Laboratory of Microbiology, Faculty of Medicine Sfax, University of Sfax-Tunisia, Avenue Majida Boulila, 3027, Sfax, Tunisia.
Research Laboratory Microorganisms and Human Disease "MPH LR03SP03", Sfax, Tunisia.
BMC Microbiol. 2023 Feb 4;23(1):36. doi: 10.1186/s12866-023-02784-2.
Streptococcus pneumoniae remains a leading cause of morbidity and mortality worldwide. In this study, we sought to analyze serotype distributions, antibiotic resistance, and genetic relationships of 106 clinical invasive pneumococcal isolates recovered in Tunisia between 2012 and 2018, prior to the routine use of pneumococcal conjugate vaccines (PCV).
We used multiplex PCR, the disk diffusion method and/or E-test, and multi-locus sequence typing (MLST).
The most frequent serotypes were 14 (17%), 19F (14.2%), and 3 (11.3%). Of the 106 S. pneumoniae isolates, 67.9% were penicillin non-susceptible (29.4% were resistant), 45.3% were amoxicillin non-susceptible (17% were resistant), and 16% were cefotaxime non-susceptible. For antibiotics other than β-lactams, resistance rates to erythromycin, tetracycline, cotrimoxazole, and chloramphenicol were 62.3, 33, 22.6, and 4.7%, respectively. Two isolates were non-susceptible to levofloxacin. Among 66 erythromycin-resistant pneumococci, 77.3% exhibited the cMLSB phenotype, and 87.9% carried ermB gene. All tetracycline-resistant strains harbored the tetM gene. The potential coverage by 7-, 10-, and 13-valent pneumococcal conjugate vaccines were 55.7, 57.5, and 81.1%, respectively. A multilocus sequence typing analysis revealed great diversity. Fifty different sequence types (STs) were identified. These STs were assigned to 10 clonal complexes and 32 singletons. The most common STs were 179, 2918, 386, and 3772 - related mainly to 19F, 14, 6B/C, and 19A serotypes, respectively.
This study demonstrated that the majority of the serotypes of invasive pneumococci in the Tunisian population were 14, 19F, and 3. Moreover, we noted a high degree of genetic diversity among invasive S. pneumoniae isolates. The highest proportions of antibiotic non-susceptible isolates were for penicillin, erythromycin, and tetracycline. Further molecular characteristics are required to monitor the genetic variations and to follow the emergence of resistant pneumococci for the post-vaccination era in Tunisia.
肺炎链球菌仍然是全球发病率和死亡率的主要原因。在这项研究中，我们旨在分析 2012 年至 2018 年在突尼斯分离的 106 例临床侵袭性肺炎链球菌分离株的血清型分布、抗生素耐药性和遗传关系，这些分离株在常规使用肺炎球菌结合疫苗（PCV）之前。
我们使用多重 PCR、纸片扩散法和/或 E 试验以及多位点序列分型（MLST）。
最常见的血清型是 14（17%）、19F（14.2%）和 3（11.3%）。在 106 株肺炎链球菌分离株中，67.9%对青霉素不敏感（29.4%耐药），45.3%对阿莫西林不敏感（17%耐药），16%对头孢噻肟不敏感。除β-内酰胺类抗生素外，对红霉素、四环素、复方磺胺甲恶唑和氯霉素的耐药率分别为 62.3%、33%、22.6%和 4.7%。有 2 株分离株对左氧氟沙星不敏感。在 66 株红霉素耐药肺炎球菌中，77.3%表现出 cMLSB 表型，87.9%携带 ermB 基因。所有四环素耐药株均携带 tetM 基因。7、10 和 13 价肺炎球菌结合疫苗的潜在覆盖率分别为 55.7%、57.5%和 81.1%。多位点序列分型分析显示出极大的多样性。鉴定出 50 种不同的序列型（ST）。这些 ST 分为 10 个克隆复合体和 32 个单倍型。最常见的 ST 是 179、2918、386 和 3772-主要与 19F、14、6B/C 和 19A 血清型有关。
本研究表明，突尼斯人群侵袭性肺炎球菌的大多数血清型为 14、19F 和 3。此外，我们注意到侵袭性肺炎链球菌分离株之间存在高度的遗传多样性。抗生素不敏感分离株的比例最高的是青霉素、红霉素和四环素。需要进一步的分子特征来监测遗传变异，并在突尼斯的疫苗接种后时代监测耐药肺炎球菌的出现。
