Clinical evaluation and validation of laboratory methods for the diagnosis of Bordetella pertussis infection: Culture, polymerase chain reaction (PCR) and anti-pertussis toxin IgG serology (IgG-PT)

Public health management of pertussis in adults: Practical challenges and future strategies

A panel of 24 international experts met in July 2022 to discuss challenges associated with pertussis detection, monitoring, and vaccination in adults; conclusions from this meeting are presented. There has been a shift in the epidemiology of pertussis toward older children and adults. This shift has been attributed to the waning of infection- or vaccine-induced immunity, newer detection techniques causing detection bias, and possibly the replacement of whole-cell pertussis with acellular vaccines in high-income countries, which may lead to immunity waning more quickly. The burden of adult pertussis is still likely under-ascertained due to widespread under-recognition by healthcare professionals (HCPs), under-diagnosis, and under-reporting in this age group. Non-standardized testing guidance and varied case definitions have contributed to under-reporting. Key barriers to HCP engagement with the tetanus, diphtheria, and pertussis (Tdap) vaccine include low awareness, lack of time/funding, and lack of motivation due to low prioritization of Tdap.

Global Resurgence of Pertussis: A Perspective from China

Pertussis (or whooping cough) is a highly infectious acute respiratory disease primarily caused by Bordetella pertussis, which is also one of the most important causes of infant death worldwide. The widespread use of vaccines has greatly reduced the morbidity and mortality of pertussis. However, since the 1980s, in a number of countries with high vaccine coverage, the incidence of pertussis has risen again after remaining low for many years, with outbreaks even occurring in some areas. The peak onset of pertussis is shifting from infancy to adolescence, and adolescence is becoming the main source of infection for infants. Despite the increasing incidence of pertussis, serological findings suggest that the true prevalence of the disease may be significantly underestimated. Therefore, in this narrative review, we summarize the pathogenic process and immune characteristics of bacteria, the diagnosis and treatment of diseases, as well as vaccination and prevalence of pertussis at home and abroad, and attempt to analyze the causes and influencing factors of pertussis resurgence and summarize some prevention and control strategies to assist in improving the understanding of pertussis and preventing unexpected outbreaks.

Association between real-time polymerase chain reaction cycle threshold value and clinical presentation in children with Bordetella pertussis

BACKGROUND

The cycle threshold (Ct) value is inversely proportional to the number of copies of the target region in a sample, suggesting that a low Ct value indicates a high pathogen load. The relationship between Ct value and clinical presentation in children with pertussis is not well-defined.

METHODS

We investigated the relationships between the Ct value of nasopharyngeal samples positive for Bordetella pertussis deoxyribonucleic acid via real-time polymerase chain reaction (PCR), collected from children on admission and their adult family members between May 2022 and March 2024 at Hangzhou Children's Hospital, China. The study focused on the correlation between Ct value and clinical presentation in children with pertussis.

RESULTS

The Ct value was positively correlated with age (r = 0.362, P = 0.001). The mean Ct value for children with pertussis was 28.0 (range: 22.0-32.0), which was lower than the 32.0 (range: 30.0-34.0) observed in adults. Ct value was inversely correlated with length of stay, an indicator of disease severity (r = -0.356, P = 0.001). Logistic regression analyses revealed that both Ct value (OR: 0.891, 95% CI: 0.799-0.993, P = 0.036) and white blood cell count (OR: 1.127, 95% CI: 1.005-1.263, P = 0.040) were independently associated with severity of pertussis.

CONCLUSIONS

Real-time PCR Ct values at initial diagnosis for pertussis may potentially predict severe disease outcomes in children.

A novel AI-based diagnostic model for pertussis pneumonia

It is still very difficult to diagnose pertussis based on a doctor's experience. Our aim is to develop a model based on machine learning algorithms combined with biochemical blood tests to diagnose pertussis. A total of 295 patients with pertussis and 295 patients with non-pertussis lower respiratory infections between January 2022 and January 2023, matched for age and gender ratio, were included in our study. Patients underwent a reverse transcription polymerase chain reaction test for pertussis and other viruses. Univariate logistic regression analysis was used to screen for clinical and blood biochemical features associated with pertussis. The optimal features and 3 machine learning algorithms including K-nearest neighbor, support vector machine, and eXtreme Gradient Boosting (XGBoost) were used to develop diagnostic models. Using univariate logistic regression analysis, 18 out of the 27 features were considered optimal features associated with pertussis The XGBoost model was significantly superior to both the support vector machine model (Delong test, P = .01) and the K-nearest neighbor model (Delong test, P = .01), with the area under the receiver operating characteristic curve of 0.96 and an accuracy of 0.923. Our diagnostic model based on blood biochemical test results at admission and XGBoost algorithm can help doctors effectively diagnose pertussis.

Assessing the Impact of the 2020 Council of State and Territorial Epidemiologists Case Definition for Pertussis on Reported Pertussis Cases

BACKGROUND

In 2020, the Council of State and Territorial Epidemiologists (CSTE) pertussis case definition was modified; the main change was classifying polymerase chain reaction (PCR)-positive cases as confirmed, regardless of cough duration. Pertussis data reported through Enhanced Pertussis Surveillance (EPS) in 7 sites and the National Notifiable Diseases Surveillance System (NNDSS) were used to evaluate the impact of the new case definition.

METHODS

We compared the number of EPS cases with cough onset in 2020 to the number that would have been reported based on the prior (2014) CSTE case definition. To assess the impact of the change nationally, the proportion of EPS cases newly reportable under the 2020 CSTE case definition was applied to 2020 NNDSS data to estimate how many additional cases were captured nationally.

RESULTS

Among 442 confirmed and probable cases reported to EPS states in 2020, 42 (9.5%) were newly reportable according to the 2020 case definition. Applying this proportion to the 6124 confirmed and probable cases reported nationally in 2020, we estimated that the new definition added 582 cases. Had the case definition not changed, reported cases in 2020 would have decreased by 70% from 2019; the observed decrease was 67%.

