Evaluation of Polymerase Chain Reaction and Culture for Diagnosis of Pertussis in the Control of a County-Wide Outbreak Focused among Adolescents and Adults

Strengthening Public Health in Wisconsin Through the Wisconsin Clinical Laboratory Network

The Wisconsin Clinical Laboratory Network (WCLN) at the University of Wisconsin-Madison is a partnership of 138 clinical and public health laboratories (as of February 2019) coordinated by the Wisconsin State Laboratory of Hygiene. This article describes the WCLN, its current activities, and lessons learned through this partnership. A laboratory technical advisory group, which consists of representatives from clinical laboratories, provides clinical laboratory perspective to the WCLN and fosters communication among laboratories. Activities and resources available through the WCLN include annual regional meetings, annual technical workshops, webinars, an email listserv, laboratory informational messages, in-person visits by a WCLN coordinator to clinical laboratories, and laboratory-based surveillance data and summaries distributed by the Wisconsin State Laboratory of Hygiene. One challenge to maintaining the WCLN is securing continual funding for network activities. Key lessons learned from this partnership of more than 20 years include the importance of in-person meetings, the clinical perspective of the laboratory technical advisory group, and providing activities and resources to clinical laboratories to foster sharing of data and clinical specimens for public health surveillance and outbreak response.

Predictors of Pertussis Polymerase Chain Reaction Positive Results in Minnesota, 2005-2009

Predictors of polymerase chain reaction (PCR) positivity for pertussis were assessed using Minnesota active surveillance data. Report of an exposure to pertussis and testing within the optimal time frame of ≤2 weeks were significantly associated with testing PCR positive, emphasizing the importance of asking about epidemiological factors when assessing patients for pertussis, and timely PCR testing.

Duration of Bordetella pertussis Polymerase Chain Reaction Positivity in Confirmed Pertussis Illness

Pertussis cases have been increasing in the United States for the past 40 years. Polymerase chain reaction (PCR) testing is now the preferred method of diagnosis, but little is known about duration of PCR positivity. We conducted a pilot study using serial B pertussis PCR testing to determine duration of PCR positivity. Kaplan-Meier survival analysis suggested a median duration of 58 days (interquartile range, 40-110 days).

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 > 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.

Pertussis Surveillance Trends in British Columbia, Canada, over a 20-year Period: 1993-2013

Objective

To provide a surveillance update on overall and age-related pertussis trends in British Columbia (BC), Canada, spanning the 20-year period from 1993-2013.

Methods

Provincial surveillance data for confirmed pertussis cases were extracted from January 1, 1993 to October 31, 2013. Annual and age-specific incidence rates were derived using provincial and regional population estimates.

Results

BC experienced substantial pertussis epidemics in the late 1990s and early 2000s with incidence ranging from 20 to 40 per 100,000 overall and peaking in pre-teens aged 10-13 years at >200 per 100,000 during the epidemic of 2000. Overall incidence dropped to historical lows ranging from 1 to 6 per 100,000 between 2005 and 2011. This low-level activity was followed by resurgence in 2012 driven by outbreaks in Lower Mainland regions of BC with overall provincial incidence reaching 10 per 100,000. Age-specific incidence in 2012 was highest among infants <1 year old (64 per 100,000) and children 12-13 years old (56-57 per 100,000), with a shift in the age distribution away from preschool-aged children toward pre-teens and young teens evident since 2000. Adult incidence remained <10 per 100,000 throughout the study period and was 5 per 100,000 in 2012. Year-to-date provincial incidence rates overall for 2013 are 6 per 100,000, with ongoing asynchronous activity observed primarily on Vancouver Island.

Conclusions

Pertussis activity in BC showed expected cyclical fluctuations, with a peak incidence observed in 2012, mostly affecting infants and pre-teens/teens but at lower levels than prior peaks. Following substantial epidemics in the 1990s and early 2000s and the incorporation of acellular pertussis vaccine into the routine immunization program, the immuno-epidemiology of pertussis may still be in transition. Further monitoring and evaluation are needed to guide possible program changes for BC.

