Rapid diagnosis of pertussis in young infants: comparison of culture, PCR, and infant's and mother's serology

Asymptomatic Infection and Transmission of Pertussis in Households: A Systematic Review

We conducted a systematic review to describe the frequency of mild, atypical, and asymptomatic infection among household contacts of pertussis cases and to explore the published literature for evidence of asymptomatic transmission. We included studies that obtained and tested laboratory specimens from household contacts regardless of symptom presentation and reported the proportion of cases with typical, mild/atypical, or asymptomatic infection. After screening 6789 articles, we included 26 studies. Fourteen studies reported household contacts with mild/atypical pertussis. These comprised up to 46.2% of all contacts tested. Twenty-four studies reported asymptomatic contacts with laboratory-confirmed pertussis, comprising up to 55.6% of those tested. Seven studies presented evidence consistent with asymptomatic pertussis transmission between household contacts. Our results demonstrate a high prevalence of subclinical infection in household contacts of pertussis cases, which may play a substantial role in the ongoing transmission of disease. Our review reveals a gap in our understanding of pertussis transmission.

Prevalence of Bordetella pertussis and Bordetella parapertussis infections in Tunisian hospitalized infants: results of a 4-year prospective study

The prevalence of pertussis in Tunisia remains undetermined essentially because of the unavailability of a basic laboratory diagnostic service. Specific diagnostic tools were applied for the first time in a Tunisian prospective study in order to get a first estimation of the prevalence of Bordetella pertussis/parapertussis infections and to evaluate their use to determine the epidemiologic characteristics of these infections in Tunisian infants. Between 2007 and 2011, a total of 626 samples from 599 infants aged <1 year with and without pertussoid cough were investigated for the presence of B. pertussis/parapertussis using culture and real-time polymerase chain reaction (PCR). The real-time PCR (RT-PCR) targets include IS481 commonly found in B. pertussis, B. bronchiseptica, and B. holmesii; IS1001 specific of B. parapertussis, in combination with the pertussis toxin promoter region gene (ptx) of B. pertussis; and the recA gene specific of B. holmesii. When possible, patients' household contacts provided nasopharyngeal aspirates (NPAs) for RT-PCR detection of B. pertussis/parapertussis or single-serum samples for anti-PT IgG quantification. All except 1 NPAs were negative by conventional culture, whereas PCR gave positive signals for 126 specimens (21%): B. pertussis, B. parapertussis, and Bordetella spp. were detected in 82%, 6%, and 4% of the samples, respectively. The simultaneous presence of B. pertussis and B. parapertussis was noted in 8% of the cases. Pertussis was reported throughout the year with a peak during the summer of the year 2009. The prevalence of Bordetella infection was 20% between 2007 and 2011. Most of these cases corresponded to patients younger than 6 months who received <3 doses of pertussis vaccine. Among the household contacts enrolled in the study, mothers seemed to be the likely source of infection. This study showed that pertussis is still prevalent in Tunisia and that the disease remains a public health problem affecting not only infants but also adults. Given this situation, sensitive and specific laboratory tests are needed to improve the accuracy of pertussis diagnosis.

[Awareness and adherence to Pertussis vaccination guidelines by occupational medicine physicians in Paris healthcare institution]

OBJECTIVE

A questionnaire was used on 44 public and private hospital physicians in Paris to evaluate their knowledge of and adherence to Vaccination Guidelines, three years after their introduction.

RESULTS

Eighty per cent of the physicians answered and 92.5% were aware of the vaccination guidelines but only 2 out of 4 respected the targeted vaccination in young adults even when the vaccine was available. A policy of pertussis vaccination was applied only in 12 institutions, but even in these, the rate of vaccinated healthcare workers remained low or was not documented.

CONCLUSION

Pertussis is a potential risk to newborns not or partially vaccinated in France. Even if the vaccine is available, adherence to pertussis vaccination guidelines must be improved. Efforts should be made to better publicize and apply pertussis vaccination guidelines.

