Bordetella pertussis isolates in Finland after acellular vaccination: serotype change and biofilm formation

OBJECTIVES

In Finland, whole cell pertussis vaccine (wP) was introduced in 1952 and was replaced by acellular pertussis vaccine (aP) without fimbrial (FIM) antigen in 2005. We aimed to analyse the changes in serotypes of circulating Bordetella pertussis before and after acellular vaccination and to explore the relationship between biofilm formation and serotype diversity after the introduction of aP vaccine.

METHODS

Serotyping of 1399 B. pertussis isolates collected at the Finnish National Reference Laboratory for Pertussis and Diphtheria in Turku, Finland, from 1974 to 2023 was performed by slide agglutination or indirect ELISA. Of 278 isolates collected after 2005, 53 were selected, genotyped for fim3 and fim2 alleles, and tested for biofilm formation. The selection criteria included maintaining a relatively equal distribution of isolates per time interval, ensuring approximately a 50:50 ratio of FIM2 (N = 26) and FIM3 (N = 27) serotypes. The reference strain Tohama I was used as a control.

RESULTS

During the wP era, the majority of circulating B. pertussis exhibited the FIM2 serotype. However, FIM3 strains have appeared since 1999 and become prevalent. After the implementation of aP vaccines, the distribution of serotypes has exhibited substantial variability. FIM3 isolates displayed an enhanced biofilm formation compared to FIM2 isolates (Geometric mean value (95% CI): 0.90 (0.79-1.03) vs. 0.75 (0.65-0.85); p < 0.05). Of the 27 FIM3 isolates, 8 harboured fim3-1 and 19 fim3-2 alleles. FIM3 isolates with fim3-2 allele were significantly associated with increased biofilm formation when compared to those with fim3-1 (1.07 (0.96-1.19) vs. 0.61 (0.52-0.72); p < 0.0001).

CONCLUSION

Following the implementation of aP vaccines, the distribution of serotypes in Finland has exhibited substantial variability. FIM3 isolates with the fim3-2 allele displayed an enhanced biofilm formation capability compared to FIM2 isolates.

Towards comprehensive understanding of bacterial genetic diversity: large-scale amplifications in Bordetella pertussis and Mycobacterium tuberculosis

Bacterial genetic diversity is often described solely using base-pair changes despite a wide variety of other mutation types likely being major contributors. Tandem duplication/amplifications are thought to be widespread among bacteria but due to their often-intractable size and instability, comprehensive studies of these mutations are rare. We define a methodology to investigate amplifications in bacterial genomes based on read depth of genome sequence data as a proxy for copy number. We demonstrate the approach with Bordetella pertussis, whose insertion sequence element-rich genome provides extensive scope for amplifications to occur. Analysis of data for 2430 B. pertussis isolates identified 272 putative amplifications, of which 94 % were located at 11 hotspot loci. We demonstrate limited phylogenetic connection for the occurrence of amplifications, suggesting unstable and sporadic characteristics. Genome instability was further described in vitro using long-read sequencing via the Nanopore platform, which revealed that clonally derived laboratory cultures produced heterogenous populations rapidly. We extended this research to analyse a population of 1000 isolates of another important pathogen, Mycobacterium tuberculosis. We found 590 amplifications in M. tuberculosis, and like B. pertussis, these occurred primarily at hotspots. Genes amplified in B. pertussis include those involved in motility and respiration, whilst in M. tuberuclosis, functions included intracellular growth and regulation of virulence. Using publicly available short-read data we predicted previously unrecognized, large amplifications in B. pertussis and M. tuberculosis. This reveals the unrecognized and dynamic genetic diversity of B. pertussis and M. tuberculosis, highlighting the need for a more holistic understanding of bacterial genetics.

Comparative genomics of Bordetella pertussis isolates from New Zealand, a country with an uncommonly high incidence of whooping cough

Whooping cough, the respiratory disease caused by Bordetella pertussis, has undergone a wide-spread resurgence over the last several decades. Previously, we developed a pipeline to assemble the repetitive B. pertussis genome into closed sequences using hybrid nanopore and Illumina sequencing. Here, this sequencing pipeline was used to conduct a more high-throughput, longitudinal screen of 66 strains isolated between 1982 and 2018 in New Zealand. New Zealand has a higher incidence of whooping cough than many other countries; usually at least twice as many cases per 100000 people as the USA and UK and often even higher, despite similar rates of vaccine uptake. To the best of our knowledge, these strains are the first New Zealand B. pertussis isolates to be sequenced. The analyses here show that, on the whole, genomic trends in New Zealand B. pertussis isolates, such as changing allelic profile in vaccine-related genes and increasing pertactin deficiency, have paralleled those seen elsewhere in the world. At the same time, phylogenetic comparisons of the New Zealand isolates with global isolates suggest that a number of strains are circulating in New Zealand, which cluster separately from other global strains, but which are closely related to each other. The results of this study add to a growing body of knowledge regarding recent changes to the B. pertussis genome, and are the first genetic investigation into B. pertussis isolates from New Zealand.

Clinical characteristics of 967 children with pertussis: a single-center analysis over an 8-year period in Beijing, China

The purpose of this study is to understand children’s clinical characteristics with pertussis and analyze risk factors on critical pertussis patients. Demographic data from patients with pertussis at Children’s Hospital affiliated to the Capital Institute of Pediatrics between March 2011 and December 2018 were collected. We retrospectively gathered more information with the positive exposure, vaccination, antibiotic usage before diagnosis, clinical manifestation, laboratory tests, therapy, and complications for hospitalized children. We divided the patients into severe and non-severe groups, comparing related factors and clinical characteristics among each group. In particular, we summarize the clinical features of the severe patients before aggravation. A total of 967 pertussis cases were diagnosed, of which 227 were hospitalized. The onset age younger than 3 months old accounted for the highest proportion, and 126 patients received hospitalization. For those patients, the incidence of post-tussive vomiting, paroxysmal cyanosis, post-tussive heart rate decrease, hypoxemia, severe pneumonia, and mechanical ventilation was significantly higher than that in the ≥ 3-month-old group (p < 0.05). Among 227 hospitalized patients, 54 suffered from severe pertussis. Risk factors for severe patients included early age of onset, pathogen exposure, and unvaccinated status. Cough paroxysms, post-tussive vomiting, paroxysmal cyanosis, facial flushing/cyanosis/fever during cough, increased WBC, and chest X-ray revealing pneumonia/consolidation/atelectasis were important indications of severe pertussis. Unvaccinated status was an independent risk factor for severe pertussis. The most vulnerable population was infants < 3 months old to pertussis, and may be on the severe end of the disease. Pediatricians must detect and treat severe cases promptly and recommend timely vaccination for all eligible children.

Comparative genomics of whole-cell pertussis vaccine strains from India

BACKGROUND

Despite high vaccination coverage using acellular (ACV) and whole-cell pertussis (WCV) vaccines, the resurgence of pertussis is observed globally. Genetic divergence in circulating strains of Bordetella pertussis has been reported as one of the contributing factors for the resurgence of the disease. Our current knowledge of B. pertussis genetic evolution in circulating strains is mostly based on studies conducted in countries using ACVs targeting only a few antigens used in the production of ACVs. To better understand the adaptation to vaccine-induced selection pressure, it will be essential to study B. pertussis populations in developing countries which are using WCVs. India is a significant user and global supplier of WCVs. We report here comparative genome analyses of vaccine and clinical isolates reported from India. Whole-genome sequences obtained from vaccine strains: WCV (J445, J446, J447 and J448), ACV (BP165) were compared with Tohama-I reference strain and recently reported clinical isolates from India (BPD1, BPD2). Core genome-based phylogenetic analysis was also performed using 166 isolates reported from countries using ACV.

