Cytochrome oxidase requirements in Bordetella reveal insights into evolution towards life in the mammalian respiratory tract.

Little is known about oxygen utilization during infection by bacterial respiratory pathogens. The classical Bordetella species, including B. pertussis, the causal agent of human whooping cough, and B. bronchiseptica, which infects nearly all mammals, are obligate aerobes that use only oxygen as the terminal electron acceptor for electron transport-coupled oxidative phosphorylation. B. bronchiseptica, which occupies many niches, has eight distinct cytochrome oxidase-encoding loci, while B. pertussis, which evolved from a B. bronchiseptica-like ancestor but now survives exclusively in and between human respiratory tracts, has only three functional cytochrome oxidase-encoding loci: cydAB1, ctaCDFGE1, and cyoABCD1. To test the hypothesis that the three cytochrome oxidases encoded within the B. pertussis genome represent the minimum number and class of cytochrome oxidase required for respiratory infection, we compared B. bronchiseptica strains lacking one or more of the eight possible cytochrome oxidases in vitro and in vivo. No individual cytochrome oxidase was required for growth in ambient air, and all three of the cytochrome oxidases conserved in B. pertussis were sufficient for growth in ambient air and low oxygen. Using a high-dose, large-volume persistence model and a low-dose, small-volume establishment of infection model, we found that B. bronchiseptica producing only the three B. pertussis-conserved cytochrome oxidases was indistinguishable from the wild-type strain for infection. We also determined that CyoABCD1 is sufficient to cause the same level of bacterial burden in mice as the wild-type strain and is thus the primary cytochrome oxidase required for murine infection, and that CydAB1 and CtaCDFGE1 fulfill auxiliary roles or are important for aspects of infection we have not assessed, such as transmission. Our results shed light on the environment at the surface of the ciliated epithelium, respiration requirements for bacteria that colonize the respiratory tract, and the evolution of virulence in bacterial pathogens.

Transient reemergence of Bordetella parapertussis in France in 2022.

Between March and October 2022, a peak of detection of Bordetella parapertussis by qPCR, real-time PCR was observed in France.Hypothesis/Gap Statement. Whether this peak was due to resurgence from previous circulating lineages or reintroduction into the country was unknown.Objective. The objective of this study is to understand B. parapertussis-transient increase observed in France in 2022 whereas it had virtually stopped being reported since the start of the COVID-19 pandemic in 2020.Methods. We analysed real-time PCR (qPCR) data from the two largest French outpatient laboratories performing whooping cough diagnosis and characterized all B. parapertussis isolates collected in the 2016-2022 period by the French National Reference Centre for Whooping Cough.Results. Microbiological analyses reveal that 13 of 18 bacterial isolates collected in 2022 produce the vaccine antigen pertactin, whereas none of the 22 isolates collected in the 2016-2021 period did.Conclusion. We hypothesize a re-introduction of B. parapertussis from regions of the world where whole-cell vaccines are still in use.

Eosinophils as drivers of bacterial immunomodulation and persistence.

Traditionally, eosinophils have been linked to parasitic infections and pathological disease states. However, emerging literature has unveiled a more nuanced and intricate role for these cells, demonstrating their key functions in maintaining mucosal homeostasis. Eosinophils exhibit diverse phenotypes and exert multifaceted effects during infections, ranging from promoting pathogen persistence to triggering allergic reactions. Our investigations primarily focus on Bordetella spp., with particular emphasis on Bordetella bronchiseptica, a natural murine pathogen that induces diseases in mice akin to pertussis in humans. Recent findings from our published work have unveiled a striking interaction between B. bronchiseptica and eosinophils, facilitated by the btrS-mediated mechanism. This interaction serves to enhance pathogen persistence while concurrently delaying adaptive immune responses. Notably, this role of eosinophils is only noted in the absence of a functional btrS signaling pathway, indicating that wild-type B. bronchiseptica, and possibly other Bordetella spp., possess such adeptness in manipulating eosinophils that the true function of these cells remains obscured during infection. In this review, we present the mounting evidence pointing toward eosinophils as targets of bacterial exploitation, facilitating pathogen persistence and fostering chronic infections in diverse mucosal sites, including the lungs, gut, and skin. We underscore the pivotal role of the master regulator of Bordetella pathogenesis, the sigma factor BtrS, in orchestrating eosinophil-dependent immunomodulation within the context of pulmonary infection. These putative convergent strategies of targeting eosinophils offer promising avenues for the development of novel therapeutics targeting respiratory and other mucosal pathogens.

Comparison of Bordetella species identification among differing rt-PCR assays in the United States.