Estimating the role of casual contact from the community in transmission of Bordetella pertussis to young infants

The proportion of infant pertussis cases due to transmission from casual contact in the community has not been estimated since before the introduction of pertussis vaccines in the 1950s. This study aimed to estimate the proportion of pertussis transmission due to casual contact using demographic and clinical data from a study of 95 infant pertussis cases and their close contacts enrolled at 14 hospitals in France, Germany, Canada, and the U.S. between February 2003 and September 2004. A complete case analysis was conducted as well as multiple imputation (MI) to account for missing data for participants and close contacts who did not participate. By considering all possible close contacts, the MI analysis estimated 66% of source cases were close contacts, implying the minimum attributable proportion of infant cases due to transmission from casual contact with community members was 34% (95% CI = 24%, 44%). Estimates from the complete case analysis were comparable but less precise. Results were sensitive to changes in the operational definition of a source case, which broadened the range of MI point estimates of transmission from casual community contact to 20%–47%. We conclude that casual contact appears to be responsible for a substantial proportion of pertussis transmission to young infants.

Medical subject headings (MeSH): multiple imputation, pertussis, transmission, casual contact, sensitivity analysis, missing data, community.

Pertussis symptoms in adolescents and children versus infants: the influence of vaccination and age

This study compared the influence of age and immunization status on symptoms in pediatric patients with pertussis. The files of 60 children, aged 7 to 18 years and 20 infants aged up to 6 months, admitted to our pediatric hospital with a diagnosis of pertussis were reviewed. There were no between-group differences in day and night cough or vomiting. The older group had a longer mean interval to diagnosis than the infants, and the infant group had more symptoms of whooping cough, facial redness during cough, cyanosis, a higher white blood count, a higher percentage of lymphocytes, and more abnormal chest X-rays. Statistically significant differences were found between vaccinated and unvaccinated older children for whooping cough and white blood cell count. Daytime and nighttime coughs are common symptoms of pertussis in all pediatric age groups, regardless of vaccination status. High white blood count is related to immunization status, and percentage of lymphocytes is related to age. In infants, symptoms are more grave but are typical, leading to early diagnosis.

Pertussis in Argentina and France

We have studied the epidemiology of pertussis in two countries, Argentina and France, which have similar histories of long-term mass vaccination with a whole-cell vaccine. Both countries display a comparable epidemiology, with an increase of the incidence of the disease in non-vaccinated newborns. We used pulsed-field gel electrophoresis (PFGE) analysis and genotyping to compare Bordetella pertussis clinical isolates recovered in Argentina and France in 2001-2004. The majority of the isolates harbors prn2 allele and belongs to PFGE IVbeta group. Isolates were found to be very similar genetically suggesting a common evolution of the disease in these two countries using the same vaccine.

Impact de la vaccination sur l’épidémiologie des maladies infectieuses : exemple de la coqueluche

Several vaccines are now routinely used since fifty years in different developed countries. Their principal impact has been to decrease morbidity and mortality of the infectious diseases they are targeting. One disease, smallpox, is eradicated, poliomyelitis will be soon, diphteria is controlled in several countries but pertussis is still endemic although an efficacious vaccine was used. Why? Pertussis is an example of an infection for which the immunity of the population has changed after the introduction of generalized vaccination with killed whole cell pertussis vaccines, from a natural immunity due to infection to different types of vaccine-induced immunity. These different types of immunity have changed the protection against infection, disease and transmission. The impact of the generalized vaccination in a human population has been an important change in the epidemiology of the disease. In fact, a child-to-child transmission observed before the introduction of vaccination is now replaced by an adolescent-adult to infant transmission. The major consequence is an increase in the mortality and morbidity in non vaccinated infants mostly contaminated by their parents. Researches undertaken on the agent of the disease, the bacterium, Bordetella pertussis, conducted to the development of subunits vaccines, efficacious and better tolerated by infants than whole-cell vaccines. Many developed countries decided to change vaccines but also to add vaccine boosters for adolescents and adults in order to stop the transmission of the disease to infants. However, even after 15 years of studies in many countries, pertussis is still underestimated in adults and generalized adult vaccination remains difficult. The new goal now is to give information to medical students and health care workers in general in order to increase adolescent and adult's vaccination coverage.

