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Panel:   Isolates with New or Novel Antibiotic Resistance (NEW)
AR Bank # 0500 Enterococcus faecium
Study ID: NEW-13

Biosample Accession #: SAMN11953784


Vancomycin Variable Enterocci (VVE) isolates firstly appear susceptible to phenotypic AST but possess vanA gene and can revert resistance to vancomycin in vitro and in vivo during sub-inhibitory vancomycin exposure. Vancomycin resistance requires vanHAX gene cassette that is regulated by vanRS. Vancomycin Variable Enterocci (VVE) has a silenced vanHAX either by truncated/deleted vanRS or attenuated transcription by Insertion Sequence, ISL3 on the upstream of vanHAX. Due to its susceptibility, it can be missed by phenotypic AST screening but develops resistance during the antibiotic therapy and later results in treatment failure.

MICs obtained by broth microdilution. Modal MIC is reported.

MIC results for each antimicrobial agent for an isolate may commonly be ± 1 log2 (doubling dilution) different than what is posted on the FDA & CDC AR Bank website because this is the normal technical variability of antimicrobial susceptibility testing (see J. H. Jorgensen. 1993. J Clin Microbiol. Vol 31[11]: 2841-2844).

Note: AR- 0349 Escherichia coli  has been removed from the collection and is now available at ATCC under catalog # BAA-3170

Panel:  Isolates with New or Novel Antibiotic Resistance (NEW)

MIC (μg/ml) Results and Interpretation
Drug MIC (μg/ml) INT
Ampicillin 128R
Chloramphenicol 16I
Daptomycin 4SDD
Doxycycline 8I
High-Level Gentamicin >500SYN-R
High-Level Streptomycin >1000SYN-R
Levofloxacin >8R
Linezolid 2S
Penicillin 256R
Quinupristin/dalfopristin 11S
Rifampin >4R
Teicoplanin 2S
Vancomycin 1S
MICs obtained by broth microdilution. Modal MIC is reported
S – I –R Interpretation (INT) derived from CLSI 2020 M100 S30

1 Reflects MIC of first component
Molecular Mechanisms of Resistance
Glycopeptides vanHAX(lacks VanRs)
AR gene prediction was performed using ARG-ANNOT, ResFinder and NCBI (ResGANNCBI) databases accessed on 2021-05-07. AR drug classes are assigned according to these databases. This analysis does not include mutations that may result in antibiotic resistance or resistance determinants added to newer versions of used database or other antimicrobial resistance gene databases. For resistance determinant detection, 99-100% sequence identity and 100% sequence coverage from GAMMA and SRST2 was used. GAMMA uses amino acid sequence to assign gene alleles from assemblies; SRST2 uses nucleotide sequence to assign gene alleles from sequencing reads. Biosample accession numbers have been provided so that users can analyze the data on their own if so desired. *Presence of Efflux Pump may not be associated with resistance. *MLST Type (and scheme), as determined by Torsten Seemann's MLST program. For Enterobacteriaceae, the Pasteur MLST schemes are used except for E. coli for which both the Pasteur and Achtman schemes are reported. SUB=novel MLST identified and "submitted".
Medium: Trypticase Soy Agar with 5% Sheep Blood (BAP)

Temperature: 35°C
Atmosphere: Aerobic


Remove the sample vial to a container with dry ice or a freezer block. Keep vial on ice or block. (Do not let vial content thaw)

Open vial aseptically to avoid contamination

Using a sterile loop, remove a small amount of frozen isolate from the top of the vial

Aseptically transfer the loop to BAP

Use streak plate method to isolate single colonies

Incubate inverted plate at 35°C ± 2°C for 18-24 hrs.

Storage Temperature & Biosafety

Appropriate safety procedures should always be used with this material. Laboratory safety is discussed in the current publication of 'BioSafety in Microbiological and Biomedical Laboratories' from the U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, and National Institutes of Health. Please Note: This AR Bank panel includes isolates that are pan-resistant, meaning they are susceptible to none of the antimicrobial agents tested which may include those commonly used to treat infections with these organisms. This represents an additional risk to staff working with these organisms and should be considered as part of the receiving facility risk assessment required by the Biosafety Compliance Agreement. The increased difficulty in treatment of any infection with those isolates should also be a consideration in deciding which protocols to use and precautions to take for working with these isolates.

This product is sent with the condition that you are responsible for its safe storage, handling, and use. All materials are the property of the Centers for Disease Control and Prevention (CDC) and have been made available on behalf of the Food and Drug Administration (FDA). This material is not for use in human subjects and may not be redistributed. While CDC uses reasonable efforts to include accurate and up-to-date information on this product sheet, CDC makes no warranties or representations as to its accuracy. CDC is not liable for damages arising from the misidentification or misrepresentation of cultures. Please refer to the Standard Letter Agreement (SLA) for further details regarding the use of this product.
Isolate History
Date Action Performed
08/22/23Interpretation was updated with a new value for Quinupristin/dalfopristin: from R to S
04/14/21MIC was updated with a new value
12/28/20Sequence Accession # changed
01/13/20MIC was updated with a new value
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