Prevalence of de-O-acetylated serogroup C meningococci before the introduction of meningococcal serogroup C conjugate vaccines in the United Kingdom

Meningococcal serogroup C conjugate (MCC) vaccines have been introduced in the UK to combat the rise in serogroup C meningococcal disease. Serogroup C meningococci may occur naturally expressing either O-acetylated (Oac(+)) o r de-O-acetylated (Oac(-)) polysaccharide capsules. In a small study in the USA in the 1970s 15% of serogroup C meningococcal case isolates were repor ted to be Oac(-) though the prevalence of these Oac(-) isolates has nor bee n recorded in the UK. This is of interest as the first MCC vaccines to be i ntroduced are Oac(+) and the potential impact of this on Oac(-) serogroup C isolates is unclear. Serogroup C isolates submitted to the Public Health L aboratory Service Meningococcal Reference Unit in January 1998 (n = 113) an d January 1999 (n = 162) were investigated by dot blotting using monoclonal s specific for Oac(+) and Oac(-) serogroup C polysaccharides. This revealed 12% Oac(-) isolates for both January 1998 and January 1999. The proportion of fatal cases was found to similar for both Oac- and Oac(+), 14 and 9% fo r 1998 and 5 and 3% for 1999, indicating that the pathogenic potential of t hese Oac(-) isolates is similar to Oac(+). The acetylation status of serogr oup C isolates needs to be monitored throughout and after the introduction of MCC vaccines. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.