Objectives

Mueller–Hinton (MH) agar is recommended by EUCAST and CLSI for disc diffusion antimicrobial susceptibility testing. Using EUCAST methodology, we evaluated the performance of 21 internationally available brands of dehydrated MH agar from 17 manufacturers.

Methods

MH plates were prepared in-house and evaluated against four quality control (QC) strains tested in triplicate, using EUCAST disc diffusion methodology. This resulted in 30 disc–QC strain combinations and 90 readings per MH brand. All brands were tested blindly and in parallel. Results were evaluated against targets and ranges in the EUCAST QC tables. The agar depth, pH and concentration of five cations were measured for all brands.

Results

Six brands of MH agar (Bio-Rad, Biolife, Oxoid, Sigma MH 2, BD BBL MH II and CRITERION) demonstrated excellent performance, with ≥99% of zone diameter readings within QC ranges and ≥70% on target ±1 mm. The poorest performance was seen for Biolab and Merck MH, with 10% (9/90) and 23% (21/90) of readings outside the QC ranges, respectively. Of all readings, 4.9% (93/1890) were out of range, mainly related to trimethoprim sulfamethoxazole (n = 25), aminoglycosides (n = 25) and fluoroquinolones (n = 15). The cation content differed considerably between the agars, and for four brands pH values were outside the acceptable range 7.2–7.4.

Discussions

This study evaluated the performance and content of 21 brands of MH dehydrated media. Six brands showed excellent performance with all investigated antimicrobial classes. Others exhibited problems with one or more classes of agents. This could partly be explained by differences in concentration of specific chemical components and pH.

中文翻译：

---

EUCAST对21个品牌的Mueller-Hinton脱水介质进行了光盘扩散测试的评估。

目标

EUCAST和CLSI建议使用Mueller-Hinton（MH）琼脂进行椎间盘扩散抗菌药敏试验。使用EUCAST方法，我们评估了来自17个制造商的21个国际可用品牌的脱水MH琼脂的性能。

方法

MH板是在内部准备的，并使用EUCAST圆盘扩散方法针对一式三份测试的四个质量控制（QC）菌株进行了评估。这样，每个MH品牌可获得30个圆盘– QC菌株组合和90个读数。所有品牌均经过盲目平行测试。根据EUCAST QC表中的目标和范围评估了结果。测量所有品牌的琼脂深度，pH和五个阳离子的浓度。

结果

六个品牌的MH琼脂（Bio-Rad，Biolife，Oxoid，Sigma MH 2，BD BBL MH II和CRITERION）表现出色，在QC范围内区域直径读数≥99％，在目标±1 mm范围内≥70％。表现最差的是Biolab和Merck MH，其QC范围以外的读数分别为10％（9/90）和23％（21/90）。在所有读数中，有4.9％（93/1890）超出范围，主要与甲氧苄啶磺胺甲恶唑（n  = 25），氨基糖苷（n  = 25）和氟喹诺酮（n  = 15）有关。琼脂之间的阳离子含量差异很大，对于四个品牌，pH值均在7.2-7.4的可接受范围之外。

讨论区

这项研究评估了MH脱水培养基的21个品牌的性能和含量。六个品牌在所有调查的抗菌剂类别中均表现出色。其他人则表现出一种或多种代理的问题。部分原因可以通过特定化学成分浓度和pH值的差异来解释。