Low prevalence of Corynebacterium diphteriae carriers in Italian schoolchildren

This study was carried aut with the aim to investigate the presence of carriers of diphtheria bacillus in a sample of 1970 healthy children, 6-14 years aged, residing in eight Italian towns. Three non-toxigenic strains ofCorynebacterium diphtheriae biotype mitis were isolatedfrom as manv healthv chi/dreno Molecular characterization by ribotyping showed close genetic relation of two of the wild strains witli the C7(h) reference stra in whereas one of the wild strains showed dose genetic relation witli two collection strains isolated in file same geographic area (Emilia¬Romagna) from diphtheria patients in the seventy years. This supports the hypothesis of the persistence of some non toxigenic C.diphtheriae strains derived from ancient endemie strains under the selective pressure of mass immunizationg against diphtheria. The persistence of carriers of diphtheria bacilli. althougli non toxigenic, suggests that high levels of immunity must be maintained, not onlv in chi/dreno but a/so in adults by booster vaccination.