Burkholderia pseudomallei, a saprophytic,
gram-negative aerobe, is the causative agent of melioidosis,
an infectious disease mainly restricted to South East Asia,
Northern Australia and other tropical and non-tropical regions.
Melioidosis manifests itself clinically as abcesses, pneumonia
and, at worst, as a fatal septicemia in susceptible hosts.
It belongs to a closely related group of organisms, which
incude Burkholderia mallei, the causative agent of
glanders in horses and other equines, and the avirulent saprophytic
species Burkholderia thailandensis, which was thought
until recently to be a biotype of B. pseudomallei capable
of assimilating arabinose. The MLST scheme developed for B.
pseudomallei is also applicable to these two latter species
and strains representing these species are available in the
REF - Daniel Godoy, Gaynor Randle,
Andrew J. Simpson, David M. Aanensen, Tyrone L. Pitt, Reimi
Kinoshita, and Brian G. Spratt. Multilocus Sequence Typing
and Evolutionary Relationships among the Causative Agents
of Melioidosis and Glanders, Burkholderia pseudomallei
and Burkholderia mallei. J. Clin. Microbiol. 2003;41
The B. pseudomallei MLST scheme has
been developed byDaniel Godoy (Imperial College) and Gaynor Randle (now at the
John Radcliffe Hospital, University of Oxford), in the laboratory
of Brian Spratt at the Department of Infectious Disease Epidemiology
at Imperial College London, in collaboration with Ty Pitt
at the Division of Hospital Infection, Central Public Health
Laboratory, Colindale, London, and Andrew Simpson at the Royal
Free Hospital, University College London, and Reimi Kinoshita
of the University of Hong Kong. For further details please
contact Erin Price (Erin Price)
Is it really B. pseudomallei?
MLST provides the best method for deciding whether an isolate is B.pseudomallei or another closely related species - see Help box on contatenation page. Click here
Obtaining an allelic profile and comparing your strains with
those in our database
The allelic profile of a B. pseudomallei
strain is obtained by sequencing internal fragments of seven
house-keeping genes. The primers for the amplification and
sequencing of these gene fragments can be obtained here.
The sequences must be obtained on both strands, and they must
be 100% accurate, since even a single error may convert a
known allele into a novel allele.
The sequences have to be trimmed so that
they correspond exactly to the region that we use to define
the alleles. The sequences of the seven loci from a typical
pneumococcus can be obtained here
and can be used to ensure that your sequences have been trimmed
For a query isolate, the sequences at the
seven loci have to be compared with those in our database.
Select the B. pseudomallei database, and the
locus query drop-down menu. Select
single locus and paste the correctly trimmed sequence
into the box. Select the appropriate locus in the drop-down
menu, followed by submit query.
The software will check that the sequence
is the correct length and that it does not contain any unrecognised
characters. A check is also made to see if the submitted sequence
is at least 70% similar to another allele at that locus (in
case you have cut and pasted a sequence into the wrong box).
If the sequence corresponds to a known allele,
the allele number will be returned. If the sequence
appears to be a new allele it should be compared with the
most similar locus (or loci) to check that any sequence differences
are real (this can be done using the Jalview module). If you are convinced you have a new allele,
the forward and reverse traces from the sequencer should be
sent to the curator
(firstname.lastname@example.org) who will check their quality and if OK
will assign a new allele number.
After you have obtained the allele numbers
at each locus for your query strain, you select profile
query and in the drop-down menu select allelic and
enter the seven allele numbers in the appropriate boxes and
submit. If the allelic profile is in the database,
the sequence type assigned to this allelic profile will be
returned. Otherwise the most similar allelic profile
will be returned. You can then search for isolates that have
allelic profiles that are similar to yours. For example, isolates
that have at least 4/7, 5/7 or 6/7 matches to the submitted
allelic profile and can show the relationships between your
query strain and these strains by using the Tree button.
Further details about strains that are identical,
or similar, to the submitted strain can be obtained by clicking
on the strain names.
Help boxes are available on some pages.