Genome-based prediction of cross-protective, HLA-DR-presented epitopes as putative vaccine antigens for multiple Bordetella species.

IMPORTANCE: Pertussis, caused by Bordetella pertussis, can cause debilitating respiratory symptoms, so whole-cell pertussis vaccines (wPVs) were introduced in the 1940s. However, reactogenicity of wPV necessitated the development of acellular pertussis vaccines (aPVs) that were introduced in the 1990s. Since then, until the COVID-19 pandemic began, reported pertussis incidence was increasing, suggesting that aPVs do not induce long-lasting immunity and may not effectively prevent transmission. Additionally, aPVs do not provide protection against other Bordetella species that are observed during outbreaks. The significance of this work is in determining potential new vaccine antigens for multiple Bordetella species that are predicted to elicit long-term immune responses. Genome-based approaches have aided the development of novel vaccines; here, these methods identified Bordetella vaccine candidates that may be cross-protective and predicted to induce strong memory responses. These targets can lead to an improved vaccine with a strong safety profile while also strengthening the longevity of the immune response.

Complete Genome Sequences of Four Macrolide-Resistant Nondiphtheritic Corynebacterium Isolates.

This report describes the complete genome sequences of four isolates of the nondiphtheritic Corynebacterium (NDC) species Corynebacterium pseudodiphtheriticum and Corynebacterium propinquum, recovered during investigation of a large diphtheria outbreak in Bangladesh. These data will assist in better delineating the boundary between these related species and understanding their virulence potential.

Prevalence and characterization of pertactin deficient Bordetella pertussis strains in Brazil, a whole-cell vaccine country.

Many countries have reported antigenic divergence among circulating Bordetella pertussis strains, mainly in those countries which introduced the acellular pertussis (aP) vaccine. This phenomenon can be seen, for example, with the recent rise of pertactin (Prn)-deficient B. pertussis strains, one of the antigens included in aP vaccine formulas. The whole cell pertussis (wP) vaccine has been used in Brazil since 1977 for the primary pertussis, diphtheria and tetanus immunization series. In 2014, the aP vaccine was recommended for women during pregnancy to protect infants in the first months of life. Our objective was to determine the prevalence of Prn-deficiency in 511 isolates of B. pertussis collected in Brazil during 2010-2016. All isolates were characterized, through PFGE and serotyping, and screened for the loss of Prn by ELISA. Prn-deficiency was confirmed by immunoblotting, and identification of the possible genetic markers was performed with PCR and Sanger sequencing. Results indicate that 110 PFGE profiles are currently circulating, with five profiles representing the majority, and the predominant serotype 3, has been gradually replaced by serotype 2 and serotype 2,3. ELISA screening and immunoblotting identified three Prn-deficient isolates. Genotypic characterization by PCR and sequencing indicated that one isolate had a promoter mutation in prn, while the other two did not have an obvious genetic explanation for their deficiency. While the lack of Prn was identified in a few isolates, this study did not detect a relevant occurrence of Prn-deficiency, until 2016, confirming previous observations that Prn-deficiency is likely aP vaccine-driven.

Effect of maternal Tdap on infant antibody response to a primary vaccination series with whole cell pertussis vaccine in São Paulo, Brazil.

BACKGROUND: Maternal Tetanus, diphtheria, and acellular pertussis (Tdap) vaccination provides antibody transfer to newborn infants and may affect their antibody response to the primary vaccination series. This study aimed to assess the effect of Tdap vaccination during pregnancy on infant antibody response to the whole cell pertussis (DTwP) primary series. METHODS: Plasma from 318 pregnant women (243 Tdap-vaccinated and 75 unvaccinated) and their infants (cord blood) was collected at delivery; infant blood was again collected at 2 and 7 months, before and after their primary DTwP series. Anti-pertussis toxin (PT), pertactin (PRN), filamentous hemagglutinin (FHA), fimbriae 2/3 (FIM) and adenylate cyclase toxin (ACT) IgG antibodies were quantified by a microsphere-based multiplex antibody capture assay and anti-PT neutralizing antibodies by the Real Time Cell analysis system. RESULTS: Infant geometric mean concentrations (GMCs) of IgG anti-Tdap antigens were significantly higher (p < 0.001) among the Tdap-vaccinated (PT: 57.22 IU/mL; PRN: 464.86 IU/mL; FHA: 424.0 IU/mL), versus the unvaccinated group (4 IU/mL, 15.43 IU/mL, 31.99 IU/mL, respectively) at delivery. Anti-FIM and ACT GMCs were similar between the two groups. At 2 months of age, anti-PT, PRN, and FHA GMCs remained higher (p < 0.001) in the Tdap-vaccinated group (12.64 IU/mL; 108.76 IU/mL; 87.41 IU/mL, respectively) than the unvaccinated group (1.02 IU/mL; 4.46 IU/mL; 6.89 IU/mL). However, at 7 months, after receiving the third DTwP dose, the anti-PT GMC was higher (p = 0.016) in the unvaccinated group (7.91 IU/mL) compared to the vaccinated group (2.27 IU/mL), but without differences for anti-PRN, FHA, FIM and ACT GMCs. CONCLUSION: Elevated antibody levels suggest that maternal Tdap vaccination might protect infants until 2 months of age. Reduced anti-PT levels at 7 months indicate potential blunting of immune response in infants. Surveillance would help determine if blunting alters vaccine immunity and impacts pertussis prevention in infants.

