 |
To my knowledge, there are no formal recommendations for additional testing of coagulase-negative Staphylococcus (CoNS) for which the vancomycin MIC is intermediate (8-16 ug/ml; CLSI) or resistant (¡Ý32 ug/ml; CLSI) when tested on an automated instrument. However, a vancomycin intermediate or resistant result for CoNS is unusual and should be investigated. A good first step would be to confirm the purity of the isolate. If the isolate is pure, the vancomycin MIC should be confirmed by another method. If possible a non-automated method, like Etest or non automated broth microdilution, should be used. The vancomycin screen agar (BHI agar with 6ug/ml vancomycin) has not been extensively evaluated for CoNS, so it is not clear that use of this agar would be helpful for investigating CoNS with reduced susceptibility to vancomycin.
Isolates with vancomycin intermediate or resistant results should be sent to a reference lab, such as the CDC, for confirmation. In particular, a MIC of ¡Ý32 ug/ml is very unusual and should be tested for the presence of van genes (the primary mechanism of vancomycin resistance in Enterococcus spp.). It is important to note that van gene-mediated resistance has not been documented in CoNS.
DISCLAIMER
Askit is for general information purposes only and may not be relied upon by users for decisions or action in specific circumstances. Neither ASM nor the expert assures the accuracy or completeness of information provided. Questions are answered based on current information, which may change over time. Please note the date that a question was answered. If an answer is more than one year old, you may want to resubmit the question for an updated answer.
The advice and comments do not necessarily reflect the views of ASM. ASM and INDIVIDUAL experts expressly disclaim any and all liability for any direct, indirect, or special damages or loss of any nature incurred as a consequence of use of this site or any advice or comment by any expert. By using Askit, the user accepts the waiver of claims and all terms of use of ASM’s site, including the disclaimers set forth in the “Legal Rights” link on ASM’s home page.
|
