Short-course Antimicrobial Therapy for Paediatric Respiratory Infections

Inclusion Criteria: Children aged 6 months to 10 years presenting with CAP will be eligible. CAP will be defined if all of the four following numeric criteria are met: 1. fever (\>37.5 C axillary, \> 37.7 C oral, or \>38 C rectal) recorded in the ED or at home in the 48h prior to presentation; 2. any one of: 1. tachypnoea on exam (\>60 bpm for age \<1 y, \>50 bpm for 1-2 y of age, \>40 bpm for 2-4 y of age, and \>30 bpm for \>4 y of age); 2. cough on exam or by history; 3. increased work of breathing on exam; or 4. auscultatory findings (focal crackles, bronchial breathing, etc.) consistent with pneumonia; 3. infiltrates on chest radiograph consistent with bacterial CAP as judged by the ED physician; and 4. the attending ED physician diagnoses the child with primary CAP. (Children treated with systemic steroids in the ED will be presumed to have primary asthma exacerbation with possible infection and therefore will not meet inclusion criteria.) Participants must be well enough to be treated as outpatients (discharged home by the ED physician, adequate volume status, able to tolerate oral medication, oxygen saturation \> 90%, no evidence of impending respiratory failure), and have no evidence of empyaema or necrotizing pneumonia on chest radiograph. Exclusion Criteria: Children will be excluded if they have any of the following: cystic fibrosis, anatomic lung disease, bronchiectasis, congenital heart disease, history of repeated aspiration or velopharyngeal incompetence, malignancy, conditions requiring treatment with immune suppressants, primary immunodeficiency, advanced HIV infection, prolonged admissions (\>48 h) to hospital within the past 2 months, pneumonia previously diagnosed within the past month, lung abscess diagnosed within the past six months, receipt of \> 24 hours of beta-lactam antibiotic therapy already received at presentation to the ED, receipt of at least a 5 day course of amoxicillin \< 72h prior to presenting to the ED, receipt of an intravenous cephalosporin or azithromycin in the ED, or suspected allergy to penicillin. Children will not be eligible to participate more than once.