Pneumonia—BacterialBasics

DESCRIPTION

Acute infection of the pulmonary parenchyma, which is associated with consolidation of alveolar spaces

EPIDEMIOLOGY

Incidence

Highest incidence in children <5 years of age (annual incidence 3–4%)

RISK FACTORS

• Asthma

• Cystic fibrosis

• Sickle cell anemia

• Cerebral palsy

• Immunocompromised status

• Altered mental status

• Tracheoesophageal fistula

• Congenital pulmonary malformations

• Bronchopulmonary dysplasia

• Seizure disorder

ETIOLOGY

Etiology of bacterial pneumonia differs by age:

• Neonates: Group B streptococcus, Enterococcus, Listeria monocytogenes, Escherichia coli, Ureaplasma urealyticum

• 1–3 months: Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Bordetellapertussis, Chlamydia trachomatis, U. urealyticum

• 4 months to 4 years: S. pneumoniae, S. aureus, H. influenzae

• >5 years of age: S. pneumoniae, Mycoplasma pneumoniae, Mycoplasma tuberculosis

Diagnosis

SIGNS AND SYMPTOMS

History

• Fever and/or chills

• Rapid breathing is a sensitive, but nonspecific finding in bacterial pneumonia.

• Difficulty breathing or shortness of breath is common and can lead to difficulty feeding in infants.

• Cough is often seen in bacterial pneumonia. B. pertussis pneumonia often presents after a catarrhal phase with a paroxysmal cough and posttussive vomiting.

• Pleuritic chest pain

• Abdominal pain and/or vomiting: Lower-lobe pneumonia can present with abdominal pain.

• Irritability, lethargy, and/or malaise

• Poor feeding or apnea in young infants

• Birth history, including maternal infections (e.g., C. trachomatis can be transmitted to an infant througha mother’s genital tract at delivery)

• Immunization status: In a fully immunized child, H. influenzae type B, B. pertussis, and S. pneumoniae infections are less common.

• Recent history of upper respiratory tract infection (URI) can predispose to bacterial pneumonia.

• History of repeated bacterial infections suggest immunodeficiency or cystic fibrosis, which are risk factors for bacterial pneumonia.

• Exposure to contacts with pertussis, tuberculosis, or history of recent travel:

1. Travelers, health care workers, and persons working in prisons or institutional settings are at greater risk for tuberculosis.

Physical Exam

• Ill appearance:

1. General examination can range from mildly ill- appearing to toxic in appearance.

2. Infants may have a paucity of exam findings disproportionate to their appearance and tachypnea.

3. Patients can be dehydrated or in shock.

• Fever:

1. Most children with bacterial pneumonia have fever.

2. Patients with atypical bacterial pneumonia and pertussis are sometimes afebrile.

• Tachypnea or increased work of breathing: Nasal flaring, grunting, and/or retracting

• Decreased oxygen saturation; therefore, oxygen saturation should be obtained by pulse oximetry in children with tachypnea or other signs of distress.

• Localized rales, rhonchi, decreased breath sounds, or wheezing:

1. These are all significant clinical findings of pneumonia. Crackles suggest the diagnosis of pneumonia.

2. With increasing consolidation, dullness to percussion and decreased breath sounds may benoted.

3. In patients who are actively wheezing, it may be difficult to distinguish rales from other auscultated sounds.

TESTS

• Not indicated for patients with uncomplicated pneumonia

• In toxic-appearing infants, blood, urine, and CSF cultures (i.e., a sepsis work-up) should be considered.

LABORATORY

• Blood culture:

1. Not usually indicated in healthy children with uncomplicated pneumonia

2. Rarely leads to identification of pathogen causing pneumonia

3. Should be obtained in toxic-appearing patients and infants <1 month old

4. Bacteremia has been noted in up to 30% of patients with pneumococcal pneumonia.

• Elevated peripheral WBC or range 15,000–40,000/mm3 is associated with bacterial pneumonia, but should not be relied upon to distinguish etiology of pneumonia.

