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NCTC Antimicrobial Resistant Reference Strains brochure revisited and revised

The proliferation of antimicrobial resistance (AMR) among clinically relevant and veterinary significant bacterial species is among the most pressing healthcare challenges of the 21st Century. As such, the detection and surveillance of AMR strains, species and lineages in both environmental and healthcare settings, as well as the discovery and development of effective novel antimicrobial compounds, continues to be a high priority for public health laboratories and researchers worldwide.

In support of this endeavour, the UK's National Collection of Type Cultures (NCTC) maintains and provides a wide variety of antimicrobial resistant bacterial strains for use as both genotypic and phenotypic diagnostic controls, for use in the assessment of novel antimicrobial compounds, and for use in the elucidation of how certain genetic elements contribute to an AMR phenotype. Many of these strains are listed in international guidelines such as EUCAST (, part of whose remit is to provide technical advice and gold standard, internationally harmonised methodologies for the detection of AMR pathogens. These bacterial strains are collated in the NCTC Antimicrobial Resistant Reference Strains Booklet, which has recently been revised to reflect the latest international standards and the control strains specified therein, and the latest accessions of AMR bacterial strains into the NCTC.

Bacterial strains are added continuously to the NCTC throughout each year by scientists globally. Scientists and researchers often proactively contact the collection to deposit bacterial strains of interest; naturally some of these AMR isolates. Otherwise, some bacterial strains are added to the collection at the request of the NCTC and the generous collaboration of the researcher in question.

One example of such strains, that have also been included in the revised edition of the NCTC AMR Reference Strain Booklet, are a set of 10 Staphylcoccocus aureus strains (NCTC 14457-14465 & NCTC 14579) positive for the mecA gene allele mecC, which confers phenotypic resistance to methicillin. Each are from human clinical provenance, and were isolated a little over a year after the discovery and description of the mecC gene1.

Strains of bacterial species with intrinsic resistance to antimicrobials have also been added such as Enterococcus casseliflavus, with vanC-type glycopeptide resistance, and Acinetobacter colisiniresistens that exhibits intrinsic phenotypic resistance to the antibiotic colisin2.

The NCTC continues to collaborate with the bacteriology reference laboratories of the UK Health Security Agency. In addition to the strains added to the NCTC to support the detection of aquired carbapenemases (, further bacterial strains have since been deposited into the collection by the Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, including numerous linezolid resistant gram positive bacteria.

Read about the range of antimicrobial resistant strains in the new edition of the NCTC Antimicrobial Resistant Reference Stains Brochure



1. Paterson GK, Morgan FJ, Harrison EM, Cartwright EJ, Török ME, Zadoks RN, Parkhill J, Peacock SJ, Holmes MA. Prevalence and characterization of human mecC methicillin-resistant Staphylococcus aureus isolates in England. J Antimicrob Chemother. 2014 Apr;69(4):907-10. PMID: 24284779; PMCID: PMC3956372.

2. Nemec A, Radolfova-Krizova L, Maixnerova M, Sedo O. Acinetobacter colistiniresistens sp. nov. (formerly genomic species 13 sensu Bouvet and Jeanjean and genomic species 14 sensu Tjernberg and Ursing), isolated from human infections and characterized by intrinsic resistance to polymyxins. Int J Syst Evol Microbiol. 2017 Jul;67(7):2134-2141. PMID: 28671519.


Written by Jake David Turnbull, follow Jake on twitter @hotchpotchjake 


December 2023