Medication Summary
The goals of pharmacotherapy are to reduce morbidity, to prevent complications, and to possibly decrease the duration of illness.
In February 2006, the United States Food and Drug Administration (FDA) approved an oral vaccine for rotavirus (RotaTeq). RotaTeq is administered in a 3-dose series starting between age 6-12 weeks and completed before age 32 weeks. It protects against types G1, G2, G3 and G4.
In April 2008, the FDA approved Rotarix, another oral vaccine, for prevention of rotavirus gastroenteritis. The current recommendation is to administer 2 separate doses of Rotarix to patients aged 6-24 weeks. Rotarix was efficacious in a large study, which reported that Rotarix protected patients with severe rotavirus gastroenteritis and decreased the rate of severe diarrhea or gastroenteritis of any cause. [23] In March 2010, Rotarix was temporarily taken off the market due to concerns with contamination with porcine circovirus type 1 (PCV1), but in May 2010 the FDA cleared use of the product again. Rotarix should not be given to children with latex allergy. It protects against type G1, G3, G4, and G 9. Rotashield, an earlier vaccine, was withdrawn from the market due to concerns with intussusception.
Antibiotics
Class Summary
Therapy must cover all likely pathogens in the context of the clinical setting.
Ciprofloxacin (Cipro)
Fluoroquinolones are the agents of choice for the empiric treatment of invasive and traveler's diarrhea syndromes in adult patients. They are also the agents of choice when treatment is indicated and the organism involved is known to be Campylobacter, E coli (non-O157:H7), nontyphoid Salmonella (although antibiotic treatment may prolong bacterial shedding), Shigella, or Yersinia.
Trimethoprim-sulfamethoxazole (Bactrim)
Excellent second choice for empiric therapy, although it is not effective against Campylobacter organisms. Increasing resistance. First drug of choice for patients younger than 18 years. Specifically recommended for 5 d for shigellosis.
Rifaximin (Xifaxan, RedActiv, Flonorm)
Nonabsorbed (< 0.4%), broad-spectrum antibiotic specific for enteric pathogens of the gastrointestinal tract (ie, gram-positive, gram-negative, aerobic, and anaerobic). Rifampin structural analog. Binds to beta-subunit of bacterial DNA-dependent RNA polymerase, thereby inhibiting RNA synthesis. Indicated for E coli (enterotoxigenic and enteroaggregative strains) associated with travelers' diarrhea.
Antiemetics
Class Summary
All these drugs are indicated in the control of nausea and vomiting. All have been associated with extrapyramidal adverse effects, especially in patients who are acutely ill, dehydrated, or children. They should be used with caution and only in the lowest effective dose. A weak association with Reye syndrome exists, and all may mask the vomiting associated with underlying CNS lesions.
Prochlorperazine (Compazine)
Antidopaminergic drug that blocks the postsynaptic mesolimbic dopamine receptors. Has an anticholinergic effect and can depress the reticular activating system, possibly responsible for relieving nausea and vomiting.
Promethazine (Phenergan)
Antidopaminergic agent effective in the treatment of emesis. Blocks postsynaptic mesolimbic dopaminergic receptors in the brain and reduces stimuli to the brainstem reticular system.
Trimethobenzamide (Tigan)
Has central effects in which it inhibits the medullary receptor trigger zone.
Ondansetron (Zofran)
Selective 5-HT3 receptor antagonist that blocks serotonin both peripherally and centrally. Indicated for nausea and vomiting due to radiation and/or chemotherapy and for postoperative nausea and vomiting. Cost considerations.
Antidiarrheal agents
Class Summary
These agents are used to decrease the frequency of diarrheal stools and possibly the duration. They should be used with caution in children and in patients with dysentery, as some reports of prolonged illness and development of toxic megacolon exist.
Loperamide (Imodium)
Antimotility DOC. Generally safe and indicated in the early treatment of travelers' diarrhea.
Diphenoxylate HCl 2.5 mg/atropine sulfate 0.025 mg (Lomotil)
Antidiarrheal agent chemically related to narcotic analgesic meperidine. A subtherapeutic dose of anticholinergic atropine sulfate is added to discourage overdosage, in which case diphenoxylate may clinically mimic the effects of codeine.
Each tab of Lomotil or 5 cc of elixir contains 2.5 mg diphenoxylate hydrochloride and 0.025 mg atropine sulfate.
Almost always the preferred antimotility agent.
Vaccines
Class Summary
Elicit active immunization to increase resistance to infection. Vaccines consist of microorganisms or cellular components, which act as antigens. Administration of the vaccine stimulates the production of antibodies with specific protective properties.
Rotavirus vaccine (RotaTeq, Rotarix)
Currently, 2 orally administered live-virus vaccines are marketed in the United States. Each is indicated to prevent rotavirus gastroenteritis, a major cause of severe diarrhea in infants.
RotaTeq is a pentavalent vaccine that contains 5 live reassortant rotaviruses and is administered as a 3-dose regimen against G1, G2, G3, and G4 serotypes, the 4 most common rotavirus group A serotypes. It also contains attachment protein P1A (genotype P[8]).
Rotarix protects against rotavirus gastroenteritis caused by G1, G3, G4, and G9 strains and is administered as a 2-dose series in infants aged 6-24 wk.
Clinical trials found that the vaccines prevented 74-78% of all rotavirus gastroenteritis cases, nearly all severe rotavirus gastroenteritis cases, and nearly all hospitalizations due to rotavirus.
-
Hektoen enteric agar with Escherichia coli colonies. Different growth media are necessary for identifying different enteric pathogens, suppressing the growth of nonpathogens, and allowing for chemical reactions to assist in identification. The appearance results from the organism's ability to ferment lactose placed in the medium. This results in the production of acid, which lowers the pH and causes a change in the pH indicator placed in the medium. Salmonella and Shigella organisms do not ferment lactose.
-
Example of Salmonella on Hektoen enteric agar. The medium also contains ferric ammonium citrate, which indicates the production of hydrogen sulfide by the appearance of a black precipitate.
-
The MacConkey medium is commonly used and differentiates lactose fermenters, which produce acid, decrease the pH, and cause the neutral red indicator to give the colonies a pink-to-red color.
-
The Christensen method is used to determine if an organism produces the enzyme urease (Yersinia) or not (Salmonella, Shigella, Vibrio). Hydrolysis of urea produces ammonia and carbon dioxide, alkalinizing the medium and turning the phenol red from light orange to magenta (pink).
-
Often, a combination of methods may be used for identification. The tube on the left is triple sugar iron (TSI) agar. The alkaline slant and acid butt (K/A) indicates an organism that ferments glucose only (not lactose or sucrose). The middle tube is indole positive, as indicated by the pink ring, and indicates the organism's ability to split tryptophan to form indole. The tube on the right is urease negative. Taken together, these tests indicate the organism is likely Shigella.
-
Gram stain may be helpful in identifying an etiologic agent. This stain shows gram-negative bacilli, which could be Salmonella or Shigella with 2 polymorphonucleocyte cells (PMNs).
