INFECTIVE PNEUMONIA
Acute infective pneumonia is the commonest cause of hospitalization and mortality in under-5 children of India, responsible for ~20% deaths in this age group.
Etiology: According to the source of infection, these cases may be classified as community-acquired pneumonia or nosocomial pneumonia (Table 16.22).
• Community-acquired pneumonia is predominantly viral (50%) or bacterial (40%) in origin.
Viral pneumonia may be caused by specific respiratory viruses, e.g. RSV, influenza, parainfluenza, adenoviruses, etc. or as a part of generalized exanthematous illnesses, e.g. measles or varicella.
TABLE 16.22: Common causes of pneumonia
Community-acquired pneumonia
• Newborns: Staph. aureus, E. coli, Klebsiella, GBS
• Infants: Hib, Staph. aureus, S. pneumoniae, viruses
• Pre-school: S. pneumoniae, S. pyogenes, Hib, viruses
• School: Myco. pneumoniae, S. pneumoniae, viruses
Nosocomial pneumonia
• Gram negative: Klebsiella, Pseudomonas
• Gram positive: Staph. aureus, CONS
• Fungal, e.g. candidiasis
Opportunistic infections
• Pneumocystis carinii
• Fungal: Candidiasis
• Viruses: CMV
Hib: H. influnzae B; CONS: coagulase negative staphylococci; GBS: Group B streptococci
Bacterial pneumonia may be primary or superimposed on viral or non-infective pneumonia. Etiology of bacterial pneumonia depends on the age as well as microbial pattern in the community.
• Nosocomial pneumonia are usually gram negative, with Klebsiella and Pseudomonas as leading pathogens, though staphylococcal and fungal infections are also common.
• Opportunistic infections, e.g. coagulase negative staphylococci (CONS), candida or Pneumocystis jiro- vecii, are common in immunocompromised children.
Epidemiology: Community-acquired pneumonias are acquired as droplet infection from a case/carrier of the organism, though hematogenous spread from distant septic focus is common in newborns or debilitated children.
Nosocomial infections may originate from any animate or inanimate source in the hospital.Risk factors for recurrent pneumonia in childhood include:
• Environmental factors, e.g. over-crowding, pollution, passive smoking, etc.
• Nutritional deficiencies, e.g. malnutrition, vitamin A deficiency.
• Recurrent aspiration, e.g. cleft-palate, gastroesophageal reflux, bulbar palsy.
• Immunodeficiency, e.g. AIDS, primary immunodeficiency disorders.
• Increased pulmonary vascularity, e.g. in congenital heart defects.
• Chronic lung disease, e.g. asthma, cystic fibrosis.
• Others: Low birth weight, top feeding.
Pathologically, pneumonia may be classified according to predominant tissue involvement as: (a) bronchopneumonia, e.g. Staph. aureus, (b) lobar pneumonia, e.g.
S. pneumoniae, (c) interstitial pneumonia, e.g. viral or mycoplasma infections, and (d) destructive pneumonia involving all pulmonary elements, e.g. pseudomonas or Hib pneumonia.
Clinical presentation varies according to the etiology, though general features include:
• Preceding history of upper respiratory infection or exanthematous illness.
• Acute, rapidly progressive course in most cases, though viral, mycoplasma or Hib pneumonias run relatively insidious course.
• Symptoms: Fever, cough and respiratory distress with tachypnea, dyspnea, feeding difficulties, grunting and cyanosis. Fever is more prominent in bacterial pneumonia. Presence of chills indicates probable pneumococcal etiology.
• Clinical signs depend on the extent of lesion and vary from diffuse crepitations (bronchopneumonia) to signs of consolidation, e.g. dull percussion note, increased vocal resonance/fremitus, and bronchial breathing (lobar pneumonia). Signs are disproportionately less and fluctuating in interstitial pneumonia. Nuchal rigidity may be present in right apical pneumonia.
• Complications, e.g. empyema, pneumothorax may complicate clinical picture in many cases.
Diagnosis of pneumonia per se depends on clinical and radiological findings (Table 16.23, Fig.
