The occurrence of Bordetella pertussis serotypes in Australia, 1950-1970

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.

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.

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.

Changes in the Dutch Bordetella pertussis population in the first 20 years after the introduction of whole-cell vaccines

Despite the introduction of mass vaccination in 1953 in The Netherlands, pertussis is currently an endemic disease with regular epidemic outbreaks. Changes in the Bordetella pertussis population in the first 20 years after the introduction of vaccination were studied by indexing IS1002 fingerprint types, fimbrial serotypes and 15 genes encoding surface proteins. Three periods were compared, the pre-vaccination period (1949-1952) and two subsequent periods, 1953-1958 and 1965-1972. Except for fimbrial serotypes, no changes were observed in the B. pertussis population between the first two periods. Mortality decreased fivefold and 543-fold in the periods 1953-1958 and 1965-1972, respectively, compared to the pre-vaccination period. The largest decrease in mortality coincided with significant changes in the B. pertussis population with respect to the frequencies of fimbrial serotypes, fingerprint types and ptxS1 alleles. A new fingerprint type (ft29), associated with the novel ptxS1 allele ptxS1A was observed in 50% of the isolates in the period 1965-1972. Of the 15 investigated genes, only ptxS1 showed a mismatch between the vaccine strains and clinical isolates, suggesting that it may have played a role in driving the observed changes. It is proposed that, within 10-20 years after the introduction of mass vaccination, an adaptive response occurred consisting of clonal expansion of strains, which expressed a pertussis toxin variant distinct from the vaccine variants. This adaptation had very little, if any, effect on mortality, however.

Infant pertussis deaths in New South Wales 1996-1997

Since 1996, south-eastern Australia has been experiencing a pertussis epidemic which has resulted in the deaths of several infants, including four from NSW in the 12 months to July 1997. All were less than six weeks of age and died from overwhelming cardiovascular compromise despite intensive care support. This excessive infant mortality from a preventable disease demonstrates the need for better pertussis immunity in the community and for erythromycin treatment of all suspected cases and family contacts, especially infants.

Immunogenicity of specific Bordetella pertussis surface antigens in diphtheria-tetanus-pertussis (DTP) vaccines

The predominant causative organism of whooping cough in Australia is of a serotype which has normally been associated overseas with unvaccinated communities. Australian DTP vaccines pass the statutory mouse test for Bordetella pertussis potency but this test is now believed to be relatively insensitive to certain factors, especially the major type-specific agglutinogens, which are presumably also important in the human host-parasite relationship. Because endemic B. bronchiseptica infections make some laboratory animals unsatisfactory for testing B. pertussis agglutinin responses, we have developed a test in which young farm sheep were immunized with vaccines. Type-specific agglutinins in their sera were assayed after absorption of non-specific agglutinins by suspensions of selected bordetella strains. Three well-reputed European DTP vaccines and two recent batches of Australian DTP vaccine were tested and compared thus. All evoked significant agglutinin responses to the main agglutinogens.

Prevalent serotypes of Bordetella pertussis in non-vaccinated communities

In many countries, the prevalent serotypes of Bordetella pertussis have changed from a mixture of types 1,2,3 and 1,2 (organisms possessing antigen 2) to a predominance of type 1,3. The timing of the change in different countries is shown to be related to the introduction of mass-vaccination with material rich in antigens 1 and 2 but weak in, or devoid of, antigen 3. In several parts of the world, there have been outbreaks of type 1,3 infection in fully vaccinated children. Non-vaccinated communities in various parts of the world still show the pattern of serotypes which existed elsewhere before mass-vaccination. In order to avoid the disappointments experienced in the past, it is essential that pertussis vaccine for use in previously non-vaccinated communities, like that for any other country, should be rich in each of the three antigens.

The serotypes of Bordetella pertussis isolated in Great Britain between 1941 and 1968 and a comparison with the serotypes observed in other countries over this period

Classification, by agglutinogens, of 634 isolates of Bordetella pertussis collected from 1971 to 1968 in Great Britain demonstrated that a change from a predominantly 1,2,0,4 serotype (75% of those examined during 1941-4) to a predominantly 1,0,3,0 serotype (73% of those examined during 1966-8) occurred sometime after 1953. Furthermore, evidence from the examination of isolates collected between 1941 and 1953 suggests that the change may have been gradual. Isolates of serotype 1,2,3,4 made up 20-30% of the total of our cross-country selection for the periods 1941-4, 1946-9, 1950-3 and 1966-8, but over shorter periods in individual areas the percentage varied from negligible to as high as half of those isolated. Results from other countries show a similar drift towards a 1,0,3 sertype but more often from a 1,2,3 than from 1,2,0 serotype. The value, in epidemiological studies, of extended information obtained by monospecific typing sera to all six, rather than only two or three agglutinogens, and confirmation of the results by agglutinin production is demonstrated: for instance not all 1,0,3 isolates were identical.

Efficacy of pertussis vaccines: a brighter horizon

A study of pertussis infections in 186 children under 11 years of age in the Manchester region during 1969-71 suggests that recently-manufactured vaccines have been more effective than those made before 1967. The earlier vaccines were effective mainly against the serotypes of Bordetella pertussis possessing antigen 2, while those made from 1967 are more nearly equal in their effectiveness against thedi fferent serotypes. A booster dose of the earlier vaccines did not prevent infection with type 1,3 organisms, but we obtained a positive culture from only one child who had received four doses of recent vaccine.Simultaneous infection of a child with two or more serotypes was frequently seen. The predominant serotype in a patient was usually type 1,3; less often it was type 1,2,3 or type 1,2; it was never type 1. A change of serotype sometimes occurs during the course of the illness and is probably directed by the vaccination status of the patient in relation to the serotype of the initial infection.Our findings emphasize the need for vaccines to contain adequate amounts of all three pertussis agglutinogens, and for satisfactory immunization schedules to be used in their administration.