CONCLUSIONS

Despite a substantial decrease in reported pertussis cases in the setting of coronavirus disease 2019 (COVID-19), our data show that the 2020 pertussis case definition change resulted in additional case reporting compared with the previous case definition, providing greater opportunities for public health interventions such as prophylaxis of close contacts.

Strengthening Bordetella pertussis genomic surveillance by direct sequencing of residual positive specimens

Whole-genome sequencing (WGS) of microbial pathogens recovered from patients with infectious disease facilitates high-resolution strain characterization and molecular epidemiology. However, increasing reliance on culture-independent methods to diagnose infectious diseases has resulted in few isolates available for WGS. Here, we report a novel culture-independent approach to genome characterization of Bordetella pertussis, the causative agent of pertussis and a paradigm for insufficient genomic surveillance due to limited culture of clinical isolates. Sequencing libraries constructed directly from residual pertussis-positive diagnostic nasopharyngeal specimens were hybridized with biotinylated RNA "baits" targeting B. pertussis fragments within complex mixtures that contained high concentrations of host and microbial background DNA. Recovery of B. pertussis genome sequence data was evaluated with mock and pooled negative clinical specimens spiked with reducing concentrations of either purified DNA or inactivated cells. Targeted enrichment increased the yield of B. pertussis sequencing reads up to 90% while simultaneously decreasing host reads to less than 10%. Filtered sequencing reads provided sufficient genome coverage to perform characterization via whole-genome single nucleotide polymorphisms and whole-genome multilocus sequencing typing. Moreover, these data were concordant with sequenced isolates recovered from the same specimens such that phylogenetic reconstructions from either consistently clustered the same putatively linked cases. The optimized protocol is suitable for nasopharyngeal specimens with diagnostic IS481 Ct < 35 and >10 ng DNA. Routine implementation of these methods could strengthen surveillance and study of pertussis resurgence by capturing additional cases with genomic characterization.

Adaptive immune response to bordetella pertussis during vaccination and infection: emerging perspectives and unanswered questions

INTRODUCTION

Whooping cough, also known as pertussis, remains a significant challenge as a vaccine-preventable disease worldwide. Since the switch from the whole-cell Pertussis (wP) vaccine to the acellular Pertussis vaccine (aP), cases of whooping cough have increased in countries using the aP vaccine. Understanding the immune system's response to pertussis vaccines and infection is crucial for improving current vaccine efficacy.

AREAS COVERED

This review of the literature using PubMed records offers an overview of the qualitative differences in antibody and T cell responses to B. pertussis (BP) in vaccination and infection, and their potential association with decreased efficacy of the aP vaccine in preventing infection and subclinical colonization. We further discuss how asymptomatic infections and carriage are widespread among vaccinated human populations, and explore methodologies that can be employed for their detection, to better understand their impact on adaptive immune responses and identify key features necessary for protection against the disease.

EXPERT OPINION

An underappreciated human BP reservoir, stemming from the decreased capacity of the aP vaccine to prevent subclinical infection, offers an alternative explanation for the increased incidence of clinical disease and recurrent outbreaks.

Maternal Pertussis Vaccination, Infant Immunization, and Risk of Pertussis

OBJECTIVES

Following the introduction of jurisdictional maternal pertussis vaccination programs in Australia, we estimated maternal vaccine effectiveness (VE) and whether maternal pertussis vaccination modified the effectiveness of the first 3 primary doses of pertussis-containing vaccines.

METHODS

We conducted a population-based cohort study of 279 418 mother-infant pairs using probabilistic linkage of administrative health records in 3 Australian jurisdictions. Infants were maternally vaccinated if their mother had a documented pertussis vaccination ≥14 days before birth. Jurisdictional immunization records were used to identify receipt of the first 3 infant doses of pertussis-containing vaccines. Infant pertussis infections were identified using notifiable disease records. VE was estimated using Cox proportional hazard models.

RESULTS

Pertussis was administered during 51.7% (n = 144 429/279 418) of pregnancies, predominantly at 28-31 weeks' gestation. VE of maternal pertussis vaccination declined from 70.4% (95% confidence interval [CI], 50.5-82.3) among infants <2 months old to 43.3% (95% CI, 6.8-65.6) among infants 7-8 months old and was not significant after 8 months of age. Although we observed slightly lower VE point estimates for the third dose of infant pertussis vaccine among maternally vaccinated compared with unvaccinated infants (76.5% vs 92.9%, P = .002), we did not observe higher rates of pertussis infection (hazard ratio, 0.70; 95% CI, 0.61-3.39).

CONCLUSIONS

Pertussis vaccination near 28 weeks' gestation was associated with lower risk of infection among infants through 8 months of age. Although there was some evidence of lower effectiveness of infant vaccination among maternally vaccinated infants, this did not appear to translate to greater risk of disease.

Pertussis in Mexico from 2000 to 2019: A real-world study of incidence, vaccination coverage, and vaccine effectiveness

BACKGROUND

The national immunization program in Mexico includes a 3-dose primary series of pertussis vaccine and a toddler booster dose. In Mexico, whole-cell pertussis vaccines (wP) were switched in 2007 to acellular pertussis vaccines (aP).

METHODS

This retrospective study using Mexican National Databases of Health and population surveillance (2000-2019) assessed the incidence of pertussis, infant pertussis vaccination coverage, and vaccine effectiveness (VE) against clinically-diagnosed and/or laboratory-confirmed pertussis in children aged 6.5-18.5 or 24.5 months for the primary series, and children aged 18.5 or 24.5-48.5 months for the toddler booster.

