Molecular characterization of a collection of Neisseria meningitidis isolates from Croatia, June 2009 to January 2014.

In the last decade, the incidence of invasive meningococcal disease (IMD) in Croatia remained stable at approximately 1 case per 100 000 inhabitants, affecting mainly children aged ≤5 years. We report the molecular characterization of meningococci causing IMD occurring from June 2009 to January 2014 in Croatia. Genomic DNA from 50 clinical isolates was analysed for serogroup, multilocus sequence typing and allele type of the two outer membrane protein genes, porA and the iron-regulated fetA. Furthermore, 22 of them were characterized by using whole-genome sequencing to define the meningococcal vaccine four-component meningococcal serogroup B (4CMenB) antigen genes factor H-binding protein (fHbp), Neisseria heparin-binding antigen (nhba) and Neisseria adhesin A (nadA) and the antimicrobial target resistance genes for penicillin (penicillin binding protein 2, penA), ciprofloxacin (DNA gyrase subunit A, gyrA) and rifampicin (β-subunit of RNA polymerase, rpoB). The Etest was used to phenotypically determine the antimicrobial susceptibility of isolated meningococci. The main serogroup/clonal complex combinations were MenB cc41/44, MenC/cc11, MenW/cc174 and MenY/cc23. PorA P1.7-2, FetA F5-5 and F1-5 were the most represented through the serogroups. Meningococci with decreased susceptibility to penicillin (38.9 %) and one strain resistant to ciprofloxacin were identified. Forty-two percent of MenB showed the presence of at least one of the 4CMenB vaccine antigens (fHbp, NHBA, NadA and PorA). Our findings highlight the genetic variability of meningococci causing IMD in Croatia, especially for the serogroup B. Molecular-based characterization of meningococci is crucial to enhance IMD surveillance and to better plan national immunization programmes.