Diagnosis of pertussis: a historical review and recent developments

Rapid and sensitive detection of nucleic acids using an RAA-CRISPR/Cas12b one-pot detection assay (Rcod)

Rapid, sensitive and specific methods are crucial for nucleic acid detection. CRISPR/Cas12b has recently been widely used in nucleic acid detection. However, due to its thermophagic property, DNA isothermal recombinase-aided amplification (RAA) and subsequent CRISPR/Cas12b detection require two separate reactions, which is cumbersome and inconvenient and may cause aerosol pollution. In this study, we propose an RAA-CRISPR/Cas12b one-pot detection assay (Rcod) for Bordetella pertussis detection without additional amplification product transfer steps. The time from sample processing to response time was less than 30 min using nucleic acid extraction-free method, and the sensitivity reached 0.2 copies/μL. In this system, Alicyclobacillus acidoterrestris Cas12b protein (AacCas12b) exhibited strong and specific trans-cleavage activity at a constant temperature of 37 °C, while the cis-cleavage activity was weak. This characteristic reduces the interference of AacCas12b with nucleic acids in the system. Compared with real-time PCR, our Rcod system detected B. pertussis in 221 clinical samples with a sensitivity and specificity of 97.96 % and 99.19 %, respectively, with nucleic acid extraction-free method. The rapid, sensitive and specific Rcod system provides ideas for the establishment of CRISPR-based one-step nucleic acid detection and may aid the development of reliable point-of-care nucleic acid tests. IMPORTANCE: Pertussis is an acute respiratory infection caused by B. pertussis that is highly contagious and potentially fatal, and early diagnosis is essential for the treatment of whooping cough. In this study, we found that AacCas12b has high and strongly specific trans-cleavage activity at lower temperatures. A RAA-CRISPR/Cas12b one-step detection platform (Rcod) without interference with amplification was developed. In addition, the combination of Rcod and nucleic acid extraction-free method can quickly and accurately detect the qualitative detection of B. pertussis, and the detection results are visualized, which makes the pathogen nucleic acid detection and analysis process simpler, and provides a new method for the rapid clinical diagnosis of B. pertussis.

The Present and Future Aspects of Life-Long Pertussis Prevention: Narrative Review with Regional Perspectives for Türkiye

Pertussis, caused by Bordetella pertussis, remains one of the most widespread, contagious, and vaccine-preventable diseases. It results in notable morbidity and mortality as well as severe medical, social, and economic burden. Despite high global vaccine coverage, pertussis continues to be a significant epidemiologic problem, with outbreak episodes every few years just as in the pre-vaccination era. In Türkiye, there is a lack of comprehensive data on the current burden of pertussis in different age and risk groups, leading to underdiagnosis and underreporting of the disease, especially in adults who are often not considered at risk. Available data from Türkiye also reveal inadequate levels of protective antibodies in preterm newborns, emphasizing the need for additional preventive measures. Authors stated that improving physician awareness of pertussis symptoms in patients with prolonged cough, increasing access to routine pertussis tests, and conducting surveillance studies would aid in accurate diagnosis and reporting in Türkiye. As the Turkish Ministry of Health Antenatal Care Management Guide suggests routine second and third pregnancy check-up visits at weeks 18-24 and 28-32 correspondingly, this period can be considered the ideal vaccination time for Türkiye. Introducing a booster dose of Tdap at around 10 years of age or during national military service would reduce transmission and protect susceptible individuals. Identifying individuals at high risk of severe pertussis and prioritizing them for a booster dose is also crucial in Türkiye. Enhancing surveillance systems, increasing healthcare professionals' awareness through training, and organizing catch-up visits for missed vaccinations during the COVID-19 pandemic are mentioned as additional strategies to improve pertussis prevention in Türkiye. This review focuses on the global and regional burden of pertussis and obstacles to effective prevention and evaluates existing strategies to achieve lifelong pertussis prevention. Literature and current strategies were also discussed from a Turkish national standpoint.

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.

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.

