Differences in the effects of Bordetella pertussis and respiratory syncytial virus infection on the composition of nasopharyngeal flora in neonates

Introduction

Bordetella pertussis and respiratory syncytial virus (RSV) are important pathogens causing cough in neonates. Few studies have investigated the differences in the effects of these two specific infections on respiratory flora. The aim of this study was to explore whether infections with Bordetella pertussis and RSV have different effects on respiratory floral composition in neonates.

Methods

Nasopharyngeal respiratory flora was assessed by 16S ribosomal RNA amplification and V3-V4 region sequencing. Shannon and Simpson indices were calculated to determine the α diversity and principal coordinate analysis was performed to determine the β diversity.

Results

In total, 111 hospitalized neonates were divided into the pertussis (n = 29), RSV (n = 57), and control groups (n = 25) according to the pathogens detected. The relative abundance of Bordetella was significantly higher in the pertussis group (median: 19.18%, interquartile range: 72.57%). In contrast, this species was not detected in the other two groups. In the RSV group, the relative abundance of Streptococcus (median: 77.15%, interquartile range: 45.84%) was significantly higher than those in the pertussis and control groups (both P < 0.001). The α diversity of the RSV group was significantly lower than that of the control group (P < 0.001). Moreover, no statistically significant differences in the Shannon and Simpson indices were observed between the pertussis and control groups (P = 0.101 and P = 0.202, respectively). Principal coordinate analysis revealed a large overlap between the pertussis and control groups and a significant distance between the RSV and control groups without any overlap.

Discussion

Thus, the effects of infections with the two species, B. pertussis and RSV, impacted the diversity of nasopharyngeal flora differently. The principles underlying the difference in the effects of different pathogens on microbial flora require further investigation.

The fluoride permeation pathway and anion recognition in Fluc family fluoride channels

Fluc family fluoride channels protect microbes against ambient environmental fluoride by undermining the cytoplasmic accumulation of this toxic halide. These proteins are structurally idiosyncratic, and thus the permeation pathway and mechanism have no analogy in other known ion channels. Although fluoride-binding sites were identified in previous structural studies, it was not evident how these ions access aqueous solution, and the molecular determinants of anion recognition and selectivity have not been elucidated. Using x-ray crystallography, planar bilayer electrophysiology, and liposome-based assays, we identified additional binding sites along the permeation pathway. We used this information to develop an oriented system for planar lipid bilayer electrophysiology and observed anion block at one of these sites, revealing insights into the mechanism of anion recognition. We propose a permeation mechanism involving alternating occupancy of anion-binding sites that are fully assembled only as the substrate approaches.

Structural Biology and Molecular Modeling to Analyze the Entry of Bacterial Toxins and Virulence Factors into Host Cells

Understanding the functions and mechanisms of biological systems is an outstanding challenge. One way to overcome it is to combine together several approaches such as molecular modeling and experimental structural biology techniques. Indeed, the interplay between structural and dynamical properties of the system is crucial to unravel the function of molecular machinery’s. In this review, we focus on how molecular simulations along with structural information can aid in interpreting biological data. Here, we examine two different cases: (i) the endosomal translocation toxins (diphtheria, tetanus, botulinum toxins) and (ii) the activation of adenylyl cyclase inside the cytoplasm (edema factor, CyA, ExoY).

Post-translational acylation controls the folding and functions of the CyaA RTX toxin

The adenylate cyclase (CyaA) toxin is a major virulence factor of Bordetella pertussis, the causative agent of whooping cough. CyaA is synthetized as a pro-toxin, pro-CyaA, and converted into its cytotoxic form upon acylation of two lysines. After secretion, CyaA invades eukaryotic cells and produces cAMP, leading to host defense subversion. To gain further insights into the effect of acylation, we compared the functional and structural properties of pro-CyaA and CyaA proteins. HDX-MS results show that the refolding process of both proteins upon progressive urea removal is initiated by calcium binding to the C-terminal RTX domain. We further identified a critical hydrophobic segment, distal from the acylation region, that folds at higher urea concentration in CyaA than in pro-CyaA. Once refolded into monomers, CyaA is more compact and stable than pro-CyaA, due to a complex set of interactions between domains. Our HDX-MS data provide direct evidence that the presence of acyl chains in CyaA induces a significant stabilization of the apolar segments of the hydrophobic domain and of most of the acylation region. We propose a refolding model dependent on calcium and driven by local and distal acylation-dependent interactions within CyaA. Therefore, CyaA acylation is not only critical for cell intoxication, but also for protein refolding into its active conformation. Our data shed light on the complex relationship between post-translational modifications, structural disorder and protein folding. Coupling calcium-binding and acylation-driven folding is likely pertinent for other repeat-in-toxin cytolysins produced by many Gram-negative bacterial pathogens.-O'Brien, D. P., Cannella, S. E., Voegele, A., Raoux-Barbot, D., Davi, M., Douché, T., Matondo, M., Brier, S., Ladant, D., Chenal, A. Post-translational acylation controls the folding and functions of the CyaA RTX toxin.

