Whidbey Christopher, Burnside Kellie, Martinez Raquel M, Gendrin Claire, Vornhagen Jay, Frando Andrew, Harrell Maria Isabel, McAdams Ryan, Rajagopal Lakshmi
Department of Pediatrics, University of Washington School of Medicine, USA.
Department of Global Health, University of Washington School of Public Health, USA.
Clin Res Infect Dis. 2015;2(2). Epub 2015 Sep 3.
Group B Streptococci (GBS) are ß-hemolytic, gram-positive bacteria that are typically associated with infections in human newborns or immunocompromised adults. However, mutation in the two-component regulator CovR/S relieves repression of hemolysin, potentially increasing virulence of GBS. We report the isolation of hyperhemolytic/hyperpigmented GBS strain from an adolescent patient who presented to the University of Washington clinic with symptoms of sore throat. While the patient also tested positive for mononucleosis, a GBS strain with increased hemolysis was isolated from the throat swab obtained from the patient. As hyperhemolytic/hyperpigmented GBS strains are typically associated with mutations in the regulator CovR/CovS, we sequenced the loci in the clinical isolate. An adenine to cytosine mutation resulting in a change in amino acid coding sequence from glutamine at position 120 to proline in CovR (Q120P) was identified. Introduction of the Q120P amino acid substitution in a CovR complementation plasmid abolished complementation of a Δ mutant derived from the wild type GBS serotype Ia strain A909; these results confirm that the hyperhemolysis observed in the clinical isolate is due to the Q120P substitution in CovR. Antibiotic was prescribed and the patient's symptoms resolved without reported complications. This study represents the first report of the isolation of a hyperhemolytic/hyperpigmented GBS strain due to a mutation from an adolescent patient with persistent sore throat who was also diagnosed with mononucleosis. The isolation of GBS CovR/S mutants indicates their presence in settings of co-infections and includes adolescents.
B族链球菌（GBS）是β溶血性革兰氏阳性菌，通常与人类新生儿或免疫功能低下成人的感染有关。然而，双组分调节因子CovR/S的突变可解除对溶血素的抑制，可能增加GBS的毒力。我们报告了从一名因喉咙痛症状就诊于华盛顿大学诊所的青少年患者中分离出高溶血/高色素沉着GBS菌株。虽然该患者单核细胞增多症检测也呈阳性，但从患者咽喉拭子中分离出了溶血增加的GBS菌株。由于高溶血/高色素沉着GBS菌株通常与调节因子CovR/CovS的突变有关，我们对临床分离株中的相关位点进行了测序。在CovR中鉴定出一个腺嘌呤到胞嘧啶的突变，导致氨基酸编码序列从第120位的谷氨酰胺变为脯氨酸（Q120P）。在CovR互补质粒中引入Q120P氨基酸取代消除了源自野生型GBS血清型Ia菌株A909的Δ突变体的互补作用；这些结果证实临床分离株中观察到的高溶血是由于CovR中的Q120P取代。患者接受了抗生素治疗，症状缓解，未报告并发症。本研究首次报道了从一名持续喉咙痛且被诊断为单核细胞增多症的青少年患者中分离出因CovR突变导致的高溶血/高色素沉着GBS菌株。GBS CovR/S突变体的分离表明它们存在于合并感染的情况下，包括青少年。
