1 Section of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Chicago Medical Center, Chicago, Illinois, USA.
2 Section of Infectious Disease and Global Health, Department of Medicine, University of Chicago Medical Center, Chicago, Illinois, USA.
Otolaryngol Head Neck Surg. 2018 May;158(5):923-929. doi: 10.1177/0194599818762382. Epub 2018 Mar 13.
Objective Despite the rising incidence of methicillin-resistant Staphylococcus aureus (MRSA) otologic infections, choice of treatment remains controversial. Only fluoroquinolone-containing ototopical preparations are approved by the US Food and Drug Administration for middle ear application. Furthermore, American Academy of Otolaryngology-Head and Neck Surgery Foundation guidelines advocate ototopical monotherapy for both tympanostomy tube otorrhea and acute otitis externa. Unfortunately, MRSA may be ciprofloxacin resistant. This causes confusion regarding antibiotic selection, because susceptibility profiles reflect a minimum inhibitory concentration (MIC), referenced against systemic, not ototopical, drug delivery dosing. The goal of this study is to determine the ciprofloxacin MIC for ciprofloxacin-resistant MRSA isolates from otologic infections and compare that value to the expected drug concentration achieved by fluoroquinolone ear drops and determine MRSA genotype for each isolate. Study Design In vitro assay with retrospective medical record review. Setting Tertiary care university hospital. Subjects and Methods Thirty otologically sourced ciprofloxacin-resistant MRSA isolates collected from adult and pediatric patients. MICs were calculated by broth dilution method. Isolates underwent multilocus sequence typing and polymerase chain reaction for arcA and Panton-Valentine leukocidin to establish the genotype. Results MICs ranged from 16 to 1025 µg/mL. There was a relationship between MIC and genotype; of the 7 isolates with an MIC value greater than 512 µg/mL, 6 were sequence type (ST)8. Conclusion These findings support the practice of ototopical monotherapy for patients with uncomplicated ciprofloxacin-resistant MRSA otitis externa. However, they raise concern that ototopical therapy may not be adequate to treat highly resistant strains of MRSA infecting the middle ear space.
目的 尽管耐甲氧西林金黄色葡萄球菌（MRSA）耳部感染的发病率不断上升，但治疗选择仍存在争议。只有含氟喹诺酮类的耳用制剂获得美国食品和药物管理局批准用于中耳应用。此外，美国耳鼻咽喉头颈外科学会基金会指南主张对鼓膜切开术管耳漏和急性外耳炎均采用耳用单药治疗。不幸的是，MRSA 可能对环丙沙星耐药。这导致了抗生素选择的困惑，因为药敏谱反映的是最低抑菌浓度（MIC），参考的是全身而不是耳用药物的给药剂量。本研究的目的是确定来自耳部感染的耐环丙沙星 MRSA 分离株的环丙沙星 MIC，并将该值与氟喹诺酮耳滴达到的预期药物浓度进行比较，并确定每个分离株的 MRSA 基因型。 研究设计 体外测定与回顾性病历审查。 地点 三级护理大学医院。 受试者和方法 从成人和儿科患者中收集了 30 株来自耳部的耐环丙沙星 MRSA 分离株。通过肉汤稀释法计算 MIC。对分离株进行多位点序列分型和聚合酶链反应，以确定 arcA 和 Panton-Valentine 白细胞毒素的基因型。 结果 MIC 范围为 16 至 1025 µg/mL。MIC 与基因型之间存在关系；在 MIC 值大于 512 µg/mL 的 7 株分离株中，有 6 株为序列型（ST）8。 结论 这些发现支持对无并发症的耐环丙沙星 MRSA 外耳炎患者进行耳用单药治疗的做法。然而，它们引起了人们的关注，即耳用疗法可能不足以治疗感染中耳空间的高耐药性 MRSA 菌株。