16.11), though etiological confirmation requires:• Direct detection of organisms on smear, culture or PCR from body fluids, e.g. sputum, gastric aspirate, bronchoalveolar lavage, pleural fluid, etc.
• Serological investigations for viral antigen or atypical pneumonia.
Other investigations, e.g. blood gas analysis, etc. are necessary to assess and monitor the severity of disease. D/D: Important differentiating features between bacterial, vial and mycoplasma pneumonia are given in Table 16.24.
Bacterial pneumonia: Presence of polymorphonuclear leukocytosis and elevated CRP or procalcitonin values support bacterial etiology. Special characteristics of some common causes are as follows:
• Staphylococcal pneumonia is most common in infants, toddlers or debilitated children with septic foci, e.g.
| TABLE 16.23: D/D X-ray picture of pneumonia | |
| X-ray findings | Probable diagnosis |
| Lobar consolidation | Pneumococci |
| Pneumatoceles/abscess | Staph. aureus, Klebsiella |
| Large effusion | Streptococci |
| Empyema/pneumothorax | Staph. aureus |
| Ground-glass (interstitial) | Viral, mycoplasma |
| Miliary mottling | TB, PCP, TPE |
| Upper lobe consolidation | Aspiration, Klebsiella* |
| Lower lobe consolidation | Foreign body |
*with bulging fissure (Fig. 16.11f). TPE: Tropical pulmonary eosinophilia
pyoderma, otitis, etc., acquired via hematogenous route. Clinical course is usually acute and rapidly progressive, with diffuse bronchopneumonia and development of pneumatoceles (thin-walled air cavities) on chest X-ray (Fig.
16.11E). Complications are common and include—(a) empyema, (b) pneumothorax, (c) distant metastatic infections, e.g. meningitis, and(d) residual lung lesions, e.g. bronchiectasis, lung abscess, etc.
• Pneumococcal pneumonia is primarily alveolar, with four pathological stages-exudation gt; red hepatization gt; gray hepatization gt; resolution. Apart from being commonest community-acquired pneumonia in 1-5 years age group, children with splenic dysfunction, e.g. sickle cell disease, asplenia, splenectomy, etc. or nephrotic syndrome are relatively more prone for pneumococcal pneumonia.
Clinico-radiological signs may vary from localized lobar pneumonia in older cases to diffuse bronchopneumonia in infants (Fig. 16.11A and B). Presence of chills, abdominal pain due to basal pleuritis and nuchal rigidity due to apical lesions strongly indicates pneumococcal etiology.
• H. influenzae B (HiB) pneumonia is most common between 3 months to 2 years of age. It is usually lobar pneumonia with destruction of airway epithelium and marked interstitial and alveolar edema. Most cases run relatively insidious course, frequently associated with otitis media and plural effusion. Extrapulmonary complications, e.g. meningitis, arthritis, pericarditis, etc. are more common than pulmonary complications. Incidence of Hib is expected to decline in recent years after universal Hib immunization.
• Streptococcal pneumonia is most common in 3-5 years age group, usually after an exanthematous illness or sore throat. Being an interstitial pneumonia, clinical signs are disproportionately less than the dyspnea. Large pleural effusions are common.
• Gram-negative pneumonia are usually nosocomial in origin, seen in newborns, sick or immunocompromised children or those with pre-existing lung disease. Fulminant and therapy-resistant course with septicaemia is common. Pneumatoceles and apical consolidation with bulging borders on X-ray is common in Klebsiella pneumonia.
Viral pneumonias, more common in winter season, are predominantly interstitial pneumonias with disproportionately less lung signs than the respiratory distress.
Chest skiagram reveals characteristic diffuse infiltrates with hyperinflation or transient lobar infiltrates (Fig. 16.11C). Diagnosis is largely empirical, based on epidemiological pattern and sterile bacterial cultures. Viral serology is unreliable for early diagnosis 
Fig. 16.11: Representative X-ray chests in various types of pneumonia.
(A) Lobar pneumonia; (B) Bronchopneumonia; (C) Interstitial pneumonia; (D) Aspiration pneumonia; (E) Staphylococcal pneumonia with pneumatoceles; (F) Klebsiella pneumonia with bulging fissure.
