PNEUMOCOCCAL INFECTIONS

Streptococcus pneumoniae is a common colonizing organism of upper respiratory tract, present in encapsulated and noncapsulated forms. Only capsulated forms are pathogenic and classified according to their type-specific capsular polysaccharide.

Pathogenesis: Pneumococcal colonization is common in under-five children, institutionalized cases and during winter season, via droplet infection from a case/carrier. Although host-defence mechanisms, e.g. mucociliary clearance and local phagocytosis limit the infection to colonized site, it may spread in susceptible host to neighboring tissues (localized disease) or via bacteremia to distant tissues (invasive disease).

High-risk factors for pneumococcal disease include: (a) impaired mucociliary clearance due to viral infec­tions, passive smoking and airway allergy, or (b) immunodeficiency states, specially with impaired splenic function, e.g. sickle cell disease, asplenia, splenectomy, etc. 0

Clinical spectrum spans from local upper respiratory tract disease to invasive disease, e.g. meningitis, pneumonia, etc. (Table 10.9). Pneumococci is the leading cause of community-acquired pneumonia, otitis media and meningitis in 1-5 years age group.

Diagnosis rests on culture from the site of infection or blood. Nasal/pharyngeal culture isolation is of little significance, due to frequent colonization.

TABLE 10.9: Clinical spectrum of pneumococcal infections

Direct spread:

• URTI: Otitis media, sinusitis, pharyngitis, croup

• LRTI: Pneumonia, pleural effusion

Hematogenous spread:

• CNS: Meningitis, epidural abscess, brain abscess

• Bones and joints: Arthritis, osteomyelitis

• Cardiac: Pericarditis, myocarditis

• GIT: Peritonitis

Immunological mechanisms

• Hemolytic-uremic syndrome

• Disseminated Intravascular Coagulation (DIC)

Treatment: Penicillin is the drug of choice in susceptible cases, while resistant or allergic cases must be treated with cefotaxime or ceftriaxone with/without vancomycin. Rifampicin (PO 20 mg/kg BD) may be added in severe, non-responsive cases.

Prevention of pneumococcal disease involves universal immunization of all children with polyvalent conjugated vaccine (PCV). NIS recommended three doses of PCV₁₀ in all infants at the age of 6 weeks, 14 weeks and 9 months. IAP recommends three primary doses of PCV₁₀/₁₃ at 6,10 and 14 weeks followed by a booster dose at 12-15 months of age (See Ch 9.2.1).

Additionally, all high-risk cases with (a) splenic dysfunction, e.g. asplenia, splenectomy or sickle cell disease, (b) nephrotic syndrome, (c) CSF leaks, (d) HIV / AIDS, and (e) chronic cardiopulmonary disease, etc. should also receive 23-valent polysaccharide vaccines (PPSV) after two years of age or before surgery (splenec­tomy, cochlear implant), etc. PPSV is not adequately immunogenic below 2 years of age and need to be repeated after 3-5 years.

Penicillin prophylaxis with 3-weekly IM benzathine penicillin or daily PO penicillin is also recommended in splenectomized children against pneumococcal infections, for at least 2 years after surgery.

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