Genomic epidemiology of nontoxigenic Corynebacterium diphtheriae from King County, Washington State, USA between July 2018 and May 2019.

Between July 2018 and May 2019, Corynebacterium diphtheriae was isolated from eight patients with non-respiratory infections, seven of whom experienced homelessness and had stayed at shelters in King County, WA, USA. All isolates were microbiologically identified as nontoxigenic C. diphtheriae biovar mitis. Whole-genome sequencing confirmed that all case isolates were genetically related, associated with sequence type 445 and differing by fewer than 24 single-nucleotide polymorphisms (SNPs). Compared to publicly available C. diphtheriae genomic data, these WA isolates formed a discrete cluster with SNP variation consistent with previously reported outbreaks. Virulence-related gene content variation within the highly related WA cluster isolates was also observed. These results indicated that genome characterization can readily support epidemiology of nontoxigenic C. diphtheriae.

Association between the timing of maternal vaccination and newborns' anti-pertussis toxin antibody levels.

BACKGROUND: Pertussis remains an important global public health concern, despite the presence of extensive immunization programs. Incidence and severity of pertussis are typically higher in neonates and young infants. As a strategy to protect these young infants, maternal vaccination with Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis) has been recommended in Brazil. The objective of this study was to evaluate the effects of Tdap vaccination during pregnancy on the anti-pertussis toxin (PT) IgG response in mothers and their infants at birth. MATERIAL AND METHODS: Maternal and cord blood samples were collected from vaccinated (n = 243) and unvaccinated (n = 75) pregnant women, at the time of delivery, from July 2015 to August 2016 in São Paulo, Brazil. Anti-PT IgG antibodies were quantified by Enzyme-Linked Immunosorbent Assay (ELISA) and geometric mean concentrations (GMC) were calculated. Relationship between timing of vaccination and antibody concentrations were evaluated. RESULTS: Maternal and cord blood GMCs among the vaccinated group were 5.4 and 5.6 fold higher [66.5 International Units (IU)/mL and 89.8 IU/mL] compared to the unvaccinated group (12.4 IU/mL and 16.1 IU/mL), respectively (p < 0.001). Higher anti-PT IgG GMCs were observed when vaccination occurred ≥60 days before delivery compared to <60 days, suggesting that vaccination early in the third trimester may be more effective than later in pregnancy. CONCLUSION: Tdap maternal vaccination results in significantly higher anti-PT IgG in newborn infants and supports the current recommendation of the Brazilian Immunization Program.

Expanding Pertussis Epidemiology in 6 Latin America Countries through the Latin American Pertussis Project.

The Latin American Pertussis Project (LAPP), established in 2009, is a collaboration between the Centers for Disease Control and Prevention, Pan American Health Organization, Sabin Vaccine Institute, and the ministries of health of 6 countries in Latin America. The project goal is to expand understanding of pertussis epidemiology in Latin America to inform strategies for control and prevention. Here we describe LAPP structure and activities. After an initial surveillance evaluation, LAPP activities are tailored to individual country needs. LAPP activities align with Global Health Security Agenda priorities and have focused on expanding laboratory diagnostic capacity, implementing a laboratory quality control and quality assurance program, and providing epidemiologic support to strengthen reporting of pertussis surveillance data. Lessons learned include that ongoing mentoring is key to the successful adoption of new technologies and that sustainability of laboratory diagnostics requires a regional commitment to procure reagents and related supplies.

Risk Factors Associated With Bordetella pertussis Among Infants ≤4 Months of Age in the Pre-Tdap Era: United States, 2002-2005.

