Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden.
Department of Laboratory medicine, Karolinska Institutet, Stockholm, Sweden.
PLoS One. 2018 Nov 7;13(11):e0205761. doi: 10.1371/journal.pone.0205761. eCollection 2018.
Methicillin-resistant Staphylococcus aureus (MRSA) USA300 isolates have been recognized globally, not only in community but also in healthcare settings. USA300 isolates were initially resistant only to methicillin, but resistance to non-β-lactams has emerged with time. To evaluate the prevalence and antimicrobial susceptibility of USA300 isolates in Stockholm, we conducted a nine-year retrospective study. Of 5359 consecutive MRSA cases in Stockholm, isolates from 285 cases were USA300 strains according to the pulsed-field gel electrophoresis pattern. Of these cases, repeated isolates with altered antibiotic resistance patterns were observed in six individuals. Therefore, antimicrobial susceptibility testing was performed on totally 291 isolates. To study the phylogenetic relatedness of isolates in transmission events and genomic resistance traits, 35 isolates were further studied by whole genome sequencing (WGS). The incidence of MRSA was increased from 17.6 per 100,000 inhabitants in 2008 to 37.3 per 100,000 inhabitants in 2016, while the proportion of USA300 cases declined from 6.6% in 2008 to 2.6% in 2016. Among the USA300 isolates, 73.5% were community-associated, 21.3% healthcare-associated, and 5.2% had unknown acquisition. The highest resistance rate among non-β-lactams was found in erythromycin (86%), followed by fluoroquinolones (68-69%). 57% of the isolates were resistant to both erythromycin and fluoroquinolone. Simultaneous resistance to four non-β-lactam antibiotic classes was found in six isolates. Four isolates were susceptible to all non-β-lactam antibiotics. Ceftaroline, daptomycin, linezolid, mupirocin, rifampicin, teicoplanin, telavancin, trimethoprim-sulfamethoxazole and vancomycin retained full activity in the study. WGS analysis indicated that isolates from an outbreak were phylogenetically closely related. In conclusion, USA300 MRSA isolates in Stockholm have neither been limited to the community setting, nor remained susceptible to non-β-lactam agents. WGS is becoming a useful tool in tracing transmission events. The results herein provide the most up-to-date and comprehensive information regarding status of USA300 strains in this geographic area.
耐甲氧西林金黄色葡萄球菌（MRSA）USA300 分离株已在全球范围内得到确认，不仅在社区中，而且在医疗保健环境中也是如此。USA300 分离株最初仅对甲氧西林耐药，但随着时间的推移，对非β-内酰胺类药物的耐药性已经出现。为了评估斯德哥尔摩 USA300 分离株的流行率和抗菌药物敏感性，我们进行了一项为期九年的回顾性研究。在斯德哥尔摩的 5359 例连续 MRSA 病例中，根据脉冲场凝胶电泳模式，285 例病例的分离株为 USA300 株。在这些病例中，有 6 名个体的抗生素耐药模式发生了改变。因此，对总共 291 株分离株进行了抗菌药物敏感性测试。为了研究传播事件中分离株的系统发育相关性和基因组耐药特征，对 35 株分离株进行了全基因组测序（WGS）研究。MRSA 的发病率从 2008 年的每 10 万人 17.6 例增加到 2016 年的每 10 万人 37.3 例，而 2008 年 USA300 病例的比例从 6.6%下降到 2016 年的 2.6%。在 USA300 分离株中，73.5%为社区获得性，21.3%为医疗保健相关性，5.2%为未知获得性。非β-内酰胺类药物中最高的耐药率出现在红霉素（86%），其次是氟喹诺酮类（68-69%）。57%的分离株对红霉素和氟喹诺酮类均耐药。在 6 株分离株中发现同时对 4 种非β-内酰胺类抗生素耐药。4 株分离株对所有非β-内酰胺类抗生素均敏感。头孢洛林、达托霉素、利奈唑胺、莫匹罗星、利福平、替考拉宁、替加环素、复方磺胺甲噁唑和万古霉素在研究中均保持完全活性。WGS 分析表明，暴发中的分离株具有密切的系统发育相关性。总之，斯德哥尔摩的 USA300 MRSA 分离株既不限于社区环境，也未对非β-内酰胺类药物保持敏感性。WGS 正在成为追踪传播事件的有用工具。本文提供了有关该地理区域 USA300 菌株现状的最新和最全面的信息。
