Frequently Asked Questions Page

What is SBT?
What's the purpose of the Legionella pneumophila SBT scheme?
What's the difference between MLST and SBT?
How does the L. pneumophila SBT scheme work?
References
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What is SBT?

SBT stands for sequence-based typing. This was first described for Legionella pneumophila serogroup 1 by Gaia et al. 2003, and extended to it's current form for Legionella pneumophila by Gaia et al. 2005 and Ratzow et al. 2007
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What's the purpose of the Legionella pneumophila SBT scheme?

The primary aim of the scheme is to provide a rapid and easily comparable method for the epidemiological typing of clinical and environmental isolates of Legionella pneumophila in outbreak investigations. As data accumulate we anticipate that this online database will allow tracking of the global distribution of specific strains.
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What's the difference between MLST and SBT?

Multilocus sequence typing (MLST) was first described for Streptococcus pneumoniae by Enright and Spratt (1998), who used seven housekeeping (non-selective) genes. Subsequently, several such schemes using non-selective genes have been described (www.mlst.net). We prefer to reserve the use of the term MLST for schemes such as those described by Enright and Spratt (1998) and others that use housekeeping genes (under stabilising pressure) and to use "sequence-based typing" (SBT) as a more universal term to describe other schemes which can include those under diversifying pressure e.g., virulence genes.
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How does the L. pneumophila SBT scheme work?

Following genomic DNA extraction from L. pneumophila, specific gene fragments are amplified and the PCR amplicons sequenced using both forward and reverse primers. Consensus sequences are entered into the online database, which allows the assignment of individual allele numbers. The resulting allelic profile is comprised of a string of the individual allele numbers separated by commas e.g., 1,4,3,1,1,1,1 in a pre-determined order, i.e. flaA, pilE, asd, mip, mompS, proA, neuA. Where all seven alleles are defined this now results in a single Sequence Type (ST). If an allele is missing, i.e not determined, a zero is entered for that position and no ST can be allocated; however the allelic profile can still be highly informative.
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References

Scaturro M., Losardo M., De Ponte G., Ricci ML. Comparison of three molecular methods used for subtyping of Legionella pneumophila strains isolated during an epidemic of Legionellosis in Rome. J Clin. Microbiol. 43: 5348-50
Gaia V., Fry N.K., Harrison T.G., Peduzzi R. 2003. Sequence-based typing of Legionella pneumophila serogroup 1 offers the potential for true portability in legionellosis outbreak investigation. J Clin Microbiol.;41:2932-9
Ratzow S, Gaia V, Helbig JH, Fry NK, Luck PC. 2007. Addition of neuA, the gene encoding N-acylneuraminate cytidylyl transferase, increases the discriminatory ability of the consensus sequence-based scheme for typing Legionella pneumophila serogroup 1 strains. J Clin Microbiol.45(6):1965-8.
Enright, MC, and Spratt BG 1998. A multilocus sequence typing scheme for Streptococcus pneumoniae: identification of clones associated with serious invasive disease. Microbiology 144:3049-60
Gaia V, Fry NK, Afshar B, Luck PC, Meugnier H, Etienne J, Peduzzi R, Harrison TG.2005, A consensus sequence-based epidemiological typing scheme for clinical and environmental isolates of Legionella pneumophila,J Clin Microbiol.;43:2047-52
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