BACKGROUND: In the United States, infants have the highest reported pertussis incidence and death rates. Improved understanding of infant risk factors is needed to optimize prevention strategies. METHODS: We prospectively enrolled infants ≤4 months of age with incident-confirmed pertussis from 4 sites during 2002-2005 (preceding pertussis antigen-containing vaccination recommendations for adolescents/adults); each case-patient was age and site matched with 2 control subjects. Caregivers completed structured interviews. Infants and their contacts ≥11 years of age were offered serologic testing for IgG; being seropositive was defined as ≥94 antipertussis toxin IgG enzyme-linked immunosorbent assay units per milliliter. RESULTS: Enrolled subjects (115 case-patients; 230 control subjects) had 4396 contacts during incubation periods; 83 (72%) case-patients had ≥1 contact with prolonged (≥5 days) new cough in primary or secondary households. In multivariable analysis, the odds for pertussis were higher for infants with primary/secondary household contacts who had a prolonged new cough, compared with infants who did not. These contacts included mother [adjusted matched odds ratio (aMOR), 43.8; 95% confidence interval (CI), 6.45-298.0] and ≥1 nonmother contact (aMOR, 20.1; 95% CI, 6.48-62.7). Infants receiving breast milk with 0-1 formula feedings daily had decreased pertussis odds (aMOR, 0.27; 95% CI, 0.08-0.89), compared with those receiving more formula. Of 41 tested case-patients, 37 (90%) were seropositive. CONCLUSIONS: Pertussis in infants was associated with prolonged new cough (≥5 days) in infants' household contacts. Findings suggest that breastfeeding protects against pertussis and warrants recommendation with pertussis prevention strategies, which currently include pertussis vaccination of pregnant mothers and infants' close contacts.

Comparative analytical evaluation of the respiratory TaqMan Array Card with real-time PCR and commercial multi-pathogen assays.

In this study, a multicenter evaluation of the Life Technologies TaqMan(®) Array Card (TAC) with 21 custom viral and bacterial respiratory assays was performed on the Applied Biosystems ViiA™ 7 Real-Time PCR System. The goal of the study was to demonstrate the analytical performance of this platform when compared to identical individual pathogen specific laboratory developed tests (LDTs) designed at the Centers for Disease Control and Prevention (CDC), equivalent LDTs provided by state public health laboratories, or to three different commercial multi-respiratory panels. CDC and Association of Public Health Laboratories (APHL) LDTs had similar analytical sensitivities for viral pathogens, while several of the bacterial pathogen APHL LDTs demonstrated sensitivities one log higher than the corresponding CDC LDT. When compared to CDC LDTs, TAC assays were generally one to two logs less sensitive depending on the site performing the analysis. Finally, TAC assays were generally more sensitive than their counterparts in three different commercial multi-respiratory panels. TAC technology allows users to spot customized assays and design TAC layout, simplify assay setup, conserve specimen, dramatically reduce contamination potential, and as demonstrated in this study, analyze multiple samples in parallel with good reproducibility between instruments and operators.

A Proteomic Characterization of Bordetella pertussis Clinical Isolates Associated with a California State Pertussis Outbreak.

Bordetella pertussis (Bp) is the etiologic agent of pertussis (whooping cough), a highly communicable infection. Although pertussis is vaccine preventable, in recent years there has been increased incidence, despite high vaccine coverage. Possible reasons for the rise in cases include the following: Bp strain adaptation, waning vaccine immunity, increased surveillance, and improved clinical diagnostics. A pertussis outbreak impacted California (USA) in 2010; children and preadolescents were the most affected but the burden of disease fell mainly on infants. To identify protein biomarkers associated with this pertussis outbreak, we report a whole cellular protein characterization of six Bp isolates plus the pertussis acellular vaccine strain Bp Tohama I (T), utilizing gel-free proteomics-based mass spectrometry (MS). MS/MS tryptic peptide detection and protein database searching combined with western blot analysis revealed three Bp isolates in this study had markedly reduced detection of pertactin (Prn), a subunit of pertussis acellular vaccines. Additionally, antibody affinity capture technologies were implemented using anti-Bp T rabbit polyclonal antisera and whole cellular proteins to identify putative immunogens. Proteome profiling could shed light on pathogenesis and potentially lay the foundation for reduced infection transmission strategies and improved clinical diagnostics.

Molecular epidemiology of the pertussis epidemic in Washington State in 2012.