RESULTS

The incidence of pertussis sharply increased in 2012 and was highest in 2012, 2015, and 2016 (0.84-0.94/100,000 person-years). Coverage was highest for the first dose in the primary series, decreasing for each subsequent dose. The VE against notified pertussis was 96.4% (95% CI: 94.7, 97.6) for the first three doses of wP vaccine (2000-2007) and 95.7% (95% CI: 95.1, 96.2) for the first three doses of aP vaccine (2008-2019).

CONCLUSIONS

Our findings suggested high levels of vaccine effectiveness overall were achieved for the aP and wP vaccines in Mexico between 2000 and 2019.

Evaluation of serum anti-pertussis toxin IgA antibodies for the diagnosis of Bordetella pertussis infection in young children

BACKGROUND

The determination of serum anti-pertussis toxin (PT) IgG antibodies is recommended for the diagnosis and surveillance of pertussis. However, the diagnostic power of anti-PT IgG can be hampered by possible interference from previous vaccinations. We aim to assess if anti-PT IgA antibodies can be well induced by Bordetella pertussis (B. pertussis) infections in children, and their capacity to improve pertussis serodiagnosis.

METHODS

Serum samples from 172 hospitalized children younger than 10 years old with confirmed pertussis were tested. Pertussis was confirmed by culture, PCR and/or serology. Anti-PT IgA antibodies were determined with commercial ELISA kits.

RESULTS

Sixty-four (37.2 %) subjects had anti-PT IgA antibodies greater than or equal to 15 IU/ml, and 52 (30.2 %) of them had anti-PT IgA antibodies greater than or equal to 20 IU/ml. No children with negative anti-PT IgG (less than 40 IU/ml) were observed to have anti-PT IgA antibodies greater than or equal to 15 IU/ml. Of patients younger than one year of age, about 50 % had an IgA antibody response. Moreover, the proportion of subjects with anti-PT IgA antibodies greater than or equal to 15 IU/ml among PCR negative subjects was significantly higher than that among PCR positive subjects (76.9 % vs 35.5 %).

CONCLUSIONS

The determination of anti-PT IgA antibodies does not seem to have added value for the serodiagnosis of pertussis in children older than one year of age. However, for infants, determination of serum anti-PT IgA antibodies appears to be useful for the diagnosis of pertussis especially when PCR and culture are negative. The results should be interpreted with caution as the number of subjects included in this study was limited.

Pertussis in India: Past, Present, and Future

While vaccines have markedly reduced the incidence of pertussis, a resurgence has occurred in many countries. Until recently, pertussis has not been recognized as an important public health challenge in India due to its successful infant immunization program. However, India still accounts for a large proportion of the world's cases, and increasing reports of pertussis in other countries and in neonates have regenerated interest in pertussis among Indian authorities. The Global Pertussis Initiative (GPI) Annual Meeting was held virtually in October 2020, in part, to gain a better understanding of the epidemiology and disease burden of pertussis and to explore opportunities to improve its prevention in India. There was a consensus that pertussis cases are being underestimated in India due to multiple factors, such as a reliance on passive surveillance and diagnostic challenges. India offers both whole-cell pertussis and acellular pertussis vaccines, but vaccine coverage is inconsistent across regions due to differences in vaccine availability, access to health care, and regional administrative challenges. This report summarizes the outcomes and considers the key clinical implications of this meeting. The GPI agreed that active surveillance of pertussis in India would be optimal and recommended several studies, including serosurveillance among women of reproductive age to assess the prevalence of recent pertussis infection and to enable policy changes that will enhance the rational use of acellular and whole-cell vaccines. It also recommended engagement with nongovernmental organizations in order to encourage pregnancy immunization in the public sector. To achieve effective control of pertussis in the future, the GPI recognizes there are opportunities to characterize the burden of pertussis in India appropriately and increase vaccination coverage in multiple age groups.

A pangenome approach-based loop-mediated isothermal amplification assay for the specific and early detection of Bordetella pertussis

Despite widespread vaccination, Bordetella pertussis continues to cause pertussis infections worldwide, leaving infants at the highest risk of severe illness and death, while people around them are likely the main sources of infection and rapidly spread the disease. Rapid and less complex molecular testing for the specific and timely diagnosis of pertussis remains a challenge that could help to prevent the disease from worsening and prevent its transmission. We aimed to develop and validate a colorimetric loop-mediated isothermal amplification (LAMP) assay using a new target uvrD_2 informed by the pangenome for the specific and early detection of B. pertussis. Compared to that of multitarget quantitative polymerase chain reaction (multitarget qPCR) using a large clinical DNA specimen (n = 600), the diagnostic sensitivity and specificity of the uvrD_2 LAMP assay were 100.0% and 98.6%, respectively, with a 99.7% degree of agreement between the two assays. The novel colorimetric uvrD_2 LAMP assay is highly sensitive and specific for detecting B. pertussis DNA in nasopharyngeal swabs and showed similar diagnostic accuracy to complex and high-cost multitarget qPCR, but it is faster, simpler, and inexpensive, which makes it very helpful for the reliable and timely diagnosis of pertussis in primary health care and resource-limited settings.

The Relationship Between Chronic Cough and Laryngopharyngeal Reflux

Chronic cough is multifactorial in origin, may affect quality of life adversely, and often poses a diagnostic challenge for physicians. Laryngopharyngeal reflux (LPR) is one common contributing factor for chronic cough, but the mechanism by which reflux causes cough remains unclear. Research investigating the relationship between chronic cough and LPR has focused largely on reflux from the perspective of gastroenterology, rather than otolaryngology.

OBJECTIVE

The purpose of our study was to investigate the relationship between chronic cough and LPR by using the objective results of 24-hour pH impedance studies.

METHODS

We conducted a retrospective chart review of all patients who presented to the voice center of the senior author (RTS) with a chief complaint of chronic cough and no previous diagnosis of reflux. Patient demographics, past medical history, laboratory data, and exam findings during the initial visit from 2015 to 2020 and at follow-up were analyzed.