Laboratory and epidemiology data of pertussis cases and close contacts: A 5-year case-based surveillance of pertussis in Indonesia, 2016–2020

Pertussis cases have been reported most frequently in developed countries, but they are predicted to be the most prevalent in developing countries. Indonesia, a developing country, routinely conducts case-based surveillance for pertussis. We reviewed the data on pertussis cases and close contacts based on clinical sample documents examined in the National Reference Laboratory for pertussis, Indonesia (2016–2020). Our objective was to analyze the laboratory and epidemiological aspects of pertussis cases and close contacts, particularly to evaluate the implementation of a 5-year case-based surveillance of pertussis in Indonesia. Data were collected from sample documents and annual laboratory reports between January 2016 and December 2020. We analyzed the proportion of pertussis cases and close contacts by geographic region, year, age, and sex. We used the χ² test to correlate the laboratory and epidemiological data. In total, 274 clinical cases of pertussis and 491 close contacts were recorded in 15 provinces. The peak number of cases occurred in 2019, with a positivity rate (percentage of laboratory-confirmed cases) of 41.23% (47/114). Clinical cases were dominated by infants aged <1 year (55.5%), and 52.9% of them were aged <6 months. Similarly, 72.3% (68/94) of the laboratory-confirmed cases were infants. Both clinical cases and positivity rates tended to be higher in females (155 cases, 38.1%) than in males (119 cases, 29.4%). No confirmed cases were found in children aged ≥10 years, although positive results still occurred in close contact. Age-group and laboratory-confirmed cases were correlated (p = 0.00). Clinical and confirmed cases of pertussis occurred mostly in the early age group and may be lower in those aged ≥10 years, especially in confirmed cases. New policies are needed for pertussis prevention at an early age, as well as the application of serology tests to increase laboratory-confirmed cases in children aged ≥10 years.

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.

Pertussis Prevention: Reasons for Resurgence, and Differences in the Current Acellular Pertussis Vaccines

Pertussis is an acute respiratory disease caused by Bordetella pertussis. Due to its frequency and severity, prevention of pertussis has been considered an important public health issue for many years. The development of the whole-cell pertussis vaccine (wPV) and its introduction into the pediatric immunization schedule was associated with a marked reduction in pertussis cases in the vaccinated cohort. However, due to the frequency of local and systemic adverse events after immunization with wPV, work on a less reactive vaccine was undertaken based on isolated B. pertussis components that induced protective immune responses with fewer local and systemic reactions. These component vaccines were termed acellular vaccines and contained one or more pertussis antigens, including pertussis toxin (PT), filamentous haemagglutinin (FHA), pertactin (PRN), and fimbrial proteins 2 (FIM2) and 3 (FIM3). Preparations containing up to five components were developed, and several efficacy trials clearly demonstrated that the aPVs were able to confer comparable short-term protection than the most effective wPVs with fewer local and systemic reactions. There has been a resurgence of pertussis observed in recent years. This paper reports the results of a Consensus Conference organized by the World Association for Infectious Disease and Immunological Disorders (WAidid) on June 22, 2018, in Perugia, Italy, with the goal of evaluating the most important reasons for the pertussis resurgence and the role of different aPVs in this resurgence.

Severe Bordetella pertussis infection and vaccine issue in Chongqing, from 2012 to 2018

OBJECTIVE

Pertussis is a highly contagious respiratory illness mainly caused by the Gram-negative bacterium Bordetella pertussis. The infection of B. pertussis has been increasing and the current diagnosis of pertussis in children is challenging; little is known of B. pertussis infection in Chongqing.

METHODS

There were 25,441 children (14,863 male and 10,578 female) with suspected pertussis enrolled in our retrospective study from December 2012 to November 2018. Then 800 children with suspected B. pertussis infection were randomly chosen to be evaluated by simultaneous amplification and testing in this prospective study.

RESULTS

Infants younger than 12 months had the greatest burden of pertussis, and the incidence of pertussis in Chongqing appeared to have a periodic pattern. The problem of vaccine quality in China was more serious than previously reported based on the fluctuation of infection rates from 2012 to 2018. Simultaneous amplification and testing to detect B. pertussis RNA (Area Under Curve: 0.900 and Kappa value: 0.831) had better diagnostic performance than real-time PCR for B. pertussis DNA (Area Under Curve: 0.869 and Kappa value: 0.690).

CONCLUSIONS

We revealed the characteristics of B. pertussis infection and vaccine issues in Chongqing. Simultaneous amplification and testing could be a potential novel assay for measuring B. pertussis infection in the future.

Clinically Diagnosing Pertussis-associated Cough in Adults and Children: CHEST Guideline and Expert Panel Report

BACKGROUND

The decision to treat a suspected case of pertussis with antibiotics is usually based on a clinical diagnosis rather than waiting for laboratory confirmation. The current guideline focuses on making the clinical diagnosis of pertussis-associated cough in adults and children.