• Cold agglutinin test:

1. A positive test suggests M. pneumoniae. This test is usually not indicated because empiric treatment of this pathogen is typically safe and effective.

• Purified protein derivative (PPD) test: Should be obtained in all patients in whom M. tuberculosis is suspected

IMAGING

• Chest radiograph (CXR), upright:

1. A CXR is not required for diagnosis if clinical symptoms and examination findings are consistent with pneumonia.

2. A CXR is typically obtained if pneumonia is suspected but clinical findings are unclear, if thepatient has evidence of respiratory distress and if a complication, (e.g., a pleural effusion) issuspected, or if the patient is not responding to treatment.

3. Characteristic CXR patterns include “alveolar or lobar infiltrate” with air bronchograms. “Round” infiltrates may be seen with S. pneumococcus. “Diffuse” interstitial infiltrates and hyperinflation may be seen with atypical pneumonia such as M. pneumoniae or chlamydial pneumonias.

4. More commonly, CXR cannot be reliably used to distinguish between viral and bacterial disease.

5. An infiltrate may not be seen (negative CXR) if the disease is diagnosed early or if the patient is dehydrated.

• CXR, lateral decubitus: More sensitive than an upright radiograph in detecting pleural effusions or foreign body aspiration

• Computed tomography (CT) scan: Not recommended as 1st-line imaging for suspected pneumonia. CT is mainly used as adjunct imaging for patients who are worsening (not improving) despite treatment, or have complications.

DIAGNOSTIC PROCEDURES

If diagnosis is unclear, consider the following:

• Flexible fiberoptic bronchoscopy with bronchoalveolar lavage or lung biopsy

• Thoracentesis if plural fluid is present

• For empyema, drainage by aspiration or chest tube may be required.

DIFFERENTIAL DIAGNOSIS

• Infectious:

1. Sepsis

2. Viral pneumonia:

• In infants: Cytomegalovirus (CMV), herpes simplex virus (HSV)

• From 1 month–3 months: CMV, respiratory syncytial virus (RSV)

• From 4 months to 4 years: RSV, adenovirus, influenza

3. Bronchiolitis

4. URI

5. Croup (laryngotracheobronchitis)

6. Fungal infection

7. Parasitic infection

• Pulmonary:

1. Asthma

2. Atelectasis

3. Pneumonitis (i.e., chemical)

4. Pneumothorax

5. Pulmonary edema

6. Pulmonary hemorrhage

7. Pulmonary embolism

• Congenital:

1. Pulmonary sequestration

2. Congenital cystic adenomatoid malformation

• Genetic: Cystic fibrosis

• Tumors:

1. Lymphoma

2. Primary lung tumor

3. Metastatic tumor

• Cardiac: CHF

• GI: Gastroesophageal reflux disease

• Miscellaneous:

1. Foreign body aspiration

2. Sarcoidosis

Treatment

GENERAL MEASURES

Outpatient: Empiric treatment:

• Unlike adults, there is no validated tool to identify those patients at low risk who can be treated as outpatients. In general, neonates should be managed as inpatients.

• 2–4 months; if afebrile:

1. Erythromycin: 50 mg/kg/d divided q6h or for infants <6 weeks consider azithromycin 10 mg/kg/d × 1 day then 5 mg/kg/d × 4 days due to concerns regarding hypertrophic pyloric stenosis

2. If febrile, hypoxic, or dehydrated, then admit (see “FAQ”)

• 5 months to 5 years:

1. Amoxicillin 80–100 mg/kg/d divided q8–12h

2. Consider for additional coverage of H. influenzae, non–type B:

• Amoxicillin/clavulanate 25–45 mg/kg/d divided b.i.d. or t.i.d.

• Cefuroxime 30 mg/kg/d divided b.i.d., cefprozil 30 mg/kg/d divided b.i.d., cefdinir 14 mg/kg/d divided daily or b.i.d., or cefpodoxime 10 mg/kg/d divided b.i.d.

