Haemophilus influenzae is one of the main bacteria responsible for otitis media (OM) among children worldwide. We aimed to estimate the distribution of encapsulated and non-capsulated variants (NTHi), biotypes, antibiotic susceptibility, and molecular epidemiology of H. influenzae isolates recovered from pediatric OM cases in Bulgaria.Capsule detection was done by PCR for bexB gene, absent in NTHi. All encapsulated strains were subjected to PCR serotyping. MIC susceptibility testing was performed according to the criteria of EUCAST. MLST was conducted for all 71 OM isolates.The capsule detection and PCR - serotyping disclosed a predominance of NTHi (90.1%) and a few "a", "f", and "c" types. Biotype I was the most widespread (42.3%). β-lactam resistance was found in 35.2% of the isolates. MLST represented heterogenic population structure, whereas the most represented clonal complexes belonged to ST-3, ST-57, ST-105, and ST-1426. 42.3% of the STs showed relatedness to globally represented clones, and 11.3% displayed affiliation to international type 2.Most of the H. influenzae isolates recovered from children with otitis media were non-typable strains from biotype I. The examined population structure was genetically diverse, with a predominance of international type 2 isolates.

中文翻译：

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保加利亚中耳炎流感嗜血杆菌的分子流行病学和抗菌药物耐药性。

流感嗜血杆菌是导致全世界儿童中耳炎 (OM) 的主要细菌之一。我们的目的是估计从保加利亚儿科 OM 病例中回收的流感嗜血杆菌分离株的包膜和非包膜变异 (NTHi) 的分布、生物型、抗生素敏感性和分子流行病学。通过 PCR 对 bexB 基因进行包膜检测，该基因在NT嗨。所有封装菌株均进行 PCR 血清分型。MIC药敏试验按照EUCAST标准进行。对所有 71 个 OM 分离株进行了 MLST。荚膜检测和 PCR 血清分型显示，NTHi 型占优势（90.1%），还有少数“a”、“f”和“c”型。生物型 I 最为普遍 (42.3%)。35.2%的分离株发现β-内酰胺耐药性。MLST 代表异源群体结构，而最具代表性的克隆复合体属于 ST-3、ST-57、ST-105 和 ST-1426。42.3% 的 ST 显示与全球代表性克隆相关，11.3% 显示与国际 2 型相关。从患有中耳炎的儿童中回收的大多数流感嗜血杆菌分离株是来自生物型 I 的不可分型菌株。所检查的群体结构在遗传上是多样化，以国际 2 型分离株为主。