Your Family Physician

Introduction

Background

Streptococcus pneumoniae colonizes the upper respiratory tract of healthy individuals and is one of the most frequent causes of bacterial infection in children. Common infections caused by this pathogen include otitis media (OM), sinusitis, occult bacteremia, pneumonia, and meningitis. Pneumococci may also cause osteomyelitis, septic arthritis, pericarditis, and peritonitis.

Pathophysiology

Pneumococci are encapsulated, lancet-shaped, gram-positive diplococci. The bacteria are transmitted person to person via respiratory droplet contact. Pneumococci can cause disease either by direct spread from colonized mucosal surfaces (eg, otitis media) or by hematogenous spread (eg, meningitis following bacteremia). Mucosal irritation resulting from factors such as viral infection or smoke often is a predisposing factor for pneumococcal infection. Ninety serotypes have been identified, with varying degrees of pathogenicity. Serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F cause most invasive disease, and pneumococci with these serotypes are often resistant to penicillin.

Frequency

United States

Invasive disease is most frequent in children younger than 2 years and in adults older than 65 years. Overall annual incidence of invasive disease in the United States is 15 cases per 100,000 individuals but widely varies by age, from 166 cases per 100,000 children younger than 2 years to 5 cases per 100,000 young adults. After the introduction of heptavalent conjugated pneumococcal vaccine, the rate of invasive pneumococcal disease (IPD) has trended down. In an active laboratory surveillance from 1997-2004, the IPD decreased by 40% from 11.8 cases to 7.2 cases per 100,000 live births. Among black infants, a marked decrease was noted in incidence of IPD from 17.1 cases to 5.3 cases per 100,000 live births compared with white infants with a decrease from 9.6 cases to 6.8 cases per 100,000 live births.

From 1999-2007, a 92% reduction in vaccine serotypes has been observed among both invasive and noninvasive isolates; during the same period, a 200% increase has been observed in vaccine-related or nonvaccine serotypes. Among these, serotypes 19A, 6C, 15, and 22F were predominantly noted.²⁸ The amoxicillin susceptibility was about 70% compared with 50% in macrolides. Serotype 6C is considered to be emerging as well.²⁹

An increased frequency of disease and increased morbidity and mortality rates are seen in children younger than 2 years and in children with humoral immunodeficiency (eg, HIV infection, agammaglobulinemia, complement deficiency), absent or deficient splenic function (eg, splenectomy, sickle cell anemia), nephrotic syndrome, chronic renal failure, organ transplantation, immunosuppressive therapy, chronic pulmonary disease, cerebral spinal fluid (CSF) leak after skull fracture, cochlear implant, diabetes mellitus, and malignancy. Parental smoking invariably increases acute otitis media by about 64% compared to no history of parental smoking (56%).

Specific Infections

Otitis media

Approximately 30% of children have at least one episode of pneumococcal otitis media by age 3 years. Pneumococci cause approximately 40% of otitis media cases. After the pneumococcal vaccination, nonvaccine serotype is encountered more frequently as a cause of otitis compared with vaccine serotypes.

Bacteremia

Pneumococci are responsible for as many as 85% of occult cases of bacteremia in children. Bacteremia is seen in 3-5% of children aged 3-36 months with fever higher than 102.5°F without another source. In the postvaccine licensure period, the annual episodes of pneumococcal bacteremia decreased from 7.2 episodes to 2.3 episodes per 100,000 emergency department visits in 1999. However, it increased to 2.8 episodes in 2004 and to 3.64 episodes per 100,000 emergency department visits in 2005. The rate of invasive disease due to serotype 19F in the conjugate vaccine has increased.

Pneumonia

S pneumoniae is the most common bacterial cause of childhood pneumonia, especially in children younger than 5 years.

Meningitis/CNS infections

S pneumoniae is the most common cause of bacterial meningitis in children. Yearly incidence in all age groups is 1-2 cases per 100,000 population.

Osteomyelitis/septic arthritis

Pneumococci are responsible for fewer than 10% of all cases of osteomyelitis and septic arthritis.

