Evaluation of molecular typing methods for identification of outbreak-associated Neisseria meningitidis isolates.

It is essential in an outbreak investigation that strain characterization of Neisseria meningitidis is performed in a rapid and accurate manner. This study evaluated two new molecular typing methods, multiple-locus variable number tandem repeat analysis (MLVA) and repetitive sequence-based PCR (rep-PCR) (DiversiLab; bioMérieux) and compared them with current recommended methodologies. This retrospective study included 36 invasive N. meningitidis serogroup C isolates collected in Sweden 2001 through 2009 and previously subjected to outbreak investigation. All strains were typed with highly variable-MLVA (HV-MLVA) and rep-PCR. The isolates were further characterized by multilocus sequence typing (MLST) and sequencing of the fetA, fHbp, penA, porA and porB genes. The results showed that HV-MLVA had the highest index of diversity (0.99) and rep-PCR had the highest congruence (40%) with the currently recommended typing methods. The HV-MLVA correlated best to the spatiotemporal connections and had the overall highest Adjusted Wallace coefficients, suggesting that HV-MLVA can predict the results of the other typing methods in the study. We therefore suggest that after initial confirmation of species, serogroup and genosubtype, HV-MLVA should be used as the most discriminatory method for first hand investigation of N. meningitidis serogroup C isolates.