Clinical and epidemiological characteristics of whooping cough in hospitalized patients of a tertiary care hospital in Peru

OBJECTIVE

Describe the clinical and epidemiological characteristics of patients under 2 years of age hospitalized with whooping cough in a tertiary care children's hospital in Peru.

METHODS

This was a case series of patients under 2 years of age who were hospitalized with a diagnosis of whooping cough in 2012.

RESULTS

A total of 121 patients were hospitalized. Diagnostic testing (direct immunofluorescence, polymerase chain reaction, culture) was carried out in 53.72% of patients. Overall, 23.15% (n = 28) were confirmed cases, all of whom were patients less than 10 months old, and none of whom had received 3 doses of whooping cough vaccine. A total of 96.43% (n = 27) of cases were under 6 months of age, 42.86% (n = 12) were younger than 3 months, and 10.71% (n = 3) were admitted to the intensive care unit. Of these cases, all were younger than 2 months old, and one patient died. The most common symptoms in the confirmed cases were coughing (96.43%), facial redness (96.43%), paroxysmal coughing (92.86%), and coughing-related cyanosis (78.57%). The most frequent probable epidemiological contact was the mother (17.86%), and the majority of cases occurred in the summer (46.43%).

CONCLUSION

Whooping cough is a cause of morbidity and mortality, especially in those younger than 6 months of age and in those who are not immunized or only partially immunized. Vaccination rates should be improved and case confirmation encouraged to prevent the underdiagnosis of this disease.

The Adenylate Cyclase (CyaA) Toxin from Bordetella pertussis Has No Detectable Phospholipase A (PLA) Activity In Vitro

The adenylate cyclase (CyaA) toxin produced in Bordetella pertussis is the causative agent of whooping cough. CyaA exhibits the remarkable capacity to translocate its N-terminal adenyl cyclase domain (ACD) directly across the plasma membrane into the cytosol of eukaryotic cells. Once translocated, calmodulin binds and activates ACD, leading to a burst of cAMP that intoxicates the target cell. Previously, Gonzalez-Bullon et al. reported that CyaA exhibits a phospholipase A activity that could destabilize the membrane to facilitate ACD membrane translocation. However, Bumba and collaborators lately reported that they could not replicate these results. To clarify this controversy, we assayed the putative PLA activity of two CyaA samples purified in two different laboratories by using two distinct fluorescent probes reporting either PLA2 or both PLA1 and PLA2 activities, as well as in various experimental conditions (i.e., neutral or negatively charged membranes in different buffers.) However, we could not detect any PLA activity in these CyaA batches. Thus, our data independently confirm that CyaA does not possess any PLA activity.

Primary transcriptome analysis reveals importance of IS elements for the shaping of the transcriptional landscape of Bordetella pertussis

Bordetella pertussis is the causative agent of whooping cough, a respiratory disease still considered as a major public health threat and for which recent re-emergence has been observed. Constant reshuffling of Bordetella pertussis genome organization was observed during evolution. These rearrangements are essentially mediated by Insertion Sequences (IS), a mobile genetic elements present in more than 230 copies in the genome, which are supposed to be one of the driving forces enabling the pathogen to escape from vaccine-induced immunity. Here we use high-throughput sequencing approaches (RNA-seq and differential RNA-seq), to decipher Bordetella pertussis transcriptome characteristics and to evaluate the impact of IS elements on transcriptome architecture. Transcriptional organization was determined by identification of transcription start sites and revealed also a large variety of non-coding RNAs including sRNAs, leaderless mRNAs or long 3' and 5'UTR including seven riboswitches. Unusual topological organizations, such as overlapping 5'- or 3'-extremities between oppositely orientated mRNA were also unveiled. The pivotal role of IS elements in the transcriptome architecture and their effect on the transcription of neighboring genes was examined. This effect is mediated by the introduction of IS harbored promoters or by emergence of hybrid promoters. This study revealed that in addition to their impact on genome rearrangements, most of the IS also impact on the expression of their flanking genes. Furthermore, the transcripts produced by IS are strain-specific due to the strain to strain variation in IS copy number and genomic context.

