Chapter 26 ICU Infections

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CHAPTER 26 • ICU Infections

accumulated, it has become clear that diarrhea may not always precede such toxic presentations. Diagnosis No routine laboratory test is diagnostic, but leuko- cytosis occurs in almost 80% of cases. As with other forms of inflammatory colitis, red blood cells and leukocytes usually are detectable in stool speci- mens. Diagnosis is confirmed by culturing C. dif- ficile in profusion from the stool or by detecting bacterial toxin in fecal products. The toxin assay is readily available and less sensitive but more spe- cific than stool culture. Some patients without C. difficile colitis have small numbers of the bacteria isolated from stool. If a diagnosis of staphylococcal or candidal antibiotic–associated diarrhea is being entertained, the microbiology laboratory should be notified when the stool specimen is submitted. Growth of Staphylococcus or Candida may not be reported as pathogenic unless near-pure cultures result or unless the laboratory is alerted in advance. The odor associated with C. difficile diarrhea is easily recognized by experienced health care per- sonnel. Though infrequently performed, sigmoidos- copy often visualizes the colonic pseudomembrane that supports the diagnosis, but in a small fraction of patients (about 10%), only the right colon is involved. In such cases, a complete colonoscopy is required to find the characteristic lesions. In clinical practice, empirical therapy is usually initiated with- out endoscopy once the diagnosis is entertained. Treatment Systemic antibiotics should be minimized, and fluid and electrolyte support should be administered. Antidiarrheal agents should be avoided, because they may prolong colonic dwell time, thereby increasing the severity of the colitis. There is no evidence that giving lactobacilli to help restore the fecal flora is beneficial. Yet, restoration of a diverse and normal gut flora by “fecal transplantation” (bac- teriotherapy) has been reported to succeed consis- tently in preventing recurrence. That procedure, seldom performed in critically ill patients, is usually attempted by colonoscopy, but success with deliv- ery by nasoduodenal tube has also been reported. Because the toxin as well as the organism may be transmitted nosocomially, all patients with this dis- ease should be placed on contact isolation. Alcohol- based hand-disinfecting products commonly used in ICUs do kill the C. difficile bacteria, but as already

noted do not kill the organism’s spores. Therefore, it is important to decontaminate one’s hands regularly with a prolonged soap and water wash. Aggressive room-disinfecting measures also must be taken for the room occupied by a recently infected patient. Because it is effective, inexpensive, and not associated with the induction of bacterial resistance seen with vancomycin, metronidazole in doses of 500 mg enterally every 8 hours for 10 days is the therapy of choice. Vancomycin (125 to 250 mg enterally every 6 hours) for 10 days is appropriate in documented metronidazole failures. Intravenous metronidazole and vancomycin are less effec- tive. Fidaxomicin, an antibiotic tightly targeted to C. difficile , appears currently to be an effective and attractive option, but experience with this agent is still accumulating. Bacitracin also has been used in doses of 25,000 units orally, four times daily, but is of uncertain benefit. Treatment may fail because of reinfection, emergence of a vancomycin-resistant strain (rare), or bacterial transformation into a dormant spore phase. When therapy fails, relapses usually occur within 2 weeks of stopping treatment and will respond to a second longer course of metronidazole. It is in these patients that fecal transplantation is a highly appropriate consideration. It should be kept in mind that most episodes of recurrent or persis- tent diarrhea are not due to colitis associated with C. difficile but with one of the more benign nonin- fectious causes outlined earlier. Sinusitis Although radiographic evidence of sinusitis can be demonstrated in many supine patients with naso- gastric tubes, nasal packing, or nasotracheal tubes, sinusitis often is overlooked as a source of occult fever in critically ill patients. Nosocomial sinusitis usually is polymicrobial with Gram-negative rods and staphylococci predominating. Cryptic fever may be the only clinical sign. Headache and facial pain may be impossible to detect in comatose or intu- bated patients. Nasal discharge usually is absent. Rarely, the paucity of overt clinical signs and inability of the patient to communicate may allow purulent sinusitis to advance to a life-threatening infection of the central nervous system. Its remote position and contiguity to vital structures render sphenoid sinusitis an unusually insidious process. Because bedside sinus radiographs are almost worthless