Evaluation of a multitarget real-time PCR assay for detection of Bordetella species during a pertussis outbreak in New Hampshire in 2011

A multitarget real-time PCR assay with three targets, including insertion sequence 481 (IS481), IS1001, and an IS1001-like element, as well as pertussis toxin subunit S1 (ptxS1), for the detection of Bordetella species was evaluated during a pertussis outbreak. The sensitivity and specificity were 77 and 88% (PCR) and 66 and 100% (culture), respectively. All patients with an IS481 C(T) of <30 also tested positive by ptxS1 assay and were clinical pertussis cases. No patients with IS481 C(T) values of ≥40 tested positive by culture. Therefore, we recommend that culture be performed only for specimens with IS481 C(T) values of 30 ≤ CT <40.

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.

Microbiological diagnosis of community-acquired respiratory tract infections by nucleic acid detection

BACKGROUND

Microbiological diagnostic procedures have changed significantly over the last decade. Initially the implementation of the polymerase chain reaction (PCR) resulted in improved detection tests for microbes that were difficult or even impossible to detect by conventional methods such as culture and serology, especially in community-acquired respiratory tract infections (CA-RTI). A further improvement was the development of real-time PCR, which allows end point detection and quantification, and many diagnostic laboratories have now implemented this powerful method.

OBJECTIVE

At present, new performant and convenient molecular tests have emerged targeting in parallel many viruses and bacteria responsible for lower and/or upper respiratory tract infections. The range of test formats and microbial agents detected is evolving very quickly and the added value of these new tests needs to be studied in terms of better use of antibiotics, better patient management, duration of hospitalization and overall costs.

CONCLUSIONS

Molecular tools for a better microbial documentation of CA-RTI are now available. Controlled studies are now required to address the relevance issue of these new methods, such as, for example, the role of some newly detected respiratory viruses or of the microbial DNA load in a particular patient at a particular time. The future challenge for molecular diagnosis will be to become easy to handle, highly efficient and cost-effective, delivering rapid results with a direct impact on clinical management.

Quantification of the adenylate cyclase toxin of Bordetella pertussis in vitro and during respiratory infection

Whooping cough results from infection of the respiratory tract with Bordetella pertussis, and the secreted adenylate cyclase toxin (ACT) is essential for the bacterium to establish infection. Despite extensive study of the mechanism of ACT cytotoxicity and its effects over a range of concentrations in vitro, ACT has not been observed or quantified in vivo, and thus the concentration of ACT at the site of infection is unknown. The recently developed baboon model of infection mimics the prolonged cough and transmissibility of pertussis, and we hypothesized that measurement of ACT in nasopharyngeal washes (NPW) from baboons, combined with human and in vitro data, would provide an estimate of the ACT concentration in the airway during infection. NPW contained up to ≈ 10(8) CFU/ml B. pertussis and 1 to 5 ng/ml ACT at the peak of infection. Nasal aspirate specimens from two human infants with pertussis contained bacterial concentrations similar to those in the baboons, with 12 to 20 ng/ml ACT. When ≈ 10(8) CFU/ml of a laboratory strain of B. pertussis was cultured in vitro, ACT production was detected in 60 min and reached a plateau of ≈ 60 ng/ml in 6 h. Furthermore, when bacteria were brought into close proximity to target cells by centrifugation, intoxication was increased 4-fold. Collectively, these data suggest that at the bacterium-target cell interface during infection of the respiratory tract, the concentration of ACT can exceed 100 ng/ml, providing a reference point for future studies of ACT and pertussis pathogenesis.

Whooping cough in adults: an update on a reemerging infection

Pertussis, or whooping cough, which is commonly thought of as a pediatric illness, is an underappreciated adult pathogen. Recent outbreaks highlight the significance of pertussis in adults and the risk of transmission to at-risk infants who are most susceptible to complications, including death. This article describes the recent epidemiologic shifts and reviews the clinical presentation, diagnosis, and treatment of pertussis. New vaccination recommendations by the Advisory Committee on Immunization Practices in response to recent outbreaks and infant deaths are highlighted.

