S. pneumoniae is commonest cause of paediatric CAP

By Joanna Lyford, Senior medwireNews Reporter

Streptococcus pneumoniae is the predominant cause of community-acquired pneumonia (CAP) among children in Belgium, with non-vaccine serotypes accounting for the majority of cases, a Belgian study shows.

Importantly, serotypes included in the 7-valent pneumococcal conjugate vaccine (PCV7) – now given to all infants in Belgium – were uncommon causes of paediatric CAP.

This observation “supports the use of higher-valent pneumococcal vaccines to reduce the remaining burden of childhood CAP and address the increasing incidence of complicated CAP”, write Iris De Schutter (Universitair Ziekenhuis Brussel, Belgium) and colleagues in PLoS ONE.

The team prospectively identified all children aged under 15 years who were admitted with radiologically confirmed CAP to 19 Belgian hospitals between September 2008 and December 2009.

Of the 561 children included in the study, 57.8% were boys, the median age was 3.6 years, and 57.9% had received pneumococcal vaccination, usually with the PCV7.

The aetiology of CAP was determined using conventional methods (blood culture, culture of pleural fluid, polymerase chain reaction in pleural fluid) and newer methods (serotype-specific serology [SSS], real-time polymerase chain reaction [rtPCR] in blood).

Combining the results of all patients with proven or suspected pneumococcal CAP indicated that the aetiology was pneumococcal in 61.7% of cases.

Pneumococcal aetiology was significantly associated with age over 5 years, pleural effusion, higher levels of C-reactive protein, higher percentage of neutrophils in the peripheral blood, admission to an intensive care unit, chest tube drainage and mechanical ventilation, the authors report.

Serotype 1 infection was most common, accounting for 42.3% of cases, followed by serotypes 5, 7F(7A), 19A and 3. The serotypes included in the PCV7 vaccine were detected in 11 patients, three of whom were otherwise healthy and completed vaccinated with PCV7.

“[T]hese three episodes are probably attributable to a natural decline in specific antibody concentration beneath the protective antibody threshold for CAP”, the researchers suggest.

They conclude: “[O]ur study confirmed that S. pneumoniae remains the leading bacterial pathogen in children hospitalised with CAP since the introduction of PCV7 and Haemophilius influenza type b universal infant vaccinations.

”Adding SSS and rtPCR in blood to conventional methods increased the detection of pneumococcal aetiology, especially for non-invasive CAP.”

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