Although pertussis disease is vaccine preventable, Washington State experienced a substantial rise in pertussis incidence beginning in 2011. By June 2012, the reported cases reached 2,520 (37.5 cases per 100,000 residents), a 1,300% increase compared with the same period in 2011. We assessed the molecular epidemiology of this statewide epidemic using 240 isolates collected from case patients reported from 19 of 39 Washington counties during 2012 to 2013. The typing methods included pulsed-field gel electrophoresis (PFGE), multilocus variable number tandem repeat analysis (MLVA), multilocus sequence typing (MLST), and pertactin gene (prn) mutational analysis. Using the scheme PFGE-MLVA-MLST-prn mutations-Prn deficiency, the 240 isolates comprised 65 distinct typing profiles. Thirty-one PFGE types were found, with the most common types, CDC013 (n = 51), CDC237 (n = 44), and CDC002 (n = 42), accounting for 57% of them. Eleven MLVA types were observed, mainly comprising type 27 (n = 183, 76%). Seven MLST types were identified, with the majority of the isolates typing as prn2-ptxP3-ptxA1-fim3-1 (n = 157, 65%). Four different prn mutations accounted for the 76% of isolates exhibiting pertactin deficiency. PFGE provided the highest discriminatory power (D = 0.87) and was found to be a more powerful typing method than MLVA and MLST combined (D = 0.67). This study provides evidence for the continued predominance of MLVA 27 and prn2-ptxP3-ptxA1 alleles, along with the reemergence of the fim3-1 allele. Our results indicate that the Bordetella pertussis population causing this epidemic was diverse, with a few molecular types predominating. The PFGE, MLVA, and MLST profiles were consistent with the predominate types circulating in the United States and other countries. For prn, several mutations were present in multiple molecular types.

Serodiagnosis as adjunct assay for pertussis infection in São Paulo, Brazil.

Pertussis remains an important public health problem in many countries despite extensive immunization. Cultures and real-time PCR (RT-PCR) assays are the recommended pertussis diagnostic tests, but they lack sensitivity at the later stage of the disease. This study introduces the IgG anti-pertussis toxin enzyme-linked immunosorbent assay (PT ELISA) in our routine diagnosis to improve disease burden estimation. Serum samples and nasopharyngeal swabs (n = 503) were collected at the same time from patients presenting with cough illness suspected of being pertussis and tested by the PT ELISA and culture and/or RT-PCR, respectively. Patients were separated into three age groups: group 1, <1 year (n = 260; mean age, 3 months), group 2, 1 to 6 years (n = 81; mean age, 3 years), and group 3, ≥7 years (n = 162; mean age, 26 years). The times (means) from cough onset to specimen collection were 16, 24, and 26 days, respectively. In group 1, 83 (82.2%) of 101 positive cases were positive for pertussis by culture/RT-PCR, while 40 (39.6%) tested positive by PT ELISA. In group 2, 6 (19.4%) of 31 positive cases were culture/RT-PCR positive, and 29 (93.6%) were seropositive. In group 3, 13 (13.8%) of 94 positive cases were positive by culture/RT-PCR and 91 (96.8%) were positive by serology. Culture/RT-PCR detected more cases of pertussis in infants (P < 0.0001), whereas the PT ELISA detected more cases in adolescents and adults (P < 0.0001). The timing between cough onset and specimen collection or recent vaccination may have partially affected our results. Serology is a suitable, cost-effective, and complementary pertussis diagnostic tool, especially among older children, adolescents, and adults during the later disease phase.

Genome Sequences of 28 Bordetella pertussis U.S. Outbreak Strains Dating from 2010 to 2012.

Despite the availability of highly effective vaccines, Bordetella pertussis incidence has been rapidly rising in highly vaccinated populations. Recent outbreaks have received media attention, feeding concerns about the emergence of dangerous new strains with increased virulence or that escape vaccine-induced immunity. To accelerate the study of this reemerging pathogen, we sequenced the genomes of 28 B. pertussis strains isolated during outbreaks from 2010 through 2012, making both strains and sequence data available to the scientific community.

Qualitative assessment of pertussis diagnostics in United States laboratories.