RESULTS

Whole-genome analysis of vaccine and clinical isolates reported from India revealed high genetic similarity and conserved genome among strains. Phylogenetic analysis showed that clinical and vaccine strains share genetic closeness with reference strain Tohama-I. The allelic profile of vaccine strains (J445:ptxP1/ptxA2/prn1/fim2-1/fim3-1; J446: ptxP2/ptxA4/prn7/fim2-2/fim3-1; J447 and J448: ptxP1/ptxA1/ prn1/fim2-1/fim3-1), which matched entirely with clinical isolates (BPD1:ptxP1/ptxA1/prn1/fim2-1 and BPD2: ptxP1/ptxA1/prn1/fim2-1) reported from India. Multi-locus sequence typing (MLST) demonstrated the presence of dominant sequence types ST2 and primitive ST1 in vaccine strains which will allow better coverage against circulating strains of B. pertussis.

CONCLUSIONS

The study provides a detailed characterization of vaccine and clinical strains reported from India, which will further facilitate epidemiological studies on genetic shifts in countries which are using WCVs in their immunization programs.

Rare Detection of Bordetella pertussis Pertactin-Deficient Strains in Argentina

Pertussis resurgence had been attributed to waning vaccine immunity and Bordetella pertussis adaptation to escape vaccine-induced immunity. Circulating bacteria differ genotypically from strains used in production of pertussis vaccine. Pertactin-deficient strains are highly prevalent in countries that use acellular vaccine (aP), suggesting strong aP-imposed selection of circulating bacteria. To corroborate this hypothesis, systematic studies on pertactin prevalence of infection in countries using whole-cell vaccine are needed. We provide pertussis epidemiologic data and molecular characterization of B. pertussis isolates from Buenos Aires, Argentina, during 2000–2017. This area used primary vaccination with whole-cell vaccine. Since 2002, pertussis case incidences increased at regular 4-year outbreaks; most cases were in infants <1 year of age. Of the B. pertussis isolates analyzed, 90.6% (317/350) contained the ptxP3-ptxA1-prn2-fim3-2 allelic profile. Immunoblotting and sequencing techniques detected only the 2 pertactin-deficient isolates. The low prevalence of pertactin-deficient strains in Argentina suggests that loss of pertactin gene expression might be driven by aP vaccine.

Genomic Survey of Bordetella pertussis Diversity, United States, 2000-2013

We characterized 170 complete genome assemblies from clinical Bordetella pertussis isolates representing geographic and temporal diversity in the United States. These data capture genotypic shifts, including increased pertactin deficiency, occurring amid the current pertussis disease resurgence and provide a foundation for needed research to direct future public health control strategies.

Pertactin-Negative and Filamentous Hemagglutinin-Negative Bordetella pertussis, Australia, 2013-2017

During the 2008–2012 pertussis epidemic in Australia, pertactin (Prn)–negative Bordetella pertussis emerged. We analyzed 78 isolates from the 2013–2017 epidemic and documented continued expansion of Prn-negative ptxP3 B. pertussis strains. We also detected a filamentous hemagglutinin-negative and Prn-negative B. pertussis isolate.

Genetic analysis of clinical and vaccine strains of Bordetella pertussis by Pulsed-Field Gel Electrophoresis (PFGE), Multi Locus Sequence Typing (MLST) and serotyping

In spite of high vaccination coverage in the Expanded Program of Immunization (EPI), pertussis has not been eradicated yet and the re-emergence of the disease is still reported worldwide. The genetic divergence study of circulating clinical strains of Bordetella pertussis among the population with high vaccination coverage is a useful tool to have an insight in the understanding of genetic patterns of this bacterium and deviation of them from vaccine strains. Different methods are accessible for studying of Bordetella pertussis that can perform appropriate assessment between populations. Strains used in this study were a collection of two pertussis vaccine strains used to create killed pertussis vaccine over years at Razi Vaccine and Serum Research Institute, 10 clinical and 2 reference strains (ATCC9797 and Tohama I) in Multilocus Sequence Typing (MLST), Pulsed-Field Gel Electrophoresis (PFGE), and serotyping. The genetic profiles of vaccine working and master seeds showed no important change(s) in frequencies of fingerprint types investigated in the vaccine strains and had homogeneity in PFGE method where the clinical isolates showed diversity in genetic profile. Serotyping method showed that all of 10 clinical strains expressing Fim 3. In MLST study, seven housekeeping genes including adk, pgm, fum C, tyr B, gly A, pep A and icd were analyzed which showed no changes in the sequence of clinical and vaccine strains with 100% homology. The genes that cause pathogenicity like ptxC, tcfA and fhaB were also evaluated and the results illustrated heterogeneity in the vaccine and circulating strains.

Genomic Sequencing of Bordetella pertussis for Epidemiology and Global Surveillance of Whooping Cough

Bordetella pertussis causes whooping cough, a highly contagious respiratory disease that is reemerging in many world regions. The spread of antigen-deficient strains may threaten acellular vaccine efficacy. Dynamics of strain transmission are poorly defined because of shortcomings in current strain genotyping methods. Our objective was to develop a whole-genome genotyping strategy with sufficient resolution for local epidemiologic questions and sufficient reproducibility to enable international comparisons of clinical isolates. We defined a core genome multilocus sequence typing scheme comprising 2,038 loci and demonstrated its congruence with whole-genome single-nucleotide polymorphism variation. Most cases of intrafamilial groups of isolates or of multiple isolates recovered from the same patient were distinguished from temporally and geographically cocirculating isolates. However, epidemiologically unrelated isolates were sometimes nearly undistinguishable. We set up a publicly accessible core genome multilocus sequence typing database to enable global comparisons of B. pertussis isolates, opening the way for internationally coordinated surveillance.

Bordetella pertussis Infection in Infants and Young Children in Shanghai, China, 2016-2017: Clinical Features, Genotype Variations of Antigenic Genes and Macrolides Resistance

BACKGROUND

The global resurgence of pertussis in countries with high vaccination coverage has been a concern of public health.

METHODS

Nasopharyngeal swabs were collected for Bordetella pertussis culture from children with suspected pertussis. Clinical and vaccination information were reviewed through electronic medical chart and immunization record. Antibiotics susceptibility was evaluated using E-test for erythromycin, azithromycin, clarithromycin and sulfamethoxazole/trimethoprim. The MLST genotypes and 7 antigenic genes (ptxP, ptxA, ptxC, Prn, fim3, fim2 and tcfA) of Bordetella pertussis were identified by polymerase chain reaction amplification and sequencing.

RESULTS

During January 2016 to September 2017, a total of 141 children 1-48 months of age were culture-confirmed with pertussis, of whom 98 (69.5%) were younger than 6 months, 25 (17.7%) had completed at least 3 doses of DTaP and 75 (53.2%) had a clear exposure to household members with persistent cough. Fully vaccinated cases manifested milder disease than unvaccinated and not-fully vaccinated cases. All strains were MLST2. High-virulent strains characteristic of ptxP3/prn2/ptxC2 constituted 41.1% (58/141) and were all susceptible to macrolides while low-virulent strains characteristic of ptxP1/prn1/ptxC1 constituted 58.9% (83/141) and 97.6% (81/83), respectively, were highly resistant to macrolides.