RESULTS

We identified 28 patients who presented with a chief complaint of chronic cough and who had not been diagnosed with or treated for reflux previously. Twenty-three had additional risk factors for chronic cough (asthma, chronic sinusitis, and bronchial schwannoma). All 28 had findings consistent with LPR upon exam. Treatment with reflux medications and lifestyle modification decreased the reflux finding score significantly from 11.39 to 9.21 (P= 0.005). Of all, 60.7% of patients reported subjective improvement in cough symptoms. The cough had improved in 50.0% and had resolved completely in 10.7%. Patients with VF paresis were less likely to report improvement in their cough. Further workup was performed for the 11 patients who had cough that did not resolve completely after reflux treatment. Detectable levels of antimycoplasma antibodies were found in nine patients, and antipertussis antibodies were found in two patients. Six patients followed up after a course of clarithromycin, three of whom had experienced improvement in their cough.

CONCLUSIONS

Our findings suggest that LPR may be a prevalent contributing or etiologic factor for chronic cough. The expected improvement after initiating reflux treatment is 60% at 3 months. Cough resolved completely in 10% of patients at 4 months. Nonresponders may have other contributing causes of cough, including esophageal dysmotility, mycoplasma, pertussis, and other contributors. Further studies are needed to confirm or refute these findings.

Evaluation of BioFire Respiratory Panel 2 plus for Detection of Bordetella pertussis in Nasopharyngeal Swab Specimens from Children with Clinically Suspected Pertussis

The objective of this study was to compare the performances of BioFire Respiratory Panel 2 (RP2) plus, quantitative real-time PCR (qPCR), and culture for the detection of Bordetella pertussis in nasopharyngeal swab (NPS) specimens. Consecutive NPS specimens were collected from patients with clinically suspected pertussis from 1 March 1 to 31 July 2018 in Shenzhen Children's Hospital. All the specimens were tested in parallel by RP2 plus, qPCR, and culture methods. A total of 464 children were enrolled in this study. The positive pertussis rates of culture, RP2 plus, and qPCR were 23.1%, 39.0%, and 38.4%, respectively. Compared to the combined reference standard, the sensitivity, specificity, positive predictive value, and negative predictive values were, respectively, 56.6% (95% confidence interval [CI], 49.2 to 63.7%), 100% (98.3 to 100%), 100% (95.7 to 100%), and 77.0% (72.2 to 81.2%) for culture, 89.9% (84.5 to 93.7%), 96.0% (92.8 to 97.9%), 93.9% (89.1 to 96.8%), and 93.3% (89.5 to 95.8%) for RP2 plus, and 86.8% (80.9 to 91.1%), 94.9% (91.4 to 97.1%), 92.1% (86.9 to 95.5%), and 91.3% (87.2 to 94.2%) for qPCR. The most prevalent codetected pathogen was human rhinovirus/enterovirus (n = 99, 52.4%), followed by parainfluenza virus (n =32, 16.9%) and respiratory syncytial virus (n = 29, 15.3%), in children with B. pertussis present, which was consistent with the top three pathogens previously found in children with B. pertussis absent. Turnaround times for RP2 plus, qPCR, and culture were 2 h, 8 h, and 120 h, respectively. RP2 plus quickly and accurately detected B. pertussis, providing valuable information for an early clinical diagnosis and optimal choice of therapy. IMPORTANCE In recent years, there have been some epidemic or local outbreaks of pertussis in countries with high vaccination rates. One of the crucial factors in controlling pertussis is early diagnosis, which is based on specific laboratory measurements, including culture, serological tests, and PCR assays. Compared to culture and serological tests, PCR is more suitable for clinical application, with a fast detection speed of several hours independent of the disease stage and individual vaccination status. BioFire Respiratory Panel 2 plus, a multiplex PCR assay for simultaneously detecting 22 respiratory pathogens, facilitates the quick detection of Bordetella pertussis and coinfecting respiratory pathogens. It also provides valuable information for an early clinical diagnosis and optimal choice of therapy for children with clinically suspected pertussis.

Clinical evaluation of a new rapid immunochromatographic test for detection of Bordetella pertussis antigen

A more rapid and less complicated test to diagnose pertussis is required in clinical settings. We need to detect Bordetella pertussis, which mainly causes pertussis, as early as possible, because pertussis is more likely to become severe in infants, and people around them can easily become a source of infection due to its strong infectivity. Nevertheless, methods that can detect B. pertussis rapidly and efficiently are lacking. Therefore, we developed a new immunochromatographic antigen kit (ICkit) for the early diagnosis of pertussis. The ICkit detects B. pertussis antigens in a nasopharyngeal swab without equipment and provides the result in about 15 min with a simple procedure. Additionally, a prospective study to evaluate the ICkit was conducted in 11 medical institutions, involving 195 cases with suspected pertussis. Compared with the real-time polymerase chain reaction (rPCR), the sensitivity and specificity of the ICkit were 86.4% (19/22) and 97.1% (168/173), respectively. The ICkit detected the antigen in both children and adults. Furthermore, the ICkit detected the antigen until the 25th day from the onset of cough, when rPCR detected the antigen. Thus, the ICkit demonstrated a high correlation with rPCR and would help diagnose pertussis more rapidly and efficiently.

Modeling Immune Evasion and Vaccine Limitations by Targeted Nasopharyngeal Bordetella pertussis Inoculation in Mice

Conventional pertussis animal models deliver hundreds of thousands of Bordetella pertussis bacteria deep into the lungs, rapidly inducing severe pneumonic pathology and a robust immune response. However, human infections usually begin with colonization and growth in the upper respiratory tract. We inoculated only the nasopharynx of mice to explore the course of infection in a more natural exposure model. Nasopharyngeal colonization resulted in robust growth in the upper respiratory tract but elicited little immune response, enabling prolonged and persistent infection. Immunization with human acellular pertussis vaccine, which prevents severe lung infections in the conventional pneumonic infection model, had little effect on nasopharyngeal colonization. Our infection model revealed that B. pertussis can efficiently colonize the mouse nasopharynx, grow and spread within and between respiratory organs, evade robust host immunity, and persist for months. This experimental approach can measure aspects of the infection processes not observed in the conventional pneumonic infection model.