BACKGROUND: United States national surveillance data show that the use of culture for pertussis diagnostics has sharply declined, whereas polymerase chain reaction (PCR) is now the most common testing method. PCR testing for pertussis is rapid and sensitive, but the lack of standardization and variable specificity is concerning. METHODS: A web-based survey containing 12 questions was sent to public health, commercial and hospital-based US laboratories performing clinical diagnostics to determine the pertussis diagnostics used. An extensive real-time PCR (RT-PCR) questionnaire accompanied a proficiency panel assessing the types of extraction methods, RT-PCR methods and current quality control in place at the laboratories. The proficiency panel of 12 specimens containing Bordetella pertussis at various concentrations and negative controls was created to detect cross-contamination and assess the lower limit of detection. RESULTS: One hundred twenty-three (35%) of 355 respondents from the web-based survey performed diagnostic tests for the presence of B. pertussis. Eighty-three (71%) labs reported performing culture, whereas 67 (54%) labs used PCR. All 41 laboratories that consented to participate in the proficiency exercise used the IS481 RT-PCR target; however, a variety of extraction and RT-PCR methods were employed. The laboratories correctly identified 92% of the B. pertussis specimens, and 5% of the laboratories (1.8% of the panel specimens) reported at least 1 false-positive. CONCLUSIONS: The small percentage of false-positives suggests that adequate procedures are in place to prevent cross-contamination. Differing extraction and PCR methods as well as variable analytic sensitivity emphasize the necessity for an external well-defined quality control program and interlaboratory pertussis PCR harmonization.

Utilization of multiple real-time PCR assays for the diagnosis of Bordetella spp. in clinical specimens.

Bordetella pertussis causes an upper respiratory infection in infants, adolescents, and adults. Diagnosis of pertussis, a vaccine-preventable disease, can be difficult, but recent implementation of real-time PCR assays in laboratories has hastened the ability of clinicians to make an accurate diagnosis. In this paper we describe the method of nasopharyngeal specimen collection, extraction of DNA, and real-time PCR assays that will allow the detection and identification of Bordetella spp. in clinical specimens.

Epidemiologic and laboratory features of a large outbreak of pertussis-like illnesses associated with cocirculating Bordetella holmesii and Bordetella pertussis--Ohio, 2010-2011.

BACKGROUND: During 9 May 2010-7 May 2011, an outbreak of pertussis-like illness (incidence, 80 cases per 100 000 persons) occurred in Franklin County, Ohio. The majority of cases were identified by IS481-directed polymerase chain reaction (PCR), which does not differentiate among Bordetella species. We sought to determine outbreak etiology and epidemiologic characteristics. METHODS: We obtained demographic, clinical, and vaccination-related data from the Ohio Disease Reporting System and Impact Statewide Immunization Information System. We tested sera from 14 patients for anti-pertussis toxin (PT) antibodies and used species-specific PCR on 298 nasopharyngeal specimens. RESULTS: Reported cases totaled 918. IS481 results were available for 10 serologically tested patients; 5 of 10 had discordant anti-PT antibody and IS481 results, suggestive of Bordetella holmesii, which lacks PT and harbors IS481. We identified specific Bordetella species in 164 of 298 specimens tested with multitarget PCR; B. holmesii and Bordetella pertussis were exclusively detected among 48 (29%) and 112 (68%), respectively; both were detected in 4 (2%). Among 48 patients with B. holmesii infections, 63% were aged 11-18 years, compared with 35% of 112 patients with B. pertussis infections (P = .001). Symptoms were similar among B. holmesii- and B. pertussis-infected patients. Adolescent pertussis ("Tdap") booster vaccinations were more effective against B. pertussis than B. holmesii (effectiveness: 67% and 36%, respectively; 95% confidence intervals, 38%-82% and -33% to 69%, respectively). CONCLUSIONS: We report the first documented mixed outbreak of B. pertussis and B. holmesii infections. Bordetella holmesii particularly affected adolescents. Although laboratory capacity limitations might inhibit routine use of multitarget PCR for clinical diagnosis, focused testing and enhanced surveillance might improve understanding the burden of B. holmesii infection.

Sorotipos e perfis genéticos de cepas de Bordetella pertussis isoladas na cidade de São Paulo, 2006-2008 / Serotypes and genetic profiles of Bordetella pertussis strains isolated in the city of São Paulo, 2006-2008

