Non-susceptibility trends and serotype distributions among Streptococcus pneumoniae from community-acquired respiratory tract infections and from bacteraemias in the UK and Ireland, 1999 to 2007

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Abstract
Pneumococcal disease is prevalent and is a cause of significant morbidity and mortality in the UK and Ireland. We describe the antimicrobial susceptibility and serotype distributions of Streptococcus pneumoniae causing bacteraemia and community-acquired pneumonia in these countries from 1999/2000 to 2006/7, predominantly prior to the introduction of the heptavalent pneumococcal conjugate vaccine (PCV7) into the standard vaccination schedule in September 2006. The BSAC Respiratory and Bacteraemia Resistance Surveillance Programmes collected S. pneumoniae from sentinel laboratories distributed across the UK and Ireland. A central laboratory for each programme re-identified the isolates, determined their serotypes and measured MICs by the BSAC agar dilution method. The prevalence of antimicrobial non-susceptibility, although significant, was generally below the global average. There was no convincing evidence of increasing non-susceptibility over time in either study. The results showed clear differences in the serotype distribution between respiratory and blood isolates, but suggested that PCV7 would provide adequate coverage of invasive isolates in the UK and Ireland. A significant and rapid increase of the non-vaccine serotype 1 among blood isolates from 2001 to 2006 was worrying, given the spread of hypervirulent serotype 1 clones elsewhere in the world. Continued surveillance of both antimicrobial non-susceptibility and serotype distribution changes following the introduction of PCV7 into the routine immunization schedule in the UK and Ireland is imperative. The data presented here, largely obtained prior to the introduction of PCV7 in the UK, provide a valuable baseline against which to monitor changes in antimicrobial non-susceptibility and serotype distribution and hence to identify the expansion of any significant clones.

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