Pertactin-Deficient Bordetella pertussis, Vaccine-Driven Evolution, and Reemergence of Pertussis

Recent reemergence of pertussis (whooping cough) in highly vaccinated populations and rapid expansion of Bordetella pertussis strains lacking pertactin (PRN), a common acellular vaccine antigen, have raised the specter of vaccine-driven evolution and potential return of what was once the major killer of children. The discovery that most circulating B. pertussis strains in the United States have acquired new and independent disruptive mutations in PRN is compelling evidence of strong selective pressure. However, the other 4 antigens included in acellular vaccines do not appear to be selected against so rapidly. We consider 3 aspects of PRN that distinguish it from other vaccine antigens, which might, individually or collectively, explain why only this antigen is being precipitously eliminated. An understanding of the increase in PRN-deficient strains should provide useful information for the current search for new protective antigens and provide broader lessons for the design of improved subunit vaccines.

Isolate-Based Surveillance of Bordetella pertussis, Austria, 2018-2020

Pertussis is a vaccine-preventable disease, and its recent resurgence might be attributable to the emergence of strains that differ genetically from the vaccine strain. We describe a novel pertussis isolate-based surveillance system and a core genome multilocus sequence typing scheme to assess Bordetella pertussis genetic variability and investigate the increased incidence of pertussis in Austria. During 2018–2020, we obtained 123 B. pertussis isolates and typed them with the new scheme (2,983 targets and preliminary cluster threshold of <6 alleles). B. pertussis isolates in Austria differed genetically from the vaccine strain, both in their core genomes and in their vaccine antigen genes; 31.7% of the isolates were pertactin-deficient. We detected 8 clusters, 1 of them with pertactin-deficient isolates and possibly part of a local outbreak. National expansion of the isolate-based surveillance system is needed to implement pertussis-control strategies.

Pertussis in Individuals with Co-morbidities: A Systematic Review

Pertussis is a highly contagious disease of the respiratory tract caused by Bordetella pertussis. Although the burden of pertussis is highest in children, available data suggests that pertussis in the elderly and those with underlying chronic conditions or illnesses can result in significant morbidity, mortality and costs. We undertook a comprehensive review to assess the association between pertussis and chronic conditions/illnesses. A search was undertaken on 17 June 2019 across EMBASE, Medline and BIOSIS. Citations were limited to those in English, in humans and published since 1 January 1990. There were 1179 papers identified with an additional 70 identified through a review of the reference lists. Of these, 34 met the inclusion criteria. Papers included were categorised in groups, those which reported: associations between prior pertussis and subsequent chronic conditions or illnesses; a link between chronic conditions/illnesses and subsequent risk of pertussis; and those which reported on the effect of the chronic conditions/illnesses on pertussis complications or exacerbations. Pertussis appears to increase the likelihood of developing some chronic conditions/illnesses, but also appears to decrease the likelihood of developing some haematological cancers. There were several chronic conditions/illnesses where the study results were mixed, and several studies that found no association with previous pertussis. There were also studies which showed that having some comorbid health condition(s) might increase the risk of developing pertussis. Three studies showed pertussis can lead to increased exacerbations of chronic conditions/illnesses and associated hospitalisations, although one study showed it reduced the effects of chronic bronchitis. Previous pertussis appears to contribute to the increased likelihood of developing some respiratory conditions like asthma, and conversely those with asthma or COPD are at increased risk of severe pertussis requiring further intervention. Further research is required to confirm or disprove these associations, and to characterise the pathophysiological mechanisms behind the potential associations with pertussis.

Pertussis among patients with clinically compatible illness in the Amhara Regional State, Ethiopia

BACKGROUND

Pertussis is an acute respiratory tract disease caused by Bordetella pertussis. In 2014, 24.1 million pertussis cases, resulting in 160,700 deaths, were estimated to have occurred worldwide. This study aimed to determine the epidemiology of pertussis among patients with clinically compatible illness who visited selected hospitals in the Amhara Regional State of Ethiopia.

METHODS

A cross-sectional study design was used to review pertussis patients with clinically compatible illness. Nasopharyngeal swabs were collected from 515 patients from July 2018 through February 2019. DNA was extracted from all nasopharyngeal swabs and samples were analyzed using real-time (RT-) PCR. Crude and adjusted odds ratios with corresponding 95% confidence intervals were estimated using bivariable and multivariable logistic regression analysis, respectively.

RESULTS

The overall prevalence of Bordetella species among the study participants was 156 of 515 (30.3%) [95% CI = 26.4-34.6] as determined by Bordetella RT-PCR, including: 65 (41.7%) B. pertussis, 89 (57.1%) indeterminate B. pertussis, one (0.6%) Bordetella holmesii and one (0.6%) Bordetella parapertussis.

CONCLUSIONS

This study found that pertussis is potentially endemic and a common health problem among patients visiting health institutions in the Amhara Regional State of Ethiopia. More data regarding pertussis in Ethiopia could inform development of effective prevention strategies.

