Show Summary Details
Page of

Pneumococcal infections 

Pneumococcal infections

Chapter:
Pneumococcal infections
Author(s):

Anthony Scott

DOI:
10.1093/med/9780199204854.003.070603_update_001

May 30, 2013: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

Update:

Serotypes and genome sequencing.

Epidemiology in West Africa.

Vaccination programmes in Africa.

Pneumococcal meningitis—investigations and short-cource therapy.

Updated on 31 May 2012. The previous version of this content can be found here.
Page of

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy).

date: 28 March 2017

Streptococcus pneumoniae is an encapsulated Gram-positive bacterium that lives almost exclusively in the human nasopharynx. Each pneumococcus expresses one of more than 90 immunologically distinguishable capsular polysaccharides that are the principal target of systemic human immunity and define its serotype.

Epidemiology

Pneumococci are transmitted through contact with infected nasal secretions or by airborne dissemination, and most preschool children carry them in their nasopharynx. The risk of acquisition is increased by contact with other children, crowded environments, and cold weather. The incidence of pneumococcal disease is highest in young children and elderly people, and also increased in males, certain indigenous populations, smokers, alcoholics, and patients with chronic medical illnesses or immune susceptibility, including HIV infection, sickle cell disease, and splenectomy.

Clinical features

Pneumonia—pneumococci are the commonest cause of severe community-acquired pneumonia at all ages in the developed and developing world. Typical presentation of pneumococcal lobar pneumonia is with abrupt onset of fever, followed by cough, difficulty breathing, pleuritic chest pain, haemoptysis, and purulent sputum. Physical signs include high pyrexia, raised respiratory rate, cyanosis, and chest features of lobar consolidation, namely reduced chest movement, dullness on percussion, fine crepitations, and bronchial breathing over the affected area. The chest radiograph shows a lobar opacity, often with a pleural effusion.

Other diseases—pneumococci cause significant morbidity in adults and children through meningitis and septicaemia, and they can also cause bronchopneumonia and multiple disease syndromes simultaneously (e.g. meningitis and pneumonia). In children, the most common pneumococcal disease is otitis media. Other less common presentations include sinusitis, pleural empyema, pericarditis, endocarditis, septic arthritis, osteomyelitis, peritonitis, and conjunctivitis.

Diagnosis

S. pneumoniae is a fastidious organism that grows successfully on blood agar, producing α‎-haemolysis. Blood culture is the principal aetiological tool to diagnose pneumococcal pneumonia, but cultures are positive in only 15 to 30% of cases. The capsular serotype is identified by a positive Quellung reaction with specific rabbit antisera. In addition: (1) pneumococci can be observed on microscopy as Gram-positive diplococci in sputum or, in cases of meningitis, in cerebrospinal fluid, and can be cultured from both specimens; (2) a urinary antigen test for the common pneumococcal constituent C-polysaccharide is sensitive and specific for pneumococcal pneumonia in adults, but not in children; (3) PCR is useful in cerebrospinal fluid, especially when the patient is partially treated and cultures are sterile.

Treatment and prognosis

Most pneumococci are sensitive to β‎-lactam antibiotics, but some are resistant. (1) Pneumonia—when caused by sensitive or intermediately resistant pneumococci, this should be treated with high-dose oral amoxicillin or intravenous cefotaxime, the latter being effective against pneumococci with cephalosporin MICs up to 1 to 2 µg/ml. Macrolides and newer fluoroquinolones may be used to treat infections that are fully resistant to β‎-lactam antibiotics. (2) Meningitis—when caused by susceptible pneumococci, ceftriaxone is effective; vancomycin should be added as empirical meningitis therapy in areas with penicillin-resistant pneumococci; dexamethasone is an effective adjunctive treatment for pneumococcal meningitis where HIV prevalence is low.

The case fatality of pneumococcal pneumonia is 5%, but in bacteraemic pneumonia and pneumococcal meningitis it is 30%.

Prevention

A single dose of 23-valent capsular polysaccharide vaccine prevents invasive pneumococcal disease in elderly or high-risk populations. In infants and young children, 10- or 13-valent pneumococcal conjugate vaccine is highly effective in preventing invasive pneumococcal disease as well as pneumococcal pneumonia, meningitis and otitis media. It is given routinely as two or three doses in infancy, with a booster dose at 12 to 15 months of age. Immunization of children reduces pneumococcal transmission and prevents pneumococcal disease in older family members.

Access to the complete content on Oxford Medicine Online requires a subscription or purchase. Public users are able to search the site and view the abstracts for each book and chapter without a subscription.

Please subscribe or login to access full text content.

If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

For questions on access or troubleshooting, please check our FAQs, and if you can''t find the answer there, please contact us.