Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2006
Publication Date: 10/25/2006
Citation: Register, K.B., Sanden, G.N. 2006. Prevalence and sequence of IS481 in Bordetella bronchiseptica: Implications for IS481-based detection of Bordetella pertussis. Journal of Clinical Microbiology. 44(12):4577-4583. Interpretive Summary: Bordetella pertussis is the causative agent of pertussis or whooping cough, an acute respiratory disease occurring exclusively in humans. Diagnostic testing for this bacterium is often based on PCR detection of a repeated DNA sequence, IS481. However, some reports suggest IS481 may also be found in at least some isolates of the closely related bacterium Bordetella bronchiseptica. B. bronchiseptica is regarded as primarily a non-human animal pathogen but its association with disease in humans has been steadily increasing in recent years. In this study, 149 B. bronchiseptica isolates, obtained from humans and 11 other companion or farm animal species, were tested for the presence of IS481. Unexpectedly, positive results were obtained from 79% of all isolates, representing all but 1 of the host species of origin. Additional analysis revealed most were false positives due to high sequence similarity between the supposedly IS481-specific primers and a second, unrelated region of the genome. The true frequency of IS481 in B. bronchiseptica was determined to be approximately 5%, with multiple copies found in some strains. These data indicate the specificity of commonly used IS481-based diagnostic PCRs for identification of B. pertussis is lower than so far believed and alternative PCR targets should be considered.
Technical Abstract: We report the prevalence in Bordetella bronchiseptica of IS481, a frequent target for diagnosis of Bordetella pertussis, as approximately 5%. However, amplicons of the predicted size were detectable in 75% of IS481-negative strains. Our results suggest conventional PCR targeting IS481 may not be sufficiently specific for reliable identification of B. pertussis.