Cefiderocol Antimicrobial Susceptibility Testing by Disk Diffusion: Influence of Agar Media and Inhibition Zone Morphology in K. pneumoniae Metallo-β-lactamase.

IF 4.3 2区 医学 Q1 INFECTIOUS DISEASES
Maciej Saar, Anna Wawrzyk, Dorota Pastuszak-Lewandoska, Filip Bielec
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Abstract

Accurate antimicrobial susceptibility testing (AST) of cefiderocol remains a diagnostic challenge, especially in infections caused by metallo-β-lactamase (MBL)-producing Klebsiella pneumoniae. While disk diffusion offers a cost-effective alternative to broth microdilution, it is highly sensitive to factors such as media composition and the presence of atypical colony morphology. The objective of this study was to evaluate how different agar media and interpretations of isolated colonies affect the performance and reliability of cefiderocol AST by disk diffusion. A total of 50 clinical K. pneumoniae MBL isolates were tested using disk diffusion on Columbia with blood, MacConkey, and chromogenic agars from three manufacturers. Inhibition zones were compared with MICs from broth microdilution. Statistical analyses included paired t-tests and Spearman correlation to assess media effects and zone morphology impact. Variability in inhibition zone diameters was observed between media, notably with chromogenic agar. The most consistent results were obtained using Graso Biotech and Thermo Fisher Columbia with blood agar. Isolated colonies were observed in over half the samples and, depending on how they were interpreted, led to major changes in classification accuracy. Up to 64% of results fell into the EUCAST area of technical uncertainty (ATU), and categorical agreement varied across media and interpretive criteria. Disk diffusion for cefiderocol may be used in resource-limited settings but only if rigorously standardized using validated media, consistent zone reading, and ATU-aware interpretive strategies. In borderline cases or when morphological anomalies are present, broth microdilution should be considered the sole reliable method. Clinical microbiologists are advised to exercise caution with ambiguous results and seek expert or confirmatory testing when needed.

圆盘扩散法检测头孢地罗对肺炎克雷伯菌金属β-内酰胺酶的药敏:琼脂培养基及抑菌带形态的影响。
头孢地罗的准确药敏试验(AST)仍然是一项诊断挑战,特别是在由产生金属β-内酰胺酶(MBL)的肺炎克雷伯菌引起的感染中。虽然磁盘扩散提供了一种具有成本效益的替代肉汤微稀释,但它对培养基组成和非典型菌落形态的存在等因素高度敏感。本研究的目的是评估不同的琼脂培养基和分离菌落的解释如何通过磁盘扩散影响头孢地罗AST的性能和可靠性。采用圆盘扩散法对50株临床分离的肺炎克雷伯菌MBL在哥伦比亚进行检测,检测对象为三家生产商的血液、麦康基和显色琼脂。比较了肉汤微量稀释mic的抑菌区。统计分析包括配对t检验和Spearman相关来评估介质效应和区域形态影响。在培养基之间观察到抑制区直径的差异,特别是显色琼脂。用Graso Biotech和Thermo Fisher Columbia的血琼脂获得了最一致的结果。在超过一半的样本中观察到孤立的菌落,这取决于它们如何被解释,导致分类准确性的重大变化。高达64%的结果落入EUCAST的技术不确定性(ATU)区域,并且不同媒体和解释标准的绝对一致性有所不同。cefiderocol的磁盘扩散可用于资源有限的环境,但必须严格标准化,使用经过验证的介质、一致的区域读取和atu感知的解释策略。在边缘病例或当形态异常存在时,微量肉汤稀释应被认为是唯一可靠的方法。临床微生物学家应谨慎对待模棱两可的结果,并在需要时寻求专家或确认性检测。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Antibiotics-Basel
Antibiotics-Basel Pharmacology, Toxicology and Pharmaceutics-General Pharmacology, Toxicology and Pharmaceutics
CiteScore
7.30
自引率
14.60%
发文量
1547
审稿时长
11 weeks
期刊介绍: Antibiotics (ISSN 2079-6382) is an open access, peer reviewed journal on all aspects of antibiotics. Antibiotics is a multi-disciplinary journal encompassing the general fields of biochemistry, chemistry, genetics, microbiology and pharmacology. Our aim is to encourage scientists to publish their experimental and theoretical results in as much detail as possible. Therefore, there is no restriction on the length of papers.
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