CONCLUSIONS

Pertussis is resurging among infants and young children in Shanghai, and household transmission is the main exposure pathway. The high-virulent strains harboring ptxP3/prn2/ptxC2 and the macrolide-resistant Bordetella pertussis strains are quite prevalent. These issues impose a public health concern in Shanghai. Our findings are important to modify the DTaP vaccination strategy and the management guideline of pertussis in China.

Pertussis epidemiology in Tunisian infants and children and characterization of Bordetella pertussis isolates: results of a 9-year surveillance study, 2007 to 2016

PURPOSE

Pertussis remains a public health concern in most countries. Our study aimed to prospectively explore the epidemiology of pertussis in the Tunis area of Tunisia between 2007 and 2016, and to characterize the virulence-associated genes of the collected Bordetella pertussis isolates.

METHODOLOGY

Infants and children hospitalized at the Children's Hospital of Tunis, Tunisia, between 2007 and 2016 for suspicion of pertussis were enrolled in the study. Culture and real-time PCR (qPCR) assays targeting IS481, IS1001, recA, H-IS1001 and ptxP were used to confirm the pertussis diagnosis. Phenotypic and genotypic characterization of recovered isolates was performed.Results/Key findings. A total of 1844 children were included in the study. Overall, 306 children (16.6 %) with Bordetella infection were confirmed by qPCR. Among them, 265 (86.6 %) were confirmed as having B. pertussis (IS481+, ptxP+, H-IS1001-), 18 (5.9 %) as having Bordetella parapertussis (IS481-, IS1001+) and 11 (3.6 %) as having Bordetella spp. (IS481+, ptxP-, H-IS1001-). No Bordetella holmesii (IS481+, IS1001-, H-IS1001+) was identified. The estimated pertussis incidence in the Tunis area was 134/100 000 in children aged less than 5 years. Two epidemic peaks were observed in 2009 and 2014. Ten B. pertussis isolates were cultured and characterized. Deficiency in pertactin expression was not observed, and genotyping of the isolates revealed a predominant allelic profile: ptxP3-ptxA1-prn2-fim2-1-fim3-2.

CONCLUSION

This study demonstrated that pertussis is still present as a cyclical disease in Tunisia, despite high primo-vaccination coverage with a pertussis whole-cell vaccine. The predominant genotype of Tunisian B. pertussis isolates is similar to isolates circulating in countries using the acellular vaccine.

Direct molecular typing of Bordetella pertussis from nasopharyngeal specimens in China in 2012-2013

Data on the molecular epidemiology of Bordetella pertussis are limited in developing countries where whole-cell pertussis vaccines (WCVs) have been used. The aim of this study was to determine the genotypes of circulating B. pertussis in China by direct molecular typing of clinical specimens. DNA extracts of 122 nasopharyngeal swabs (NPs) positive for B. pertussis by polymerase chain reaction (PCR) (targeting IS481 and ptx-Pr) from 2012 to 2013 were used for typing using the multiple-locus variable number tandem repeat analysis (MLVA) and also by PCR-based multilocus sequence typing (MLST) of B. pertussis virulence genes (ptxP, prn, and fim3). One hundred and eight DNA extracts (89 %) generated a complete MLVA type (MT). Among the 18 MTs obtained, MT55 (52 %) and MT104 (13 %) were the most common. MT27, which is linked to the ptxP3 allele and is prevalent in many developed countries using acellular pertussis vaccines (ACVs), was only found in 7 (6 %) DNA extracts. Eighty-seven DNA extracts (71 %) produced a complete multiantigen sequence typing (MAST) type. Of them, 77 (89 %) had the ptxP1/prn1/fim3-1 allele profile. Four DNA extracts (5 %) had the ptxP3/prn2/fim3-2 profile and 3 (4 %) had the ptxP3/prn1/fim3-2 allele profile. These seven DNA extracts also harbored MT27. Our result shows that B. pertussis circulating in China was different from those found in countries where ACVs have been in use, supporting the notion that selection pressure induced by WCVs and ACVs on the bacterial population differs.

[Antigenic variability of Bordetella pertussis strains isolated in 1967-2010 in the Czech Republic--possible explanation for the rise in cases of pertussis?]

OBJECTIVE

Comparison of antigenic structures of Bordetella pertussis (B. pertussis) strains isolated from 1967 to 2010 in the Czech Republic.

MATERIAL AND METHODS

Seventy strains of B. pertussis were referred to the National Reference Laboratory (NRL) for Pertussis and Diphtheria within the surveillance of pertussis from all over the Czech Republic (CR) between 1967 and 2010. To study the strains, the analysis was performed of the genome sequences encoding the surface immunogenic structures--the pertussis toxin S1 subunit gene (ptxA), pertactin gene region 1 (prnA), type 3 fimbriae gene (fim3)--and pertussis toxin promoter (ptxP) responsible for the regulation of the production of pertussis toxin.

RESULTS

For the study set of B. pertussis strains, the sequencing analysis revealed changes in all genomic regions studied. The isolates from three periods differ in the allelic profile. In period I (19671978) with the use of whole cell pertussis vaccine (wP), the following two profiles were the most common: ptxP(1), ptxA(2), prnA(1), fim3(1) and ptxP(1), ptxA(1), prnA(3), fim3(1). In period 2 (19902007) with the switch to acellular pertussis vaccine (aP), the most common profile was: ptxP(3), ptxA(1), prnA(2), fim3(2). Period 3 (20082010) with the use of aP was characterized by the predominance of the following two profiles which had never been found in period 1: ptxP(3), ptxA(1), prnA(2), fim3(2) and ptxP(3) ptxA(1), prnA(2), fim3(1).

CONCLUSIONS

Sequencing of the genomic regions ptxP, ptxA, prnA, and fim3 of B. pertussis strains isolated in the CR between 1967 and 2010 confirmed changes in the allelic variants of these regions. The incidence of strains carrying the new allelic variants was increasing after 1995 at the expense of those carrying the original variants. The study results can be interpreted as a partial genetic escape of pathogenic strains of B. pertussis beyond the reach of the pertussis vaccines.

Genetic Variation of Bordetella pertussis in Austria

In Austria, vaccination coverage against Bordetella pertussis infections during infancy is estimated at around 90%. Within the last years, however, the number of pertussis cases has increased steadily, not only in children but also in adolescents and adults, indicating both insufficient herd immunity and vaccine coverage. Waning immunity in the host and/or adaptation of the bacterium to the immunised hosts could contribute to the observed re-emergence of pertussis. In this study we therefore addressed the genetic variability in B. pertussis strains from several Austrian cities. Between the years 2002 and 2008, 110 samples were collected from Vienna (n = 32), Linz (n = 63) and Graz (n = 15) by nasopharyngeal swabs. DNA was extracted from the swabs, and bacterial sequence polymorphisms were examined by MLVA (multiple-locus variable number of tandem repeat analysis) (n = 77), by PCR amplification and conventional Sanger sequencing of the polymorphic regions of the prn (pertactin) gene (n = 110), and by amplification refractory mutation system quantitative PCR (ARMS-qPCR) (n = 110) to directly address polymorphisms in the genes encoding two pertussis toxin subunits (ptxA and ptxB), a fimbrial adhesin (fimD), tracheal colonisation factor (tcfA), and the virulence sensor protein (bvgS). Finally, the ptxP promoter region was screened by ARMS-qPCR for the presence of the ptxP3 allele, which has been associated with elevated production of pertussis toxin. The MLVA analysis revealed the highest level of polymorphisms with an absence of MLVA Type 29, which is found outside Austria. Only Prn subtypes Prn1/7, Prn2 and Prn3 were found with a predominance of the non-vaccine type Prn2. The analysis of the ptxA, ptxB, fimD, tcfA and bvgS polymorphisms showed a genotype mixed between the vaccine strain Tohama I and a clinical isolate from 2006 (L517). The major part of the samples (93%) displayed the ptxP3 allele. The consequences for the vaccination strategy are discussed.