METHODS

The American College of Chest Physicians (CHEST) methodologic guidelines and the Grading of Recommendations, Assessment, Development, and Evaluation framework were used. The Expert Cough Panel based their recommendations on findings from a systematic review that was recently published on the topic; final grading was reached by consensus according to Delphi methodology. The systematic review was carried out to answer the Key Clinical Question: In patients presenting with cough, how can we most accurately diagnose from clinical features alone those who have pertussis-associated cough as opposed to other causes of cough?

RESULTS

In adults, after pre-specified meta-analysis exclusions, pooled estimates of sensitivity and specificity were generated for only 4 clinical features: paroxysmal cough, post-tussive vomiting, inspiratory whooping, and absence of fever. Both paroxysmal cough and absence of fever had high sensitivity (93.2% [95% CI, 83.2-97.4] and 81.8% [95% CI, 72.2-88.7], respectively) and low specificity (20.6% [95% CI, 14.7-28.1] and 18.8% [95% CI, 8.1-37.9]). Inspiratory whooping and posttussive vomiting had a low sensitivity (32.5% [95% CI, 24.5-41.6] and 29.8% [95% CI, 18.0-45.2]) but high specificity (77.7% [95% CI, 73.1-81.7] and 79.5% [95% CI, 69.4-86.9]). In children, after pre-specified meta-analysis exclusions, pooled estimates of sensitivity and specificity were generated for only 1 clinical feature in children (0-18 years): posttussive vomiting. Posttussive vomiting in children was only moderately sensitive (60.0% [95% CI, 40.3-77.0]) and specific (66.0% [95% CI, 52.5-77.3]).

CONCLUSIONS

In adults with acute (< 3 weeks) or subacute (3-8 weeks) cough, the presence of whooping or posttussive vomiting should rule in a possible diagnosis of pertussis, whereas the lack of a paroxysmal cough or the presence of fever should rule it out. In children with acute (< 4 weeks) cough, posttussive vomiting is suggestive of pertussis but is much less helpful as a clinical diagnostic test. Guideline suggestions are made based upon these findings and conclusions.

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)

Introduction

The appropriate use of clinically accurate diagnostic tests is essential for the detection of pertussis, a poorly controlled vaccine-preventable disease. The purpose of this study was to estimate the sensitivity and specificity of different diagnostic criteria including culture, multi-target polymerase chain reaction (PCR), anti-pertussis toxin IgG (IgG-PT) serology, and the use of a clinical case definition. An additional objective was to describe the optimal timing of specimen collection for the various tests.

Methods

Clinical specimens were collected from patients with cough illness at seven locations across the United States between 2007 and 2011. Nasopharyngeal and blood specimens were collected from each patient during the enrollment visit. Patients who had been coughing for ≤ 2 weeks were asked to return in 2–4 weeks for collection of a second, convalescent blood specimen. Sensitivity and specificity of each diagnostic test were estimated using three methods—pertussis culture as the “gold standard,” composite reference standard analysis (CRS), and latent class analysis (LCA).

Results

Overall, 868 patients were enrolled and 13.6% were B. pertussis positive by at least one diagnostic test. In a sample of 545 participants with non-missing data on all four diagnostic criteria, culture was 64.0% sensitive, PCR was 90.6% sensitive, and both were 100% specific by LCA. CRS and LCA methods increased the sensitivity estimates for convalescent serology and the clinical case definition over the culture-based estimates. Culture and PCR were most sensitive when performed during the first two weeks of cough; serology was optimally sensitive after the second week of cough.

Conclusions

Timing of specimen collection in relation to onset of illness should be considered when ordering diagnostic tests for pertussis. Consideration should be given to including IgG-PT serology as a confirmatory test in the Council of State and Territorial Epidemiologists (CSTE) case definition for pertussis.

Comparing the Yield of Nasopharyngeal Swabs, Nasal Aspirates, and Induced Sputum for Detection of Bordetella pertussis in Hospitalized Infants

Background. Advances in molecular laboratory techniques are changing the landscape of Bordetella pertussis illness diagnosis. Polymerase chain reaction (PCR) assays have greatly improved the sensitivity detection and the turnaround time to diagnosis compared to culture. Moreover, different respiratory specimens, such as flocked nasopharyngeal swabs (NPSs), nasopharyngeal aspirates (NPAs), and induced sputum, have been used for B. pertussis detection, although there is limited head-to-head comparison to evaluating the PCR yield from the 3 sampling methods.

