RESUMEN
In Sweden, acellular pertussis vaccines were introduced at 3, 5 and 12 months of age in 1996, after a 17-year hiatus without pertussis vaccination. An intensified surveillance of pertussis was initiated in October 1997, including collection of clinical data as well as Bordetella pertussis isolates in culture or PCR-confirmed cases of pertussis among children born from January 1996 to September 2004. We analysed the association of pulsed-field gel electrophoresis (PFGE) profile and serotype with severity of disease for all children followed during the first 7 years of the project. There were in all 927 children for whom both clinical information and strain characterisation data were available. 260 of these children were hospitalised during the pertussis episode. When duration of hospital stay was compared between children with different groups of strains, characterised by PFGE profile or serotype, there was a significantly higher proportion of children with long duration of hospital stay in the most frequent PFGE profile group (BpSR11) compared to the PFGE group of all other profiles (p=0.041). There was no statistically significant association between serotype and hospitalisation rate or duration of hospital stay, neither was there any statistically significant association between serotype or PFGE profile and duration of spasmodic cough or presence of complications.
Asunto(s)
Bordetella pertussis/química , Vacuna contra Difteria, Tétanos y Tos Ferina/administración & dosificación , Tos Ferina/inmunología , Niño , Vacuna contra Difteria, Tétanos y Tos Ferina/inmunología , Electroforesis en Gel de Campo Pulsado , Humanos , Vigilancia de la Población , Serotipificación , Suecia/epidemiología , Vacunación , Tos Ferina/clasificación , Tos Ferina/epidemiología , Tos Ferina/prevención & controlRESUMEN
In a surveillance programme undertaken from 1997 through 2004, Bordetella pertussis isolates and clinical information were collected after introduction of acellular pertussis vaccines (Pa) in 1996. Changes in the B. pertussis population were studied in three incidence peaks: 1999-2000, 2002 and 2004. Available isolates from 158 fully vaccinated children representing all of Sweden, plus 37 from the Gothenburg area 2003-2004, were analysed by pulsed-field gel electrophoresis (PFGE), serotyping and sequencing of the virulence factor genes pertussis toxin subunits 1 and 3 (ptxA, ptxC), pertactin (prn), tracheal colonisation factor (tcfA) and fimbria3 (fim3). Allele ptxA1 was found in all isolates. There was a statistically significant increasing trend in three out of five studied genes, ptxC, prn and tcfA, and for a fourth, Fim3, if Gothenburg strains were included. The PFGE profile BpSR11 appearing in the 1999-2000 peak dominated by >or=23% during the entire period, bringing with it the allele combination 1/2/2/2/B (ptxA1/ptxC2/prn2/tcfA2/fim3B). Other BpSR11-related profiles with the same allele combination and more than 82% similarity--BpSR5 in the 2002 peak and BpSR12 in the 2004 peak--appeared with an increasing trend. Although vaccination with Pa has reduced disease, new variants have emerged representing clones surviving in the immunized population.
Asunto(s)
Bordetella pertussis/aislamiento & purificación , Vacuna contra la Tos Ferina/administración & dosificación , Tos Ferina/epidemiología , Tos Ferina/prevención & control , Alelos , Bordetella pertussis/genética , Preescolar , ADN Bacteriano/análisis , Electroforesis en Gel de Campo Pulsado , Femenino , Humanos , Incidencia , Masculino , Población , Serotipificación , Suecia , Vacunación , Virulencia , Factores de Virulencia de Bordetella/genéticaRESUMEN
Pertussis is an infectious disease of the respiratory tract in humans caused by Bordetella pertussis. Despite extensive vaccinations, pertussis has remained endemic and re-emerged. In Finland, a whole-cell pertussis vaccine has been used since 1952 with high coverage. In Sweden, whole-cell vaccinations were introduced in 1953 but ceased in 1979, and pertussis vaccinations with acellular vaccines were introduced in 1996. Two epidemic peaks occurred in Sweden in 1999 and 2002 and in Finland in 1999 and 2003. We compared Finnish (N=193) and Swedish (N=455) B. pertussis isolates circulating in 1998-2003 together with vaccine strains used in these neighbouring countries with different vaccination histories. The isolates were analysed by serotyping, genotyping of pertussis toxin S1 subunit and pertactin, and pulsed-field gel electrophoresis. The results suggest that the sequential epidemics were caused by clonal expansion of a certain B. pertussis strain possibly transmitted from Sweden to Finland. The roles of antigenic variation in immunity-driven evolution of B. pertussis in both countries are discussed.
