培养基对采用纸片扩散法检测金黄色葡萄球菌和凝固酶阴性葡萄球菌中甲氧西林耐药性的影响。

Effects of culture media on detection of methicillin resistance in Staphylococcus aureus and coagulase negative staphylococci by disc diffusion methods.

作者信息

Milne L M, Crow M R, Emptage A G, Selkon J B

机构信息

Public Health Laboratory, John Radcliffe Hospital, Headington, Oxford.

出版信息

J Clin Pathol. 1993 May;46(5):394-7. doi: 10.1136/jcp.46.5.394.

DOI:10.1136/jcp.46.5.394

PMID:8320317

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC501243/

Abstract

AIMS

To test 10 culture media for their ability to detect resistance and sensitivity of staphylococci to methicillin by disc diffusion.

METHODS

Fifty strains of Staphylococcus aureus and 135 strains of coagulase negative staphylococci were tested using Columbia, Diagnostic Sensitivity Test, Mueller Hinton, Sensitest and Iso-sensitest agars with and without 5% added sodium chloride. Cultures were examined after 18 and 40 hours of incubation. The diameter of the zone and its characteristics were recorded and these media were assessed for their ability to produce clear, readable zones of inhibition. Changes in the variables which determined resistance were investigated. Results were analysed allowing a zone diameter reduction of 8 mm and 10 mm compared with the control in addition to the standard 6 mm.

RESULTS

Columbia agar with added sodium chloride supported the growth of all strains, detected the highest number of resistant strains, and was the easiest to read. Resistance was detected after 18 hours in most resistant strains, but some required 40 hours of incubation. There was poor agreement, however, on this medium (63-94%) between disc diffusion and the reference MIC method for sensitive strains. Allowing a greater reduction in zone size resulted in more agreement with sensitive strains but with consequently lowered detection of resistant strains. The other media showed some growth failures and more zones that were difficult to read. More resistance was detected when incubation was prolonged to 40 hours but this was consistently less than on Columbia agar with added salt.

CONCLUSIONS

None of the media detected all of the resistant strains. Columbia agar with added salt was the most satisfactory medium in this respect, but it misidentified up to 37% of the sensitive strains as resistant. Methicillin susceptibility testing by disc diffusion testing is unreliable.

摘要

目的

通过纸片扩散法测试10种培养基检测葡萄球菌对甲氧西林耐药性和敏感性的能力。

方法

使用添加和不添加5%氯化钠的哥伦比亚琼脂、诊断敏感性试验琼脂、穆勒-欣顿琼脂、Sensitest琼脂和Iso-sensitest琼脂，对50株金黄色葡萄球菌和135株凝固酶阴性葡萄球菌进行测试。培养18小时和40小时后检查培养物。记录抑菌圈直径及其特征，并评估这些培养基产生清晰、可读抑菌圈的能力。研究了决定耐药性的变量变化。分析结果时，除标准的6mm外，允许抑菌圈直径与对照相比减少8mm和10mm。

结果

添加氯化钠的哥伦比亚琼脂支持所有菌株生长，检测到的耐药菌株数量最多，且最易于判读。大多数耐药菌株在18小时后即可检测到耐药性，但有些需要培养40小时。然而，对于敏感菌株，在该培养基上纸片扩散法与参考MIC法之间的一致性较差（63%-94%）。允许抑菌圈大小有更大程度的减小会使与敏感菌株的一致性更高，但耐药菌株的检出率相应降低。其他培养基出现了一些生长失败情况，且有更多难以判读的抑菌圈。延长培养至40小时可检测到更多耐药性，但始终低于添加盐的哥伦比亚琼脂。