OBJETIVO: O conhecimento de Bordetella pertussis circulante na América Latina é limitado. Portanto, o objetivo deste estudo foi usar a técnica da eletroforese em campo pulsado e a sorotipagem para caracterizar cepas de B. pertussis isoladas na cidade de São Paulo (SP). MÉTODOS: Este estudo, conduzido entre 2006 e 2008, analisou 652 swabs de nasofaringe coletados de casos suspeitos e comunicantes de coqueluche, provenientes de 37 hospitais sentinela de São Paulo. Foram realizadas as técnicas da eletroforese em campo pulsado e sorotipagem em 91 (70%) cepas de B. pertussis, escolhidas aleatoriamente. RESULTADOS: Noventa e sete por cento das cepas de São Paulo foram sorotipadas como Fim3. Foram identificados 14 perfis genéticos pela eletroforese em campo pulsado; o mais prevalente (57%) também é o mais prevalente nos EUA. CONCLUSÕES: Esses dados, em conjunto com ações da vigilância, podem ter um impacto nas estratégias de prevenção e controle de coqueluche na região, oferecendo informações úteis para a introdução de estratégias novas de vacinação e redução do risco de transmissão para bebês menores de 6 meses de idade.

OBJECTIVE: Knowledge of Bordetella pertussis circulating in Latin America is limited. Therefore, the goal of this study was to use pulsed-field gel electrophoresis and serotyping to characterize B. pertussis strains isolated in the city of São Paulo, Brazil. METHODS: This study, conducted between 2006 and 2008, analyzed 652 nasopharyngeal swabs from suspected pertussis cases and contacts, collected from 37 sentinel hospitals in São Paulo. Randomized samples of 91 (70%) strains of B. pertussis were subtyped by pulsed-field gel electrophoresis and serotyping. RESULTS: Ninety-seven percent of strains from São Paulo were serotyped as Fim3. Fourteen pulsed-field gel electrophoresis profiles were identified; the most prevalent (57%) is also the most prevalent in the USA. CONCLUSIONS: These data, in conjunction with surveillance activities, may impact strategies regarding prevention and control of pertussis in the region, providing useful information for introduction of new vaccination strategies and reduction of risk of transmission to infants less than 6 months of age.

Serotypes and genetic profiles of Bordetella pertussis strains isolated in the city of São Paulo, 2006-2008.

OBJECTIVE: Knowledge of Bordetella pertussis circulating in Latin America is limited. Therefore, the goal of this study was to use pulsed-field gel electrophoresis and serotyping to characterize B. pertussis strains isolated in the city of São Paulo, Brazil. METHODS: This study, conducted between 2006 and 2008, analyzed 652 nasopharyngeal swabs from suspected pertussis cases and contacts, collected from 37 sentinel hospitals in São Paulo. Randomized samples of 91 (70%) strains of B. pertussis were subtyped by pulsed-field gel electrophoresis and serotyping. RESULTS: Ninety-seven percent of strains from São Paulo were serotyped as Fim3. Fourteen pulsed-field gel electrophoresis profiles were identified; the most prevalent (57%) is also the most prevalent in the USA. CONCLUSIONS: These data, in conjunction with surveillance activities, may impact strategies regarding prevention and control of pertussis in the region, providing useful information for introduction of new vaccination strategies and reduction of risk of transmission to infants less than 6 months of age.

Does tetanus-diphtheria-acellular pertussis vaccination interfere with serodiagnosis of pertussis infection?

An anti-pertussis toxin (PT) IgG enzyme-linked immunosorbent assay (ELISA) was analytically validated for the diagnosis of pertussis at a cutoff of 94 ELISA units (EU)/ml. Little was known about the performance of this ELISA in the diagnosis of adults recently vaccinated with tetanus-diphtheria-acellular pertussis (Tdap) vaccine, which contains PT. The goal of this study was to determine when the assay can be used following Tdap vaccination. A cohort of 102 asymptomatic health care personnel (HCP) vaccinated with Tdap (Adacel; Sanofi Pasteur) were aged 19 to 79 years (median, 47 years) at vaccination. For each HCP, specimens were available for evaluation at 2 to 10 time points (prevaccination to 24 months postvaccination), and geometric mean concentrations (GMC) for the cohort were calculated at each time point. Among 97 HCP who responded to vaccination, a mixed-model analysis with prediction and tolerance intervals was performed to estimate the time at which serodiagnosis can be used following vaccination. The GMCs were 8, 21, and 9 EU/ml at prevaccination and 4 and 12 months postvaccination, respectively. Eight (8%) of the 102 HCP reached antibody titers of ≥94 EU/ml during their peak response, but none had these titers by 6 months postvaccination. The calculated prediction and tolerance intervals were <94 EU/ml by 45 and 75 days postvaccination, respectively. Tdap vaccination 6 months prior to testing did not confound result interpretation. This seroassay remains a valuable diagnostic tool for adult pertussis.

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.