Other unusual infections caused by pneumococci are sporadic.

Vaccination

The recent inclusion of the pneumococcal conjugate vaccine in the routine pediatric immunization schedule has markedly decreased the incidence of invasive pneumococcal disease. The vaccine is about 50-60% efficacious in reducing otitis media caused by the vaccine strains of S pneumoniae compared with 80-100% in preventing invasive disease. In children younger than 5 years, IPD has decreased from 98.7 cases per 100,000 population in 1998-99 to 23.4 cases per 100,000 population in 2005, with 77% reduction.^1,2 An increase in serotype 19A from 2.6 cases in 98-99 to 9.3 cases in 2005 has been reported in this age group.

International

Pneumococcal pneumonia is estimated to cause 1.2 million deaths per year worldwide in children younger than 5 years.

Mortality/Morbidity

Death resulting from complications of pneumococcal otitis, sinusitis, bacteremia, and pneumonia is rare in otherwise healthy children. As a complication of pneumonia, pneumococcal empyema is not infrequent, even in developed countries, and it remains a significant problem in developing nations.

The case-fatality rate for pneumococcal meningitis is 5-10%. Between 25-35% of children with pneumococcal meningitis develop permanent neurologic sequelae (eg, hearing deficits, paralysis, hydrocephalus). The risk of fulminant pneumococcal infection and death in the high-risk patient population outlined above (eg, children with humoral immunodeficiency, functional asplenia, nephrotic syndrome) is much higher than the risk in otherwise healthy children.

Race

An increased incidence of invasive pneumococcal disease has been documented in blacks, American Indians (white Mountain Apache, Navajo), and Alaskan Eskimos.

Sex

Pneumococcal disease is slightly more frequent in males than in females, with a male-to-female ratio of 3:2 for pneumococcal bacteremia.

Age

Pneumococcal infections are most common in children aged 1-24 months.

• Otitis media and bacteremia are most common in children aged 6 months to 2 years.
• Sinusitis is most common in children 2 years and older.
• Pneumonia and meningitis are most common in children younger than 5 years.

Clinical

History

Children with pneumococcal infections usually have a temperature higher than 102°F. Children with invasive infections also demonstrate signs and symptoms related to the site of infection. Symptoms of specific infections in addition to fever are as follows:

• Otitis media
  • Otalgia (irritability and ear pulling in younger children)
  • Upper respiratory symptoms
  • Vomiting
• Sinusitis
  • Headache
  • Facial tenderness (much less frequent than in adults)
  • Symptoms of upper respiratory infection (cough, nasal drainage, congestion) lasting for 10 days or longer
• Occult bacteremia - Fever without a localizing source in children aged 2-24 months
• Pneumonia
  • Cough
  • Chest pain, shortness of breath, or respiratory difficulty
  • Malaise and poor appetite
• Meningitis
  • Stiff neck
  • Vomiting
  • Headache (older children)
  • High fever (temperature >103°F)
  • Lethargy
  • Irritability
  • Poor feeding
  • Unconsolable crying

Physical

• Otitis media - Bulging, erythematous, or yellow tympanic membrane with poor mobility and purulent fluid seen behind the tympanic membrane
• Sinusitis
  • Tenderness to palpation over maxillary or frontal sinuses
  • Nasal discharge of any color
  • Swollen nasal turbinates
• Bacteremia - No physical findings except fever (temperature of 102°F or higher) and tachycardia associated with the fever
• Pneumonia
  • Crackles or decreased breath sounds in the area of lobar consolidation on chest auscultation, with egophony in patients with severe consolidation and dullness to percussion
  • Retractions, tachypnea, or both
• Meningitis/CNS infections
  • Ill appearance
  • Nuchal rigidity (may not be present in infants <4>
  • Altered mental status, poorly responsive (patient may present in comatose state)
  • Other neurologic abnormalities possible, such as cranial nerve deficits, ataxia, and weakness
  • Poor perfusion and signs of shock in patients with concurrent pneumococcal sepsis

Source : http://emedicine.medscape.com/article/967694-overview