Minimum inhibitory concentrations of erythromycin and other antibiotics for Czech strains of Bordetella pertussis

AIM OF THE STUDY

To test the susceptibility to first-line and alternative antibiotics of 70 Bordetella pertussis (B. pertussis) strains recovered from patients with whooping cough through national pertussis surveillance in the Czech Republic (CR) in 1967-2010.

MATERIAL AND METHODS

The minimum inhibitory concentrations (MICs) of erythromycin, clarithromycin, azithromycin, ciprofloxacin, and co-trimoxazole were tested by the reference agar dilution method on Bordet-Gengou agar with 15 % defibrinated sheep blood.

RESULTS

Each of the 70 study strains was inhibited by two concentrations of erythromycin and azithromycin (0.06 and 0.12 mg/l) and by three concentrations of clarithromycin (0.03, 0.06, and 0.12 mg/l), with the highest concentration of the MIC range being 0.12 mg/l for all these similar antibiotics. Tested in a 2-fold geometric dilution series, the concentration of erythromycin required to inhibit 90 % of the study strains (MIC90) was one dilution step lower (0.06 mg/l) than those of clarithromycin and azithromycin (0.12 mg/l). All study strains were inhibited by a single concentration of ciprofloxacin (0.06 mg/l) and two concentrations of co-trimoxazole (0.12 and 0.25 mg/l).

CONCLUSION

The panel of 70 Czech strains of B. pertussis appears to be homogeneous in terms of the MICs of the antibiotics tested, with two to three low concentrations being effective against all strains. To be inhibited, no strain required a higher concentration of erythromycin, clarithromycin, azithromycin, ciprofloxacin, or co-trimoxazole.

Global population structure and evolution of Bordetella pertussis and their relationship with vaccination

Bordetella pertussis causes pertussis, a respiratory disease that is most severe for infants. Vaccination was introduced in the 1950s, and in recent years, a resurgence of disease was observed worldwide, with significant mortality in infants. Possible causes for this include the switch from whole-cell vaccines (WCVs) to less effective acellular vaccines (ACVs), waning immunity, and pathogen adaptation. Pathogen adaptation is suggested by antigenic divergence between vaccine strains and circulating strains and by the emergence of strains with increased pertussis toxin production. We applied comparative genomics to a worldwide collection of 343 B. pertussis strains isolated between 1920 and 2010. The global phylogeny showed two deep branches; the largest of these contained 98% of all strains, and its expansion correlated temporally with the first descriptions of pertussis outbreaks in Europe in the 16th century. We found little evidence of recent geographical clustering of the strains within this lineage, suggesting rapid strain flow between countries. We observed that changes in genes encoding proteins implicated in protective immunity that are included in ACVs occurred after the introduction of WCVs but before the switch to ACVs. Furthermore, our analyses consistently suggested that virulence-associated genes and genes coding for surface-exposed proteins were involved in adaptation. However, many of the putative adaptive loci identified have a physiological role, and further studies of these loci may reveal less obvious ways in which B. pertussis and the host interact. This work provides insight into ways in which pathogens may adapt to vaccination and suggests ways to improve pertussis vaccines. IMPORTANCE Whooping cough is mainly caused by Bordetella pertussis, and current vaccines are targeted against this organism. Recently, there have been increasing outbreaks of whooping cough, even where vaccine coverage is high. Analysis of the genomes of 343 B. pertussis isolates from around the world over the last 100 years suggests that the organism has emerged within the last 500 years, consistent with historical records. We show that global transmission of new strains is very rapid and that the worldwide population of B. pertussis is evolving in response to vaccine introduction, potentially enabling vaccine escape.

[Evaluation of Bordetella pertussis strains toxicity in vitro using CHO cell lines]

INTRODUCTION

Whooping cough is still a significant disease with regular outbreaks despite the decades of mass vaccination and good immunization coverage. The aim of this study was to evaluate the capacity of Bordetella pertussis toxicity testing among strains harbouring different alleles of the pertussis toxin promoter ptxP using hamster ovary cell line CHO (Hamster Ovary).

METHODS

The study assessed the limits of detection of high and low Ptx levels producing strains using a reference preparation ofpertussis toxin and B. pertussis strains that increased toxicity in vitro has been previously correlated with ptxP3 allele presence.

RESULTS

The presence of the strong agglomerates on CHO cell line confirmed the higher toxicity of B. pertussis strains isolated in France. Preliminary toxicity study with use of selected strains of B. pertussis differing by ptxP1 and ptxP3 promdter alleles with respect to relevant reference preparation indicate lower toxicity of strains B. pertussis isolated in Poland.

CONCLUSIONS

The toxicity measured on CHO line will be used to assess the virulence of all available B. pertussis strains isolated in Poland.

Effectiveness of experimental whole-cell pertussis vaccines in murine model

INTRODUCTION

Since the 1990s pertussis re-emergence has been observed in many highly immunized countries. Genetic divergence between circulating B. pertussis isolates and vaccine strains has been suggested as one of the reasons responsible for the resurgence of pertussis. This divergence was observed in some studies to affect the effectiveness of pertussis vaccine when tested in murine model. In the study, using the murine intranasal challenge model we evaluated the effectiveness of four experimental wP vaccines, prepared with B. pertussis isolates belonging to different PFGE groups, in the elimination of the bacterial infection induced with mixture of the four B. pertussis isolates.

METHODS

The experimental wP vaccines were prepared with clinical isolates belonging to PFGE groups V, IVγ and C, used individually or together. The mixture of four isolates classified to PFGE groups V, IVγ, III and C was used as intranasal mice challenge. The chosen strains represent PFGE groups characteristic for isolates currently circulating in Europe (PFGE groups IV and V), specific for Poland (PFGE group C) and vaccine strains of Polish wP vaccine (PFGE group III). Additionally, to study bacterial fitness, changes in the proportions of four isolates used as the challenge within the course of infection in mice lungs were monitored.

RESULTS AND CONCLUSIONS

All experimental wP vaccines were found to be equally effective in eliminating B. pertussis from mice lungs. Their effectiveness was independent on PFGE group of vaccine strain. The results on bacterial fitness during mixed infections induced in the non-immunized mice found the isolate of PFGE group IVγ dominating among the other isolates used in the mixture belonging to PFGE group III, V, and C. This data might suggest that the isolates belonging to PFGE group IV, so commonly seen in Europe, might be more fitted to explore in conditions of waning immunity.

[Reproducibility of Fim2 and Fim3 antigens determination in Bordetella pertussis by serotyping method]

INTRODUCTION

Serotyping is a commonly used method to characterize the presence of Fimbriae 2 and 3 in Bordetella pertussis strains for epidemiological purposes and optimal choice of strain composition of the pertussis whole-cell vaccine. Monoclonal antisera against Fim2 and Fim3 are recommended to be used for microplate serotyping instead ofpolyclonal. Reliable evaluation offimbriae expressed by B. pertussis strains influence interpretation of vaccine-driven strain evolution.