Methods. Hospitalized infants <6 months of age who fulfilled a broad syndromic criteria of respiratory illness were tested for B. pertussis infection by PCR on paired NPSs and NPAs; or paired NPSs and induced sputum. An exploratory analysis of B. pertussis culture was performed on induced sputum specimens and in a subset of NPSs.

Results. From November 2014 to May 2015, 484 infants with paired NPSs and NPAs were tested; 15 (3.1%) PCR-confirmed pertussis cases were identified, 13 of which were PCR positive on both samples, while 1 each were positive only on NPS or NPA. From March to October 2015, 320 infants had NPSs and induced sputum collected, and 11 (3.4%) pertussis cases were identified by PCR, including 8 (72.7%) positive on both samples, 1 (9.1%) only positive on NPS, and 2 (18.2%) only positive on induced sputum. The 3 types of specimens had similar negative predictive value >99% and sensitivity >83%. Compared to PCR, culture sensitivity was 60% in induced sputum and 40% in NPSs.

Conclusions. Flocked nasopharyngeal swabs, nasopharyngeal aspirates, and induced sputum performed similarly for the detection of B. pertussis infection in young infants by PCR.

Decreased incidence of pertussis in young adults after the introduction of booster vaccine in military conscripts: Epidemiological analyses of pertussis in Finland, 1995-2015

INTRODUCTION

In 2005, in Finland, the whole-cell pertussis vaccine was replaced by acellular given at 3-5-12months, and boosters at 4 and 11-15years of age. From July 2012, military conscripts have been offered a pertussis booster dose. Conscription is mandatory for Finnish men, and >95% were 19-21years old when enrolled during 2012-2015. We describe the epidemiology of pertussis in Finland during 1995-2015, and show the indirect effect of the booster in conscripts on pertussis incidence in the Finnish population.

MATERIALS AND METHODS

We extracted data on laboratory confirmed notified pertussis cases from the National Infectious Diseases Register. We calculated annual incidence using as denominator population data and incidence rate ratios (IRR) using Poisson regression.

RESULTS

The overall pertussis incidence peaked in 2004 (31/100,000) and was lowest in 2015 (3.0/100,000), with 66 reported cases in <3months infants in 2004 versus 6 in 2015. The majority of the cases were female (59%) with a male-to-female case ratio of 1:1.5. Cases were spread throughout the year with highest incidence during August-February. Among the 19- to 21-year-olds in the general population, incidence decreased from 49/100,000 in 2011 to 0.51/100,000 in 2015 (IRR=0.01; 95%CI, 0.00-0.16). Among the same age group, comparing the 3.5-year period before and after July 2012, incidence decreased from 33/100,000 to 5.3/100,000 (IRR=0.16; 95%CI, 0.06-0.40) in males and from 16/100,000 to 5.0/100,000 (IRR=0.31; 95%CI, 0.11-0.84) in females.

CONCLUSIONS

Implementation of the pertussis booster dose in Finnish military conscripts was followed by a significant decrease in pertussis incidence both among the 19- to 21-year-old males and females, possibly reflecting herd immunity effect. Together with booster doses in adolescents this has resulted in low incidence in the whole population including infants. Our results support the implementation of the booster dose for conscripts. We recommend continuing monitoring pertussis epidemiology to optimize pertussis vaccination strategies in Finland.

Pertussis Reinfection in an Adult: A Cause of Persistent Cough Not to Be Ignored

Pertussis is traditionally considered as a disease of the childhood; however, accumulating evidence suggests a stable increase of its incidence among adults and adolescents, during the last decades. Despite the fact that reinfection after natural disease or vaccination is not uncommon, the index of clinical suspicion of pertussis diagnosis in adults remains low. In this article, we report a case of pertussis reinfection 30 years after natural infection, which was complicated by pneumonia, and we discuss our diagnostic and therapeutic approach, aiming to raise clinicians' degree of suspicion regarding pertussis diagnosis in adults. Prompt recognition and appropriate therapy of adult patients can result in the effective control of the symptoms, prevention of severe complications, and spread of the infection to children; thus, they are of great clinical and public health importance.

Clinical Characteristics of Pertussis-Associated Cough in Adults and Children: A Diagnostic Systematic Review and Meta-Analysis

BACKGROUND

Pertussis (whooping cough) is a highly infective cause of cough that causes significant morbidity and mortality. Existing case definitions include paroxysmal cough, whooping, and posttussive vomiting, but diagnosis can be difficult. We determined the diagnostic accuracy of clinical characteristics of pertussis-associated cough.

