Medication Summary
The goals of pharmacotherapy in cases of gastroenteritis are to reduce morbidity and to prevent complications. The following is a list of standard antimicrobial therapies for bacterial gastroenteritis (although, as previously stated, many conditions are self-limited and require no therapy):
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Aeromonas species - Use cefixime and most third-generation and fourth-generation cephalosporins
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Bacillus species - No antibiotics are necessary for self-limited gastroenteritis, but vancomycin and clindamycin are first-line drugs for severe disease
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Campylobacter species - Erythromycin may shorten the illness duration and shedding; delaying therapy beyond 4 days from the onset of symptoms appears to produce no clinical benefit
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C difficile - Discontinue potential causative antibiotics; if antibiotics cannot be stopped or this does not resolve the diarrhea, use oral metronidazole or vancomycin (vancomycin is reserved for seriously ill patients whose condition does not respond to metronidazole)
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C perfringens - Do not treat with antibiotics
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Listeria species - No antibiotics are needed unless invasive disease occurs; ampicillin and Bactrim are first-line drugs for invasive disease
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Plesiomonas species - Use trimethoprim-sulfamethoxazole or any cephalosporin
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V cholerae - Tetracycline is the usual antibiotic of choice, but resistance to it is increasing; other antibiotics that are effective when V cholerae is sensitive to tetracycline include cotrimoxazole, erythromycin, doxycycline, chloramphenicol, and furazolidone
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Yersinia species - Treatment (ie, trimethoprim-sulfamethoxazole, fluoroquinolones,* aminoglycosides) does not shorten the disease duration and should be reserved for complicated cases
* Note that fluoroquinolone resistance in Salmonella is increasingly being reported worldwide, with several molecular mechanisms described. [40]
E coli
Antibiotic treatment appears to increase the likelihood of developing HUS. Consider antibiotics if diarrhea is moderate or severe. Trimethoprim-sulfamethoxazole is a first-line drug, but a parenteral second-generation or third-generation cephalosporin for systemic complications should be used.
Salmonella species
Antibiotic treatment prolongs the carrier state and is associated with relapse; thus, treatment is not indicated for nontyphoid, uncomplicated diarrhea. Consider treatment for infants younger than 3 months and for high-risk patients, such as patients who are immunocompromised or who have sickle cell disease.
Ampicillin is recommended for drug-sensitive strains. Trimethoprim-sulfamethoxazole, fluoroquinolones,* or third-generation cephalosporins (fluoroquinolones are not recommended for use in children) are also acceptable alternatives. S typhimurium T104 is a multidrug-resistant organism. Sensitivities from the cultured specimens are important to guide therapy.
In July 2018, the FDA ordered ordered label changes for fluoroquinolones to strengthen warnings about the antibiotics' risks for mental health side effects and serious blood sugar disturbances. [41, 42]
Shigella species
Antibiotic treatment may shorten illness duration and shedding but does not prevent complications. Most mild infections will recover without antibiotics. Moderate to severe cases should be treated with antibiotics. Ampicillin is preferred for drug-sensitive strains. For ampicillin-resistant strains or in cases of penicillin allergy, trimethoprim-sulfamethoxazole is the drug of choice, although resistance does occur. Fluoroquinolones* may be considered in patients with highly resistant organisms.
Antibiotics
Class Summary
Along with the immune system, antibiotics help to destroy offending organisms.
Cefixime (Suprax)
Cefixime is a potent, long-acting oral cephalosporin with increased gram-negative coverage. It arrests bacterial growth by binding to 1 or more penicillin-binding proteins.
Ceftriaxone (Rocephin)
Ceftriaxone is a third-generation parenteral antibiotic with wide coverage, including of gram-negative bacilli. It arrests bacterial growth by binding to 1 or more penicillin-binding proteins.
Cefotaxime (Claforan)
Cefotaxime is a third-generation parenteral antibiotic with wide coverage, including of gram-negative bacilli. It arrests bacterial cell wall synthesis, which, in turn, inhibits bacterial growth.
Erythromycin (E.E.S., EryPed, Erythrocin, Ery-Tab)
Erythromycin is an old bacteriostatic macrolide with activity against most gram-positive organisms and atypical respiratory organisms. It is useful for Campylobacter and Vibrio enteritis. Nausea is a common adverse effect and may be tolerated poorly by some patients. Enteric-coated tablets are associated with less nausea.
Trimethoprim-sulfamethoxazole (Bactrim, Bactrim DS, Septra DS)
This is a folate synthesis blocker that has wide antibiotic coverage.
Vancomycin (Vancocin)
Vancomycin therapy is a powerful treatment for antibiotic-associated colitis. Vancomycin is indicated for patients who cannot receive or whose condition has not responded to penicillins and cephalosporins or who are infected with resistant staphylococci.
To avoid toxicity, the current recommendation is to assay trough levels after the third dose drawn 0.5 hour before the next dosing. Use creatinine clearance to adjust the dose in patients diagnosed with renal impairment.
Vancomycin is used in conjunction with gentamicin for prophylaxis in patients allergic to penicillin who are undergoing a gastrointestinal or genitourinary procedure.
