Standards for Microbiology Investigations (UK SMIs)
UK Standards for Microbiology Investigations (UK SMIs) are a comprehensive referenced collection of recommended algorithms and procedures for clinical microbiology.
UK Health Security Agency (UKHSA) in conjunction with its partner organisations develops UK SMIs to help to assure equivalence of investigation strategies in different laboratories; all the UK SMI Test Procedures (TPs) for bacteriology stipulate the use of control strains from the National Collection of Type Cultures (NCTC). Controls are necessary to help demonstrate that laboratory procedures are being operated and interpreted correctly.
You can view the UK Standards for Microbiology Investigations document to see example reference strains for UK Standards for Microbiology Investigations test procedures. For further information or to download any of the Standards for Microbiological Investigations go to the RCPath’s UK Standards for Microbiology Investigations webpage.
Culture Collections now provide a cost-effective means for clinical microbiology laboratories to update their stock cultures of the 17 NCTC strains needed for the SMI TPs in a single order. The SMI TP NCTC set includes controls listed below.
UK SMI |
Example reference strain for both phenotypic and EUCAST disc susceptibility tests |
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Bacteria |
Alternative bacteria |
Fungi |
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Positive control Negative control |
Enterococcus faecalis NCTC 12697 Streptococcus agalactiae NCTC 8181 |
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Positive control Negative control |
N/A **
|
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Positive control Negative control |
Streptococcus pneumoniae NCTC 12977 Streptococcus mitis NCTC 10712 |
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Positive control Negative control |
Staphylococcus aureus NCTC 6571 Streptococcus mitis NCTC 10712 |
Staphylococcus aureus NCTC 12973
|
Cryptococcus neoformans NCPF 3168
|
|
Positive control Negative control |
Staphylococcus aureus NCTC 6571 Staphylococcus haemolyticus NCTC 11042
|
Staphylococcus aureus NCTC 12973
|
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Positive control Negative control |
Staphylococcus aureus NCTC 6571 Staphylococcus haemolyticus NCTC 11042 |
Staphylococcus aureus NCTC 12973
|
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Positive control Negative control |
Escherichia coli NCTC 10418 Proteus mirabilis NCTC 10975 |
Escherichia coli NCTC 12241
|
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Positive control Negative control |
Proteus mirabilis NCTC 10975 Acinetobacter lwoffii NCTC 5866 |
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TP 24 - ONPG (ß-Galactosidase) test (for Enterobacteriaceae) |
Positive control Negative control |
Escherichia coli NCTC 10418 Proteus mirabilis NCTC 10975 |
Escherichia coli NCTC 12241
|
|
Positive control Negative control |
Neisseria lactamica NCTC 10617 Neisseria gonorrhoeae NCTC 8375 |
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Positive control Negative control |
Streptococcus pneumoniae NCTC 12977 Streptococcus mitis NCTC 10712 |
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Positive control Negative control |
Pseudomonas aeruginosa NCTC 10662 Escherichia coli NCTC 10418 |
Pseudomonas aeruginosa NCTC 12903
|
Candida albicans NCPF 3281
|
|
TP 27 - Oxidation/fermentation of glucose test (Gram negative roots)
|
Oxidation: Positive control Negative control |
Pseudomonas aeruginosa NCTC 10662 Acinetobacter Iwoffii NCTC 5866 |
Pseudomonas aeruginosa NCTC 12903
|
|
Fermentation: Positive control Negative control |
Escherichia coli NCTC 10418 Acinetobacter Iwoffii NCTC 5866 |
Escherichia coli NCTC 12241
|
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TP 27 - Oxidation/fermentation of glucose test (Gram positive cocci)
|
Oxidation: Positive control Negative control |
Micrococcus luteus NCTC 2665
|
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Fermentation: Positive control Negative control |
Staphylococcus aureus NCTC 6571 OF basal medium without carbohydrate |
Staphylococcus aureus NCTC 12973
|
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Positive control Negative control |
Haemophilus parainfluenzae NCTC 10665 Haemophilus influenzae NCTC 11931 |
Haemophilus influenzae NCTC 12975
|
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Positive control Negative control |
Escherichia coli NCTC 10418 Staphylococcus aureus NCTC 6571 |
Escherichia coli NCTC 12241
|
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Positive control Negative control |
N/A** |
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Positive control Negative control |
Staphylococcus aureus NCTC 6571 Staphylococcus haemolyticus NCTC 11042 |
Staphylococcus aureus NCTC 12973
|
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Positive control Negative control |
Proteus mirabilis NCTC 10975 Escherichia coli NCTC 10418 |
Escherichia coli NCTC 12241
|
Cryptococcus neoformans NCPF 3168
|
|
|
X and V factor |
Haemophilus influenzae NCTC 11931 |
Haemophilus influenzae NCTC 12975
|
|
V factor only |
Haemophilus parainfluenzae NCTC 10665 |
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X factor only |
Haemophilus haemoglobinophilus NCTC 8540 |
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Positive control Negative control |
Use the recommended controls within . However, if controls used are other than those recommended, laboratories should ensure that these are validated prior to use. |
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Positive control Negative control |
The quality control organisms used is dependent on what the manufacturer provides. Follow manufacturer’s instructions. Laboratories should include their own validated positive and negative controls. |
*The reference bacterial strains have not been validated by NCTC for the test shown.
**N/A – Not Applicable
*** The reference fungal strains have not been validated by NCTC for the tests at the time of publication.
There is validation data for all the strains tested.
Those listed as “alternative strains” in this table are also EUCAST control strain, and are suitable for use for both purposes.