In the United States, the general laboratory method for diagnosing pertussis, caused by Bordetella pertussis, is real-time PCR (rt-PCR) targeting insertion sequence 481 (IS481). Other Bordetella species (parapertussis, holmesii, and bronchiseptica) can also cause a pertussis-like syndrome, and some commercial laboratory assays include the insertion sequence 1001 (pIS1001) that can detect B. parapertussis/B. bronchiseptica (BppBb). Because IS481 exists in B. pertussis and B. holmesii, current commercial assays cannot differentiate these two species. We used a multiplex rt-PCR assay containing species-specific targets to Bordetella to evaluate clinical specimens detected as B. pertussis/B. holmesii (BpBh) or BppBb by commercial laboratories. A sample of 3,984 clinical specimens positive for IS481 or pIS1001 from two commercial laboratories during 2012-2019 were re-tested at CDC. Agreement of Bordetella species between the CDC and commercial laboratory assays, and the proportion of commercial laboratory specimens that were non-B. pertussis by CDC's assay was assessed. Overall agreement in Bordetella species detection and identification between the CDC and commercial lab assays was 85%. Agreement for identifying B. pertussis was 87% for 3,663 BpBh specimens and 98% for identifying B. parapertussis in 310 BppBb specimens. CDC's assay detected B. holmesii in 55/3,984 (1.4%) specimens. Most discrepant results (410/490, 82%) were BpBh specimens interpreted as indeterminate B. pertussis at CDC. We found a small portion of B. holmesii in a sample of IS481-positive clinical specimens originally identified by commercial laboratory rt-PCR assays, suggesting that commercial PCR assays are a reliable diagnostic tool for correctly identifying Bordetella species in most patients with suspected pertussis. IMPORTANCE: When testing specimens collected from patients with suspected pertussis, large-scale commercial laboratories in the United States employ an IS481-based assay that cannot differentiate between Bordetella pertussis and Bordetella holmseii. The level of B. holmesii causing pertussis-like illness in the United States is not well-understood given that only B. pertussis is nationally notifiable. After re-testing with a multiplex, species-specific rt-PCR assay, our data show low levels of B. holmesii identified in a sample of IS481-positive clinical specimens originally identified by commercial laboratory rt-PCR assays. These results reinforce the validity of large-scale commercial rt-PCR testing as a reliable diagnostic tool for pertussis in the United States.

Detection of Bordetella spp. in children with pertussis-like illness from 2018 to 2024 in China.

OBJECTIVE: To evaluate the role of Bordetella pertussis (B. pertussis), B. parapertussis, B. holmesii, and B. bronchiseptica on pertussis resurgence in China, particularly the sharp rise since the latest winter. METHODS: Nasopharyngeal swabs collected from children with pertussis-like illness from January 2018 to March 2024 were cultured to detect B. pertussis, B. parapertussis, B. holmesii, and B. bronchiseptica, and tested for all of these except for B. bronchiseptica using a pooled real-time polymerase chain reaction (PCR) kit targeting insertion sequences ptxS1, IS481, IS1001, and hIS1001. RESULTS: Out of the collected 7732 nasopharyngeal swabs, 1531 cases tested positive for B. pertussis (19.8%, 1531/7732), and 10 cases were positive for B. parapertussis (0.1%, 10/7732). B. holmesii and B.bronchiseptica were not detected. The number of specimens and the detection rate of B. pertussis were 1709 and 26.9% (459/1709) in 2018, 1936 and 20.7% (400/1936) in 2019, which sharply declined to 308 and 11.4% (35/308) in 2020, 306 and 4.2% (13/306) in 2021, and then notably increased to 754 and 17.6% (133/754) in 2022, 1842 and 16.0% (295/1842) in 2023, 877 and 22.3% (196/877) in the first quarter of 2024. The proportion of children aged 3 to less than 6 years (preschool age) and 6 to 16 years (school age) in pertussis cases increased significantly during the study period, especially the proportion of school-aged children increased from 2.0% (9/459) in 2018 to 40.8% (80/196) in 2024. CONCLUSIONS: B. pertussis was the predominant pathogen among children with pertussis-like illness in China, with sporadic detection of B. parapertussis and no detection of B. holmesii or B.bronchiseptica. The preschool and school-age children are increasingly prevalent in B. pertussis infection cases, which may be associated with the latest rapid escalation of pertussis outbreak.

Evaluation of the ELITe InGenius and Bordetella ELITe MGB Kit for the detection and identification of B. pertussis, B. parapertussis and B. holmesii.

Bordetella pertussis is the causative pathogen of whooping cough or pertussis, a contagious respiratory disease. Aside from serodiagnosis, laboratory confirmation of pertussis is done through PCR, as B. pertussis is difficult to culture. The ELITe InGenius instrument (ELITechGroup, France) with accompanying Bordetella ELITe MGB Kit was evaluated against a laboratory-developed assay. Both assays combine two screening (IS481, IS1001) and two confirmation targets (recA, ptxA-Pr or IS1002) for optimal sensitivity and specificity. The company's stated claims on sensitivity and reproducibility were confirmed. Accuracy testing showed full concordance between both assays for the screening targets. Minor discrepancies were seen for the B. pertussis confirmation target. Some cross-reactivity with other Bordetella species was observed for the IS481-target, however, none of these were confirmed in the ptxA-Pr target. These results show the suitability of the Bordetella ELITe MGB Kit for the detection and differentiation of B. pertussis, B. parapertussis and B. holmesii.