Recent developments in pertussis

Pertussis causes nearly 300,000 deaths in children every year. Most deaths take place in developing countries, but the infection remains a priority everywhere. Pertussis vaccination protects infants and children against death and admission to hospital, but breakthrough disease in vaccinated people can happen. In high-mortality countries, the challenge is to improve timeliness and coverage of childhood vaccination and surveillance. In regions with low mortality and highest coverage, pertussis is frequently the least well-controlled disease in childhood vaccination programmes. Some countries have reported a rise in pertussis in adolescents, adults, and pre-vaccination infants, but how much these changes are real or a result of improved recognition and surveillance remains uncertain. In response, several countries have introduced adolescent and adult acellular pertussis vaccine boosters. The effect so far is unknown; assessment is impeded by poor data. Uncertainties still persist about key variables needed to model and design vaccination programmes, such as risk of transmission from adults and adolescents to infants. New vaccination strategies under investigation include vaccination of neonates, family members, and pregnant women.

Conduite à tenir devant un ou plusieurs cas de coqueluche

The evolution of the epidemiology of pertussis, new licensed macrolides and vaccines, new recommendations for vaccination among adolescents and adults need an update of the French guidelines for prevention of the disease around one or grouped cases of the disease. A particular attention should be raised to the diagnosis of whooping cough in adults who are presently the main reservoir of Bordetella pertussis. Whooping cough in adults presents as an unexplained prolonged cough with nocturnal exacerbation witch accounts for most of the contaminations of young infants. A bacteriological confirmation of pertussis should be provided before implementation of preventive measures: culture and PCR are presently the gold standard for the diagnosis of pertussis in infants, children and even adults who have been coughing for less than 20 days. Later on, serology (Elisa, immuno-empreinte) is the only technique available, but cannot be interpreted if the patient has been vaccinated less than one year ago. Infants under three months should be admitted to hospital and every case submitted to respiratory isolation. Eviction from the community should be pronounced within the five first days following the onset of an effective antibiotic treatment. New macrolides should be favoured: clarithromycin for seven days or azithromycin for five days. Household contacts should be given the same prophylactic antibiotic treatment: children and adolescent not correctly immunized, parents of the index case as adults parents of not or not completely immunized infants. The vaccination program of the household should be updated. The same measures should be applied in case of grouped cases (at least two contemporary or consecutive cases in the same area). In that case, the Public Health System doctors should be involved in the investigation and the classification of the cases. The close contacts not or not completely immunized should be prescribed and antibiotic prophylaxis and an update of their vaccination program. Among the occasional contacts, high-risk people only should be treated. In the day care centres an antibiotic prophylaxis should be given to children who have received less than four vaccine shots against pertussis and to the personnel contact to the cases as well. In the schools, the antibiotic prophylaxis should be prescribed to all children of the classroom(s) not completely vaccinated and to the teacher(s) as well. In the boarding schools and institutions with handicapped children, antibiotic prophylaxis could be applied to every member if the pertussis vaccine coverage is at less than 50%. In hospitals, coughing personnel should wear masks and investigations towards pertussis should be performed in people with a more than seven day unexplained cough. Preventive measures should be applied in case of confirmation of pertussis.

Defining pertussis epidemiology: clinical, microbiologic and serologic perspectives

In the past decade, numerous sources have noted an increase in reported pertussis in highly immunized populations. This has been accompanied by a perceived change in disease epidemiology, characterized by a significant increase in reported pertussis incidence among adolescents and adults. In populations where children are routinely immunized, adolescents and adults now constitute the main source of infection in infants. However, a range of factors makes delineation of these epidemiologic trends difficult. Reported cases of pertussis represent only a fraction of the actual number of Bordetella pertussis symptomatic infections, because underconsulting, underrecognition and underdiagnosis are widespread and are a particular problem in adolescents and adults. Possible explanations for failure to diagnose pertussis include the heterogeneity in pertussis disease expression and low physician awareness and index of suspicion. Consequently defining pertussis from a clinical perspective is difficult, and this is reflected by a lack of consistency between case definitions. Although case definitions for specific circumstances have been established by the World Health Organization and the United States Centers for Disease Control, these are not universally useful, making intercountry comparisons and global evaluation difficult. Less-than-optimal and poorly performed laboratory tests, or their lack of availability, also make confirmation of B. pertussis infection difficult. To overcome these problems, clinical case definitions should be standardized for outbreak and endemic situations. Rapid, easy-to-use and inexpensive laboratory diagnostic techniques also must be made available and be widely implemented. In particular, polymerase chain reaction and single serum serology are 2 techniques that should be more widely adopted.