METHODS

We systematically searched CINAHL, Embase, Medline, and SCI-EXPANDED/CPCI-S up to June 2016. Eligible studies compared clinical characteristics in those positive and negative for Bordetella pertussis infection, confirmed by laboratory investigations. Two authors independently completed screening, data extraction, and quality and bias assessments. For each characteristic, RevMan was used to produce descriptive forest plots. The bivariate meta-analysis method was used to generate pooled estimates of sensitivity and specificity.

RESULTS

Of 1,969 identified papers, 53 were included. Forty-one clinical characteristics were assessed for diagnostic accuracy. In adult patients, paroxysmal cough and absence of fever have a high sensitivity (93.2% [CI, 83.2-97.4] and 81.8% [CI, 72.2-88.7], respectively) and low specificity (20.6% [CI, 14.7-28.1] and 18.8% [CI, 8.1-37.9]), whereas posttussive vomiting and whooping have low sensitivity (32.5% [CI, 24.5-41.6] and 29.8% [CI, 8.0-45.2]) and high specificity (77.7% [CI, 73.1-81.7] and 79.5% [CI, 69.4-86.9]). Posttussive vomiting in children is moderately sensitive (60.0% [CI, 40.3-77.0]) and specific (66.0% [CI, 52.5-77.3]).

CONCLUSIONS

In adult patients, the presence of whooping or posttussive vomiting should rule in a possible diagnosis of pertussis, whereas the lack of a paroxysmal cough or the presence of fever should rule it out. In children, posttussive vomiting is much less helpful as a clinical diagnostic test.

Whooping cough in 2014 and beyond: an update and review

Pertussis, or whooping cough, has had a dramatic resurgence in the past several years and is the most common vaccine-preventable disease in the world. The year 2012 marked the most cases in the United States in &gt; 50 years. Large outbreaks have occurred in multiple states, and infant deaths have drawn the attention of not only health-care providers but also the media. Although the disease is theoretically preventable by vaccination, it remains a challenge to control. New vaccination strategies have been implemented across different age groups and populations of patients, but vaccine coverage remains dismally low. Acellular vaccines, although safe, do not afford the same long-lasting immunity as the previously used whole-cell vaccine. Ultimately, improvements in the development of vaccines and in vaccination coverage will be essential to decrease the burden of pertussis on society. This article provides a review of pertussis infection and discusses advances related to the epidemiology, diagnosis, treatment, and prevention of infection, as well as continued areas of uncertainty.

Using a bayesian latent class model to evaluate the utility of investigating persons with negative polymerase chain reaction results for pertussis

Pertussis remains difficult to control. Imperfect sensitivity of diagnostic tests and lack of specific guidance regarding interpretation of negative test results among patients with compatible symptoms may contribute to its spread. In this study, we examined whether additional pertussis cases could be identified if persons with negative pertussis test results were routinely investigated. We conducted interviews among 250 subjects aged ≤18 years with pertussis polymerase chain reaction (PCR) results reported from 2 reference laboratories in Wisconsin during July-September 2010 to determine whether their illnesses met the Centers for Disease Control and Prevention's clinical case definition (CCD) for pertussis. PCR validity measures were calculated using the CCD as the standard for pertussis disease. Two Bayesian latent class models were used to adjust the validity measures for pertussis detectable by 1) culture alone and 2) culture and/or more sensitive measures such as serology. Among 190 PCR-negative subjects, 54 (28%) had illnesses meeting the CCD. In adjusted analyses, PCR sensitivity and the negative predictive value were 1) 94% and 99% and 2) 43% and 87% in the 2 types of models, respectively. The models suggested that public health follow-up of reported pertussis patients with PCR-negative results leads to the detection of more true pertussis cases than follow-up of PCR-positive persons alone. The results also suggest a need for a more specific pertussis CCD.

