Increase of Neisseria meningitidis W:cc11 invasive disease in Chile has no correlation with carriage in adolescents

Abstract

Neisseria meningitidis is a human exclusive pathogen that can lead to invasive meningococcal disease or may be carried in the upper respiratory tract without symptoms. The relationship between carriage and disease remains poorly understood but it is widely accepted that decreasing carriage by immunization should lead to a reduction of invasive cases. Latin America has experienced an increased incidence of serogroup W invasive cases of Neisseria meningitidis in the last decade. Specifically in Chile, despite low total incidence of invasive cases, serogroup W has become predominant since 2011 and has been associated with elevated mortality. Expecting to gain insight into the epidemiology of this disease, this study has used molecular typing schemes to compare Neisseria meningitidis isolates causing invasive disease with those isolates collected from adolescent carriers during the same period in Chile. A lower carriage of the serogroup W clonal complex ST-11/ET37 than expected was found; whereas, the same clonal complex accounted for 66% of total invasive meningococcal disease cases in the country that year. A high diversity of PorA variable regions and fHbp peptides was also ascertained in the carrier isolates compared to the invasive ones. According to the results shown here, the elevated number of serogroup W invasive cases in our country cannot be explained by a rise of carriage of pathogenic isolates. Overall, this study supports the idea that some strains, as W:cc11 found in Chile, possess an enhanced virulence to invade the host. Notwithstanding hypervirulence, this strain has not caused an epidemic in Chile. Finally, as genetic transfer occurs often, close surveillance of Neisseria meningitidis strains causing disease, and particularly hypervirulent W:cc11, should be kept as a priority in our country, in order to prepare the best response to face genetic changes that could lead to enhanced fitness of this pathogen.

Carriage of Neisseria Meningitidis in Low and Middle Income Countries of the Americas and Asia: A Review of the Literature

“…No statistically significant differences were seen between carriers and noncarriers in univariate analysis. Unlike the findings by Rubilar and colleagues [40], none of the MenW carriage isolates were attributed to cc11 [41].…”

“…Interestingly, studies from Chile found a high rate of MenW cc11 among disease isolates, with only a very small percentage, if any, of carriage isolates attributed to cc11 [40,41]. The authors hypothesized that the low carriage of MenW cc11 in Chile could be attributed to enhanced virulence of this strain, allowing most infections to result in disease rather than carriage.…”

“…1). Of these, 14 met the inclusion criteria and were included in the review, including seven studies from Brazil [33][34][35][36][37][38][39], three from Chile [40][41][42], and one each from Colombia [43], Cuba [32], Mexico [44], and Paraguay [45] (Fig. 2; Table 2).…”

“…Three studies from Chile assessed carriage. The most recently published was a study by Rubilar and colleagues on the correlation of IMD serogroups with meningococcal carriage serogroups in children and adolescents aged 9-19 years [40]. The study included 184 carriage samples from children and adolescents and 119 invasive samples from all ages obtained from the national reference laboratory.…”

Atypical presentation of invasive meningococcal disease caused by serogroup W meningococci

“…Three cases were described in Chile (2013) in which MenW IMD presented as a primary respiratory tract infection; rapid clinical deterioration with an intense systemic inflammatory response soon followed [32]. All of Chile's MenW IMD cases in 2013 were caused by ST-11 [33]. At early stages, meningococcal disease usually presents as cold-like symptoms, including sore throat, cough, coryza and otalgia [2].…”