METHODS

To evaluate the impact of tests conditions on the reproducibility of serotyping, results of serotyping based on a standardized protocol for microplate agglutination with monoclonal antisera performed in three different accredited laboratories were compared. For the study isolates of three vaccine strains of B. pertussis deposited within seed lot system originating from different liofilization lots were compared.

RESULTS

Lack of the complete agreement on serotyping results among three labs might relates to the differences of media used, subjective reading, test conditions, and specificity of the reagents.

CONCLUSIONS

Serotyping results should be interpreted with caution and the type of media and culture conditions used should be precisely recommended after validation studies. Inconsistent results should be confirmed using an alternative technique, eg. ELISA or by reference laboratory.

Small mutations in Bordetella pertussis are associated with selective sweeps

Bordetella pertussis is the causative agent of pertussis, a highly contagious disease of the human respiratory tract. Despite high vaccination coverage, pertussis has resurged and has become one of the most prevalent vaccine-preventable diseases in developed countries. We have proposed that both waning immunity and pathogen adaptation have contributed to the persistence and resurgence of pertussis. Allelic variation has been found in virulence-associated genes coding for the pertussis toxin A subunit (ptxA), pertactin (prn), serotype 2 fimbriae (fim2), serotype 3 fimbriae (fim3) and the promoter for pertussis toxin (ptxP). In this study, we investigated how more than 60 years of vaccination has affected the Dutch B. pertussis population by combining data from phylogeny, genomics and temporal trends in strain frequencies. Our main focus was on the ptxA, prn, fim3 and ptxP genes. However, we also compared the genomes of 11 Dutch strains belonging to successful lineages. Our results showed that, between 1949 and 2010, the Dutch B. pertussis population has undergone as least four selective sweeps that were associated with small mutations in ptxA, prn, fim3 and ptxP. Phylogenetic analysis revealed a stepwise adaptation in which mutations accumulated clonally. Genomic analysis revealed a number of additional mutations which may have a contributed to the selective sweeps. Five large deletions were identified which were fixed in the pathogen population. However, only one was linked to a selective sweep. No evidence was found for a role of gene acquisition in pathogen adaptation. Our results suggest that the B. pertussis gene repertoire is already well adapted to its current niche and required only fine tuning to persist in the face of vaccination. Further, this work shows that small mutations, even single SNPs, can drive large changes in the populations of bacterial pathogens within a time span of six to 19 years.

SNP-based typing: a useful tool to study Bordetella pertussis populations

To monitor changes in Bordetella pertussis populations, mainly two typing methods are used; Pulsed-Field Gel Electrophoresis (PFGE) and Multiple-Locus Variable-Number Tandem Repeat Analysis (MLVA). In this study, a single nucleotide polymorphism (SNP) typing method, based on 87 SNPs, was developed and compared with PFGE and MLVA. The discriminatory indices of SNP typing, PFGE and MLVA were found to be 0.85, 0.95 and 0.83, respectively. Phylogenetic analysis, using SNP typing as Gold Standard, revealed false homoplasies in the PFGE and MLVA trees. Further, in contrast to the SNP-based tree, the PFGE- and MLVA-based trees did not reveal a positive correlation between root-to-tip distance and the isolation year of strains. Thus PFGE and MLVA do not allow an estimation of the relative age of the selected strains. In conclusion, SNP typing was found to be phylogenetically more informative than PFGE and more discriminative than MLVA. Further, in contrast to PFGE, it is readily standardized allowing interlaboratory comparisons. We applied SNP typing to study strains with a novel allele for the pertussis toxin promoter, ptxP3, which have a worldwide distribution and which have replaced the resident ptxP1 strains in the last 20 years. Previously, we showed that ptxP3 strains showed increased pertussis toxin expression and that their emergence was associated with increased notification in the Netherlands. SNP typing showed that the ptxP3 strains isolated in the Americas, Asia, Australia and Europe formed a monophyletic branch which recently diverged from ptxP1 strains. Two predominant ptxP3 SNP types were identified which spread worldwide. The widespread use of SNP typing will enhance our understanding of the evolution and global epidemiology of B. pertussis.

Strain variation among Bordetella pertussis isolates circulating in Poland after 50 years of whole-cell pertussis vaccine use

In the present study, clinical isolates of Bordetella pertussis collected in Poland from 1960 to 2005 were analyzed by pulsed-field gel electrophoresis (PFGE) according to protocols recommended in previous studies. Among the 110 isolates from 1995 to 2005, 59 PFGE patterns were found, most of which were different from those currently circulating in other European Union (EU) countries for which data are available. The PFGE patterns of currently disseminating B. pertussis clones were found within PFGE groups III and IV, as elsewhere in the EU, and in newly identified clusters A and C. Up to 70, 26, and 4%, respectively, of the currently isolated strains in Poland harbored ptxA1-prn1, ptxA1-prn2, and ptxA1-prn3 allele combinations, and most (82%) were found to be of the Fim2 phenotype. Differences in the extent of heterogeneity estimated by PFGE typing in B. pertussis populations circulating in Poland in comparison to other EU countries may be due to the different vaccine composition strategy, since routine pertussis vaccination was initiated in Poland in 1960.

A specific real-time PCR assay for the detection of Bordetella pertussis

A novel real-time PCR (RT-PCR) assay was developed for detection of Bordetella pertussis in respiratory specimens by targeting the pertactin gene. In vitro evaluation with reference strains and quality control samples showed analytical sensitivity equivalent to and specificity superior to those of PCR assays which target the IS481 element. The pertactin-based RT-PCR assay offers better discrimination between B. pertussis and other Bordetella species than previously described assays.

Pulsed-field gel electrophoresis, pertactin, pertussis toxin S1 subunit polymorphisms, and surfaceome analysis of vaccine and clinical Bordetella pertussis strains

To add new insight to our previous work on the molecular epidemiology of Bordetella pertussis in Argentina, the prn and ptxS1 gene sequences and pulsed-field gel electrophoresis (PFGE) profiles of 57 clinical isolates obtained during two periods, 1969 to 1989 and 1997 to 2006, were analyzed. Non-vaccine-type ptxS1A was detected in isolates obtained since 1969. From 1989 on, a shift of predominance from the vaccine prn1 type to the nonvaccine prn2 type was observed. This was also reflected in a transition of PFGE group IV to group VI. These results show that nonvaccine B. pertussis strains are currently circulating. To analyze whether the observed genomic divergences between vaccine strains and clinical isolates have functional implications, protection assays using the intranasal mouse challenge model were performed. For such experiments, the clinical isolate B. pertussis 106 was selected as representative of circulating bacteria, since it came from the major group of the PFGE dendrogram (PFGE group VI). Groups of mice were immunized either with diphtheria-tetanus-whole-cell pertussis vaccine (ptxS1B prn1) or a vaccine prepared by us containing B. pertussis 106. Immunized mice were then challenged with a B. pertussis vaccine strain (Tohama, harboring ptxS1B and prn1) or the clinical isolate B. pertussis 106 (ptxS1A prn2). An adequate bacterial-elimination rate was observed only when mice were immunized and challenged with the same kind of strain. For further characterization, comparative proteomic profiling of enriched membrane proteins was done using three vaccine strains and the selected B. pertussis 106 clinical isolate. By matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis, a total of 54 proteins were identified. This methodology allowed us to detect differing proteins among the four strains studied and, in particular, to distinguish the three vaccine strains from each other, as well as the vaccine strains from the clinical isolate. The differing proteins observed have cellular roles associated with amino acid and carbohydrate transport and metabolism. Some of them have been proposed as novel vaccine candidate proteins for other pathogens. Overall, the global strategy described here is presented as a good tool for the development of next-generation acellular vaccines.

