), a carbapenem combination, and sanfetrinem, a tricyclic beta-lactam antibiotic. These are powerful new antibiotics that can combat a wide spectrum of bacteria that have become resistant to standard drugs. Unfortunately, some newer studies show that patients with infections resistant to cephalosporins may also have a cross-resistance to the fluoroquinolones. Repeated exposure even to these antibiotics, however, will eventually result in bacterial resistance. It is essential, therefore, that patients who require antibiotics be rigorous about completing their regimen and that those caring for them adhere to aseptic technique rigidly.

At highest risk for antibiotic-resistant pneumococci are children under two who live in areas of high antibiotic use and who have used antibiotics in the previous year. Efforts to reduce the number of resistant bacteria include teaching both the public and health care workers that a conservative approach is best when it comes to antibiotics use: not every infection needs medication. A program in Finland, for example, has nearly halved the incidence of erythromycin-resistant bacteria by limiting the use of penicillin and similar antibiotics to only serious infections. Many infections, in fact, are viral, and do not respond to antibiotic therapy.

Fungal infections are treated with antifungal medications, such as amphotericin B, nystatin, ketoconazole, itraconazole, and fluconazole, but many of these drugs have negative interactions with other medications that the patient may be using. A number of antiviral drugs have been developed that slow the growth or reproduction of viruses, and these include acyclovir, ganciclovir, foscarnet, and amantadine.

Prognosis

Cross infections are serious illnesses that can cause death in about 1% of all cases. Blood stream infections in intensive care unit (ICU) patients have a mortality rate of almost 35%. Rapid diagnosis and identification of the responsible microorganism are necessary, so that specific antimicrobial therapy can be started as quickly as possible.

Health care team roles

In all cases, medication for cross infection is administered by a registered nurse in a health care facility, by an intravenous infusion nurse who does home health care, or by a licensed practical nurse in a nursing home. These nurses must be extremely careful that the medication is given exactly as ordered and that they use sterile technique to prevent any additional cross infection. The nurse must also remain alert to additional complications or symptoms that may be significant and report these to the physician or nurse practitioner. Laboratory personnel must be very careful in utilizing sterile technique when drawing blood, as should respiratory therapists who may provide breathing treatments or suction for patients with pneumonia.

Patient education

If possible, the registered nurse can use the time during treatments to teach the patient how cross infection occurs. This is especially important when the patient is immunocompromised and, therefore, more susceptible to further infection. The nurse could explain the importance of taking medications exactly as ordered and why antibiotics are sometimes not given for illnesses. All health care personnel should explain procedures as they are performed and include the reasons for the particular treatment. The patient's family may be included in the session to further enforce the necessity of the treatment as well as the appropriate way to perform it.

KEY TERMS

Abscess— A localized pocket of pus at a site of infection.

Candida albicans— A yeast-like fungal organism.

Catheter— A thin, hollow tube inserted into the body at specific points in order to inject or withdraw fluids.

Culture— The reproduction of microorganisms or of living tissue cells in special media that encourages their growth.

Generalized infection— An infection that has entered the bloodstream and has general systemic symptoms such as fever, chills, and low blood pressure.

Incubating— The development of an infectious disease from time of the entrance of the pathogen to the appearance of clinical symptoms.

Intubation— Placement of a tube inside the body to keep a lumen open, especially the trachea.

Localized infection— An infection that is limited to a specific part of the body.

Nosocomial infection— An infection acquired during or after hospitalization and that was not present or incubating at the time of the patient's admission. It includes any infection acquired in a facility that appears after discharge and any newborn infection that is the result of passage through the birth canal.

Peritoneal dialysis— A procedure for cleaning the blood when a patient's kidneys have failed. A catheter implanted in the patient's abdomen is used to add and remove cleansing fluid that removes waste and impurities from the bloodstream. Unlike hemodialysis, peritoneal dialysis can usually be done at home.

Systemic— Affecting the whole body.

Tracheostomy— The creation of an opening into the trachea (windpipe) through the neck, with insertion of an indwelling tube to facilitate passage of air or evacuation of secretions.

Prevention

Hospitals and other health care facilities have developed extensive infection-control programs to identify all possible sources of infection, including medical procedures, that put patients at risk. The first infection-control committees and policies were developed in the late 1950s and early 1960s when a pandemic of highly virulent antibiotic-resistant Staphylococcus aureus swept through American hospitals. In response, the Centers for Disease Control and Prevention (CDC; then the Communicable Disease Center) in Atlanta recommended that hospitals determine the sources of infection in hospital patients, so they could develop and apply preventive measures. One result of this was a CDC-sanctioned maximum of 250 beds for each infection control nurse. They further noted that programs were most successful when data were communicated effectively to hospital staff.

Further recommendations that resulted from these initiatives included analyzing procedures with high risk of contamination, such as urinary catheterization. To minimize cross infection, it was recommended that these procedures be performed only when necessary, and that catheters or other medical devices be left in for as little time as possible. Medical instruments and equipment should be properly sterilized, with appropriate documentation and check devices, to ensure they were not contaminated. Frequent hand washing by health care workers and visitors is absolutely essential to prevent transferring infectious microorganisms to patients, and was cited as the procedure most important for prevention. Patients should be encouraged to ask their health care provider if they washed their hands before allowing them to proceed with an examination. Antibiotics should only be used when necessary because their use not only creates favorable conditions for infection with the fungal organism Candida albicans but their overuse has helped develop antibiotic-resistant bacteria.

Resources

BOOKS

Braunwald, E., A. Fauci, D. Kasper, S. Hauser, D. Longo, and J. Jameson. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 2001.

Cecil, R., and L. Goldman. Cecil Textbook of Medicine. Philadelphia: W.B. Saunders, 1999.

Rhinehart, E., M. Friedman. Infection Control in Home Care. Aspen Publishers, Inc., 1999.

Tortora, G. J., B. R. Funke, C. L. Case. Microbiology: An Introduction. San Francisco: Addison Wesley Longman, Inc., 2001.

PERIODICALS

Wenzel, R.P., M.B. Edmond. "The Impact of Hospital-Acquired Bloodstream Infections. Emerging Infectious Diseases 7, no. 2 (March/April 2001).

OTHER

Centers for Disease Control and Prevention. 〈http://www.cdc.gov/〉.

"Hospital-Acquired Infection: General Information." (Abstracts of Articles from Scientific Journals). 〈http://member.aol.com/shuckskbee/uih30011.htm〉.

Hospital-Acquired Infections and Resistant Bacteria. 〈http://www.gentlebirth.org/archives/nosocoml.html/〉.