During reinforced surveillance of acute bacterial meningitis in Burkina Faso, meningococcal strains of phenotype NG:NT:NST were isolated from cerebrospinal fluid samples from 3 patients. The strains were negative for the ctrA gene but were positive for the crgA gene. Molecular typing revealed that the strains harbored the capsule null locus (cnl) and belonged to the multilocus sequence type (ST)-192. PorA sequencing showed that all strains were either P1.18-11,42; P1.18,42-1; P1.18-11,42-1; P1.18-11,42-3; or P1.18-12,42-1. Sequencing also showed that all strains were negative for the FetA receptor gene. Serum killing assays showed these strains to be resistant, with the resistance comparable with that of a fully capsular serogroup B strain, MC58. The same strains were found in 14 healthy carriers in the general population of Bobo-Dioulasso (100% of ST-192 isolates tested for cnl). The presence of cnl meningococci that can escape serum killing and cause invasive disease is of concern for future vaccination strategies and should promote rigorous surveillance of cnl meningococcal disease.
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Potential conflicts of interest: R.B. has received financial support for attending meetings from, served as consultant for, and performed contract research for Alexion Pharmaceuticals, Baxter Bioscience, Chiron Vaccines, Fujisawa, GlaxoSmithKline, Microscience, Sanofi Pasteur, Wyeth Vaccines, and Xenova Research. H.F. has received financial support for attending meetings from and performed contract research for Alexion Pharmaceuticals, Chiron Vaccines, Sanofi Pasteur, and Wyeth Vaccines. S.J.G. has received financial support for attending meetings from vaccine manufacturers. U.V. has received honoraria for oral presentations from Baxter, Chiron Vaccines, and Becton Dickinson and has presented at a meeting sponsored by Sanofi-Pasteur; Pfizer has provided financial support for workshops organized by himself. None of these financial contributions influenced the work presented here. J.E.M., B.-M.N.-L., and B.D.G. work for the Agence de Médecine Préventive, which receives substantial financial support from Sanofi Pasteur, a manufacturer of meningococcal vaccines. S.Y., Y.T., L.S., P.N., A.C., and H.C. declare no potential conflicts of interest.
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