Pertussis Pseudo-outbreak linked to specimens contaminated by Bordetella pertussis DNA From clinic surfaces

BACKGROUND AND OBJECTIVES

We investigated a pertussis outbreak characterized by atypical cases, confirmed by polymerase chain reaction (PCR) alone at a single laboratory, which persisted despite high vaccine coverage and routine control measures. We aimed to determine whether Bordetella pertussis was the causative agent and advise on control interventions.

METHODS

We conducted case ascertainment, confirmatory testing for pertussis and other pathogens, and an assessment for possible sources of specimen contamination, including a survey of clinic practices, sampling clinics for B pertussis DNA, and review of laboratory quality indicators.

RESULTS

Between November 28, 2008, and September 4, 2009, 125 cases were reported, of which 92 (74%) were PCR positive. Cases occurring after April 2009 (n = 79; 63%) had fewer classic pertussis symptoms (63% vs 98%; P < .01), smaller amounts of B pertussis DNA (mean PCR cycle threshold value: 40.9 vs 33.1; P < .01), and a greater proportion of PCR-positive results (34% vs 6%; P < .01). Cultures and serology for B pertussis were negative. Other common respiratory pathogens were detected. We identified factors that likely resulted in specimen contamination at the point of collection: environmentally present B pertussis DNA in clinics from vaccine, clinic standard specimen collection practices, use of liquid transport medium, and lack of clinically relevant PCR cutoffs.

CONCLUSIONS

A summer pertussis pseudo-outbreak, multifactorial in cause, likely occurred. Recommendations beyond standard practice were made to providers on specimen collection and environmental cleaning, and to laboratories on standardizing PCR protocols and reporting results, to minimize false-positive results from contaminated clinical specimens.

Guidelines for the management of adult lower respiratory tract infections--summary

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Guidelines for the management of adult lower respiratory tract infections--full version

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. Background sections and graded evidence tables are also included. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Emerging advances in rapid diagnostics of respiratory infections

Recent developments in rapid diagnostics for respiratory infections have mostly occurred in the areas of antigen and nucleic acid detection. Nucleic acid amplification tests have improved the ability to identify respiratory viruses in clinical specimens and have played pivotal roles in the rapid characterization of new viral pathogens. Antigen-detection assays in immunochromatographic or similar formats are most easily developed as near-patient tests, although they have been developed commercially only for a limited range of respiratory pathogens. New approaches for respiratory pathogen detection are needed, and breath analysis is an exciting area with enormous potential.

Outbreak of atypical pertussis detected by polymerase chain reaction in immunized preschool-aged children

BACKGROUND

From October 2005 to March 2006, a laboratory-confirmed outbreak of pertussis occurred in preschool-aged children (1-4 years) in Toronto, Canada. A case-control study in children was done to identify the risk factors for being positive for Bordetella pertussis by polymerase chain reaction (PCR).

METHODS

A case was defined as an individual 0 to 18 years of age who tested positive for B. pertussis by PCR in Toronto from October 2005 to March 2006. Each case was matched to 2 controls (negative for B. pertussis by PCR) by: (1) age, (2) geographic region of testing, and (3) date of testing.

RESULTS

One hundred eighty-nine cases and 296 controls were enrolled. Only 42% of cases (vs. 25% controls, P < 0.0001) met a clinical definition of pertussis, 3 cases (4 controls) were hospitalized, and the secondary household attack rate was 8%. One-third of cases were positive for another respiratory pathogen and >90% of cases and controls were up-to-date with pertussis immunization. Children attending school (matched odds ratio [ORm] = 5.2; 95% confidence intervals [CI]: 1.4-19.0), day care (ORm = 2.2; 95% CI: 1.2-4.0), visiting a doctor's office (ORm = 1.6; 95% CI: 1.0-2.5), or exposed to a household member (median age: 4-5 years) with a pertussis-like cough (ORm = 1.9; 95% CI: 1.0-3.6) were significantly more likely to have a positive PCR test for B. pertussis.

