Molecular characterisation and antibiotic susceptibility of meningococcal isolates from healthy men who have sex with men.

Objectives: To evaluate and characterise meningococcal carriage among healthy men who have sex with men (MSM) within a screening programme for Neisseria gonorrhoeae infection at the San Gallicano Dermatological Institute, Italy.
Methods: A total of 441 MSM attending the STI/HIV Centre of the San Gallicano Institute, Rome, Italy, in 2016 were routinely screened for N. gonorrhoeae infection by pharyngeal and rectal swabs. N. meningitidis isolates were evaluated for antibiotic susceptibility and characterised by whole genome sequencing. Genetic relationships among the meningococcal carriage isolates were determined using core genome multilocus sequence typing analysis. The soluble domain of AniA (sAniA) protein expression by western blotting was also evaluated.
Results: A total of 62 (14.1%, 95% CI 11.1 to 17.6) carriage meningococci were found among 441 MSM. Forty-three viable N. meningitidis isolates were cultivated (42 from pharyngeal and 1 from rectal swabs). All the viable isolates were susceptible to cefotaxime, ceftriaxone, ciprofloxacin and rifampicin. Four isolates were penicillin G-resistant and 73% of those penicillin G-susceptible showed a minimum inhibitory concentration from 0.064 μg/mL to 0.25 μg/mL. Serogroup B was the most frequent (44.2%), followed by Z (16.3%), E (9.3%), and Y and W (2.3%), respectively. Multilocus sequence typing analysis identified 29 sequence types belonging to 12 clonal complexes. The sAniA protein was expressed in 8 out of 28 (29%) screened meningococcal carriage isolates.
Conclusions: Serogroup B meningococcal carriage identified from oral and anal specimens among healthy MSM was the most frequent serogroup identified in this study. Molecular evaluation revealed a degree of similarity among strains belonging to the same clonal complex.
Competing Interests: Competing interests: None declared.
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