[Modern strains of Bordetella pertussis: immunobiological properties and vaccine improvement]

Strains of B. pertussis isolated from patients in Moscow in 2001-2005 as well as strains included in locally produced diphtheria-tetanus-whole cell pertussis (DTP) vaccine were studied. Nucleotide sequences in genes of pertactin and S1-subunit of pertussis toxin of isolated strains, their immunobiological properties and opportunity to use for producing of the acellular pertussis vaccine were determined. Genes of pertactin and S1-subunit of pertussis toxin in the isolated wild strains differed from the same genes in strains included in the local DTP vaccine. Majority of the isolated strains belonged to serotype 1.0.3 and were markedly virulent.

Pertussis in Argentina and France

We have studied the epidemiology of pertussis in two countries, Argentina and France, which have similar histories of long-term mass vaccination with a whole-cell vaccine. Both countries display a comparable epidemiology, with an increase of the incidence of the disease in non-vaccinated newborns. We used pulsed-field gel electrophoresis (PFGE) analysis and genotyping to compare Bordetella pertussis clinical isolates recovered in Argentina and France in 2001-2004. The majority of the isolates harbors prn2 allele and belongs to PFGE IVbeta group. Isolates were found to be very similar genetically suggesting a common evolution of the disease in these two countries using the same vaccine.

Prevention of pertussis: Recommendations derived from the second Global Pertussis Initiative roundtable meeting

The Global Pertussis Initiative (GPI) was established in 2001 to assess the global extent of the ongoing problem of pertussis and to evaluate and prioritize pertussis control strategies. Exchange of data, knowledge, and experience, facilitated by discussion and debate, resulted in the formulation, in 2002, of the following recommendation: all countries should consider expanding existing vaccination strategies to include adding pertussis booster doses to pre-school children (4-6 years old), to adolescents, and to those specific adults that have the highest risk of transmitting Bordetella pertussis infection to vulnerable infants. The GPI met again in 2005, where it reinforced its previous recommendation for universal adolescent immunization. Additionally, the GPI recommended implementation of the cocoon strategy (immunization of family members and close contacts of the newborn) in countries where it is economically feasible, and encouraged efforts toward global standardization of pertussis disease clinical definitions and diagnostics. Universal adult vaccination is a logical goal for the ultimate elimination of pertussis disease, but feasibility issues remain obstacles to implementation.

Detection and differentiation of Bordetella spp. by real-time PCR

Molecular detection of Bordetella pertussis DNA is a sensitive and specific method for the rapid diagnosis of pertussis. In this study, a new molecular assay for the detection and differentiation of Bordetella spp. based on automated DNA extraction and real-time PCR was evaluated. The analytical sensitivity of the new assay was determined by Probit analysis of serial dilutions of both cloned PCR products IS481 and IS1001 and cell suspensions of B. pertussis, B. parapertussis, and B. bronchiseptica. The specificity was analyzed by testing a number of pathogens producing respiratory infections. Moreover, a total of 92 clinical samples were investigated. The results were compared to those obtained by an in-house assay based on manual DNA extraction, followed by real-time PCR and detection of IS481. The analytical sensitivity of the new assay for the detection of IS481 and IS1001 was determined to be 2.2 and 1.2 genome equivalents/mul, respectively. The analytical sensitivity for the detection of B. pertussis, B. parapertussis, and B. bronchiseptica was determined to be 1.6, 1.0, and 2.7 genome equivalents/mul, respectively. When clinical specimens were tested with the new assay, 46 of 92 were found to be positive for Bordetella DNA. With the in-house assay, 45 samples tested positive. The new molecular assay proved to be suitable for the rapid diagnosis of pertussis in the routine diagnostic laboratory.

Multitarget PCR for diagnosis of pertussis and its clinical implications

PCR has greatly facilitated pertussis diagnosis due to the speed, sensitivity, and specificity of this assay compared to other detection methods. Various single-target PCR assays are currently utilized, but none is universally considered to be the "gold standard." Our aim was to assess the use of multitarget versus single-target PCR for the diagnosis of pertussis in clinical samples. PCR assays targeting insertion sequence IS481 (IS), pertussis toxin ptxA promoter region (PT), and outer membrane porin (PO), or recA (RA) were evaluated in respiratory specimens collected from 4,442 patients with suspected pertussis. The diagnosis of pertussis was confirmed in 309 (6.96%) patients by the 3-target IS-PT-PO/RA PCR versus 247 (5.56%) by the conventional single-target IS (P=0.007). Compared to single-target IS, the three-target combination increased the proportion of positive specimens by 1.25-fold, and two-target combinations increased the proportion of positive specimens by 1.10- to 1.24-fold. In addition, nine cases of B. parapertussis infection were also confirmed by using the discriminative features of this multitarget PCR. Of the 89 culture-proven pertussis cases, 17 (19.1%) and 5 of the 16 patients (31.3%) admitted to intensive care unit would have been missed had only the single-target IS PCR been applied. Patients with mild disease (P=0.004) and shorter hospitalization (P=0.006) were less likely to have positive cultures. This consensus generating real-time PCR approach permits a sensitive detection, as well as an accurate species identification of the causative Bordetella pathogens for the timely management of patients.

Characterization of a highly conserved island in the otherwise divergent Bordetella holmesii and Bordetella pertussis genomes

The recently discovered pathogen Bordetella holmesii has been isolated from the airways and blood of diseased humans. Genetic events contributing to the emergence of B. holmesii are not understood, and its phylogenetic position among the bordetellae remains unclear. To address these questions, B. holmesii strains were analyzed by comparative genomic hybridization (CGH) to a Bordetella pertussis microarray and by multilocus sequence typing. Both methods indicated substantial sequence divergence between B. pertussis and B. holmesii. However, CGH identified a putative pathogenicity island of 66 kb that is highly conserved between these species and contains several IS481 elements that may have been laterally transferred from B. pertussis to B. holmesii. This island contains, among other genes, a functional, iron-regulated locus encoding the biosynthesis, export, and uptake of the siderophore alcaligin. The acquisition of this genomic island by B. holmesii may have significantly contributed to its emergence as a human pathogen. Horizontal gene transfer between B. pertussis and B. holmesii may also explain the unusually high sequence identity of their 16S rRNA genes.

Development and evaluation of a loop-mediated isothermal amplification method for rapid diagnosis of Bordetella pertussis infection

We developed a loop-mediated isothermal amplification (LAMP) method to detect Bordetella pertussis infection. This LAMP assay detected B. pertussis with high sensitivity, but not other Bordetella species. Among nasopharyngeal swab samples from subjects with suspected pertussis, LAMP results showed a high level of agreement with results of conventional PCR. This method is a rapid, sensitive, and specific method for diagnosis of B. pertussis infection even in clinical laboratories with no specific equipment.

Bordetella pertussis, Finland and France

We used pulsed-field gel electrophoresis analysis and genotyping to compare clinical isolates of Bordetella pertussis recovered since the early 1990s in Finland and France, 2 countries with similar histories of long-term mass vaccination with whole-cell pertussis vaccines. Isolates from both countries were similar genetically but varied temporally.