Clinical presentation of pertussis in unvaccinated and vaccinated children in the first six years of life

OBJECTIVES

Identifying the determinants of the clinical presentation of pertussis is important for the purposes of diagnosis, therapy, and control and for predicting the disease's clinical course and choosing an appropriate case definition for surveillance. Potential determinants include vaccination status, antibiotic treatment, age at diagnosis, and sex, although the available data are inconsistent. The objective of this study was to compare the clinical course of pertussis in unvaccinated and vaccinated children in a well-defined and strictly studied population and to identify determinants of the disease's clinical presentation.

METHODS

The clinical presentation of pertussis was studied in children who participated in a randomized, controlled clinical trial of efficacy of acellular pertussis vaccine. The children belonged to the same birth cohort and were followed from infancy to 6 years of age in 3 distinct periods (stages 1, 2, and 3). Children had received 1 of 2 three-component acellular pertussis vaccines produced by 2 manufacturers (diphtheria-tetanus-acellular pertussis from, Chiron Biocine [DTaP CB]; DTaP from SmithKline Beecham [DTaP SB]) or a diphtheria-tetanus vaccine only (DT; Chiron Biocine). Pertussis was confirmed through culture or serology. For each pertussis episode, information was collected on age at onset, sex, type of vaccine received, antibiotic treatment, culture results, duration of cough, spasmodic cough, and other symptoms. The simultaneous effect of potential determinants of clinical presentation of pertussis on the duration of cough and spasmodic cough was studied through analysis of variance models.

RESULTS

The analysis was conducted on 788 laboratory-confirmed cases of pertussis. The median duration of cough in DT recipients varied from 52 to 61 days across the 3 stages, whereas the median duration of cough in DTaP recipients varied from 29 to 39 days. The median duration of spasmodic cough varied from 20 to 45 days in DT recipients and from 14 to 29 days in DTaP recipients. The results of the analysis of variance models showed that vaccination against pertussis reduced the length of cough from 3 to 10 days and the length of spasmodic cough from 4 to 8 days. Culture-positive patients had a cough 11 to 22 days longer and a spasmodic cough 12 to 22 days longer than culture-negative patients. Children who received an antibiotic had a duration of cough 6 to 11 days longer and spasmodic cough 4 to 13 days longer than untreated patients. Girls had a duration of spasmodic cough 7 days longer than boys only after 3 years of age. Age was directly related to duration of cough, whereas it was inversely related to duration of spasmodic cough after 3 years of age.

CONCLUSIONS

Duration of cough can be greatly influenced by vaccination status. A positive culture for Bordetella pertussis is more frequently found in patients with long duration of cough, and antibiotic therapy may be a marker of severe disease. Gender may affect the clinical presentation of pertussis only after infancy. Pertussis in older children may be characterized by short duration of spasmodic cough. These results should be taken into account in the clinical evaluation of patients with suspected pertussis. Clinical case definitions for the purpose of surveillance based on the presence of 2 weeks of spasmodic cough may not be appropriate where pertussis vaccination uptake is high.

Coqueluche : diagnostics biologiques

Whooping cough is a respiratory infection particularly severe for infants. The agents of the disease are the bacteria Bordetella pertussis and B. parapertussis. Before vaccination, the disease affected majority of the children. Due to the high circulation of the bacteria, adolescents and adults were regularly in contact with the bacteria and had natural boosters. Forty years after generalized vaccination in some countries, a change in the transmission of the disease is observed. Children between 2 and 5-10 years of age are not infected (depending of the vaccine used and the vaccine calendar) because they were vaccinated in their infancy. However, adolescents and adults are becoming susceptible because they do not receive any vaccinal or natural boosters. They can be infected and contaminated infants are too young to be vaccinated. Clinical symptoms in adolescents and adults, previously vaccinated or infected, are very variable and for this reason biological diagnosis are now necessary to confirm the infection. These diagnostics are culture, PCR and serology.

[Routine use of gene amplification for pertussis diagnosis in children]

OBJECTIVES

The resurgence of whooping cough observed in France convinced us to develop a specific PCR assay to detect B. pertussis in nasopharyngeal secretions in parallel of the culture. The aim of our study was to show the value of the PCR in routine diagnosis.

MATERIAL AND METHODS

From November 1996 to August 2000, in two hospitals located in the Yvelines (France), the children consulting for a cough compatible with the diagnosis of whooping cough were included in this study. A questionnaire including clinical, biological and radiological items was completed for each one of these patients. A culture of Bordetella and a detection by PCR of B. pertussis were carried out on each nasopharyngeal aspirate. The diagnosis of whooping cough was retained if the detection was positive in PCR and/or culture.