PCR-based diagnosis of whooping cough in the Russian Federation

The aim was to determine how often the PCR method is used in different laboratories in Russia. In 2018, we conducted a questionnaire survey in diagnostic laboratories of medical organizations and the Centers of Hygiene and Epidemiology that performed PCR studies to identify microorganisms of the genus Bordetella in all 85 Russian regions. We found that in 2013 the PCR was used in 33 (38.8%) regions, but in 2017 the number of regions increased to 64 (75.3%). During 2013-2017 the study has not been applied in 21 regions. The number of PCR tests performed in the laboratories of medical organizations was significantly different. There has been an increase in the number of tests for the diagnosis of pertussis among people with clinical signs of infection and among contact persons in foci of infection. Compared to the Centers of Hygiene and Epidemiology, in medical organizations the rate of introduction of the PCR was higher. Between 2013 and 2017 the proportion of samples containing DNA B.pertussis decreased, but the proportion of samples containing DNA of other representatives of the genus Bordetella increased. Moreover, in the case of isolation DNA Bordetella spp. clinicians diagnose «Whooping cough, other unspecified organism», since there is no information on the species of the pathogen. Thus, in order to improve the diagnosis of pertussis, it is necessary to optimize PCR tests by including target genes that allow to identify of currently relevant DNAs of different representatives of the genus Bordetella.

A systematic review of the burden of pertussis in South Korea

This review summarizes the published data on epidemiology and burden of pertussis in South Korea as these may be under-categorized. A systematic literature review of PubMed, SCOPUS, EMBASE and KMBASE was performed to identify published literature in South Korea since 2000. Pertussis detection rates among 19 eligible studies range from 0.7% to 100% across different age groups, detection methods and study settings. Highest rates are observed in infants, while adolescents and adults with pertussis infection may suffer from persistent coughing. Vaccination uptake of pertussis booster dose among adolescents and adults remains low while seropositivity (detection of anti-pertussis immunoglobulin G), is high among adults. This review reveals a high burden of vaccine-preventable pertussis in South Korea. Besides primary childhood vaccination, strategies like maternal immunization and decennial revaccination of adults should be considered. Active testing, reporting and better utilization of vaccine registries may provide insights for decision-makers nationwide.

Multicenter Performance Evaluation of the Simplexa Bordetella Direct Kit in Nasopharyngeal Swab Specimens

Detection of Bordetella pertussis and Bordetella parapertussis using molecular methods is sensitive and specific with a short turnaround time compared to other diagnostic methods. In this multicenter study, we compared the performance of the Simplexa Bordetella Direct kit to those of other molecular assays in detecting and differentiating B. pertussis and B. parapertussis in nasopharyngeal swab specimens. The limits of detection (LODs) were 150 CFU/ml or 3 fg/μl of DNA for B. pertussis and 1,500 CFU/ml or 10 fg/μl of DNA for B. parapertussis A total of 1,103 fresh and residual frozen specimens from eight clinical sites were tested. Combining the data from individual clinical sites using different comparative assays, the overall positive percent agreement (PPA) and negative percent agreement (NPA) for B. pertussis were 98.7% and 97.3%, respectively. The overall PPA and NPA for B. parapertussis were 96.7% and 100%, respectively. For prospective fresh specimens, the overall PPA and NPA for both targets were 97.7% and 99.3%, respectively. For retrospective frozen specimens, the overall PPA and NPA for both targets were 92.6% and 93.2%, respectively. The percentage of invalid results was 1.0%. A cross-reactivity study using 74 non-Bordetella bacterial species and five yeast species revealed that the Simplexa Bordetella Direct kit was 100% specific. The hands-on time and assay run time of the Simplexa Bordetella Direct kit are favorable compared to those of other commercial and laboratory-developed tests. In summary, the Simplexa Bordetella Direct kit has a performance comparable to those of other molecular assays for the detection of B. pertussis and B. parapertussis.

Can Comprehensive Respiratory Pathogen Panels be Used to Exclude Pertussis Infection?

BACKGROUND

Pertussis is a serious public health concern and accurate diagnosis is imperative. Comprehensive, multiplex respiratory pathogen polymerase chain reaction (PCR) panels (RPPs) have recently become popular, but their utility in excluding pertussis infection has not been fully explored.

OBJECTIVES

To determine RPP testing results for pertussis using frozen banked samples that previously tested positive on dedicated Bordetella pertussis PCR testing, and to describe positive test rates for other respiratory pathogens on these samples via RPP.

METHODS

Our microbiology laboratory retrieved banked nasopharyngeal samples from inpatient, ambulatory, and emergency department sources that were positive for pertussis using B. pertussis PCR testing from March 2015 to October 2017. RPP was performed on thawed, archived samples. Rate of pertussis identification on RPP was determined, and positive tests for other pathogens were tabulated.

RESULTS

A total of 3482 specimens were submitted for pertussis PCR testing during the study period. Of those, 138 (4%) were positive for B. pertussis, and 102 (74%) samples were banked and available for RPP testing. Fifty-seven of 102 (56%) of the banked samples had positive RPP testing for pertussis. Of the 45 samples negative for pertussis on RPP testing, 20 (44%) tested positive for other respiratory pathogens.

CONCLUSION

Negative testing for B. pertussis and positive testing for other respiratory pathogens on RPP was common in samples that previously tested positive on dedicated B. pertussis PCR testing, both of which could lead to missed diagnoses of pertussis infection. Clinicians should consider using dedicated pertussis PCR testing if pertussis infection is suspected.

Discrepancies between Vaccine Documentation and Serologic Status for Diphtheria, Tetanus, and Hepatitis B in Internationally Adopted Children

Internationally Adopted Children (IAC) often show suboptimal immunisation coverage, but available data are discordant. Data at the first evaluation of 2073 IAC (median age: 6 years) referred to the Meyer Children’s University Hospital (Florence, Italy) in 2009–2019 were analysed in order to evaluate their immunisation status against diphtheria, tetanus, and hepatitis B. Negative antibody titres were observed in 11.5% of the IAC for diphtheria, 18.6% for tetanus, and 39.0% for hepatitis B. At multivariate analysis, originating from Africa was an independent risk factor for seronegativity for the three diseases (p < 0.001), while age below four years was an independent factor associated with protective immunity, only considering hepatitis B (p < 0.001). Vaccine documentation was an additional factor independently associated with protective immunity. However, a discrepancy between documentation (indicating previous vaccinations) and serology (showing negative antibody titres) was evidenced in 3.8% of the children for diphtheria, 12.6% for tetanus, and 29.6% for hepatitis B. This finding suggests that although vaccine documentation may reflect the presence of protective antibody titres, it should not be accepted as absolute evidence of protective immunity, underlining the importance of a complete assessment of immunisation status in IAC, particularly in those originating from Africa and aged over four years.

