Dynamics of Meningococcal Long-Term Carriage among University Students and Their Implications for Mass Vaccination

Abstract

In the 1997-98 academic year, we conducted a longitudinal study of meningococcal carriage and acquisition among first-year students at Nottingham University, Nottingham, United Kingdom. We examined the dynamics of long-term meningococcal carriage with detailed characterization of the isolates. Pharyngeal swabs were obtained from 2,453 first-year students at the start of the academic year (October), later on during the autumn term, and again in March. Swabs were immediately cultured on selective media, and meningococci were identified and serologically characterized. Nongroupable strains were genetically grouped using a PCR-based assay. Pulsed-field gel electrophoresis was used to determine the link between sequential isolates. Of the carriers initially identified in October, 44.1% (98 of 222) were still positive later on in the autumn (November or December); 57.1% of these remained persistent carriers at 6 months. Of the index carriers who lost carriage during the autumn, 16% were recolonized at 6 months. Of 344 index noncarriers followed up, 22.1% acquired carriage during the autumn term and another 13.7% acquired carriage by March. Overall, 43.9% (397 of 904) of the isolates were noncapsulated (serologically nongroupable); by PCR-based genogrouping, a quarter of these belonged to the capsular groups B and C. The ratio of capsulated to noncapsulated forms for group B and C strains was 2.9 and 0.95, respectively. Sequential isolates of persistent carriers revealed that individuals may carry the same or entirely different organisms at different times. We identified three strains that clearly switched their capsular expression on and off at different times in vivo. One student developed invasive meningococcal disease after carrying the same organism for over 7 weeks. The study revealed a high rate of turnover of meningococcal carriage among students. Noncapsulated organisms are capable of switching their capsular expression on and off (both ways) in the nasopharynx, and group C strains are more likely to be noncapsulated than group B strains. Carriage of a particular meningococcal strain does not necessarily protect against colonization or invasion by a homologous or heterologous strain.

Kingella kingae Surface Polysaccharides Promote Resistance to Human Serum and Virulence in a Juvenile Rat Model

“…In N. meningitidis, transposon mutagenesis and large-scale analysis of the genome searching for genes contributing to serum resistance identified only genes involved in polysaccharide capsule or lipooligosaccharide synthesis (14). Consistent with the conclusion that the polysaccharide capsule is important for N. meningitidis serum resistance, almost all meningococcal isolates recovered from blood are encapsulated, while 30 to 70% of carrier isolates are nonencapsulated (48)(49)(50). Similarly, in H. influenzae, loss of capsule reduces or eliminates serum resistance, and overexpression of the serotype b capsule synthesis genes due to duplication events promotes greater serum resistance (13,51,52).…”

Prevalence of Neisseria meningitidis carriers in children under five years of age and teenagers in certain populations of Mexico City

“…3,4 In our study, we did not find a single nasopharyngeal carrier in the university population, despite the fact that they are among the age group (15 to 19 years old) with the highest prevalence of colonization; it is also the age in which more cases of fatal invasive disease are reported. 3,4,25 The low prevalence in this group could be explained because only one nasopharyngeal sample was taken and/or because the population studied was immune with specific antibodies to the most prevalent types of N.meningitidis seen in the carrier state. 9,26 We know that N meningitidis is transmitted by direct person-to-person contact via micro drops of pflugge that contain the meningococcus, 17 and that this increases in closed populations in contrast to open populations where transmission is low.…”

Use of Mesoporous Silica SBa-15 and SBa-16 in Association of Outer Membrane Vesicles - OMV from Neisseria meningitidis

“…Recently, Hollanda et al (Hollanda, et al) and Mattos had been described the influence of mesopororus silica in the transformation process in Neisseria meningitides [19]. These nanoparticles are implicated in the protection of foreign DNA responsible for transformation process and involved in the capsular switching process [20], an important virulence mechanism of immunological escape of human vaccinated host [21,22].…”