RESULTS

Among the 215 investigated children with suspected cases of whooping cough, the diagnosis was positive for 45 (20.9%), of which 39 were less than one year old (median: three months). Sixteen (35.5,%) were positive at the same time for both the PCR and the culture, 26 (57.8%) for only PCR and three (6.7%) for only culture. The PCR was positive in 93.3% of the cases. The results were obtained with an average time of 48 hours. The culture was positive in 61.2% of the cases with an average time of six days. The monthly distribution of the cases of whooping cough was very inhomogeneous and of epidemic appearance. The majority of the cases was located between two periods: 42% between November 1996 and September 1997 and 40% between November 1999 and August 2000. Among the infected children, 15 were less than two months old and were not yet vaccinated; among the 24 others infants, a delay in the vaccine calendar was noted in 50% of the cases. Four children between six and 14 years old were correctly vaccinated. The evolution was favourable in all the children.

CONCLUSION

The PCR due to its sensitivity, its specificity and its rapidity offers to the clinician a powerful tool for the diagnosis of whooping cough. Nevertheless, the culture must be associated with the PCR, in order to follow the epidemiology and the sensitivity to antibiotics of B. pertussis.

Polymorphism of Bordetella pertussis isolates circulating for the last 10 years in France, where a single effective whole-cell vaccine has been used for more than 30 years

We compared Bordetella pertussis isolates collected in France over the last 10 years, the vaccine strains used for more than 30 years, and isolates collected before the introduction of generalized vaccination. The analysis included serotyping, pulsed-field gel electrophoresis of chromosomal DNA after digestion with XbaI and SpeI, and sequencing of the pt S1 gene, encoding the S1 subunit of pertussis toxin, and the prn gene, encoding the adhesin pertactin. We found that the incidence of infection increases every 3 years. Ninety-five per cent of the isolates analyzed express type 3 fimbriae. Most of the isolates circulating since 1991, unlike the vaccinal strains, express a type A pertussis toxin and a type 2 pertactin. The isolates could be classified into five major groups by pulsed-field gel electrophoresis. Most of these groups correlated with the pertactin type expressed by the isolates. Pulsed-field gel electrophoresis is more discriminative than sequencing particular genes since it could differentiate isolates expressing type 2 pertactin into two subgroups: those circulating in 1993 to 1997 and those circulating in 1997 to 2001. This observation suggests that there has been continuous evolution of the B. pertussis population.

Nosocomial pertussis in healthcare workers from a pediatric emergency unit in France

OBJECTIVE

After pertussis was diagnosed in July 1997 in a 55-year-old nurse (case) from a pediatric emergency unit who had a respiratory illness and paroxysmal cough for 5 weeks, an epidemiological investigation was initiated to determine if other healthcare workers (HCWs) from the same unit also had pertussis.

DESIGN

Interviews were conducted to assess symptoms occurring in the previous months. Two sera were collected 2 to 3 months apart for 59 of 61 HCWs of the unit. The IgG response to pertussis toxin was determined using Western blot assay.

SETTING

Pediatric emergency unit (61 HCWs) of a 2,500-bed university hospital.

RESULTS

There was a total of 10 (5 confirmed and 5 probable) cases of pertussis identified in this outbreak. Nine HCWs (15%) had results suggesting recent or acute pertussis. To avoid transmission to patients and other HCWs, all HCWs with cough were treated for 14 days with erythromycin, and those having acute cough were given a 5-day sick leave. Despite these measures, a new acute pertussis case was identified in a 41-year-old nurse, with a positive culture from nasopharyngeal aspirates. Thus, all HCWs in the unit were prescribed spiramycin for 10 days to prevent any further spread of pertussis.

CONCLUSION

Pertussis should be considered a threat to HCWs who are in contact with children. For HCWs, diagnosis of pertussis should be made on a clinical basis, giving greater importance to sensitivity of diagnosis criteria, and on early bacterial identification by culture of the organism or by polymerase chain reaction.

RECOMMENDATIONS

In case of pertussis in an HCW, all staff in the unit who have had unprotected and intensive contact with that person should be provided with macrolide treatment to stop any transmission to colleagues and to young patients. Furthermore, the possibility of providing these HCWs with acellular pertussis vaccines warrants further investigation.