An infection acquired while a patient is in a hospital is called a nosocomial infection, as opposed to one contracted outside a hospital, which is called a community-acquired infection. Nosocomial infections are not necessarily different from community-acquired ones, but they do tend to occur in a specific site, such as the lungs, the urinary tract and the colon, and to involve different species of bacteria than those acquired outside a hospital. Antibiotic resistance is also more common in nosocomial infections, since the bacteria are much more likely to have had extensive antibiotic exposure in the past.
UrinaryTract Infections
Urinary tract infections, or UTIs, are the most common nosocomial infections. According to a July 1998 article published in the journal "Emerging Infectious Disease," UTIs comprised 34 percent of all nosocomial infections from 1990 through 1996. Most nosocomial UTIs occur as a result of long-term use of urinary catheters. Nosocomial UTIs are much more likely to involve a bacteria called Pseudomonas aeruginosa then community-acquired infections (see reference 2, chap. 269). Bacteria in the Pseudomonas genus require special antibiotics, such as imipenem, and when encountered in a hospital environment frequently have resistances to several antibiotics (see reference 2, chap. 136). In addition, nosocomial UTIs sometimes involve the bacteria Staph. Aureus, which almost always has multiple drug resistances (see reference 2, chap. 269). The best treatment for a drug resistance UTI ultimately depends upon the antibiotic sensitivity results from a urine culture, but therapy frequently begins with an antibiotic of the cephalosporin class that is effective against Pseudomonas combined with another antibiotic, a regimen rarely used in community-acquired infections. Fortunately, simply removing the urinary catheter is an effective treatment for nosocomial UTIs in many cases (see reference 2, chap. 269).
Nosocomial Pneumonia
Pneumonia is a common nosocomial infection, particularly in intensive-care units, since mechanical ventilation increases the chances of an infection getting into the lungs. According to "Emerging Infectious Disease", pneumonia comprised 13% of all nosocomial infections in 1990-1996. Like catheter-associated UTIs, ventilator-associated pneumonia is distinguished from community-acquired pneumonia by a greater likelihood of infection by Pseudomonas or multi-drug resistant Staph. bacteria, according to "Harrison's Principles of Internal Medicine." Accurate bacteria cultures are difficult to obtain in cases of pneumonia, so most antibiotic treatment for nosocomial pneumonia is based upon the resistance patterns seen at a particular hospital and the perceived risk of infection with pseudomonas or resistant bacteria. Low-risk patients may be treated with just a cephalosporin or a just fluroquinolone, such as Levaquin, while higher-risk patients usually receive combinations of antibiotics. A hospital that is having particular trouble with multi-drug resistant staph will usually include the antibiotic vancomycin in the initial regimen.
C. Diff. Colitis
The bacteria Clostridium difficile, or C. diff., causes one of the most troublesome nosocomial infections. C. diff. colonizes the lining of the large intestines, causing inflammation of the colon, or colitis. The usual consequence of this colitis is chronic diarrhea, although severe cases can be life threatening, according to "Harrison's Principles of Internal Medicine." C. diff. infection occurs in patients who have previously had intensive antibiotic therapy for other infections and are then exposed to the bacteria. C. diff. infections are notoriously difficult to treat, in part because, due to prior antibiotic exposure, most strains of the bacteria are highly resistant. Fortunately, discontinuing the antibiotics that preceded the infection will improve symptoms in some patients and even completely eliminate them in a few. But most patients require antibiotic therapy specifically for the C. diff. Treatment for C. diff. colitis usually begins with the antibiotic metronidazole, trade name Flagyl, and if this fails oral vancomycin is the next step. Initial C. diff. colitis requires one to two weeks of antibiotic treatment, although if the symptoms recur, which is fairly common, up to six weeks of salvage therapy may be needed.
References
- Centers for Disease Control and Prevention: Emerging Infectous Disease: Nosocomial Infection Update
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper; 2005