Leukemoid Reaction in Infant Pertussis: Is There a Place for Hydroxyurea? A Case Report

A 73-days old infant of 34 weeks' gestation was hospitalized with a co-infection of respiratory syncytial virus (RSV) and Bordetella pertussis (BP). She required invasive ventilation for 9 days in the context of malignant pertussis with persistent hypoxemia and hypercapnia secondary to a leukemoid reaction. Despite an increase of white blood cell (WBC) count up to 70 G/L and ensuing pulmonary hypertension, no hemodynamic compromise occurred. Without clear indication for leukapheresis nor exchange transfusion, an off-label treatment with hydroxyurea was given for 5 days with gradual decrease of WBC count, without any complication and hospital discharge on day 29. To our knowledge, no effective therapy for malignant pertussis has been described in the literature and complications are frequent with leukoreduction procedures. We discuss an alternative to invasive procedures in young infants to fulfill the need to decrease rapidly leukocyte counts in a leukemoid reaction associated with Bordetella pertussis infection. To our knowledge, hydroxyurea has never been used in malignant pertussis but is a well-known medication for oncologic and hematologic diseases such as acute myeloid leukemia or sickle cell anemia. Its effects in this setting are not well understood but the positive outcome in our patient supports the need for further studies.

Randomized clinical trial of the safety and immunogenicity of the Tdap vaccine in pregnant Mexican women

Immunization with the tetanus, diphtheria, and pertussis (Tdap) vaccine raises controversies on immunogenicity and possible antibody interference. We performed an experimental, double-blind, parallel group controlled clinical trial to evaluate the safety and immunogenicity of the Tdap vaccine in 204 pregnant women and their children and to determine its interference in antibody production. Pregnant women 18 to 38 y of age with 12 to 24 weeks gestation, a low obstetric risk, and without serious disease were randomly selected. The experimental group received 0.5 mL IM of Tdap and the control group normal saline. Six blood samples were drawn before and after solution application, and from the umbilical cord of the infants and at 2, 4, and 6 months of age. Pertactin and Pertussis toxin antibodies and possible interference of maternal antibodies with the vaccine were determined. In the experimental group, antibodies against Bordetella pertussis pertactin (anti-PRN) (112 E/mL 95% CI 89.9-139.9) and antibodies against pertussis toxin (anti-PT) (24.0 E/mL, 95% CI 18.3-31.4) were elevated in the mother before vaccination. These were higher in the umbilical cord and descended in the infant at 2 months (71.4 (95% CI 56.8-89.7 and 10.9; 95% CI 8.7-13.7, respectively). Anti-PT showed a delay in production. Tdap safety was confirmed with only mild local pain at 24 and 48 hours. Anti-PRN and anti-PT antibodies in the infant descend at 2 months of age. There is a delay in anti-PT in children of immunized mothers. Further studies are needed to elucidate its clinical significance.

Investigating Bordetella pertussis colonisation and immunity: protocol for an inpatient controlled human infection model

INTRODUCTION

We summarise an ethically approved protocol for the development of an experimental human challenge colonisation model. Globally Bordetella pertussis is one of the leading causes of vaccine-preventable death. Many countries have replaced whole cell vaccines with acellular vaccines over the last 20 years during which pertussis appears to be resurgent in a number of countries in the developed world that boast high immunisation coverage. The acellular vaccine provides relatively short-lived immunity and, in contrast to whole cell vaccines, may be less effective against colonisation and subsequent transmission. To improve vaccine strategies, a greater understanding of human B. pertussis colonisation is required. This article summarises a protocol and does not contain any results.

METHODS AND ANALYSIS

A controlled human colonisation model will be developed over two phases. In phase A, a low dose of the inoculum will be given intranasally to healthy participants. This dose will be escalated or de-escalated until colonisation is achieved in approximately 70% (95% CI 47% to 93%) of the exposed volunteers without causing disease. The colonisation period, shedding and exploratory immunology will be assessed during a 17-day inpatient stay and follow-up over 1 year. The dose of inoculum that achieves 70% colonisation will then be confirmed in phase B, comparing healthy participants exposed to B. pertussis with a control group receiving a sham inoculum.