Establishment and application of a multiple cross displacement amplification combined with nanoparticles-based biosensor method for the detection of Bordetella pertussis

Background

Bordetella pertussis is the causative agent of pertussis, a respiratory tract infectious disease.

Efficient techniques for detection of B. pertussis isolates are important for clinical diagnosis.

Multiple cross displacement amplification (MCDA), a novel isothermal amplification based molecular detection method, has been developed to overcome the technical drawback of the current methods in recent years. This aim of this study is to develop a MCDA with Nanoparticles-based Lateral Flow Biosensor (MCDA-LFB) for the detection of B. pertussis.

Results

A set of 10 primers based on the pertussis toxin (PT) promoter region sequence of B. pertussis was designed. The B. pertussis-MCDA-LFB assay was successfully established and optimized at 64 °C for reaction of 40 min. The detection limit was determined as 10 fg/reaction of pure DNA, and no cross-reactions to non-B. pertussis strains were observed, based on the specificity validation. The whole operation, ranging from template preparation to result reporting, could be completed within 70 min without requirement of costly equipment. The B. pertussis-MCDA-LFB in clinic sample detection yielded identical positive rates with traditional culture and showed higher sensitivity than conventional PCR. The results of MCDA-LFB are easier to read due to the usage of LFB.

Conclusions

The isothermal amplification based MCDA-LFB established in the present study is a specific, sensitive, rapid and economical technique for the detection of B. pertussis.

A data driven clinical algorithm for differential diagnosis of pertussis and other respiratory infections in infants

Background

Clinical criteria for pertussis diagnosis and clinical case definitions for surveillance are based on a cough lasting two or more weeks. As several pertussis cases seek care earlier, a clinical tool independent of cough duration may support earlier recognition. We developed a data-driven algorithm aimed at predicting a laboratory confirmed pertussis.

Methods

We enrolled children <12 months of age presenting with apnoea, paroxistic cough, whooping, or post-tussive vomiting, irrespective of the duration of cough. Patients underwent a RT-PCR test for pertussis and other viruses. Through a logistic regression model, we identified symptoms associated with laboratory confirmed pertussis. We then developed a predictive decision tree through Quinlan's C4.5 algorithm to predict laboratory confirmed pertussis.

Results

We enrolled 543 children, of which 160 had a positive RT-PCR for pertussis. A suspicion of pertussis by a physician (aOR 5.44) or a blood count showing leukocytosis and lymphocytosis (aOR 4.48) were highly predictive of lab confirmed pertussis. An algorithm including a suspicion of pertussis by a physician, whooping, cyanosis and absence of fever was accurate (79.9%) and specific (94.0%) and had high positive and negative predictive values (PPV 76.3% NPV 80.7%).

Conclusions

An algorithm based on clinical symptoms, not including the duration of cough, is accurate and has high predictive values for lab confirmed pertussis. Such a tool may be useful in low resource settings where lab confirmation is unavailable, to guide differential diagnosis and clinical decisions. Algorithms may also be useful to improve surveillance for pertussis and anticipating classification of cases.

Neurologic alterations in an HIV adult patient with pertussis: a case report

Background

Pertussis is a highly contagious disease of public health interest caused by the bacterium Bordetella pertussis. Although its incidence has decreased substantially after the introduction of a vaccination, the burden of the disease remains high. Although the paroxysmal phase is highly disabling, complications are uncommon and more prevalent in children than in adults. The most frequent neurological complication is encephalopathy, but seizures, paresis, paraplegia, ataxias, aphasias, and decerebration postures have also been described. The complication of decerebration postures has not been previously reported in adults.

Case presentation

We present a video case of an adult HIV patient with severe coughing paroxysms, post-tussive emesis and syncope, whose workup confirmed the diagnosis of a B. pertussis respiratory infection. During hospitalization, he had fluctuant encephalopathy and post-tussive decerebration postures following paroxysms. He was treated with antibiotic therapy and finally sent home without residual neurological deficits.

Conclusion

This case illustrates the biological plausibility of neurologic complications of pertussis in adults, which, albeit rare, can cause important morbidities. Future research should explore whether there are differences in the clinical presentation, risk factors and pathophysiology of the disease among adults or interventions aimed at preventing or treating pertussis encephalopathy.

Urgent Bordetella PCR in infants under 3 months, a useful tool in the Pediatric Emergency Department

INTRODUCTION

Whooping cough in patients aged under 3 months has higher rates of morbimortality. Hospitalization and treatment with azithromycin is generally recommended. Many patients with cough without other signs of alarm, are admitted and started antibiotic therapy until a result of Bordetella-PCR is available. This technique, when performed urgently, can provide the diagnosis in a few hours. The objective of this study is to determine if its generalisation in the Emergency Department allows to improve patient management.

METHODS

Retrospective cohort study of patients aged under 3 months who underwent Bordetella-PCR testing from upper respiratory tract secretions since March 2011 to December 2017. From December 2015 the test was performed urgently.

RESULTS

One hundred and fifty-eight PCR were performed, 16 (10%) were positive for B. pertussis. Negative results (142; 90%) were divided in 2 cohorts: conventional-PCR, with 74 cases, and urgent-PCR, with 68 cases. The 2 groups were homogeneous in terms of clinical and analytical characteristics. In the urgent-PCR group there was 18% reduction in chest X-rays performed (P=.008). There were 33 (48.5%) patients admitted in the urgent-PCR group, compared to 49 (66.2%) in the conventional-PCR (P=.042). Antibiotic treatment was initiated in 32% of the patients in the urgent-PCR group compared to 67% in the conventional-PCR group (P=.000047), without observing any significant increase in the number of visits to the Emergency Department or worse clinical performance.

