Infectious Diarrhea

Hoonmo Koo Key Point

• Most acute diarrheal illness is viral and can be managed symptomatically and with appropriate attention to hydration.

• Travelers' diarrhea is usually caused by diarrheogenic Escherichia coli.

• The infection in travelers' diarrhea is usually self-limited.

• Antibiotics may shorten the duration of diarrhea by 1 to 3 days.

• The most common cause of antibiotic-associated diarrhea is Clostridium difficile.

• Treatment of antibiotic-associated diarrhea involves discontinuing the offending agent, if possible.

Table 16-20 Empiric Antibiotics for Initial Treatment of Bacterial Meningitis

Age/Risk Factors

Empiric Antibiotic Therapy

<1 month

Ampicillin + cefotaxime or amp + aminoglycoside

1 month to 2 years

Vancomycin + ceftriaxone or cefotaxime*

2 to 50 years

Vancomycin + ceftriaxone or cefotaxime*

>50 years

Ampicillin + vancomycin + ceftriaxone or cefotaxime*

Basilar skull fracture

Vancomycin + ceftriaxone or cefotaxime

Penetrating head trauma

Vancomycin + ceftazidime, cefepime, or meropenem+

Postneurosurgery status

Vancomycin + ceftazidime, cefepime, or meropenem

Cerebrospinal fluid (CSF) shunt

Vancomycin + ceftazidime, cefepime, or meropenem

Modified from Practice Guidelines for Bacterial Meningitis, CID 2004:39. "Consider adding rifampin if dexamethasone is also given. fImipenem should be avoided because it increases the risk of seizures.

Evaluate severity and duration Obtain history and physical examination1-5 Treat dehydration Report suspected outbreaks6 Check all that apply:7

A. Community-acquired or travelers' diarrhea

(esp. if accompanied by significant fever or blood in stool)

Culture or test for: Salmonella Shigella Campylobacter

E. coli O157:H7 (if blood in stool also test for

Shiga toxin and refer isolates if toxin pos.) C. difficile toxins A ± B (if antibiotics or chemotherapy taken in recent weeks)

Consider quinolone for suspected shigellosis in adults (fever, inflammation); macrolide for suspected resistant Campylobacter; avoid antimotility or certain antimicrobial drugs if suspected STEC (afebrile, bloody diarrhea)8

B. Nosocomial diarrhea

(onset after >3 d in hospital)

Test for C. difficile toxins A ± B

(In suspect nosocomial outbreaks, in patients with bloody stools, and in infants, also add tests in panel A)

Discontinue antimicrobials if possible; consider metronidazole if illness worsens or persists

C. Persistent diarrhea >7 d

(esp. if immunocompromised)

Consider parasites9 Giardia

Cryptosporidium Cyclospora Isospora belli

+ Inflammatory screen7


(Gram-chromotrope) M. avium complex + panel A

Treat per results of tests

Figure 16-12 Recommendations for diagnosis and management of diarrheal illnesses. HIV, Human immunodeficiency virus; Pos., positive. 1Seafood or seacoast exposure should prompt culture for Vibrio spp. 2Travelers'diarrhea that has not responded to empiric therapy with rifaximin, a quinolone, or azithromycin should be managed with the above approach. 3Persistent abdominal pain and fever should prompt culture for Yersiniaenterocolitica and cold enrichment. Right-side abdominal pain without high fever but with bloody or nonbloody diarrhea should prompt culture for Shiga toxin producing E. coli (STEC) O157. 4Proctitis in symptomatic homosexual men can be diagnosed with sigmoidoscopy. Involvement in only the distal 15 cm suggests herpesvirus, gonococcal, chlamydial, or syphilitic infection; colitis extending more proximally suggests Campylobacter, Shigella, Clostridium difficile, or chlamydial (LGV serotype) infection, and noninflammatory diarrhea suggests giardiasis. 5Postdiarrheal hemolytic uremic syndrome (HUS) should prompt testing of stools for STEC O157 and for Shiga toxin (send isolates to reference laboratory if toxin-positive but STEC-negative). 6Outbreaks should prompt reporting to the health department. Consider saving culture plates and isolates and freeze whole stools or swabs at -70° C. 7Fecal lactoferrin testing or microscopy for leukocytes can help document inflammation, which may be present in invasive colitis with Salmonella, Shigella, Campylobacter, or C. difficile colitis, and with inflammatory bowel disease. 8Some experts recommend avoiding administration of antimicrobial agents to persons in the United States who have bloody diarrhea. 9Commonly used tests for parasitic causes of diarrhea include fluorescence and EIA for Giardia and Cryptosporidium; acid-fast stains for Cryptosporidium, Cyclospora, Isospora, or Mycobacterium spp. (as well as culture for Mycobacterium avium complex); and special chromatrope or other stains for Microsporidia. From Guerrant RL, Van Gilder T, Steiner TS, et al. Practice guidelines for the management of infectious diarrhea. Clin Infect Dis 200i;32:334.

Diarrhea is a common presenting complaint in the primary care physician's office. Not all causes of diarrhea are infectious, and not all infectious causes of diarrhea require specific antibiotic therapy. Diarrhea remains a major cause of morbidity and mortality, particularly for children in the developing world. Diarrhea is an alteration of normal bowel function, characterized by an increase in the water content, volume, or frequency of stools. Acute diarrhea is typically defined as present less than 14 days, and diarrhea is considered chronic when symptoms persist longer than 30 days (Figure 16-12).

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