Niveditha N, Sistla Sujatha
Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education & Research, Puducherry, India.
Indian J Med Res. 2016 Jul;144(1):87-91. doi: 10.4103/0971-5916.193294.
BACKGROUND & OBJECTIVES: Methicillin resistant Staphylococcus aureus (MRSA) remains a major cause of health care-associated infections. Rapid detection of MRSA facilitates the early initiation of appropriate treatment and infection control. Hence, the present study was undertaken to standardize and evaluate the performance of rapid colorimetric nitrate reductase assay (NRA) for determining methicillin resistance in S.aureus.
A total of 160 clinical isolates of S. aureus, (80 each of methicillin susceptible and methicillin resistant) were included in the study. Minimum inhibitory concentration (MIC) was determined by NRA and reference broth micro dilution (BMD) methods. Results of NRA were compared with BMD and analyzed.
For MRSA, the MIC values ranged from 4 to ≥ 16 μg/ml and for MSSA, ≤ 0.5 to 2 μg/ml. Category and essential agreement for NRA as compared with BMD were found to be 99.4 and 89.7 per cent, respectively. No minor or major discrepancy was observed. A single resistant isolate showed very major discrepancy.
INTERPRETATION & CONCLUSIONS: Colorimetric NRA being an inexpensive test requiring no special equipment can be employed as an alternative method for rapid detection of MRSA in resource limited settings.
耐甲氧西林金黄色葡萄球菌（MRSA）仍是医疗保健相关感染的主要原因。快速检测MRSA有助于尽早开始适当的治疗和感染控制。因此，本研究旨在标准化并评估快速比色硝酸还原酶测定法（NRA）在测定金黄色葡萄球菌中甲氧西林耐药性方面的性能。
本研究共纳入160株金黄色葡萄球菌临床分离株（甲氧西林敏感株和耐甲氧西林株各80株）。通过NRA和参考肉汤微量稀释法（BMD）测定最低抑菌浓度（MIC）。将NRA的结果与BMD进行比较并分析。
对于MRSA，MIC值范围为4至≥16μg/ml，对于甲氧西林敏感金黄色葡萄球菌（MSSA），MIC值范围为≤0.5至2μg/ml。与BMD相比，NRA的类别一致性和基本一致性分别为99.4%和89.7%。未观察到小的或大的差异。有一株耐药分离株显示出非常大的差异。
比色NRA作为一种无需特殊设备的廉价检测方法，可作为资源有限环境中快速检测MRSA的替代方法。