Rifaximin (Xifaxan)
Rifaximin is a nonabsorbed (< 0.4%), broad-spectrum antibiotic specific for enteric pathogens of the gastrointestinal tract (ie, gram-positive, gram-negative, aerobic, anaerobic). Rifampin is a structural analogue. It binds to the beta subunit of bacterial deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase, thereby inhibiting RNA synthesis. It is indicated for E coli (enterotoxigenic and enteroaggregative strains) associated with travelers' diarrhea.
Rifamycin (Aemcolo, Rifamycin SV MMX)
Oral nonabsorbable antibiotic which can be used for the treatment of bacterial infections of the colon. Belongs to the ansamycin antibacterial drug class and acts by inhibiting the beta-subunit of bacterial DNA-dependent RNA polymerase, blocking 1 of the DNA transcription steps, which results in bacterial synthesis inhibition and consequently bacterial growth. It is indicated for traveler’s diarrhea caused by noninvasive strains of E coli, not complicated by fever or blood in the stool.
Tables
Stool Characteristics |
Small Bowel |
Large Bowel |
Appearance |
Watery |
Mucus and/or blood |
Volume |
Large |
Small |
Frequency |
Increased |
Increased |
Blood |
Possibly heme-positive but never gross blood |
Possibly grossly bloody |
pH |
Possibly < 5.5 |
>5.5 |
Reducing substances |
Possibly positive |
Negative |
White blood cell (WBC) count |
< 5/high-power field (HPF) |
Possibly >10/HPF |
Serum WBC count |
Normal |
Possible leukocytosis, bandemia |
Organisms |
Preformed toxins: Bacillus species, Staphylococcus aureus |
Invasive bacteria: E coli and Shigella, Salmonella, Campylobacter, Yersinia, Aeromonas, and Plesiomonas species |
Toxic bacteria: E coli, cholera, C perfringens, Vibrio species, Listeria monocytogenes |
Toxic bacteria: C difficile |
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Other causes: rotavirus, adenovirus, calicivirus, astrovirus, Norwalk virus, and Giardia and Cryptosporidium species |
Other causes: Entamoeba species |
Organism |
Incubation |
Duration |
Vomiting |
Fever |
Abdominal Pain |
Aeromonas species |
None |
0-2 weeks |
+/- |
+/- |
No |
Bacillus species |
1-16 hours |
1-2 days |
Yes |
No |
Yes |
Campylobacter species |
2-4 days |
5-7 days |
No |
Yes |
Yes |
C difficile |
Variable |
Variable |
No |
Few |
Few |
C perfringens |
0-1 |
1 day |
Mild |
No |
Yes |
Enterohemorrhagic E coli |
1-8 days |
3-6 days |
No |
+/- |
Yes |
Enterotoxigenic E coli |
1-3 days |
3-5 days |
Yes |
Low |
Yes |
Listeria species |
20 hours |
2 days |
Few |
Yes |
+/- |
Plesiomonas species |
None |
0-2 weeks |
+/- |
+/- |
+/- |
Salmonella species |
0-3 days |
2-7 days |
Yes |
Yes |
Yes |
Shigella species |
0-2 days |
2-7 days |
No |
High |
Yes |
S aureus |
2-6 hours |
1 day |
Yes |
No |
Yes |
Vibrio species |
0-1 days |
5-7 days |
Yes |
No |
Yes |
Y enterocolitica |
0-6 |
1-46 days |
Yes |
Yes |
Yes |
Organism |
Detection Method |
Microbiologic Characteristics |
Aeromonas species |
Blood agar |
Oxidase-positive, flagellated GNB |
Bacillus species |
Blood agar |
Facultatively aerobic, spore-forming GPR; beta hemolytic; reduces nitrates; ferments carbohydrates |
Campylobacter species |
Skirrow agar |
Rapidly motile, curved GNR; Campylobacter jejuni 90% of infections, Campylobacter coli 5% of infections |
C difficile |
CCFE agar, EIA for toxin, LA for protein |
Anaerobic, spore-forming GPR; toxin-mediated diarrhea; produces pseudomembranous colitis |
C perfringens |
None available |
Anaerobic, spore-forming GPR; toxin-mediated diarrhea |
E coli |
MacConkey, EMB, or SM agar |
Lactose-producing GNR |
Listeria species |
Blood agar |
Flagellated GPB |
Plesiomonas species |
Blood agar |
Oxidase-positive GNR |
Salmonella species |
Blood, MacConkey, EMB, XLD, or HE agar |
Nonlactose, non–H2S-producing GNR |
Shigella species |
Blood, MacConkey, EMB, XLD, or HE agar |
Nonlactose and H2S-producing GNR; verotoxin (neurotoxin) |
Staphylococcus species |
Blood agar |
Heat-stable, preformed toxin-mediated GPC |
Vibrio species |
Blood or TCBS agar |
Oxidase-positive, motile, curved GNB |
Y enterocolitica |
CIN agar |
Nonlactose-producing, oval GNR |
CCFE = cycloserine-cefoxitin-fructose-egg; CIN = cefsulodin-irgasan-novobiocin; EIA= enzyme immunoassay; EMB = e-methylene blue; GNB = gram-negative bacillus; GNR = gram-negative rod; GPB = gram-positive bacillus; GPC = gram-positive cocci; GPR = gram-positive rod; H2S = hydrogen sulfide; HE = Hektoen enteric; LA = latex agglutination; SM = Sorbitol-MacConkey; TCBS = thiosulfate-citrate-bile-sucrose; XLD = xylose-lysine-deoxycholate. |
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