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Serotype 1 pneumococcus and empyema

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Empyema has increased in incidence among children in the UK over the last 10 years but the reasons are unknown. In the USA the most common pathogen in childhood empyema is Streptococcus pneumoniae serotype 1 and in Sweden the emergence of a new clone of this serotype was associated with a quadruple increase in invasive pneumococcal disease. Experience in Newcastle upon Tyne (OpenUrlAbstract/FREE Full Text) has confirmed the importance of serotype 1.

Between February 1997 and August 2001 a total of 47 children were referred from district hospitals to the regional centre with empyema or parapneumonic effusion. There was a steady increase in numbers from four in 1998 to 15 in the first 8 months of 2001. Boys outnumbered girls by two to one and the mean age was 5.6 years (range 0.6–16.9 years). Thirty-one children had had no significant previous or concurrent illnesses; four had a concurrent infection (varicella zoster 3, campylobacter 1), eight had had previous respiratory problems (bronchiolitis 3, recurrent respiratory infection 3, asthma 2), two had haematological malignancy, and two had severe neurological disability. The median length of illness before hospital admission was 5 days and median stay in the district hospital 3 days. Almost all children (45) were treated with antibiotics before transfer. Thirty-seven children were infected with S pneumoniae, one also had Staphylococcus aureus, one was infected with Streptococcus pyogenes, and one with Streptococcus viridans. One child had tuberculosis. Bacterial culture of pleural fluid at the regional centre produced no organism in 44 cases, S pyogenes in one, S aureus in one, and Staphylococcus epidermidis (considered contaminant) in one. One child who was receiving chemotherapy for leukaemia had cytomegalovirus in her pleural fluid. PCR assay for pneumococcal DNA in pleural fluid was positive in 32 of 43 cases tested whereas pneumococcal latex antigen testing was positive in only 12 of 47. The 32 DNA-positive samples were submitted to a second PCR test for a conserved sequence of the pbp2b gene associated with penicillin susceptibility and all were positive. Seventeen of the 32 were serotype 1, four serotype 14, and three serotype 3. Eight were not serotyped. Thirty-two children underwent decortication and median postoperative inpatient stay was 4 days. At one month 41 were well, two were treated for haematological malignancy, three had a persistent cough, and one was breathless on exercise.

The number of children referred to this regional paediatric respiratory centre with empyema increased between 1998 and 2001 and this high rate has continued (there were 28 cases in the 2 years, August 2001–July 2003). Penicillin-sensitive pneumococci of serotype 1 appear to be the cause in many cases. The 7-valent conjugate vaccine does not contain serotypes 1 or 5 but a new 9-valent conjugate vaccine does. In a recent study in Soweto, South Africa the 9-valent vaccine given to HIV-negative infants had an efficacy of 83% in the prevention of invasive pneumococcal disease.

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