Bead-based polymerase chain reaction on a microchip

We present a bead-based approach to microfluidic polymerase chain reaction (PCR), enabling fluorescent detection and sample conditioning in a single microchamber. Bead-based PCR, while not extensively investigated in microchip format, has been used in a variety of bioanalytical applications in recent years. We leverage the ability of bead-based PCR to accumulate fluorescent labels following DNA amplification to explore a novel DNA detection scheme on a microchip. The microchip uses an integrated microheater and temperature sensor for rapid control of thermal cycling temperatures, while the sample is held in a microchamber fabricated from (poly)dimethylsiloxane and coated with Parylene. The effects of key bead-based PCR parameters, including annealing temperature and concentration of microbeads in the reaction mixture, are studied to achieve optimized device sensitivity and detection time. The device is capable of detecting a synthetically prepared section of the Bordetella pertussis genome in as few as 10 temperature cycles with times as short as 15 min. We then demonstrate the use of the procedure in an integrated device; capturing, amplifying, detecting, and purifying template DNA in a single microfluidic chamber. These results show that this method is an effective method of DNA detection which is easily integrated in a microfluidic device to perform additional steps such as sample pre-conditioning.

Detection of Bordetella pertussis in Infants Suspected to have Whooping Cough

Background:

Even with high coverage of vaccination programs, Bordetella pertussis is still reported in various countries. It causes a high rate of mortality and morbidity in infants while it could be asymptomatic in adults. At the present study, we are going to evaluate the frequency of B. pertussis among received specimens.

Methods:

This cross-sectional study was performed on 138 children under one year who were suspected to have whooping cough from October 2008 to March in 2011. Nasopharyngeal dacron and rayon swabs and sera were used for PCR and serology respectively.

Results:

The mean age of the subjects was 1.9± 0.9 months. PCR was positive in 12 cases; ELISA was in agreement with PCR results except in one case that showed the specific antibody at borderline limit.

Conclusion:

The rate of reported positive results showed that pertussis not only is still present in the community, but the number of the asymptomatic cases who are able to transmit the disease may be considerable.

Comparative study of different sources of pertussis toxin (PT) as coating antigens in IgG anti-PT enzyme-linked immunosorbent assays

In an effort to improve the reliability and reproducibility of serological assays for Bordetella pertussis, a collaborative study was conducted to compare four different sources of pertussis toxin (PT) as coating antigens in the immunoglobulin G (IgG) anti-PT enzyme-linked immunosorbent assay (ELISA). Four sources of PT were used as coating antigens in the IgG anti-PT ELISA in four different testing laboratories (labs A to D) to determine whether the different antigen preparations and different laboratories influenced assay results. A panel of 60 sera consisting of deidentified human specimens from previous vaccination trials of healthy adults and infants and clinical specimens from outbreak settings was tested. In the four laboratories, each sample was tested three times with the four PT antigens according to the standard coating optimization and IgG anti-PT ELISA testing procedures used in that laboratory. Differences among the antigens, as well as intra- and interlaboratory variability, were evaluated. Excellent agreement was observed with the test panel results among the four antigens within each laboratory. Concordance correlation coefficient (r(c)) measurements among the different antigens ranged from 0.99, 0.99 to 1.00, 1.00, and 0.97 to 1.00 for labs A to D, respectively. The comparisons between pairs of laboratories also indicated a high degree of concordance for each PT preparation, with r(c) measurements between 0.90 and 0.98, 0.93 and 0.99, 0.92 and 0.98, and 0.93 and 0.99 for antigens 1 to 4, respectively. Relatively minor differences in results were observed among laboratories or among antigens, suggesting that the four PT antigens are quite similar and could be considered for acceptance in harmonized immunoassays used for serodiagnosis or vaccine evaluation.

The diagnosis of pertussis: which method to choose?

Despite the introduction of routine vaccination against pertussis for more than a half century, leading to a drastic decline in the number of reported cases, pertussis continues to be an important respiratory disease afflicting unvaccinated infants and previously vaccinated children as well as adults in whom immunity has waned. The diagnosis of pertussis is challenging and accurate laboratory identification of Bordetella infections remains problematic. Common laboratory diagnostic methods used for pertussis diagnosis include culture, direct-fluorescent-antibody testing (DFA), serology and polymerase chain reaction (PCR). Culture of Bordetella pertussis is highly specific but fastidious and has limited sensitivity. DFA provides a much more rapid result, but has the disadvantage of poor sensitivity and specificity. Serology is not useful in infants. In older persons, it is hampered by the limitations of paired sera and it provides mainly a retrospective diagnosis. Such limitations of conventional diagnosis testing have led to the development of PCR assays. Notwithstanding its lack of standardization, PCR has been found to be more sensitive and more specific than other methods. In this report, we aimed to review current knowledge about the available diagnostic methods and tests that accurately diagnose pertussis.