Uncovering the Unseen: Bordetella hinzii Emerges in a Lung Transplant Recipient.

Bordetella hinzii (B. hinzii), a Gram-negative bacillus commonly associated with respiratory infections in animals, has garnered attention for its sporadic cases in humans, particularly in immunocompromised individuals. Despite its opportunistic nature, there remains limited understanding regarding its pathogenicity, diagnostic challenges, and optimal treatment strategies, especially in the context of immunosuppression. Herein, we present the first documented case of acute bronchitis caused by B. hinzii in an immunocompromised patient following double-lung transplantation. The patient, a former smoker with sarcoidosis stage IV, underwent transplant surgery and subsequently developed a febrile episode, leading to the identification of B. hinzii in broncho-alveolar lavage samples. Antimicrobial susceptibility testing revealed resistance to multiple antibiotics, necessitating tailored treatment adjustments. Our case underscores the importance of heightened awareness among clinicians regarding B. hinzii infections and the imperative for further research to elucidate its epidemiology and optimal management strategies, particularly in immunocompromised populations.

Reemergence of Bordetella parapertussis, United States, 2019-2023.

To determine changes in Bordetella pertussis and B. parapertussis detection rates, we analyzed 1.43 million respiratory multiplex PCR test results from US facilities from 2019 through mid-2023. From mid-2022 through mid-2023, Bordetella spp. detection increased 8.5-fold; 95% of detections were B. parapertussis. While B. parapertussis rates increased, B. pertussis rates decreased.

Comparative structural and immunological analysis of outer membrane proteins and dermonecrotic toxin in Bordetella bronchiseptica canine isolate.

Bordetella bronchiseptica is a pathogen causing respiratory infections in mammals. With the improving understanding of companion animals' welfare, addressing the side effects of bordetella vaccine gains importance in dogs. Studies on diverse subunit vaccines are actively pursued in humans to safely and effectively control bordetellosis. Therefore, our objective was to develop a canine bordetella vaccine inspired by human vaccine development. We evaluated the immunogenicity of the two bacterial components: the outer membrane proteins (OMPs) and the dermonecrotic toxin (DNT) from a canine isolate of B. bronchiseptica. In-silico analysis identified eight domains of DNT, and Domain 3 was selected as the most promising antigen candidate. Additionally, the OMPs were extracted and examined using SDS-PAGE and Western blot analysis. The distinct immunological characteristic of OMPs and DNT-3 were examined individually and in combination. Gene expression and cytokine production were also evaluated in DH82 cells after stimulation with those antigens. Treatment with OMPs resulted in higher level of Th1 related cytokines, while DNT-3 induced a predominant response associated with Th17 and Th2 in the cytokine production. Synergistic effects were observed exclusively on IL-23, indicating increase of a potential risk of side effects when OMPs and DNT act together. These findings provide valuable insights into the reactogenicity of conventional Bordetella vaccines. Further, the presented preclinical data in this study offer an alternative method of the development for an optimal next-generation Bordetella vaccine for companion animals and humans, replacing the acellular vaccines containing both toxin and protein components.

Effect of carbohydrates on the adhesion of Bordetella bronchiseptica to the respiratory epithelium in rabbits.

This study proposes an ecological approach for preventing respiratory tract infections caused by Bordetella bronchiseptica in mammals using a mixture of carbohydrates. In an in vivo study, 51-day-old New Zealand rabbits were treated with a solution containing 1 × 107 CFUs of B. bronchiseptica and 250 µg of one of the following carbohydrates: N acetylglucosamine (GlcNAc), N acetylgalactosamine (GalNAc), alpha methyl mannose (AmeMan), alpha methyl glucose (AmeGlc) and sialic acid (Neu5AC). Positive (B. bronchiseptica) and negative (Physiological Saline Solution (PSS)) controls were included. Animals treated with GlcNAc or AmeGlc showed no clinical signs of infection and exhibited a significant reduction (p < 0.05) in the severity of microscopic lesions evaluated in the nasal cavity and lung compared with the positive controls. Additionally, the presence of bacteria was not detected through microbiological isolation or PCR in the lungs of animals treated with these sugars. Use of a mixture of GlcNAc and AmeGlc resulted in greater inhibition of microscopic lesions, with a significant reduction (p < 0.05) in the severity of these lesions compared to the results obtained using individual sugars. Furthermore, the bacterium was not detected through microbiological isolation, Polymerase Chain Reaction (PCR) or indirect immunoperoxidase (IIP) in this group.