CONCLUSIONS

The main risk factors for PCR positivity for B. pertussis were school or day care attendance. Atypical symptoms were likely moderated by high immunization rates or may have been caused by other respiratory pathogens. In some cases, a positive PCR result might simply have reflected transient nasopharyngeal carriage of B. pertussis.

Epidemiology of pertussis and Haemophilus influenzae type b disease in Canada with exclusive use of a diphtheria-tetanus-acellular pertussis-inactivated poliovirus-Haemophilus influenzae type b pediatric combination vaccine and an adolescent-adult tetanus-diphtheria-acellular pertussis vaccine: implications for disease prevention in the United States

BACKGROUND

During the decade 1998-2007, a combination DTaP(5)-IPV/Hib vaccine was used exclusively in Canada to immunize infants and young children against diphtheria, tetanus, pertussis, polio, and invasive Haemophilus influenzae type b (Hib) disease.

METHODS

Medline was used to search for publications during 1996-2008 related to the epidemiology and vaccine prevention of pertussis and invasive Hib disease in Canada. Related abstracts and presentations were reviewed, when available, and epidemiologic data since 1985 were obtained from the Public Health Agency of Canada public Web site.

RESULTS

Reports of pertussis have declined substantially in preschool and school-aged children during the past decade, and cyclical peaks in disease incidence have been blunted or eliminated. In provinces and territories where Tdap(5) vaccine has been administered to 14- to 16-year-olds, marked reductions of pertussis have been documented in adolescents as well as younger age groups, possibly due to herd immunity. Incidence rates of invasive Hib disease among Canadian children <5 years declined markedly after introduction of Hib conjugate vaccines, and the disease has remained under control with exclusive use of DTaP(5)-IPV/Hib vaccine. Most cases of invasive Hib disease occur among unimmunized or only partially vaccinated children. The reduction of Hib case reports has been documented throughout Canada, including among Aboriginal children who are at high risk for this disease.

CONCLUSIONS

The Canadian experience with DTaP(5)-IPV/Hib and Tdap(5) vaccines is relevant to the United States because immunization schedules, vaccination coverage rates, and epidemiologic patterns of pertussis and Hib diseases are similar in the 2 countries, and because both vaccines are licensed for use in the United States.

Pertussis vaccination for health care workers

Pertussis, an acute respiratory infection caused by Bordetella pertussis, classically manifests as a protracted cough illness. The incidence of pertussis in the United States has been increasing in recent years. Immunity wanes after childhood vaccination, leaving adolescents and adults susceptible to infection. The transmission of pertussis in health care settings has important medical and economic consequences. Acellular pertussis booster vaccines are now available for use and have been recommended for all adolescents and adults. These vaccines are safe, immunogenic, and effective. Health care workers are a priority group for vaccination because of their increased risk of acquiring infection and the potential to transmit pertussis to high-risk patients. Health care worker vaccination programs are likely to be cost-effective, but further research is needed to determine the acceptability of pertussis vaccines among health care workers, the duration of immunity after booster doses, and the impact of vaccination on the management of pertussis exposures in health care settings.

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.

New, and some not-so-new, vaccines for adolescents and diseases they prevent

Adolescents in the United States now have the opportunity to receive new vaccines that prevent invasive meningococcal infections, pertussis (whooping cough), and cervical cancer. Except for their potential to cause serious illness, these infections could not be more different. Their incidence ranges from extremely low to quite high. Early clinical manifestations of infection range from none to life-threatening illness. Two of the vaccines are similar to those already in use, whereas 1 is completely new. In conjunction with the 4 vaccines previously recommended for adolescents (the tetanus and diphtheria booster, hepatitis B, measles-mumps-rubella, and varicella), the 3 new vaccines (meningococcal, human papillomavirus, and the tetanus-diphtheria-pertussis booster [which replaced the tetanus-diphtheria booster]) bring the number recommended for adolescents to 6. In this article, we describe key characteristics of the 3 new vaccines and infections they were designed to prevent. We also briefly discuss other vaccines recommended for all adolescents who have not already received them and new vaccines that are still under development.