Department of Infectious Diseases, Istituto Superiore di Sanità, Roma, Italy.
Microbiology and Virology Laboratory, Molinette Hospital, Torino, Italy.
Int J Med Microbiol. 2019 May-Jun;309(3-4):182-188. doi: 10.1016/j.ijmm.2019.03.004. Epub 2019 Mar 6.
Meningococcal disease incidence in Italy remains quite low in the overall population except for infants. Within a study on carriage isolates among high school students we aimed to define: i) the prevalence of carriage isolates, ii) the phenotypic and iii) the molecular features of meningococci by Whole Genome Sequencing (WGS). A total of 1697 pharyngeal samples from undergraduate students (age range 14-19 years) were collected from 2012 to 2013 from six larger cities in Italy. One hundred and twenty culture positive meningococci (7%) were analyzed. Carriage isolates were sent to the National Reference Laboratory for invasive meningococcal disease (IMD) for PCR-based serogroup identification, Multilocus Sequence Typing, PorA and FetA typing. Moreover, factor H binding protein (fHbp), Neisseria Heparin Binding Antigen (NHBA) and Neisserial adhesin A (NadA) were typed. Core genome MLST (cgMLST) was performed on a subsample of 75 carriage isolates. Capsule null locus (cnl) predominated (47%), followed by serogroup B (27%). The antimicrobial susceptibility profile revealed an high prevalence of reduced susceptibility to penicillin G (54%) and a full susceptibility to ceftriaxone, ciprofloxacin and rifampicin. Carriage isolates presented a high genetic diversity: the clonal complexes (cc) cc1136, cc198 and cc41/44, were the predominant. An high heterogeneity was also observed for PorA and FetA types. The fhbp and nhba genes were identified in all the carriage isolates; only 5% of the carriage isolates presented the nadA gene. The core genome MLST analysis revealed that the majority of the cnl isolates clustered in a distinct group. The evidence gathered during this study provides the estimate of carriage isolates in high school students in a non-epidemic period in Italy that was lower than expected. Moreover, the highest proportion of carriage isolates were cnl and, overall, they were molecular heterogeneous.
意大利除婴儿外,整体人群中脑膜炎球菌病的发病率仍然较低。在一项针对高中生带菌者分离株的研究中,我们旨在定义:i)带菌者分离株的流行率,ii)表型和 iii)通过全基因组测序(WGS)的脑膜炎球菌的分子特征。2012 年至 2013 年,从意大利六个较大城市的 1697 名本科生(年龄在 14-19 岁之间)中采集了 1697 份咽拭子样本。对 120 株培养阳性脑膜炎球菌(7%)进行了分析。带菌者分离株被送往国家侵袭性脑膜炎球菌病(IMD)参考实验室,进行基于 PCR 的血清群鉴定、多位点序列分型、PorA 和 FetA 分型。此外,还对因子 H 结合蛋白(fHbp)、奈瑟氏菌肝素结合抗原(NHBA)和奈瑟氏菌粘附素 A(NadA)进行了分型。对 75 个带菌者分离株的亚样本进行了核心基因组 MLST(cgMLST)。胶囊缺失基因座(cnl)占主导地位(47%),其次是血清群 B(27%)。抗菌药物敏感性谱显示,青霉素 G 耐药率(54%)较高,对头孢曲松、环丙沙星和利福平完全敏感。带菌者分离株具有较高的遗传多样性:优势克隆复合体(cc)为 cc1136、cc198 和 cc41/44。PorA 和 FetA 型也存在高度异质性。所有带菌者分离株均携带 fhbp 和 nhba 基因;只有 5%的带菌者分离株携带 nadA 基因。核心基因组 MLST 分析显示,大多数 cnl 分离株聚集在一个不同的群体中。本研究获得的证据提供了意大利非流行期高中生带菌者的估计,该比例低于预期。此外,携带 cnl 的分离株比例最高,总体上它们具有分子异质性。