Molecular epidemiology of Bordetella pertussis in Taiwan, 1993–2004: suggests one possible explanation for the outbreak of pertussis in 1997

Pertussis reemerges periodically despite high pertussis vaccination coverage in many countries. We used prn and fim3 gene sequences and pulsed-field gel electrophoresis (PFGE) to analyze the molecular epidemiology of 168 clinical isolates of Bordetella pertussis during 1993-2004, and deduced possible reasons for an outbreak in 1997 in Taiwan. In Taiwan, during 1996-1997, a shift of prn1 to prn2 was reflected in a transition of PFGE group I to group IIIa; during 2000-2001, the change from fim3A to fim3B was displayed in transition of PFGE group IIIa to group IIIb. These changes were also consistent with the two peaks of pertussis incidence in 1997 and 2000. In 1997, a larger than expected increase in the incidence of pertussis occurred and isolates were characterized by complicated pulsotypes, appearance of many new profiles and an unusual presence of prn3. Based on a high resemblance of PFGE profiles and the same virulence genes, a similar shift of circulating strains was observed in European countries as well as Taiwan; thus, the high incidence of pertussis in 1997 may be due to an international expansion of B. pertussis strains from a similar source. This study provides further elucidation of the global molecular epidemiology of B. pertussis.

Temporal analysis of French Bordetella pertussis isolates by comparative whole-genome hybridization

Bordetella pertussis, a gram-negative beta-proteobacterium, is the agent of whooping cough in humans. Whooping cough remains a public health problem worldwide, despite well-implemented infant/child vaccination programs. It continues to be endemic and is observed cyclically in vaccinated populations. Classical molecular subtyping methods indicate that genome diversity among B. pertussis isolates is limited. Although the whole bacterial genome has been studied by pulsed-field gel electrophoresis, the genes implicated in the diversity have not been identified. We developed a B. pertussis whole-genome DNA microarray representing over 91% of the predicted coding sequences of the sequenced strain Tohama I. Genomic DNA from clinical isolates with various pulsed-field gel electrophoresis profile patterns was competitively hybridized with the DNA microarray and coding sequences were classified as present, absent or duplicated. Our data strongly suggest that the B. pertussis population is dynamic. In France, with highly vaccinated population, the genetic diversity is low and decreasing with time, and clonal expansion correlates with cycles of the disease. This decrease in diversity is essentially due to loss of genes and pseudogenes. The genes deleted are most of the time flanked by insertion sequences.

Genetic and antigenic analysis of Bordetella pertussis isolates recovered from clinical cases in Ontario, Canada, before and after the introduction of the acellular pertussis vaccine

Sixty-eight Bordetella pertussis isolates (obtained between 1994 and 2004 from the province of Ontario in Canada) were compared by the following phenotypic and genetic analyses: serotyping; pulsed-field gel electrophoresis; and partial DNA sequence analysis of their pertactin, pertussis toxin, and fimbriae genes. Although temporal genetic variations were observed among the isolates, which is consistent with the current view that B. pertussis evolves over time, no specific antigenic or genetic type was detected in 48 isolates collected shortly after the introduction of the acellular pertussis vaccine. Further surveillance with clinical data and isolates collected periodically will be required to ensure that any genetic divergence that could affect vaccine efficacy will not be occurring.

Comparison of real-time PCR and pyrosequencing for typing Bordetella pertussis toxin subunit 1 variants

We describe two newly developed methods for rapid typing of the pertussis toxin subunit 1 gene (ptxS1). A real-time PCR assay based on hybridization probes and a Pyrosequencing assay were developed and the specificity, sensitivity, cost, hands-on time and post-assay data processing were compared to Sanger sequencing. Both methods enabled discrimination of all four allelic variants, correctly identified all ptxS1 alleles of 143 strains tested and proved suitable for large-scale screening of B. pertussis strains.

[Molecular typing of the strains of Bordetella pertussis circulating in St. Petersburg during an outbreak of the disease]

Growth of the whooping-cough morbidity during the last years in Russia and other countries with 40-year-long history of immunization gave rise to significant interest of researchers to variability of the Bordetella pertussis population. Comparative assay of the genomes of the B. pertussis strains circulating in St. Petersburg in 1998-2000 and strains used to produce domestic vaccines AKDS was performed using the pulse-field electrophoresis and sequencing. It was found that most strains of B. pertussis circulating during this period were distinguished from the vaccine strains by the DNA-profile and structure of genes involved in encoding of biosynthesis of the S1 subunit of the whooping-cough toxin (ptxS1) and pertactin (prn). It was shown that 62% of wild-type strains had electrophoretic profiles IV alpha and IV beta, whereas vaccine strains had electrophoretic profiles II and III. Circulation of strains with profiles IV alpha and IV beta was found to correlate with the whooping-cough morbidity rate in vaccinated children. Our results and data of other researchers were compared and analyzed.

[Genetic diversity analysis of isolates belonging to Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica species]

In this study, Amplified Fragment Length Polymorphism (AFLP) method was used to track differences among human and animal isolates of B. pertussis, B. parapertussis and B. bronchiseptica species. One hundred and sixty representative strains of these species orginated from international and Polish bacterial collections were genotyped according to AFLP involving EcoRI/Msel and SpeI/ApaI restriction/ligation/amplification procedures. This study has confirmed high potential AFLP SpeI/ApaI procedure for intra-species differentiation of B. pertussis and B. bronchiseptica strains. Both AFLP EcoRI/MseI and SpeI/ApaI procedures have been found to be useful for species-specific classification in case of B. pertussis strains. In case of B. bronchiseptica or B. parapertussis species-specific classification, SpeI/ApaI procedure has been found more precise than EcoRI/MseI one.

Antigenic divergence of Bordetella pertussis isolates in Taiwan

In recent studies, antigenic divergence has been observed in Bordetella pertussis circulating isolates. We collected 80 Bordetella pertussis isolates in Taiwan from 1998 to 2004 and analyzed them using a combination of pulsed-field gel electrophoresis (PFGE) and sequencing of the ptxS1 and prn genes. The incidence of pertussis increases every 3 years, and most of the isolates prevalent since 1998 have expressed nonvaccine ptxS1A and prn2 alleles. Through PFGE analysis, all isolates could be classified into four major groups, and the incidence of these groups exhibited a correlation with the prn allele expressed by the isolates. We found that PFGE is more discriminative than gene sequencing, since it could divide the isolates expressing the prn2 allele into two groups: one group circulating from 1998 to 2001 and another group circulating from 2001 to 2004. The transition between the two groups in 2000 coincided with an outbreak of 326 cases. This research indicates that the antigenic divergence of B. pertussis circulating isolates has evolved over time in Taiwan. Such information will have implications for vaccine policy in Taiwan.

