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BMC Infect Dis. 2019 Jan 8;19(1):29. doi: 10.1186/s12879-018-3598-3.

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.

Author information

1
Department of Infectious Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161, Rome, Italy. alessandro.miglietta@uslcentro.toscana.it.
2
Regional Health Agency of Tuscany, Epidemiologic Observatory, Via Pietro Dazzi, 1, Flroence, Italy. alessandro.miglietta@uslcentro.toscana.it.
3
Units of Epidemiology and Preventive Medicine, Central Tuscany Health Authority, Via di San Salvi , 12 - Palazzina 16 -, 50135, Florence, Italy. alessandro.miglietta@uslcentro.toscana.it.
4
Regional Health Agency of Tuscany, Epidemiologic Observatory, Via Pietro Dazzi, 1, Flroence, Italy.
5
Department of Infectious Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161, Rome, Italy.
6
Clinical Microbiology and Virology Unit, Careggi University Hospital, Largo Brambilla, 3, 50134, Florence, Italy.
7
Laboratory of Immunology and Infectious Diseases, Anna Meyer Children's University Hospital, University of Florence, Viale Gaetano Pieraccini, 24, 50139, Florence, Italy.
8
Department of Experimental and Clinical Medicine, University of Florence, Largo Brambilla, 3, 50134, Florence, Italy.
9
Living Environment, Food and Veterinary Prevention and Safety Office, Tuscany Region, Via Taddeo Alderotti, 26/N, 50139, Florence, Italy.

Abstract

BACKGROUND:

During 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.

METHODS:

A 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.

RESULTS:

A 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).

CONCLUSIONS:

A 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.

KEYWORDS:

Carrier state; Cross-sectional studies; Disease outbreaks; Neisseria meninigitidis

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