What is the first line treatment for gastroenteritis in a patient with a history of penicillin allergy and bacterial lymphadenitis?

First-Line Treatment for Gastroenteritis

The first-line treatment for gastroenteritis is oral rehydration therapy (ORT), regardless of penicillin allergy status, as gastroenteritis is predominantly viral and does not require antibiotics in most cases. 1, 2

Primary Management Approach

Rehydration Strategy

• Oral rehydration solution is as effective as intravenous therapy for mild-to-moderate dehydration and should be the first-line treatment. 2, 3
• Nasogastric or intravenous hydration should be reserved for patients who cannot tolerate oral intake or have severe dehydration. 1
• The oral rehydration solution remains underutilized despite strong evidence supporting its effectiveness. 2

Symptom Management

• Antiemetics (particularly ondansetron) can enhance compliance with oral rehydration therapy and decrease hospitalization rates, though they are not routinely recommended for all cases. 2
• Antimotility and antisecretory drugs may be used for symptom control in appropriate cases. 1

When Antibiotics Are Actually Indicated

Antibiotics are NOT needed for most gastroenteritis cases, as viruses cause approximately 70% of episodes. 2 However, antimicrobial therapy is specifically indicated for:

• Clostridioides difficile infections 1
• Travel-related diarrhea 1
• Bacterial infections with severe symptoms (bloody stool, high fever, systemic toxicity) 1, 4
• Parasitic infections 1

Diagnostic Approach for Antibiotic Decision

• Mild symptoms resolving within one week do not require microbial studies. 1
• Longer-lasting or severe symptoms (including bloody stool) warrant multiplex antimicrobial testing, which is now preferred over traditional stool cultures. 1
• Recent antibiotic exposure should prompt testing for C. difficile. 1

Penicillin Allergy Considerations

The penicillin allergy label is irrelevant for most gastroenteritis cases since antibiotics are rarely indicated. 5 However, if bacterial gastroenteritis requiring antibiotics is confirmed:

Important Penicillin Allergy Context

• Approximately 90% of patients reporting penicillin allergy can actually tolerate penicillins when properly tested. 5
• A proactive effort should be made to delabel patients with reported penicillin allergy when appropriate, as the mislabel leads to use of less effective, more toxic, or more expensive antibiotics. 5
• Patients with penicillin allergy labels have a 14% increased risk of death over 6 years due to suboptimal antibiotic choices. 5

If Antibiotics Are Needed in Penicillin-Allergic Patients

• The specific antibiotic choice depends on the identified pathogen and local resistance patterns. 4
• For patients with non-severe, delayed-type penicillin reactions occurring >1 year ago, certain cephalosporins with dissimilar side chains may be considered (cross-reactivity only 0.1%). 5, 6
• Never use cephalosporins in patients with immediate-type (anaphylactic) penicillin reactions due to up to 10% cross-reactivity risk. 5, 6

Critical Pitfalls to Avoid

• Do not routinely prescribe antibiotics for gastroenteritis without confirmed bacterial etiology and severe symptoms. 1, 2
• Avoid assuming all penicillin allergies are true allergies; most are not confirmed immunologic reactions. 5
• Do not underutilize oral rehydration therapy in favor of intravenous therapy for mild-to-moderate dehydration. 2, 3
• Prudent antibiotic use is essential to prevent C. difficile infections, which are increasing in prevalence. 7