Tulyaprawat Orawan, Pharkjaksu Sujiraphong, Shrestha Raj Kumar, Ngamskulrungroj Popchai
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Front Microbiol. 2021 Sep 8;12:719353. doi: 10.3389/fmicb.2021.719353. eCollection 2021.
Group B streptococcus (GBS) or is an opportunistic pathogen that causes serious illness in newborns, pregnant women, and adults. However, insufficient detection methods and disease prevention programs have contributed to an increase in the incidence and fatality rates associated with this pathogen in non-neonatal patients. This study aimed to investigate factors of the observed increased incidence by investigation of serotype distribution, virulence factors, and antimicrobial susceptibility patterns from invasive GBS disease among non-neonatal patients in Thailand. During 2017-2018, a total of 109 isolates were collected from non-pregnant patients. There were 62 males and 47 females, with an average age of 63.5 years (range: 20 - 96). Serotypes were determined by latex agglutination assay and multiplex polymerase chain reaction (PCR)-based assay. Among those isolates, seven virulence genes (, , , , , , and ) were detected by PCR amplification, and were determined for their susceptibility to 20 antimicrobial agents using a Sensititre Streptococcus species STP6F AST plate. Among the study isolates, serotype III was predominant (52.3%), followed by serotype V and serotype VI (13.8% for each), serotype Ib (11.9%), and other serotypes (8.2%). Of the seven virulence genes, was found in 67.0%. Except for one, there were no significant differences in virulence genes between serotype III and non-serotype III. Study isolates showed an overall rate of non-susceptibility to penicillin, the first-line antibiotic, of only 0.9%, whereas the resistance rates measured in tetracycline, clindamycin, azithromycin, and erythromycin were 41.3, 22.0, 22.0, and 22.0%, respectively. Strains that were resistant to all four of those drugs were significantly associated with non-serotype III ( < 0.001). Using multi-locus sequence typing (MLST), 40.0% of the four-drug-resistant isolates belonged to serotype VI/ST1, followed by serotype Ib/ST1 (35.0%). Cluster analysis with global GBS isolates suggested that the multiple drug-resistant isolates to be strongly associated with the clonal complex (CC) 1 ( < 0.001). Compared to the 2014 study of 210 invasive GBS isolates conducted in 12 tertiary hospitals in Thailand, the proportion of serotype III has dramatically dropped from nearly 90% to about 50%. This suggests that resistances to the second-line antibiotics for GBS might be the selective pressure causing the high prevalence of non-serotype III isolates.
B族链球菌（GBS）是一种机会致病菌，可导致新生儿、孕妇和成人患重病。然而，检测方法不足和疾病预防计划不力导致非新生儿患者中与该病原体相关的发病率和死亡率上升。本研究旨在通过调查泰国非新生儿侵袭性GBS疾病的血清型分布、毒力因子和抗菌药物敏感性模式，来探究观察到的发病率上升的因素。在2017年至2018年期间，共从非妊娠患者中收集了109株分离株。其中男性62例，女性47例，平均年龄63.5岁（范围：20 - 96岁）。血清型通过乳胶凝集试验和基于多重聚合酶链反应（PCR）的检测方法确定。在这些分离株中，通过PCR扩增检测到7个毒力基因（、、、、、和），并使用Sensititre链球菌种STP6F AST平板测定它们对20种抗菌药物的敏感性。在研究分离株中，III型血清型占主导（52.3%），其次是V型和VI型血清型（各占13.8%），Ib型血清型（11.9%），以及其他血清型（8.2%）。在7个毒力基因中，67.0%的分离株中发现了。除1株外，III型血清型和非III型血清型之间的毒力基因无显著差异。研究分离株对一线抗生素青霉素的总体不敏感率仅为0.9%，而四环素、克林霉素、阿奇霉素和红霉素的耐药率分别为41.3%、22.0%、22.0%和22.0%。对这四种药物均耐药的菌株与非III型血清型显著相关（<0.001）。使用多位点序列分型（MLST）方法，40.0%的四重耐药分离株属于VI型/ST1血清型，其次是Ib型/ST1血清型（35.0%）。对全球GBS分离株进行聚类分析表明，多重耐药分离株与克隆复合体（CC）1密切相关（<0.001）。与2014年在泰国12家三级医院对210株侵袭性GBS分离株进行的研究相比，III型血清型的比例已从近90%大幅降至约50%。这表明GBS对二线抗生素的耐药性可能是导致非III型血清型分离株高流行率的选择压力。