ETHICS AND DISSEMINATION

This study has been approved by the ethical committee reference: 17/SC/0006, 24 February 2017. Findings will be published in peer-reviewed open access journals as soon as possible.

The relationship between mucosal immunity, nasopharyngeal carriage, asymptomatic transmission and the resurgence of Bordetella pertussis

The incidence of whooping cough in the US has been rising slowly since the 1970s, but the pace of this has accelerated sharply since acellular pertussis vaccines replaced the earlier whole cell vaccines in the late 1990s. A similar trend occurred in many other countries, including the UK, Canada, Australia, Ireland, and Spain, following the switch to acellular vaccines. The key question is why. Two leading theories (short duration of protective immunologic persistence and evolutionary shifts in the pathogen to evade the vaccine) explain some but not all of these shifts, suggesting that other factors may also be important.

In this synthesis, we argue that sterilizing mucosal immunity that blocks or abbreviates the duration of nasopharyngeal carriage of Bordetella pertussis and impedes person-to-person transmission (including between asymptomatically infected individuals) is a critical factor in this dynamic. Moreover, we argue that the ability to induce such mucosal immunity is fundamentally what distinguishes whole cell and acellular pertussis vaccines and may be pivotal to understanding much of the resurgence of this disease in many countries that adopted acellular vaccines. Additionally, we offer the hypothesis that observed herd effects generated by acellular vaccines may reflect a modification of disease presentation leading to reduced potential for transmission by those already infected, as opposed to inducing resistance to infection among those who have been exposed.

Bordetella pertussis is an uncommon pathogen in children hospitalized with bronchiolitis during the winter season

BACKGROUND

In the United States (U.S.), Bordetella pertussis incidence has increased. Cough and apnea are common findings in pertussis and also in bronchiolitis, the most common cause of hospitalization in U.S. infants. The objective was to determine the prevalence of B. pertussis infection in children hospitalized with bronchiolitis and to describe its clinical course.

METHODS

Children hospitalized with bronchiolitis and age <2 years were eligible for a prospective, multicenter cohort study during 3 consecutive winter seasons (November-March) from 2007 to 2010. Sixteen sites in 12 states participated using a standardized enrollment protocol. Families were asked the 2010 Centers for Disease Control and Prevention pertussis classification questions. Nasopharyngeal aspirates were obtained and tested by real-time polymerase chain reaction for 16 viruses, Mycoplasma pneumoniae and B. pertussis.

RESULTS

Two thousand sixty-eight (94%) of 2207 children had 1 or more respiratory pathogens. B. pertussis was identified in 4 children [0.2%; 95% confidence interval (CI): 0.1-0.5%] with 3 having a viral co-infection. All 4 were younger than 4 months; 2 met the Centers for Disease Control and Prevention definition of probable pertussis; and 3 had received at least 1 dose of an acellular pertussis vaccine. During the hospitalization, 2 had paroxysmal cough, 1 required intensive care unit care and the median length of stay was 13 days.

CONCLUSIONS

Our data support that B. pertussis is an uncommon pathogen in U.S. children hospitalized with bronchiolitis in the winter. Making a diagnosis of pertussis can be challenging because the disease can be atypical and may not meet the Centers for Disease Control and Prevention definition of probable infection.

What is new in pertussis?

Despite high vaccination coverage, over the last fifteen years there has been a worldwide resurgence of B. pertussis infection. While classical pertussis in the prevaccine era was primarily a childhood disease, today with widespread vaccination, there has been a shift in the incidence of disease to adolescents and adults. Centers of Disease Control and Prevention (CDC) data from 2004 reveal a nearly 19-fold increase in the number of cases in individuals 10-19 years and a 16-fold increase in persons over 20 years. Indeed adolescent and adults play a significant role in the transmission of pertussis to neonates and infants who are vulnerable to substantial morbidity and mortality from pertussis infection. Several explanations have been proposed to explain the increasing incidence of disease, with waning immunity after natural infection or immunization being widely cited as a significant factor. Improving molecular biology diagnostic techniques, namely PCR assays, also accounts for the increasing laboratory diagnosis of pertussis. Expanding vaccination strategies including universal immunization of adolescents, targeted immunization of adults, and in particular, healthcare workers, childcare providers and parents of newborns, will likely improve pertussis control. With pertussis continuing to pose a serious threat to infants, and greatly affecting adolescents and adults, there remains a need to: (a) increase the awareness of physicians as to the growing pertussis problem, (b) standardize diagnostic techniques, and (c) implement various new vaccine strategies to enhance its control.