CONCLUSIONS

The introduction of urgent PCR in the Emergency Department is a useful tool in the management of infants under 3 months of age with suspected pertussis, since it can avoid unnecessary admissions, diagnostic tests and antibiotic treatments.

Case report of massive hemoptysis in pregnancy requiring veno-venous extracorporeal membrane oxygenation

Hemoptysis in pregnancy is rare and can be life-threatening. This case describes management of hemoptysis in pregnancy requiring veno-venous extracorporeal membrane oxygenation (VV-ECMO). The patient presented with massive hemoptysis in respiratory failure at 26 weeks gestation. VV-ECMO was utilized for maternal stability due to severe hypoxia from lung parenchymal damage. An extensive work-up for hemoptysis returned negative except for an elevated Bordetella pertussis IgG antibody. The patient was delivered via cesarean section with a complicated post-partum course. She and the infant were discharged in stable condition after long hospital stays. Prior publications describing VV-ECMO use in pregnancy are limited to treatment of respiratory infections such as influenza or pneumonia. This case is the first in the literature to describe VV-ECMO utilization for hemoptysis in pregnancy, specifically, and demonstrates its significant benefit in cases of respiratory failure due to hemoptysis.

Acellular Pertussis Vaccine Effectiveness Over Time

OBJECTIVES

To determine pertussis risk by diphtheria-tetanus-acellular pertussis (DTaP) vaccination status and time since last DTaP dose.

METHODS

Children born at Kaiser Permanente Northern California between 1999 and 2016 were followed from 3 months of age until they tested positive for pertussis; disenrolled from Kaiser Permanente Northern California; received the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis, adsorbed vaccine; turned 11 years of age, or the end of the study period. DTaP vaccination status was categorized on the basis of the number of doses received in relation to the number of doses expected according to the Advisory Committee on Immunization Practice-recommended ages.

RESULTS

Among 469 982 children ages 3 months to 11 years, we identified 738 pertussis cases. A total of 99 cases were unvaccinated, 36 were undervaccinated, 515 were fully vaccinated, and 88 were fully vaccinated plus 1 dose. Pertussis risk was 13 times higher among unvaccinated (adjusted hazard ratio [aHR] = 13.53; 95% confidence interval [CI] 10.64-17.21) compared with fully vaccinated children and 1.9 times higher (aHR = 1.86; 95% CI 1.32-2.63) among undervaccinated children. Among vaccinated children ages 19 to <84 months, pertussis risk was 5 times higher (aHR = 5.04; 95% CI 1.84-13.80) ≥3 years vs <1 year after vaccination. Among children ages 84 to 132 months, risk was 2 times higher (aHR = 2.32; 95% CI 0.97-5.59) ≥6 years vs <3 years after vaccination.

CONCLUSIONS

Undervaccinated and especially unvaccinated children were at greater risk of pertussis. However, most pertussis cases occurred among children age-appropriately vaccinated who were further away from their last DTaP dose, suggesting that suboptimal vaccine effectiveness played a major role in recent pertussis epidemics.

Validation and Implementation of a Diagnostic Algorithm for DNA Detection of Bordetella pertussis, B. parapertussis, and B. holmesii in a Pediatric Referral Hospital in Barcelona, Spain

This study aimed to validate a comprehensive diagnostic protocol based on real-time PCR for the rapid detection and identification of Bordetella pertussis, Bordetella parapertussis, and Bordetella holmesii, as well as its implementation in the diagnostic routine of a reference children's hospital. The new algorithm included a triplex quantitative PCR (qPCR) targeting IS481 gene (in B. pertussis, B. holmesii, and some Bordetella bronchiseptica strains), pIS1001 (B. parapertussis-specific) and rnase P as the human internal control. Two confirmatory singleplex tests for B. pertussis (ptxA-Pr) and B. holmesii (hIS1001) were performed if IS481 was positive. Analytical validation included determination of linear range, linearity, efficiency, precision, sensitivity, and a reference panel with clinical samples. Once validated, the new algorithm was prospectively implemented in children with clinical suspicion of whooping cough presenting to Hospital Sant Joan de Deu (Barcelona, Spain) over 12 months. Lower limits of detection obtained were 4.4, 13.9, and 27.3 genomic equivalents/ml of sample for IS481 (on B. pertussis), pIS1001 and hIS1001, and 777.9 for ptxA-Pr. qPCR efficiencies ranged from 86.0% to 96.9%. Intra- and interassay variabilities were <3% and <5%, respectively. Among 566 samples analyzed, B. pertussis, B. holmesii, and B. parapertussis were detected in 11.1%, 0.9% (only in females >4 years old), and 0.2% of samples, respectively. The new algorithm proved to be a useful microbiological diagnostic tool for whooping cough, demonstrating a low rate of other non-pertussis Bordetella species in our surveilled area.

Pertussis: Identification, Prevention and Control

Pertussis is a vaccine-preventable disease. Despite the high vaccination coverage among children, pertussis is considered a re-emerging disease for which identification, prevention and control strategies need to be improved. To control pertussis it is important to maintain a high vaccination coverage to protect the age groups considered at high risk for the disease. Laboratory confirmation of Bordetella pertussis infection together with a differential diagnostic test for other Bordetellae are prerequisite for a correct and timely diagnosis of pertussis. Moreover, investigations of antimicrobial susceptibility and whole genome sequencing may permit to monitor the circulation of antimicrobials resistant and/or vaccine-escape strains. Finally, the preventive framework should no longer consider pertussis exclusively as a childhood infectious disease, since adults may play a role in transmission events.