Pathogen Specific Therapy Bacterial Pathogens


Nontyphoidal species of Salmonella cause approximately 1.4 million cases of gastroenteritis and diarrhea annually. Contaminated meat, poultry, and eggs are common sources of infection, although bean sprouts, tomatoes, and orange juice have also been linked to outbreaks of salmonellosis. Other than diarrhea, clinical features may include abdominal pain, fever, and chills. Grossly bloody diarrhea is uncommon. Patients may carry Salmonella in their stools for weeks after symptoms resolve and 0.2 to 0.6% of patients may carry Salmonella over 1 year (long term carriers). The majority of cases in healthy adults are self-limited and do not require antibiotics. However, Salmonella can invade vascular sites and cause systemic toxicity in compromised hosts. Therapy (see Table 49-2) is indicated for patients with systemic toxicity or bacteremia, aged under 6 months or over 50 years, and in patients with prosthetic joints, heart valves or vascular grafts, severe atherosclerosis, malignancy, HIV/acquired immunodeficiency syndrome (AIDS), or uremia. Typhoidal Salmonella is uncommon in the United States and often associated with constipation rather than diarrhea.


The four species/serogroups of Shigella are as follows: (1) serogroup A (S. dysenteriae, the agent of bacillary dysentery), (2) serogroup B (S.flexneri), (3) serogroup C (S. boydii), and (4) serogroup D (S. sonnei, the most common species in the United States). Shigella sp are extremely contagious and ingestion of < 100 bacteria may cause infection. Raw vegetables, cheeses, and eggs are common sources of infection. Shigellosis is an inflammatory colitis, often characterized by dysentery (small volume stools with abdominal cramping, fever, and tenesmus). Systemic signs of fever, toxicity, and cramping are often present, although bacteremia is rare. Unlike salmonellosis, all patients with confirmed shigellosis should be treated (see Table 49-2). Co-trimoxazole (twice daily for 3 days for normal hosts) or fluroquinolones are the agents of choice. Co-trimoxazole is preferable if the Shigella isolate is susceptible to this agent.


E. coli are aerobic gram-negative rods and normal inhabitants of the human small and large intestine. Several forms of E. coli cause diarrhea and distinct clinical manifestations based on the different toxins and virulence factors produced. Forms include enterotoxigenic E. coli (ETEC) which causes travelers' diarrhea, and enterohemorrhagic E. coli (EHEC), which cause a hemorrhagic colitis associated with the hemolytic uremic syndrome. The serotypes of EHEC include E. coli O157:H7, which has been associated with several

TABLE 49-2. Therapy of Infectious Diarrhea


Antimicrobial Agent

Special Circumstances

Bacterial nontyphoid Salmonella

Campylobacter species

Shigella sp

Escherichia coli ETEC traveler's diarrhea £ coli O157:H7 Yersinia sp Clostridium difficile

Parasitic Pathogens Cryptosporidium parvum

Not recommended routinely

Erythromycin 500 mg po qid Cotrimoxazole ds po bid for 3 days (if sensitive)

Ciprofloxacin 1 g po for 1 day

Not recommended1

Antibiotics not required

Metronidazole 500 mg po tid for 10 to 14 days

Self-limited illness in normal hosts

Giardia lamblia Cyclospora cayentensis Isospora belli Viral Pathogens Toxin-mediated diarrhea

Bacillus cereus, Clostridium perfringens Supportive care

Vibrio cholerae Doxycyline 300 mg po for 1 day

Vibrio parahemolyticus Supportive care

Metronidazole 250 mg po tid for 5 to 10 days Cotrimoxazole 1 ds bid for 3 days Cotrimoxazole 2 ds po bid for 2 to 4 weeks Supportive care

Ciprofloxacin 500 mg po bid for 5 days Treat 14 days if immunocompromised* Multidrug resistant Salmonella exists Ciprofloxacin 500 mg po bid for 5 days also effective, avoid due to resistant strains Treat immunocompromised patient for 7 to 10 days If resistant, ciprofloxacin 500 mg bid for 3 days

Ciprofloxacin 500 mg po bid for 3 days

For serious infections: ciprofloxacin or doxycyline and AG In severe infections, vancomycin 125 mg po qid Metronidazole 500 mg IV every 8 hours'

In immunocompromised or severe hosts, paromomycin 500 mg po tid for 14 to 28 days

Ciprofloxacin 1 mg po for one day

Adapted, in part, from Kirkpatrick, 2003.

AG = aminoglycoside antibiotic; bid = twice daily; ds = double strength; ETEC = enterotoxigenic Escherichia coli; IV = intravenous; po = by mouth; qid = four times daily; tid = three times daily.

*See text for recommendations.

increased risk of hemolytic uremic syndrome.

*If unable to take orally.

large-scale food and water outbreaks. Enteroaggregative E. coli and enteropathogenic E. coli are important causes of persistent and chronic diarrhea in young children, particularly in underdeveloped nations, and enteroinvasive E. coli causes a Shigella-like dysentery. As previously discussed, treatment with a fluoroquinolone is effective in ETEC travelers' diarrhea. Caution is advised when using antibiotics in EHEC infections, due to the association of antibiotic use and the development of hemolytic uremic syndrome in children.


Campylobacter jejuni is the most commonly identified bacterial pathogen in stool cultures and is associated with over 2 million cases of foodborne disease in the United States annually. The spectrum of illness due to Campybbacter ranges from mild watery diarrhea to inflammatory enteritis or colitis. Treatment is rarely needed for normal hosts, who clear the infection spontaneously. For patients with systemic symptoms, severe disease or immunosuppression, therapy is recommended with erythromycin. Fluoroquinolones are also useful to treat sensitive Campylobacter, however, there is a worldwide increase in flu-oroquinolone resistance and these infections may clinically worsen when quinolones alter normal flora.

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

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