Pertussis serodiagnosis in Belgium from 1990 to 2009

Diagnosis of pertussis by culture and PCR is most sensitive when performed on nasopharyngeal specimens collected <2 weeks and <3 weeks, respectively, after the onset of clinical disease. Conversely, serological testing allows the diagnosis of patients (mostly adults) with less typical whooping cough symptoms, for whom clinical samples are often collected at later time points. Here, we report on a 20-year serodiagnostic survey of pertussis in Belgium from 1990 to 2009. In total, 13,163 patients were analyzed for Bordetella pertussis-specific antibodies by agglutination, complement fixation, immunofluorescence, and ELISA. The number of positive pertussis cases detected by serodiagnosis ranged between 50 and 150 annually. The mean age of positive cases increased from 9.9 years in 1990 to 33.9 years in 2009. Whereas from 1990 to 2003, children and young adolescents made up the majority of cases, from 2004 onwards, cases were detected in all age groups and the distribution became bimodal, with a first peak at the age of 10 to 20 years and a second at the age of 35 to 50 years. In contrast, patients diagnosed since 2001 by PCR and/or culture were mostly children younger than 1 year of age. Despite extensive childhood vaccination campaigns, whooping cough is still present in Belgium. Our findings confirm the potential role of adults in the continued transmission of pertussis and strongly warrant booster or cocoon vaccinations in older age groups.

Development and analytical validation of an immunoassay for quantifying serum anti-pertussis toxin antibodies resulting from Bordetella pertussis infection

Adequately sensitive and specific methods to diagnose pertussis in adolescents and adults are not widely available. Currently, no Food and Drug Administration-approved diagnostic assays are available for the serodiagnosis of Bordetella pertussis. Since concentrations of B. pertussis-specific antibodies tend to be high during the later phases of disease, a simple, rapid, easily transferable serodiagnostic test was developed. This article describes test development, initial evaluation of a prototype kit enzyme-linked immunosorbent assay (ELISA) in an interlaboratory collaborative study, and analytical validation. The data presented here demonstrate that the kit met all prespecified criteria for precision, linearity, and accuracy for samples with anti-pertussis toxin (PT) immunoglobulin G (IgG) antibody concentrations in the range of 50 to 150 ELISA units (EU)/ml, the range believed to be most relevant for serodiagnosis. The assay met the precision and linearity criteria for a wider range, namely, from 50 to 200 EU/ml; however, the accuracy criterion was not met at 200 EU/ml. When the newly adopted World Health Organization International Standard for pertussis antiserum (human) reference reagent was used to evaluate accuracy, the accuracy criteria were met from 50 to 200 international units/ml. In conclusion, the IgG anti-PT ELISA met all assay validation parameters within the range considered most relevant for serodiagnosis. This ELISA was developed and analytically validated as a user-friendly kit that can be used in both qualitative and quantitative formats. The technology for producing the kit is transferable to public health laboratories.

International Bordetella pertussis assay standardization and harmonization meeting report. Centers for Disease Control and Prevention, Atlanta, Georgia, United States, 19-20 July 2007

An international meeting on Bordetella pertussis assay standardization and harmonization was held at the Centers for Disease Control and Prevention (CDC), Atlanta, GA, 19–20 July 2007. The goal of the meeting was to harmonize the immunoassays used for pertussis diagnostics and vaccine evaluation, as agreed upon by academic and government researchers, regulatory authorities, vaccine manufacturers, and the World Health Organization (WHO).

The primary objectives were (1) to provide epidemiologic, laboratory, and statistical background for support of global harmonization; (2) to overview the current status of global epidemiology, pathogenesis and immunology of pertussis; (3) to develop a consensus opinion on existing gaps in understanding standardization of pertussis assays used for serodiagnosis and vaccine evaluation; and (4) to search for a multicenter process for addressing these priority gaps. Presentations and discussions by content experts addressed these objectives. A prioritized list of action items to improve standardization and harmonization of pertussis assays was identified during a group discussion at the end of the meeting. The major items included: (1) to identify a group that will organize, prepare, maintain, and distribute proficiency panels and key reagents such as reference and control sera; (2) to encourage the development and identification of one or more reference laboratories that can serve as an anchor and resource for other laboratories; (3) to define a performance-based assay method that can serve as a reference point for evaluating laboratory differences; (4) to develop guidance on quality of other reagents, e.g., pertussis toxin and other antigens, and methods to demonstrate their suitability; (5) to establish an international working group to harmonize the criteria to evaluate the results obtained on reference and proficiency panel sera; (6) to create an inventory to determine the amount of appropriate and well-characterized sera that are available globally to be used as bridging reagents for vaccine licensure; and (7) to seek specific guidance from regulatory authorities regarding the expectations and requirements for the licensure of new multicomponent pertussis vaccines.