Epitope of the vaccine-type Bordetella pertussis strain 186 lipooligosaccharide and antiendotoxin activity of antibodies directed against the terminal pentasaccharide-tetanus toxoid conjugate

Lipooligosaccharides (LOS) isolated from Bordetella pertussis strains 186 and 606 were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-resolution magic angle spinning nuclear magnetic resonance (NMR). These analyses distinguished between the LOS of strains 186 and 606, suggesting that the structure of LOS in B. pertussis is heterogeneous. The pentasaccharide was selectively cleaved from LOS of B. pertussis strain 186, purified, and covalently linked to a monomer fraction of tetanus toxoid. Injection of rabbits with the neoglycoconjugate emulsified in complete Freund's adjuvant yielded immunoglobulin G antibodies that were reactive with the LOS. These antibodies reacted strongly with B. pertussis LOS possessing the complete dodecasaccharide, as determined by an enzyme-linked immunosorbent assay, immunoblotting, and flow cytometry with intact, live bacterial cells. The binding epitope within the pentasaccharide was investigated by saturation transfer difference (STD) NMR spectroscopy. Protons H-1 and H-4 of the terminal alpha-D-GlcpNAc and proton H-6 and protons of an N-methyl group at H-4 of 3-substituted beta-L-FucpNAc4NMe exhibited the largest saturation transfers. STD NMR experiments confirmed that the immunodominant epitope recognized by the antineoglycoconjugate antibodies is located predominantly in the distal trisaccharide of B. pertussis 186 LOS. The antipentasaccharide antibodies induced by the conjugate inhibited the secretion of tumor necrosis factor alpha, interleukin-6, and NO by LOS-stimulated J774A.1 cells.

Strain variation among Bordetella pertussis isolates in finland, where the whole-cell pertussis vaccine has been used for 50 years

Pertussis is an infectious disease of the respiratory tract caused by Bordetella pertussis. Despite the introduction of mass vaccination against pertussis in Finland in 1952, pertussis has remained an endemic disease with regular epidemics. To monitor changes in the Finnish B. pertussis population, 101 isolates selected from 1991 to 2003 and 21 isolates selected from 1953 to 1982 were studied together with two Finnish vaccine strains. The analyses included serotyping of fimbriae (Fim), genotyping of the pertussis toxin S1 subunit (ptxA) and pertactin (prn), and pulsed-field gel electrophoresis (PFGE) after digestion of B. pertussis genomic DNA with XbaI restriction enzyme. Strains isolated before 1977 were found to harbor the same ptxA as the strains used in the Finnish whole-cell pertussis vaccine, and strains isolated before 1982 harbored the same prn as the strains used in the Finnish whole-cell pertussis vaccine. All recent isolates, however, represented genotypes distinct from those of the two vaccine strains. A marked shift of predominant serotype from Fim serotype 2 (Fim2) to Fim3 has been observed since the late 1990s. Temporal changes were seen in the genome of B. pertussis by PFGE analysis. Three PFGE profiles (BpSR1, BpSR11, and BpSR147) were distinguished by their prevalence between 1991 and 2003. The yearly emergence of the three profiles was distributed periodically. Our study stresses the importance of the continuous monitoring of emerging strains of B. pertussis and the need to obtain a better understanding of the relationship of the evolution of B. pertussis in vaccinated populations.

[Epidemic process of pertussis in Moscow]

Materials reflecting the dynamics of pertussis morbidity during the period of 1958 - 2003 under the conditions of prolonged mass immunization of the child population with adsorbed DPT vaccine are presented. The planned vaccination of children led to the decrease of pertussis morbidity during the first 10 years, but groundless abstentions from vaccination during the 1980s - 1990s contributed to a sharp rise in morbidity among children of younger age groups. During the recent four years a rise in pertussis morbidity was registered in 2000 (71.79 per 100,000 of the population), followed by the most significant for the last 20 years drop in morbidity in 2002--down to 9.89. But in 2003 the growth of morbidity was again registered (38.67). Recently periodic rises and drops in morbidity occurred simultaneously with the increased coverage of children of younger age groups with vaccination. In recent years changes in the age structure of patients were observed: the specific proportion of school children increased (in 2003 morbidity rates in children aged 6 - 10 years were 288.6 - 270.7), simultaneously high morbidity among children aged up to one year (274.9) was registered. The specific proportion of pertussis-affected children aged above 7 years reached 65%. From the late 1990s until present in 87.1% of cases strains of serotype 1.0.3 prevailed in the population of B. pertussis strains. But in recent years the circulation of strains 1.2.3, spread in the prevaccination period and having toxicity similar to that of strains of serotype 1.0.3, while exceeding them in virulence, in sufficiently high proportion (7.0% in 2002) was noted. This was indicative of the possibility of the unfavorable development of the epidemic process of pertussis infection.

Analysis of Bordetella pertussis populations in European countries with different vaccination policies

Despite the widespread use of pertussis vaccines during the last decades, pertussis has remained an endemic disease with frequent epidemic outbreaks. Currently two types of vaccines are used: whole-cell vaccines (WCVs) and recently developed acellular vaccines (ACVs). The long-term aim of our studies is to assess the effect of different vaccination policies on the population structure of Bordetella pertussis and ultimately on the disease burden in Europe. In the present study, a total of 102 B. pertussis isolates from the period 1998 to 2001 from five European countries (Finland, Sweden, Germany, The Netherlands, and France) were characterized. The isolates were analyzed by typing based on variable number of tandem repeats (VNTR); by sequencing of polymorphic genes encoding the surface proteins pertussis toxin S1 and S3 subunits (ptxA and ptxC), pertactin (prn), and tracheal colonization factor (tcfA); and by fimbrial serotyping. The results reveal a relationship between geographic location and VNTR types, the frequency of the ptxC alleles, and serotypes. We have not observed a relationship between the strain characteristics we studied and vaccination programs. Our results provide a baseline which can be used to reveal changes in the B. pertussis population in Europe in the coming years.

Shifts of Bordetella pertussis variants in Sweden from 1970 to 2003, during three periods marked by different vaccination programs

The Swedish population of Bordetella pertussis strains was characterized from 1,247 isolates covering a whole-cell vaccine program up to 1979, a 17-year period without vaccination (1979 to 1996), and a period after the introduction of general vaccination among newborns with acellular pertussis vaccines (1997 to 2003). Strains were characterized by serotyping and genotyping of pertactin and ptxA and by means of pulsed-field gel electrophoresis (PFGE). With emphasis on vaccine-related markers, the vast majority of circulating strains were of nonvaccine type. There were shifts of serotype connected with shifts of vaccination program. Serotype Fim3 was most frequent during the periods with general vaccination schedules, whereas serotype Fim2 was predominant during the 17-year vaccine-free period. Pertactin 1 was predominant during the pertussis whole-cell (Pw) vaccine period but was thereafter replaced by prn2 and has not reappeared after the introduction of acellular pertussis (Pa) vaccines. ptxA (1) was predominant over all three decades. There was a significant difference in the distribution of serotypes between vaccinated and unvaccinated individuals, but not for pertactin. A few PFGE profiles were predominant over the years: BpSR25 (serotype Fim3 prn1/7) and BpSR18 (serotype Fim3 prn2) during the Pw period, BpSR1 (serotype Fim2 prn2) during the 17 years without general vaccination, and BpSR11 (serotype Fim3 prn2) after the reintroduction of general vaccination in 1996. Despite differences between the pertactin and toxin types of Pa vaccines and circulating strains, there is no evidence that there is a threat, i.e., the vaccination program so far has been effective against whooping cough, and there seems to be no impact on the effectiveness of the vaccination program from the bacterial polymorphism.

Use of monoclonal antibodies to serotype Bordetella pertussis isolates: comparison of results obtained by indirect whole-cell enzyme-linked immunosorbent assay and bacterial microagglutination methods

Sixty-one Bordetella pertussis isolates were tested blindly in two laboratories to determine their serotype nature by monoclonal antibodies using two independent methods: the standard bacterial microagglutination assay and an indirect whole-cell enzyme-linked immunosorbent assay. Both methods gave concordant results in 60 of the 61 isolates.