Evaluation of chromogenic meticillin-resistant Staphylococcus aureus media: sensitivity versus turnaround time

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• 作者：K. Morris^a ; ^{kirsti.morris@leedsth.nhs.uk} ; C. Wilson^a ; M.H. Wilcox^a ; ^b
• 关键词：Culture ; Incubation length ; Meticillin-resistant Staphylococcus aureus ; Screening
• 刊名：Journal of Hospital Infection
• 出版年：2012
• 期刊代码：177_01956701
• 类别：med
• 出版时间：May, 2012
• 卷：81
• 期：1
• 页码：20-24
• 文件大小：140 K

摘要

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Summary

Background

Chromogenic media offer the potential for improved detection of meticillin-resistant Staphylococcus aureus (MRSA). Incubation times in a clinical setting vary, generally between 16 and 48聽h.

Aim

To investigate the effects of incubation time on the performance of commercial chromogenic MRSA media.

Methods

We initially compared the early recovery of MRSA isolates from routine screening swabs following 16-23聽h to that after 22-24聽h of incubation using ChromID MRSA (bioM茅rieux). We also compared ChromID MRSA, ChromID MRSA V2 (bioM茅rieux), Brilliance MRSA 2 Agar (Oxoid) and Colorex MRSA (E&O Laboratories Ltd) as selective media for 6035 MRSA screening swabs.

Findings

Only 303 of 623 (48.6%) MRSA isolates detected by this medium after 48聽h were recovered after 16-23聽h compared with 726 of 1018 (71.3%) isolates after 22-24聽h. Following implementation of the 22-24聽h incubation period, 50 (4.4%) isolates exhibiting a positive chromogenic reaction gave conflicting coagulase latex and DNase results. In 88%of these cases, DNase gave the correct result of non-MRSA. ChromID MRSA demonstrated the highest sensitivity overall at 93.2%, followed by Colorex MRSA Agar (87.1%), ChromID V2 (83.7%) and Brilliance Agar (78.2%). All media exhibited specificities of >99.7%.

Conclusion

Early detection of MRSA using ChromID MRSA is best achieved after incubation for 22-24聽h. Latex agglutination coagulase tests alone should not be relied upon for identification of MRSA isolates from this medium. Although ChromID MRSA was deemed the superior medium in terms of MRSA recovery, the disadvantages of increased turnaround time (48 vs 24聽h) must be considered.