Young-adult carriers of Neisseria meningitidis in Puglia (Italy): will the pattern of circulating meningococci change following the introduction of meningococcal serogroup C conjugate vaccines?

Studies of meningococcal carriage are essential in improving knowledge of the epidemiology of meningococcal disease. The aim of this study is to ascertain the carrier rate and the serogroups of Neisseria Meningitidis circulating in a sample of students from the University of Bari. The population consisted of university students from the University of Bari - School of Medicine, who were invited to take a nasopharyngeal swab. The swabs were plated on selective plate medium; cultural and MLST tests were performed. Of 583 university students 12 carriers were identified (2%). 9 isolates proved auto-agglutinable. The other strains belonged to serogroups B, W135 and Y. Auto-agglutinable strains belonged to different clonal complexes, of which ST-53 was the most common. Only one strain, that belonged to ST-23/cluster A3 clonal complex, could cause meningococcal disease. No type C serogroup strain was detected and this could be directly related to immunization policies that provided meningococcal serogroup C conjugate vaccines for newborns and adolescents. The changing pattern of circulating serogroups of Neisseria meningitidis in healthy carriers could support a new immunization strategy which could provide quadrivalent meningococcal conjugate vaccines to pre-adolescents and adults.