Carriage rates and risk factors during an outbreak of invasive meningococcal disease due to Neisseria meningitidis serogroup C ST-11 (cc11) in Tuscany, Italy: a cross-sectional study

Abstract

BackgroundDuring 2015–2016 an outbreak of invasive meningococcal disease due to N. meningitidis serogroup C ST-11 (cc11) occurred in Tuscany, Italy. The outbreak affected mainly the age group 20–30 years, men who have sex with men, and the area located between the cities of Firenze, Prato and Empoli, with discos and gay-venues associated-clusters. A cross-sectional-survey was conducted to assess the prevalence and risk factors for meningococcal-carriage, in order to address public health interventions.MethodsA convenience sample of people aged 11–45 years provided oropharyngeal swab specimens and completed questionnaires on risk factors for meningococcal carriage during a 3 months study-period, conducted either in the outbreak-area and in a control-area not affected by the outbreak (cities of Grosseto and Siena). Isolates were tested by culture plus polymerase chain reaction. Serogroup C meningococcal isolates were further characterized using multilocus sequence typing. Univariate and multivariate analyses were performed to estimate adjusted odds ratios (AORs) for meningococcal carriage.ResultsA total of 2285 oropharyngeal samples were collected. Overall, meningococcal carriage prevalence was 4.8% (n = 110), with nonencapsulated meningococci most prevalent (2.3%; n = 52). Among encapsulated meningococci, serogroup B was the most prevalent (1.8%; n = 41), followed by serogroup Y (0.5%; n = 11) and serogroup C (0.2%; n = 4); one carrier of serogroup E and one of serogroup Z, were also found (0.04%). Three individuals from the city of Empoli were found to carry the outbreak strain, C:ST-11 (cc11); this city also had the highest serogroup C carriage prevalence (0.5%). At the multivariate analyses, risk factors for meningococcal carriage were: illicit-drugs consumption (AOR 6.30; p < 0.01), active smoking (AOR 2.78; p = 0.01), disco/clubs/parties attendance (AOR 2.06; p = 0.04), being aged 20–30 years (AOR 3.08; p < 0.01), and have had same-sex intercourses (AOR 6.69; p < 0.01).ConclusionsA low prevalence of meningococcal serogroup C carriage in an area affected by an outbreak due to the hypervirulent N. meningitidis serogroup C ST-11 (cc11) strain was found. The city of Empoli had the highest attack-rate during the outbreak and also the highest meningococcal serogroup C carriage-prevalence due to the outbreak-strain. Multivariate analyses underlined a convergence of risk factors, which partially confirmed those observed among meningococcal outbreak-cases, and that should be considered in targeted immunization campaigns.Electronic supplementary materialThe online version of this article (10.1186/s12879-018-3598-3) contains supplementary material, which is available to authorized users.

Pharyngeal carriage rates of Neisseria meningitidis in health care professionals at a tertiary university pediatric hospital

“…Interestingly, we did not observe any non-groupable meningococci, although non-encapsulated N. meningitidis are frequently found among carriers according to the literature [ 26 , 40 – 42 ].…”

“…A cross-sectional study in Tuscany, Italy, found a carriage prevalence of 4.8% in individuals aged 11-45 years presenting at immunization clinics. Among the age group 31-45 years, the carriage prevalence was 2.4% (20/ 828), while it was 9% (37/434) in the age group 20-30 years [26]. A study conducted in 2014 in Hajj pilgrims with a mean age of 50 years found 1.3% meningococcal carriers in individuals originating from low endemic countries, while 8.9% of pilgrims from high endemic regions (sub-Saharan meningitis belt) were tested positive for N. meningitidis [27].…”

Genomic analysis of Neisseria meningitidis carriage isolates during an outbreak of serogroup C clonal complex 11, Tuscany, Italy

“…As already published [19], 110 carriage samples resulted positives for N . meningitidis and 85 of them were cultivated in vitro.…”

“…Ethical approval was obtained by the Regional Ethic Committee of Tuscany (registration no. 965) [19]. A written informed consent was signed by all the participants and by the parents/legal guardians of subjects aged less than 18 years.…”

“…Between 2015–2016, Tuscany Region reported an unexpected increase of IMD cases due to the meningococcal C:P1.5–1,10–8:F3-6:ST-11 (cc11) strain [15–17]. As already described [18], several initiatives and studies were implemented in the Region, of which: 1) a reactive vaccination campaign with a single dose of the tetravalent ACYW conjugate vaccine or monovalent MCC vaccine, targeting the population aged between 11 and 45 years and, from December 2016, discos and lesbian, gay, bisexual, and transgender (LGBT) associations; 2) a cross-sectional carriage survey with the aim to characterize meningococcal carriage prevalence and related risk factors in the outbreak context [19].…”