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Quality control strains (or reference strains)are typed cultures of microorganisms with known antimicrobial susceptibility patterns and which are used to ensure consistency, accuracy and reproducibility of a particular susceptibility test. They are important in any disk diffusion test because susceptibility tests are affected by plethora of factors such as incubation temperature, size of the test organism and test medium. When antimicrobial susceptibility is to be carried out, it is imperative that the clinical microbiologist also run a test using the reference strain corresponding to the test culture. Quality control strains helps to balance the result of an antibiogram.

And if the result obtained for a given control strain against a particular antibiotic is outside the specified range (as given by the manufacturer or CLSI/NCCLS guidelines), the patient’s susceptibility test result should not be reported and the disk/antibiotic should not be used until the reason for the discrepancy is deciphered. Reasons for poor performance of a control strain may include media used, inoculum size, incubation temperature and incorrect storage of disks or control strain.

Quality control strains are commercially available as pellets of desiccated pure cultures, and are made into suspensions prior to their usage by following the manufacturer’s instruction. Reference strains of microorganisms can be obtained from national culture collection centers such as the American Type Culture Collection (ATCC) in the United States of America. There are other culture collection centers across the globe; and these culture collection centers continue to serve as sources of pure microbial cultures for research and commercialization.

Examples of some quality control organisms include:

  • Escherichia coli ATCC 25922
  • Klebsiella pneumoniae ATCC 700603
  • Pseudomonas aeruginosa ATCC 27853
  • Staphylococcus aureus ATCC 25923
  • Candida albicans ATCC 10231
  • Haemophilus influenzae ATCC 33930
  • Streptococcus pneumoniae ATCC 27336
  • Enterococcus faecalis ATCC 29212. 

Table 1. World Federation for Culture Collections (WFCC) affiliated culture collections contributed to WDCM Reference Strain Catalogue

Culture CollectionFull NameCountry/Region
1AHUAHU Culture CollectionJapan
2ATCCAmerican Type Culture CollectionU.S.A.
3BCRCBioresource Collection and Research CenterChinese Taipei
4BTCCBulgarian Type Culture CollectionBulgaria
5CBSCentraalbureau voor Schimmelcultures, Filamentous fungi and Yeast CollectionNetherlands
6CCMCzech Collection of MicroorganismsCzech
7CCTMCentre de Collection de Type MicrobienSwitzerland
8CCUGCulture Collection University of GoteborgSweden
9CGMCCChina General Microbiological Culture Collection CenterChina
10CICCChina Center of Industrial Culture CollectionChina
11CIPCollection de L’Institut PasteurFrance
12CNCTCCzech National Collection of Type CulturesCzech
14DSMZLeibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbHGermany
17GIFUGifu Type Culture Collection (GTC), Gifu University Culture Collection (GIFU)Japan
18HNCMBHungarian National Collection of Medical BacteriaHungary
19IAMIAM Culture CollectionJapan
20IFOInstitute for Fermentation, OsakaJapan
21IHEMBelgian Coordinated Collections of Microorganisms / IHEM Fungi collecitonGermany
22IIDLaboratory Culture Collection, University of TokyoJapan
23IMICABI Genetic Resource CollectionU.K.
25JCMJapan Collection of MicroorganismsJapan
26LMGBelgian Coordinated Collections of Microorganisms/ LMG Bacteria CollectionBelgium
27MUCLBelgian Coordinated Collections of Microorganisms / MUCL Agro-environmental Fungi CollectionBelgium
28NBIMCCNational Bank for Industrial Microorganisms and Cell CulturesBulgaria
29NBRCNBRC Culture CollectionJapan
30NCCBNCCB, the Netherlands Culture Collection of Bacteria (formerly LMD and Phabagen Collection)Netherlands
34NCIMBNational Collections of Industrial Food and Marine Bacteria (incorporating the NCFB)U.K.
35NCPFNational Collection of Pathogenic FungiU.K.
36NCPPBNational Collection of Plant Pathogenic BacteriaU.K.
37NCTCNational Collection of Type CulturesU.K.
38NCYCNational Collection of Yeast CulturesU.K.
39NRICNODAI Research Institute Culture CollectionJapan
40NRRLAgricultural Research Service Culture CollectionU.S.A.
41OUTDepartment of Biotechnology, Osaka UniversityJapan
42QMQuartermaster Research & Engineering CenterU.S.A.
43RIMDResearch Institute for Microbial Diseases, Research Center for Emerging Infectious DiseasesJapan
44UMIPCollection de Champignons et Actinomycetes PathogenesFrance
45VKMAll-Russian Collection of MicroorganismsRussia
46VTTVTT Culture CollectionFinland



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Ejikeugwu Chika, Iroha Ifeanyichukwu, Adikwu Michael and Esimone Charles (2013). Susceptibility and Detection of Extended Spectrum β-Lactamase Enzymes from Otitis Media Pathogens. American Journal of Infectious Diseases. 9(1):24-29.

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