Pertussis: not only a disease of childhood

INTRODUCTION

Pertussis is not just a childhood disease, but a respiratory infection that causes persistent cough in all age groups, from newborns to the elderly.

METHODS

The authors performed a selective literature search and reviewed national and international recommendations for treatment and vaccination.

RESULTS

Pertussis is found principally in young unvaccinated infants, but school-age children, adolescents, and adults are also affected. Up to 1% of infants contract pertussis, and their respiratory symptoms are often accompanied by apnea. School-age children occasionally display the coughing spasms typical of the disease. Annually, 0.2% to 0.5% of all adolescents and adults are infected and suffer from prolonged, frequently non-paroxysmal coughing. Severe and fatal cases of pertussis occur mainly in newborns and infants, and 25% of affected adults experience complications. Bordetella DNA may be detected by polymerase chain reaction (PCR) for four weeks after symptom onset; except in infants, the sensitivity of this diagnostic technique is low. Although the diagnosis can be confirmed by serological tests, the methods are not well standardized. Treatment with a macrolide prevents the spread of infection, but generally does not alleviate the symptoms. Combination vaccines are the most effective means of prophylaxis.

DISCUSSION

Pertussis is usually not included in the differential diagnosis of persistent respiratory symptoms. The considerable burden of disease could be reduced in adults and young infants by vaccinating adults with acellular combination vaccines.

Development and evaluation of dual-target real-time polymerase chain reaction assays to detect Bordetella spp

Novel, highly specific, and sensitive real-time polymerase chain reaction (PCR) assays using 2 targets, insertion sequence (IS481) and pertussis toxin subunit 1 (ptxS1), were developed to detect Bordetella pertussis and to differentiate between relevant Bordetella spp. Sixty-four non-Bordetella isolates were negative by both assays, demonstrating the specificity of the assays. B. pertussis, Bordetella parapertussis, and Bordetella holmesii isolates were specifically identified using the assays. The lower limit of detection was less than 10 genomic equivalents per reaction for the IS481 and ptxS1 assays. These assays were evaluated using 145 human clinical specimens obtained during cough-illness outbreak investigations, and PCR results were compared with Bordetella spp. culture results. Twenty-seven (18.6%) specimens had late positive cycle threshold (Ct) values (35 <or= Ct < 40) using the IS481 assay with corresponding negative results using the ptxS1 assay and culture and were considered indeterminate. Guidelines for use of PCR testing and interpretation of results during cough-illness outbreaks are discussed.

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.

Utility of composite reference standards and latent class analysis in evaluating the clinical accuracy of diagnostic tests for pertussis

Numerous evaluations of the clinical sensitivity and specificity of PCR and serologic assays for Bordetella pertussis have been hampered by the low sensitivity of culture, the gold standard test, which leads to biased accuracy estimates. The bias can be reduced by using statistical approaches such as the composite reference standard (CRS) (e.g., positive if culture or serology positive; negative otherwise) or latent class analysis (LCA), an internal reference standard based on a statistical model. We illustrated the benefits of the CRS and LCA approaches by reanalyzing data from a 1995 to 1996 study of cough illness among 212 patients. The accuracy of PCR in this study was evaluated using three reference standards: culture, CRS, and LCA. Using specimens obtained 0 to 34 days after cough onset, estimates of the sensitivity of PCR obtained using CRS (47%) and LCA (34%) were lower than the culture-based estimate (62%). The CRS and LCA approaches, which utilized more than one diagnostic marker of pertussis, likely produced more accurate reference standards than culture alone. In general, the CRS approach is simple, with a well-defined disease status. LCA requires statistical modeling but incorporates more indicators of disease than CRS. When three or more indicators of pertussis are available, these approaches should be used in evaluations of pertussis diagnostic tests.

Real-time polymerase chain reaction detection of Bordetella pertussis DNA in acellular pertussis vaccines

Using 2 real-time polymerase chain reaction (PCR) assays for Bordetella pertussis, 2 of 5 acellular pertussis vaccines were found to contain B. pertussis DNA. Because residual DNA in vaccines can cause environmental contamination, the administration of acellular pertussis vaccines to patients should be physically separated from the collection of patients' specimens for testing of B. pertussis DNA by real-time PCR.