Evaluation and selection of tandem repeat loci for Streptococcus pneumoniae MLVA strain typing.
BACKGROUND
Precise identification of bacterial pathogens at the strain level is essential for epidemiological purposes. In Streptococcus pneumoniae, the existence of 90 different serotypes makes the typing particularly difficult and requires the use of highly informative tools. Available methods are relatively expensive and cannot be used for large-scale or routine typing of any new isolate. We explore here the potential of MLVA (Multiple Loci VNTR Analysis; VNTR, Variable Number of Tandem Repeats), a method of growing importance in the field of molecular epidemiology, for genotyping of Streptococcus pneumoniae.


RESULTS
Available genome sequences were searched for polymorphic tandem repeats. The loci identified were typed across a collection of 56 diverse isolates and including a group of serotype 1 isolates from Africa. Eventually a set of 16 VNTRs was proposed for MLVA-typing of S. pneumoniae. These robust markers were sufficient to discriminate 49 genotypes and to aggregate strains on the basis of the serotype and geographical origin, although some exceptions were found. Such exceptions may reflect serotype switching or horizontal transfer of genetic material.


CONCLUSIONS
We describe a simple PCR-based MLVA genotyping scheme for S. pneumoniae which may prove to be a powerful complement to existing tools for epidemiological studies. Using this technique we uncovered a clonal population of strains, responsible for infections in Burkina Faso. We believe that the proposed MLVA typing scheme can become a standard for epidemiological studies of S. pneumoniae.
Koeck
Jean-Louis
JL
Laboratoire de Biologie Clinique, HIA Robert Picqué, 351, Route de Toulouse, 33 140 Villenave d'Ornon, France. jlkoeck@gmail.com
Njanpop-Lafourcade
Berthe-Marie
BM
Cade
Sonia
S
Varon
Emmanuelle
E
Sangare
Lassana
L
Valjevac
Samina
S
Vergnaud
Gilles
G
Pourcel
Christine
C
D015373:Bacterial Typing Techniques; D016680:Genome, Bacterial; D005838:Genotype; D006801:Humans; D011008:Pneumococcal Infections / Q000175:diagnosis; D011110:Polymorphism, Genetic; D011650:Pulmonary Alveoli / Q000382:microbiology; D012091:Repetitive Sequences, Nucleic Acid; D013183:Sputum / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity