Data_Sheet_1_A Cross-Sectional Study Revealing the Emergence of Erythromycin-Resistant Bordetella pertussis Carrying ptxP3 Alleles in China.PDF

BackgroundPrevious limited studies have identified that Bordetella pertussis (B. pertussis) isolates circulating in China possess distinct molecular features and high rates of erythromycin-resistance (ER). Their evolution and potential impact on the prevention and control of global pertussis are worthy of attention.
MethodsThe present cross-sectional study involved 311 non-duplicate and unrelated B. pertussis strains isolated from Chinese children from 2017 to 2019. Their antimicrobial susceptibilities were assessed using both E-test strips and Kirby-Bauer (KB) disk diffusion methods. Seven virulence-related genes (ptxA, ptxC, ptxP, prn, fim2, fim3, and tcfA2) and the A2047G mutation in the 23S rRNA gene were detected by PCR. Based on the susceptibilities and genotypes, 50 isolates were selected for multi-locus variable-number tandem-repeat analysis (MLVA) typing and whole-genome sequencing.
ResultsA total of 311 B. pertussis strains were isolated from children with a median age of 4 months (interquartile range: 2–9 months). Strains carrying the ptxP1 allele were more frequent (84.9%, 264/311), were always ER (except for one strain), and were mainly related to ptxA1/ptxC1/prn1 alleles (99.6%, 263/264). The remaining 47 (15.1%) strains carried the ptxP3 allele, mainly harboring the ptxA1/ptxC2/prn2 alleles (93.6%, 44/47), and were sensitive to erythromycin (except for two strains). The two ER-ptxP3 isolates were first identified in China, belonged to MT27 and MT28 according to MLVA, and were classified into sub-lineage IVd by phylogenetic analysis of their genome sequences. This sub-lineage also includes many strains carrying the ptxP3 allele spreading in developed countries. For each tested antimicrobial, the susceptibilities judged by KB disks were consistent with those determined by E-test strips.
ConclusionThe present results reveal that B. pertussis strains with the ptxP1-ER profile still dominate in China, and a few strains carrying the ptxP3 allele have acquired the A2047G mutation in the 23S rRNA gene and the ER phenotype. The surveillance of the drug susceptibility of B. pertussis is necessary for all countries, and the KB disk method can be adopted as a screening test.

背景 既往有限的研究表明，在中国流行的百日咳博德特氏菌（Bordetella pertussis，B. pertussis）分离株具有独特的分子特征，且红霉素耐药（erythromycin-resistance, ER）率较高。这类菌株的演化过程及其对全球百日咳防控工作的潜在影响值得关注。

方法 本横断面研究纳入了2017年至2019年从中国儿童体内分离得到的311株非重复、无关联的百日咳博德特氏菌菌株。采用E试验条（E-test strips）与柯比-鲍尔（Kirby-Bauer, KB）纸片扩散法对其进行抗菌药物敏感性检测。通过聚合酶链式反应（PCR）检测了7个毒力相关基因（ptxA、ptxC、ptxP、prn、fim2、fim3及tcfA2）以及23S rRNA基因中的A2047G突变位点。基于药敏结果与基因型，选取50株分离株进行多位点可变数目串联重复序列分析（multi-locus variable-number tandem-repeat analysis, MLVA）分型及全基因组测序。

结果 本研究共从儿童患者体内分离得到311株百日咳博德特氏菌，受试儿童的中位年龄为4个月（四分位距：2~9个月）。携带ptxP1等位基因的菌株占比更高（84.9%，264/311），且几乎均表现为红霉素耐药（仅1株例外），该类菌株主要与ptxA1/ptxC1/prn1等位基因相关（99.6%，263/264）。剩余47株（15.1%）菌株携带ptxP3等位基因，主要携带ptxA1/ptxC2/prn2等位基因（93.6%，44/47），且对红霉素敏感（仅2株例外）。本研究首次在中国鉴定出2株红霉素耐药的ptxP3型菌株，经MLVA分型分别属于MT27与MT28型，通过基因组序列系统发育分析被归类为亚谱系IVd。该亚谱系还包含众多在发达国家流行的ptxP3型菌株。针对每种受试抗菌药物，柯比-鲍尔纸片扩散法的药敏检测结果与E试验条检测结果完全一致。

结论 本研究结果显示，携带ptxP1-红霉素耐药表型的百日咳博德特氏菌菌株仍在中国占主导地位，少数携带ptxP3等位基因的菌株已获得23S rRNA基因的A2047G突变，并表现出红霉素耐药表型。所有国家均有必要开展百日咳博德特氏菌的药敏监测，且可采用柯比-鲍尔纸片扩散法作为筛查手段。