Fulminant pertussis: a multi-center study with new insights into the clinico-pathological mechanisms

Bordetella pertussis and concomitant viral respiratory tract infections are rare in children with cough illness

BACKGROUND

Case reports, case series, and retrospective and prospective studies have reported concomitant Bordetella pertussis and viral respiratory tract pathogen infections in children with cough illness with conflicting results regarding their frequency.

METHOD

A prospective 1-year study was performed in ambulatory and hospitalized patients aged 0 to 17 years with a cough illness. Polymerase chain reaction for viral (influenza A and B, parainfluenza 1 and 3, respiratory syncytial, metapneumovirus, and adenovirus) and bacterial pathogens including B. pertussis and B. parapertussis was applied to nasopharyngeal aspirate (NPA) specimens. The primary goal of the study was to assess the frequency of unsuspected Bordetella infections in patients thought to have a viral respiratory tract infection. The secondary goal was to determine the frequency of concomitant viral respiratory tract and Bordetella infections.

RESULTS

B. pertussis and B. parapertussis DNA was amplified in 21 (2.0%) and 5 (0.5%) cases, respectively, of 1059 NPA specimens. Of the 1059 NPA specimens, 877 were tested in parallel for respiratory viruses, B. pertussis, and B. parapertussis; >1 virus was identified in 427 (48.7%) and Bordetella species was identified in 10 (1.1%) of these 877 NPA specimens but only 2 (0.2%) concomitant virus/Bordetella infections were identified. Specifically, of 268 NPAs positive for RSV, 1 (0.37%) was concomitant with B. pertussis infection as was 1 (3.7%) of 27 NPAs positive for hMPV.

CONCLUSIONS

B. pertussis and B. parapertussis infections were rare in patients with cough illness and so were concomitant virus/Bordetella infections. We propose that virus/Bordetella coinfections primarily occur by chance.

The Collaborative Pediatric Critical Care Research Network Critical Pertussis Study: collaborative research in pediatric critical care medicine

OBJECTIVE

To provide an updated overview of critical pertussis to the pediatric critical care community and describe a study of critical pertussis recently undertaken.

SETTING

The six sites, seven hospitals of the Collaborative Pediatric Critical Care Research Network, and 17 outside sites at academic medical centers with pediatric intensive care units.

RESULTS

Despite high coverage for childhood vaccination, pertussis causes substantial morbidity and mortality in US children, especially among infants. In pediatric intensive care units, Bordetella pertussis is a community-acquired pathogen associated with critical illness and death. The incidence of medical and developmental sequelae in critical pertussis survivors remains unknown, and the appropriate strategies for treatment and support remain unclear. The Collaborative Pediatric Critical Care Research Network Critical Pertussis Study has begun to evaluate critical pertussis in a prospective cohort.

CONCLUSION

Research is urgently needed to provide an evidence base that might optimize management for critical pertussis, a serious, disabling, and too often fatal illness for U.S. children and those in the developing world.

Bordetella pertussis infection exacerbates influenza virus infection through pertussis toxin-mediated suppression of innate immunity

Pertussis (whooping cough) is frequently complicated by concomitant infections with respiratory viruses. Here we report the effect of Bordetella pertussis infection on subsequent influenza virus (PR8) infection in mouse models and the role of pertussis toxin (PT) in this effect. BALB/c mice infected with a wild-type strain of B. pertussis (WT) and subsequently (up to 14 days later) infected with PR8 had significantly increased pulmonary viral titers, lung pathology and mortality compared to mice similarly infected with a PT-deficient mutant strain (ΔPT) and PR8. Substitution of WT infection by intranasal treatment with purified active PT was sufficient to replicate the exacerbating effects on PR8 infection in BALB/c and C57/BL6 mice, but the effects of PT were lost when toxin was administered 24 h after virus inoculation. PT had no effect on virus titers in primary cultures of murine tracheal epithelial cells (mTECs) in vitro, suggesting the toxin targets an early immune response to increase viral titers in the mouse model. However, type I interferon responses were not affected by PT. Whole genome microarray analysis of gene expression in lung tissue from PT-treated and control PR8-infected mice at 12 and 36 h post-virus inoculation revealed that PT treatment suppressed numerous genes associated with communication between innate and adaptive immune responses. In mice depleted of alveolar macrophages, increase of pulmonary viral titers by PT treatment was lost. PT also suppressed levels of IL-1β, IL-12, IFN-γ, IL-6, KC, MCP-1 and TNF-α in the airways after PR8 infection. Furthermore PT treatment inhibited early recruitment of neutrophils and NK cells to the airways. Together these findings demonstrate that infection with B. pertussis through PT activity predisposes the host to exacerbated influenza infection by countering protective innate immune responses that control virus titers.

Real-time PCR-based detection of Bordetella pertussis and Bordetella parapertussis in an Irish paediatric population

Novel real-time PCR assays targeting the Bordetella pertussis insertion sequence IS481, the toxin promoter region and Bordetella parapertussis insertion sequence IS1001 were designed. PCR assays were capable of detecting ≤10 copies of target DNA per reaction, with an amplification efficiency of ≥90 %. From September 2003 to December 2009, per-nasal swabs and nasopharyngeal aspirates submitted for B. pertussis culture from patients ≤1 month to >15 years of age were examined by real-time PCR. Among 1324 patients, 76 (5.7 %) were B. pertussis culture positive and 145 (10.95 %) were B. pertussis PCR positive. Of the B. pertussis PCR-positive patients, 117 (81 %) were aged 6 months or less. A total of 1548 samples were examined, of which 87 (5.6 %) were culture positive for B. pertussis and 169 (10.92 %) were B. pertussis PCR positive. All culture-positive samples were PCR positive. Seven specimens (0.5 %) were B. parapertussis culture positive and 10 (0.8 %) were B. parapertussis PCR positive, with all culture-positive samples yielding PCR-positive results. A review of patient laboratory records showed that of the 1324 patients tested for pertussis 555 (42 %) had samples referred for respiratory syncytial virus (RSV) testing and 165 (30 %) were positive, as compared to 19.4 % of the total 5719 patients tested for RSV in this period. Analysis of the age distribution of RSV-positive patients identified that 129 (78 %) were aged 6 months or less, similar to the incidence observed for pertussis in that patient age group. In conclusion, the introduction of the real-time PCR assays for the routine detection of B. pertussis resulted in a 91 % increase in the detection of the organism as compared to microbiological culture. The incidence of infection with B. parapertussis is low while the incidence of RSV infection in infants suspected of having pertussis is high, with a similar age distribution to B. pertussis infection.

Selective translocation of the Bordetella pertussis adenylate cyclase toxin across the basolateral membranes of polarized epithelial cells

The catalytic domain of Bordetella pertussis adenylate cyclase toxin (ACT) translocates directly across the plasma membrane of mammalian cells to induce toxicity by the production of cAMP. Here, we use electrophysiology to examine the translocation of toxin into polarized epithelial cells that model the mucosal surfaces of the host. We find that both polarized T84 cell monolayers and human airway epithelial cultures respond to nanomolar concentrations of ACT when applied to basolateral membranes, with little or no response to toxin applied apically. The induction of toxicity is rapid and fully explained by increases in intracellular cAMP, consistent with toxin translocation directly across the basolateral membrane. Intoxication of T84 cells occurs in the absence of CD11b/CD18 or evidence of another specific membrane receptor, and it is not dependent on post-translational acylation of the toxin or on host cell membrane potential, both previously reported to be required for toxin action. Thus, elements of the basolateral membrane render epithelial cells highly sensitive to the entry of ACT in the absence of a specific receptor for toxin binding.