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Assessing gastrointestinal infections



Common but rarely life-threatening, GI infections have many possible causes. Here's how to gather the clues so your patient gets appropriate care.

Whether foodborne or hospital-acquired, a GI infection makes your patient miserable. Read how to sort through the many possible causes and treat him appropriately.

MOST GASTROINTESTINAL (GI) infections are self-limited, but some can be fatal. Can you tell them apart? In this article, I'll describe foodborne and hospital-acquired GI infections and how you can recognize them and intervene appropriately.

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Foodborne infections: Trouble on the menu

If you're caring for a patient who may have a food-related illness, document his signs and symptoms; time of symptom onset; foods eaten in the last few days, including anything unusual he's eaten; and whether family or friends have similar signs and symptoms.

The potential course of illness ranges from mild to fatal, depending on the type and amount of organism present, the patient's susceptibility to infection, and his overall health. The severity of symptoms varies widely: Older and debilitated people, and the very young, tend to have more serious illness and may be hospitalized for dehydration; healthier people may have only mild, transient effects. For details on specific organisms, see Comparing Foodborne GI Infections.

If you suspect a bacterial cause for the patient's diarrhea, obtain a stool specimen for culturing. Because culture results won't be available for several days, they won't influence initial treatment, but they'll guide subsequent treatment if bacterial infection is present.

Culture results also help investigators probe outbreaks of foodborne illness. Local health departments usually won't investigate a restaurant or other facility on the basis of a single report of GI illness following a meal. But the health department will investigate if multiple cases occur or if a stool culture reveals a dangerous pathogen, such as enterotoxigenic Escherichia coli.

Treatment for most foodborne GI infections is primarily supportive, with the focus on increasing fluid intake, replacing electrolytes, and taking measures to prevent the infection from spreading to others (more on this later). But some serious infections require more aggressive treatment; for example, those caused by E. coli O157:H7, which can lead to hemolytic uremic syndrome and in some cases require hospitalization for hemodynamic control and early dialysis because of reduced kidney function.

Now let's look at a case of GI infection and examine how you'd ferret out the clues pointing to the cause.

Arthur Lee, 80, is in your unit with severe dehydration due to suspected food poisoning. The previous day, he'd attended a church picnic. That night, he and several other parishioners came to the emergency department with GI complaints, primarily nausea, vomiting, and diarrhea. Mr. Lee's daughter, who also attended the picnic, tells you that she'd had a bout of diarrhea around midnight but attributed it to her irritable bowel syndrome. When the local health department contacted her for her food history, she learned that everyone who'd gotten ill had eaten the pasta salad about 8 hours earlier—but not everyone who ate the pasta salad got ill.

This scenario indicates a common-source bacterial cause, probably Staphylococcus, based on the timing and type of symptoms and the food history. Possibly the mayonnaise or eggs were contaminated with the organism. But it's more likely that the person preparing the pasta salad was either ill or an asymptomatic carrier. If her hand hygiene was poor, she could easily have transferred bacteria to the food. If the food sat at room temperature for a few hours, the organism could proliferate to the point of infecting the picnickers.



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Hospital-acquired infections: Double trouble

Normally, the GI tract includes millions of beneficial microorganisms that are as individual to that person as his fingerprints. Disruption of the balance of a person's normal bowel flora by illness, medication, or introduction of foreign organisms can lead to overgrowth of usually benevolent organisms, causing infection.

Hospitalized patients who are already compromised by illness are at risk for GI infections, either from overgrowth of normal flora or from nosocomial (hospital-acquired) pathogens. If the patient is asymptomatic but pathogens such as Clostridium difficile or Staphylococcus aureus are present on stool culture, he's considered colonized, rather than infected, with the pathogen and may not need treatment. If his personal hygiene is poor, he could infect others.

The patient is considered infected when he has symptoms such as diarrhea that doesn't respond to over-the-counter medications, fever, elevated white blood cell count, and dehydration.

Antibiotic-associated diarrhea occurs when antibiotic therapy has the unintended effect of disrupting the normal balance of bowel flora, allowing an overgrowth of aggressive, harmful bacteria and yeasts. More than 75% of cases are mild and self-limited and can be treated simply by discontinuing the antibiotic. But antibiotic-associated diarrhea caused by C. difficile, a spore-forming bacterium that produces toxins in the bowel, may require more treatment.