• May consider use of ceftriaxone50 mg/kg intramuscular (IM) to initiate therapy

• For penicillin-allergic patients, may use macrolide or cephalosporin

3. Age >5 years (unless organism other than atypical pathogen suspected; atypical pathogensare much more common in this age group):

• Erythromycin 30–50 mg/kg/d divided q6h to q8h or other macrolide

• Azithromycin 10 mg/kg/d × 1 day (max dose 500 mg) then 5 mg/kg/d (max dose 250 mg) × 4 days

• May consider doxycyline 4 mg/kg/d divided by 2 doses in patients 9 years of age or older. Not to exceed 200 mg/d.

• May consider fluoroquinolones in patients ≥16 years of age

4. If specific pathogen is known or suspected, use appropriate antibiotic therapy.

5. For patients with more severe disease, may consider combining β-lactam antibiotic and macrolide

Inpatient:

• Oxygen as needed to keep oxygen saturations >94–95%

• Intubation and positive pressure ventilation if clinically indicated

• Empiric antibiotic treatment:

1. <1 month:

• Ampicillin 200 mg/kg/d divided q6–8h

2. Age 1–3 months:

• Erythromycin: 10 mg/kg IV q6h or azithromycin 2.5 mg/kg IV q12h. For infants <6weeks, consider azithromycin due to concerns regarding hypertrophic pyloric stenosis.

• If febrile, add cefotaxime 200 mg/kg/d divided q8h.

3. Age 4 months to 5 years (if atypical pathogens are not suspected):

• Ceftriaxone 50–75 mg/kg/d q12–24h or cefotaxime 200 mg/kg/d divided q8h

4. Age ≥5 years: Add macrolide to above therapy.

5. For seriously ill patients, add vancomycin 60 mg/kg/d divided q6h.

6. For antistaphylococcal coverage, add vancomycin 15 mg/kg/dose q6–8h or clindamycin 25–40 mg/kg/d divided q6–8h.

7. If atypical pneumonia also suspected, may add macrolide

8. May also consider macrolides or clindamycin IV as alternative for cephalosporin-allergic patients

Follow-up Recommendations

EXPECTED COURSE/PROGNOSIS

Otherwise healthy children with uncomplicated pneumonia typically have rapid improvement with treatment (3–5 days).

POSSIBLE COMPLICATIONS

• Pleural effusion

• Empyema

• Lung abscess

• Pneumatoceles

• Pneumothorax

• Bacteremia/sepsis

PATIENT MONITORING

• If treated as outpatient, follow up within 1–3 days.

• If worsening or not responding to treatment, consider repeated or additional diagnostic studies. For

example, persistent fever may be due to loculated pleural fluid or an empyema.

• CXR may be abnormal for up to 10 weeks after successful treatment. Consider follow-up CXR only if indicated for severe disease or complications (e.g., effusion, empyema).

• For children with recurrent bacterial pneumonia, consider an underlying anatomical or immunologic disorder (e.g., abnormal antibody production, cystic fibrosis, tracheoesophageal fistula, pulmonary sequestration).

Frequently Asked Questions

• Q: What are the indications for admission and inpatient treatment of pneumonia in children?

• A: Failure of outpatient therapy, hypoxemia, inability to maintain hydration orally or dehydration, respiratory distress, apnea, toxic appearance, presence of complications such as effusion or empyema and risk factors that predispose to complications, such as age <2 months, or immunocompromised status

• Q: What is the most common causative organism of pulmonary abscess, and what is the appropriate treatment?

• A: S. aureus is the most common causative organism. Treatment includes ampicillin/sulbactam (200 mg/kg divided by 6 hours) or cefuroxime (150 mg/kg/d divided by 8 hours)

• Q: What is the case fatality rate for pneumonia in hospitalized children?

• A: Based on data from 1995–1997, case fatality rates for children differ by age and are as high as 4% for children <2 years of age, and 2% for children aged 2–17 years.