Abstract：
Despite the first-line recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are pressing barriers for optimizing its use for the treatment of non-Escherichia coli Enterobacterales UTI. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for minimal inhibitory concentration (MIC) determination is largely impractical. Using 160 clinical Klebsiella pneumoniae isolates, we sought to understand rates of skipped wells and MIC imprecision in broth microdilution (BMD) and how that compares to rates of error using AD. Though the Clinical and Laboratory Standards Institute refers to the skipped well phenomena in their recommendation against the use of BMD, there is a paucity of data on its frequency. While AD and BMD produced similar MIC50/90 values (32/256 µg/mL for AD and 64/256 µg/mL for BMD), essential agreement was poor. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells at a given concentration, as the most frequent scientific error. Growth in concentrations above the measured MIC occurred in up to 3.3% of wells and was seen within three dilutions of the MIC for BMD. Observation of single colonies either at or beyond the measured MIC for AD was also common and occurred up to 8.3% and 2.5% of the time, respectively. The frequent scientific error in both testing methods should prompt re-evaluation of AD guidelines and expansion of MIC testing methods for fosfomycin susceptibility testing, as poor agreement with another method prone to scientific error should not be the main detractor from BMD use.IMPORTANCEDespite the recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are barriers for optimizing its use. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for MIC determination is largely impractical. The use of broth microdilution (BMD) for fosfomycin testing is not recommended by the Clinical and Laboratory Standards Institute due to unsatisfactory precision and skipped wells-occurrence of no-growth in a single well before the minimal inhibitory concentration (MIC)-and trailing endpoints. We sought to understand rates of skipped wells and growth at concentrations above measured MICs in BMD and how that compares to scientific error using AD. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells for BMD and single colonies at or beyond measured MICs for AD were also common. Frequent scientific error in both methods should prompt re-evaluation of both AD and BMD for fosfomycin susceptibility testing.
摘要：
尽管一线推荐磷霉素治疗简单的尿路感染（UTI），优化其用于治疗非大肠杆菌肠杆菌UTI的用途存在紧迫的障碍。没有批准的针对其他肠杆菌的口服断点，并且推荐的琼脂稀释（AD）参考方法用于最低抑菌浓度（MIC）测定在很大程度上是不切实际的。使用160株临床肺炎克雷伯菌，我们试图了解肉汤微量稀释(BMD)中的跳孔率和MIC不精确性,以及这与使用AD时的错误率的比较.尽管临床和实验室标准研究所在他们反对使用BMD的建议中提到了跳井现象，关于其频率的数据很少。虽然AD和BMD产生相似的MIC50/90值（AD为32/256µg/mL，BMD为64/256µg/mL），基本协议很差。在给定浓度下，浓度低于MIC的无生长孔出现在高达10.9％的孔中，最常见的科学错误。在高达3.3%的孔中发生高于测量的MIC的浓度的生长,并且在BMD的MIC的三个稀释度内观察到。观察到处于或超过AD测得的MIC的单菌落也很常见，发生时间高达8.3％和2.5％，分别。两种测试方法中频繁出现的科学错误应促使重新评估AD指南和扩展磷霉素敏感性测试的MIC测试方法，因为与另一种容易产生科学错误的方法的不良一致性不应该是BMD使用的主要利弊。IMPORTANCEAlthoughtherecommendedoffosfomycinforuncomplicated尿路感染(UTIs),优化其使用存在障碍。没有批准的针对其他肠杆菌的口服断点，建议的琼脂稀释（AD）参考方法用于MIC测定在很大程度上是不切实际的。临床和实验室标准研究所不建议使用肉汤微量稀释（BMD）进行磷霉素测试，因为精度不令人满意，并且跳过了孔-在最小抑制浓度（MIC）之前在单个孔中出现无生长-和尾随终点。我们试图了解跳过孔的速率和在BMD中测得的MIC以上的浓度下的生长，以及如何将其与使用AD的科学误差进行比较。对于BMD,在高达10.9%的孔中出现低于MIC的浓度的无生长孔,并且对于AD,处于或超过测量的MIC的单菌落也是常见的。两种方法中频繁出现的科学错误应促使重新评估AD和BMD以进行磷霉素敏感性测试。
