Search

An acellular pertussis vaccine containing five substances may be safe and effective in preventing pertussis, while an acellular vaccine containing two substances and a whole-cell vaccine appear to be less effective. Acellular vaccines contain proteins derived from the pertussis bacteria, while whole-cell vaccines contain inactivated bacteria which may be unsafe. Of 9,829 infants, 2589 received a five-component acellular diphtheria-tetanus-pertussis (DTP) vaccine, 2566 received a two-component DTP acellular vaccine, 2102 received a whole-cell DTP vaccine, and 2574 received a diphtheria-tetanus vaccine (control group). Based on an average follow-up of 21 to 24 months, the calculated efficacy of three doses of the vaccines were 85% for the five-component acellular vaccine, 58% for the two-component acellular vaccine, and 48% for the whole-cell vaccine. The whole-cell vaccine was more likely than the others to cause side effects such as long periods of crying and fever.

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. [ABSTRACT FROM AUTHOR]

A real-time PCR method targeting the Bordetella pertussis IS 481 gene fragment was evaluated in a vaccine trial setting in which real-time PCR results could be validated against culture and serology results. Two commonly used DNA extraction methods, Amplicor® Respiratory Preparation kit and the QIAamp® DNA Mini Kit, were compared. An approximately 50-fold higher sensitivity was achieved using the Amplicor kit. 89 of 276 aspirates analysed with the IS 481 real-time PCR were positive. Interestingly, six of these were culture negative and came from serology-negative patients. Defining true positive cases either as culture-positive or as PCR-positive cases that had been confirmed with a serology-positive result or verified with a newly constructed recA PCR, the sensitivity and specificity of the IS 481 real-time PCR were 89% and 98%, respectively. This study confirms the specificity and high diagnostic sensitivity of IS 481-based PCR methods for diagnosis of B. pertussis. [ABSTRACT FROM AUTHOR]

Material collected during a prospective pertussis vaccine trial in 1992-95 was examined for Bordetella pertussis (culture and serology), Bordetella parapertussis (culture), Mycoplasma pneumoniae and Chlamydia pneumoniae (PCR). From 64% (99/155) of episodes with cough for less than 100 d, 115 aetiological agents were identified in one southern and one northern subset of DT-recipients. The most common single agent was B. pertussis, representing 56% (64/115), with a median cough period of 51 d, followed by M. pneumoniae 26% (30/115), 23 d, C. pneumoniae 17% (19/115), 26 d, and B. parapertussis 2% (2/115). For co-infections, the median duration of cough was about 60 d. Spasmodic cough for 21 d or more (clinical WHO criteria for pertussis) was present in 82% (41/50) of infections with B. pertussis as single agent, 38% (17/45) with B. parapertussis, 38% (5/13) with C. pneumoniae, 26% (5/19) with M. pneumoniae and 30% (17/56) in cases where no aetiology was found. In children with cough for more than 100 d (n=78) using all vaccine arms, B. pertussis was responsible in 83% (65/78), in 21% (16/78) together with other agents. Acellular vaccines were more efficient against serious disease than whole cell vaccine. Antibiotic treatment was more common at the southern (34%) study site than at the northern one (12%). The findings indicate that diagnosis should rely on laboratory confirmation, both for rational treatment of an individual case and for monitoring outbreaks. [ABSTRACT FROM AUTHOR]