Asunto(s)
Bordetella pertussis/aislamiento & purificación , Vacuna contra la Tos Ferina/inmunología , Vacunación , Adolescente , Adulto , Anciano , Bordetella pertussis/genética , Niño , Preescolar , Brotes de Enfermedades , Electroforesis en Gel de Campo Pulsado , Evolución Molecular , Finlandia/epidemiología , Humanos , Lactante , Recién Nacido , Persona de Mediana Edad , Suecia/epidemiología , Factores de Tiempo , Tos Ferina/inmunología , Tos Ferina/prevención & controlRESUMEN
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.
Asunto(s)
Bordetella pertussis/clasificación , Vacuna contra la Tos Ferina/inmunología , Bordetella pertussis/genética , Electroforesis en Gel de Campo Pulsado , Genotipo , Humanos , Serotipificación , VacunaciónRESUMEN
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.
Asunto(s)
Bordetella pertussis/clasificación , Bordetella pertussis/genética , Variación Genética , Programas de Inmunización/métodos , Vacuna contra la Tos Ferina/administración & dosificación , Vacunas Acelulares/administración & dosificación , Tos Ferina/epidemiología , Proteínas de la Membrana Bacteriana Externa/genética , Bordetella pertussis/aislamiento & purificación , Niño , Preescolar , Electroforesis en Gel de Campo Pulsado , Genotipo , Humanos , Recién Nacido , Toxina del Pertussis/genética , Serotipificación , Suecia/epidemiología , Vacunación , Factores de Virulencia de Bordetella/genética , Tos Ferina/microbiologíaRESUMEN
Pulsed-field gel electrophoresis (PFGE) has been used as an epidemiological tool for surveillance studies of Bordetella pertussis since the early 1990s. To date there is no standardized procedure for comparison of results, and therefore it has been difficult to directly compare PFGE results between laboratories. We propose a profile-based reference system for PFGE characterization of B. pertussis strain variation and to establish traceability of B. pertussis PFGE results. We initially suggest 35 Swedish reference strains as reference material for PFGE traceability. This reference material is deposited at the Culture Collection of the University of Gothenburg, Gothenburg, Sweden. Altogether, 1,810 Swedish clinical isolates from between 1970 and 2003 were studied, together with the Swedish Pw vaccine strain, six reference strains, and two U.S. isolates. Our system provides evidence that profiles obtained by using only one enzyme, i.e., XbaI, give enough data to analyze the epidemiological relationship between them. Characterization with one enzyme is far less labor intensive, yielding results in half the time than when a two-enzyme procedure is used. Also, we can see that there is a correlation between PFGE profile and pertactin type. One common PFGE profile, BpSR11 (n = 455), showed 100% prn2 and 100% Fim3 when analyzed for pertactin type and serotype. On the other hand, strains with the same profile may express various serotypes when isolated over longer periods of time. Subculturing of the same isolate eight times or lyophilization caused no change in PFGE profile.
Asunto(s)
Bordetella pertussis/genética , Electroforesis en Gel de Campo Pulsado/normas , Humanos , Reproducibilidad de los Resultados , SerotipificaciónRESUMEN
A multiple-primer DNA sequencing approach suitable for genotyping, detection and identification of microorganisms and viruses has been developed. In this new method two or more sequencing primers, combined in a pool, are added to a DNA sample of interest. The oligonucleotide that hybridizes to the DNA sample will function as a primer during the subsequent DNA sequencing procedure. This strategy is suited for selective detection and genotyping of relevant microorganisms and samples harboring different DNA targets such as multiple variant/infected samples as well as unspecific amplification products. This method is used here in a model system for detection and typing of high-risk oncogenic human papilloma viruses (HPVs) in samples containing multiple infections/variants or unspecific amplification products. Type-specific sequencing primers were designed for four of the most oncogenic (high-risk) HPV types (HPV-16, HPV-18, HPV-33, and HPV-45). The primers were combined and added to a sample containing a mixture of one high-risk (16, 18, 33, or 45) and one or two low-risk types. The DNA samples were sequenced by the Pyrosequencing technology and the Sanger dideoxy sequencing method. Correct genotyping was achieved in all tested combinations. This multiple-sequencing primer approach also improved the sequence data quality for samples containing unspecific amplification products. The new strategy is highly suitable for diagnostic typing of relevant species/genotypes of microorganisms.