TABLE 16.24: D/D bacterial, viral and mycoplasma pneumonia
Antiviral therapy with oral Oseltamivir is recommended in all cases of Influenza-Iike illness (ILI) with Category B and C disease (Ch 10.26), while nebulized ribavarin (RSV) is recommended only in cases with chronic lung or heart disease. Bronchiolitis obliterans is an important late complication of viral pneumonia.
Giant cell pneumonia with typical giant cells containing inclusion bodies-Hetch cells, is occasionally seen in sub- clinical measles infection or after measles vaccination in immunocompromised children.
Atypical pneumonia denotes a heterogeneous group with milder course, minimum lung signs and sterile bacterial cultures. Common causes of atypical pneumonia include— mycoplasma, chlamydia and legionella infections.
• Mycoplasma pneumoniae (primary atypical pneumonia) is the commonest cause of community-acquired pneumonia in school-children (5-12 years), presenting as interstitial pneumonia of gradual onset after preceding upper respiratory tract infection. Clinical signs are disproportionately less than X-ray findings, which reveal extensive and diffuse fluffy exudates with hilar lymphadenopathy.
Diagnosis usually rests on elevated cold agglutinin titers (gt;1:64) or positive IgM-ELISA test.
Confirmation by throat/sputum cultures or PCR is not possible. Complications are rare and include autoimmune illnesses, e.g. Steven-Johnson syndrome, acute transverse myelitis, Guillain-Barre syndrome and hemolytic anemia.• Chlamydia pneumoniae is an emerging cause of community-acquired pneumonia in school children. Diagnosis usually rests on serology (IgM gt;1:16). Tissue cultures from nasopharynx, sputum or bronchial lavage are confirmatory but rarely available.
• Legionnaire's pneumonia is an emerging cause of atypical nosocomial pneumonia in immunocompromised children. Legionella is an intracellular parasite, which grows inside the protozoans present in water tanks/pipes and infection is acquired on ingestion or inhalation of contaminated water or aerosols. Extrapulmonary manifestations, e.g. hepatorenal dysfunction and CNS involvement are common. Erythromycin with/without rifampicin is the drug of choice in these cases.
Management of pneumonia includes supportive as well as specific antimicrobial therapy. Hospitalization is indicated in: (a) young children lt;6 months, (b) moderate to severe respiratory distress, (c) toxic appearance, (d) poor oral intake or vomiting, (e) immunocompromised children, (f) complicated pneumonia, e.g. presence of empyema, and (f) no response to domiciliary antibiotic therapy.
A. Specific therapy: Choice of empirical antimicrobial therapy on admission depends on the age, severity and local experience with antibiotic resistance (Table 16.25), which should be modified after culture reports or in cases with unsatisfactory therapeutic response.
Antibiotics should be continued until the patient is afebrile for 72 hr for minimum 10 days in uncomplicated pneumonia. Shorter duration may be used in patients treated on OPD basis or by Azithromycin.
*Higher dose of amoxicillin upto 90 mg/kg/day are recommended in high-resistance populations for Pneumococci.
**Cloxacillin, vancomycin or Clindamycin for suspected Staph. pneumonia
Presently, empirical antiviral therapy with oral Oselta- mivir is recommended in all cases of influenza-like illness (ILI) with Category B and C disease (Ch 10.26), due to ongoing pandemic.
B. Supportive therapy includes:
• Fluid and electrolyte correction and maintenance.
• Monitoring for progressive respiratory distress clinically and by pulse oximetry. Sedatives are contraindicated and may mask clinical signs.
• Respiratory support, including humidified oxygen, continuous positive airway pressure (CPAP) or non- invasive/invasive mechanical ventilation.
• Management of co-existing sepsis or circulatory shock.
• Treatment of pulmonary (empyema/pneumothorax) or extrapulmonary complications.
• Symptomatic treatment for fever, cough, etc. Oral zinc 10-20 mg/day has been shown to reduce mortality in clinically defined severe pneumonia in developing countries.
16.9.2