Clostridium difficile–associated diarrhea (CDAD) most often affects patients who've taken antibiotics recently, usually within the past 2 months. Treatment for CDAD is to discontinue the antibiotic and administer oral metronidazole or oral vancomycin.

Some researchers believe that a patient is more likely to develop CDAD from colonization of bacteria acquired in the hospital rather than from his own flora. Up to 20% of hospitalized patients have strains of the bacteria present in their stool, possibly acquired from the hands of health care personnel or the hospital environment.

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In general, up to 3% of people are asymptomatic carriers of C. difficile. The presence of toxin or bacteria in the stool doesn't predict which patients will become ill, and treatment of asymptomatic carriers isn't indicated.

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More antibiotics defeat PMC

Infection with toxin-producing strains of C. difficile can, if not treated, lead to pseudomembranous colitis (PMC), which damages the colonic mucosa. Pseudomembranes form on the bowel lining, preventing absorption of nutrients and fluids. Risk factors for developing PMC include antimicrobial therapy, certain cancer chemotherapeutic drugs, prolonged hospital stay, advanced age, and parenteral feedings.

Ironically, treatment for PMC includes giving additional antibiotics after the offending antibiotic is discontinued. Oral metronidazole is the treatment of choice; oral vancomycin is an alternative. Administering probiotics such as lactobacillus (which resist colonization and restore normal bowel flora) with metronidazole or vancomycin may also be effective.

Diarrhea should resolve in 3 to 7 days, but up to 20% of patients experience a recurrence. After treatment, a patient may continue to carry the bacteria asymptomatically and shouldn't be retreated unless infection recurs.

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Meeting resistance with VRE

Resistant bacterial infections, such as vancomycin-resistant enterococci (VRE), are a major threat to hospitalized patients. Enterococci account for 12% of all nosocomial infections and have a 13% mortality rate. Enterococci are intrinsically resistant to many antibiotics, and their ability to resist treatment is increasing.

In the hospital, VRE is more likely to cause GI colonization than infection. The patient has a VRE infection at another site first—typically a urinary tract or bloodstream infection. The resistant bacteria may replace the patient's normal bowel flora, and after the original infection has healed, the patient's GI tract is colonized, making him infectious even though he's not ill.

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Caring for your patient

Consider any patient with diarrhea potentially infectious. If you're caring for a patient with a known or suspected GI infection, or bowel colonization with resistant bacteria, follow standard infection control precautions, including meticulous hand hygiene. Use barrier precautions such as gloves and a gown when you anticipate contact with blood, body fluids, secretions, excretions, or contaminated items.

Restrict to the infected patient's room any equipment that normally would be shared by patients, such as electronic thermometers and BP cuffs. If sharing equipment or items can't be avoided, don't use them on another patient until the items are cleaned and disinfected with hospital-grade disinfectants, following infection control guidelines and the manufacturer's recommendations.

Educate the patient and family to keep the infection from spreading to other patients or to family members at home. Tell them that many GI pathogens can spread for days to weeks after the acute episode is over. Teach the patient and his family good hand hygiene and urge them to continue this practice after discharge. Also teach them about preventing bacterial contamination at home.

By knowing how to reduce the risk of transmitting GI infections—and how to manage infection if it occurs—you can protect your patients from dangerous, difficult-to-control infections.

Barbara Wyand Walker is an infection control/employee health nurse at Greenbrier Valley Medical Center in Ronceverte, W.Va.

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Association for Professionals in Infection Control and Epidemiology, Inc.

Centers for Disease Control and Prevention

Partnership for Food Safety Education

Last accessed on April 1, 2004.

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Brooks, K. (ed): Ready Reference to Microbes. Washington, D.C., Association for Professionals in Infection Control and Epidemiology, Inc., 2002.
    Chin, J. (ed): Control of Communicable Diseases Manual, 17th edition. Washington, D.C., American Public Health Association, 2000.
      © 2004 Lippincott Williams & Wilkins, Inc.