Multiple-Locus Variable-Number Tandem Repeat Analysis of Dutch Bordetella pertussis Strains Reveals Rapid Genetic Changes with Clonal Expansion during the Late 1990s

Abstract

Bordetella pertussis, the causative agent of whooping cough, has remained endemic in The Netherlands despite extensive nationwide vaccination since 1953. In the 1990s, several epidemic periods have resulted in many cases of pertussis. We have proposed that strain variation has played a major role in the upsurges of this disease in The Netherlands. Therefore, molecular characterization of strains is important in identifying the causes of pertussis epidemiology. For this reason, we have developed a multiple-locus variable-number tandem repeat analysis (MLVA) typing system for B. pertussis. By combining the MLVA profile with the allelic profile based on multiple-antigen sequence typing, we were able to further differentiate strains. The relationships between the various genotypes were visualized by constructing a minimum spanning tree. MLVA of Dutch strains of B. pertussis revealed that the genotypes of the strains isolated in the prevaccination period were diverse and clearly distinct from the strains isolated in the 1990s. Furthermore, there was a decrease in diversity in the strains from the late 1990s, with a remarkable clonal expansion that coincided with the epidemic periods. Using this genotyping, we have been able to show that B. pertussis is much more dynamic than expected.

Direct molecular typing of Bordetella pertussis from clinical specimens submitted for diagnostic quantitative (real-time) PCR

“…Proof of concept for generating MLVA typing data from DNA extracts of clinical samples was demonstrated by Schouls et al (2004) when they generated 10 complete profiles from 17 samples that were positive for the IS481 PCR target. Using a modified MLVA method, we generated full profiles on .80 % of a collection of respiratory samples that scored positive for IS481 (using our in-house qPCR).…”

“…Unfortunately, it was not possible to confirm the identity of the species present in this particular sample. However, it is worth noting that B. bronchiseptica and B. parapertussis should generate complete profiles under this MLVA scheme and B. holmesii produces products in the VNTR2 and VNTR3 PCRs (Schouls et al, 2004;and our unpublished results).…”

“…Polymorphisms in the pertussis toxin promoter (ptxP) have also been proposed to affect the virulence of B. pertussis through increased Ptx production (Mooi et al, 2009;Mooi, 2010), although an increase in virulence was not seen in a recent study using a murine model of infection (Hegerle et al, 2012). Other methods designed to distinguish isolates, which are not linked to virulence factors, include PFGE, multilocus variablenumber tandem repeat analysis (MLVA) and genome-wide single nucleotide polymorphism (SNP) analysis (Mooi et al, 2000;Octavia et al, 2011;Schouls et al, 2004;van Gent et al, 2011).…”

“…Furthermore, diagnostic qPCR is generally accepted to be more sensitive than culture, and is gaining in popularity (Mattoo & Cherry, 2005). The ability to type bacterial DNA in qPCR samples will also be valuable in outbreak investigations, when PCR-positive samples, but no cultures, may be available.Proof of concept for generating MLVA typing data from DNA extracts of clinical samples was demonstrated by Schouls et al (2004) when they generated 10 complete profiles from 17 samples that were positive for the IS481 PCR target. Using a modified MLVA method, we generated full profiles on .80 % of a collection of respiratory samples that scored positive for IS481 (using our in-house qPCR).…”

Impact de la vaccination sur l’épidémiologie des maladies infectieuses : exemple de la coqueluche

“…L'analyse et la comparaison des isolats bactériens ont été réalisées, soit au niveau des protéines qu'ils expriment, soit au niveau de portions de leur génome, soit enfin au niveau de leur génome tout entier [22][23][24]. Il s'avère que le polymorphisme des isolats est très restreint.…”