Rapid molecular genetic assay for direct identification of Bordetella from patients specimens

Biological diagnosis of whooping cough is increasingly necessary to confirm respiratory tract infection. Indeed, clinical symptoms are variable especially in adolescents and adults who contaminate newborns too young to be vaccinated. The PCR assay was proven highly sensitive for the diagnosis of pertussis. In this study, we reported the use of a new test (GenoQuick^® Bordetella [GQB], Hain Life Science, Germany) which permits the fast molecular genetic identification of Bordetella pertussis and parapertussis directly from patients specimens, i.e. swabs from nose or throat. The test was performed over a three months period on 40 specimens from patients (1 month to 65 years old), most of them were young children admitted in paediatric emergency with paroxysmal cough or prolonged cough.     

Methods for isolation ofBordetella pertussis from patients with whooping cough

Culture remains the standard method for diagnosis of whooping cough. While in the past attempts at isolatingBordetella pertussis from patients with suspected whooping cough were often unsuccessful, new methods have recently been developed which are suitable for use in routine microbiology laboratories. Recent advances include the use of calcium alginate tipped swabs for taking nasopharyngeal swabs, use of charcoal horse blood agar for transport and culture, and the inclusion of cephalexin as a selective agent in agar media. Experience shows that careful application of these new methods often enablesBordetella pertussis to be isolated from clinical specimens, thereby permitting a diagnosis to be made at an early stage of the disease.     

Role of pertussis toxin in causing symptoms ofBordetella parapertussis infection

Whooping cough can be caused by eitherBordetella pertussis orBordetella parapertussis. Although the two species share an almost complete DNA identity,Bordetella parapertussis does not produce pertussis toxin, which is thought to be the main virulence factor ofBordetella pertussis. In order to elucidate the role of pertussis toxin in causing the typical symptoms of whooping cough, clinical information from 33 patients with culture-positiveBordetella parapertussis infection was collected and compared to that from 331 patients with infection caused byBordetella pertussis. Isolated strains ofBordetella parapertussis lacked pertussis toxin expression, as was demonstrated by negative tests for histamine sensitization. This was further substantiated in vivo by a significantly lower leukocyte count in the parapertussis group as compared to the pertussis group. Frequencies of typical symptoms of whooping cough, such as paroxysmal coughing, whooping and vomiting, were almost identical in the two groups. Nocturnal coughing and contact anamnesis were noted more often in theBordetella pertussis group. Children in the parapertussis group were significantly more often vaccinated with whole-cell pertussis vaccine than children infected withBordetella pertussis. The results indicate that pertussis toxin may not play a decisive role in causing the typical symptoms of whooping cough, such as paroxysmal coughing, whooping and vomiting.     

Prevalence and Genotype Distribution of Pneumocystis jirovecii in Cuban Infants and Toddlers with Whooping Cough

This study describes the prevalence and genotype distribution of Pneumocystis jirovecii obtained from nasopharyngeal (NP) swabs from immunocompetent Cuban infants and toddlers with whooping cough (WC). A total of 163 NP swabs from 163 young Cuban children with WC who were admitted to the respiratory care units at two pediatric centers were studied. The prevalence of the organism was determined by a quantitative PCR (qPCR) assay targeting the P. jirovecii mitochondrial large subunit (mtLSU) rRNA gene. Genotypes were identified by direct sequencing of mtLSU ribosomal DNA (rDNA) and restriction fragment length polymorphism (RFLP) analysis of the dihydropteroate synthase (DHPS) gene amplicons. qPCR detected P. jirovecii DNA in 48/163 (29.4%) samples. mtLSU rDNA sequence analysis revealed the presence of three different genotypes in the population. Genotype 2 was most common (48%), followed in prevalence by genotypes 1 (23%) and 3 (19%); mixed-genotype infections were seen in 10% of the cases. RFLP analysis of DHPS PCR products revealed four genotypes, 18% of which were associated with resistance to sulfa drugs. Only contact with coughers (prevalence ratio [PR], 3.51 [95% confidence interval {CI}, 1.79 to 6.87]; P = 0.000) and exposure to tobacco smoke (PR, 1.82 [95% CI, 1.14 to 2.92]; P = 0.009) were statistically associated with being colonized by P. jirovecii. The prevalence of P. jirovecii in infants and toddlers with WC and the genotyping results provide evidence that this population represents a potential reservoir and transmission source of P. jirovecii.     

Use of supplemented Stainer-Scholte broth for the isolation of Bordetella pertussis from clinical material.

The use of Stainer-Scholte broth supplemented with (2,6-O-dimethyl)beta-cyclodextrin (heptakis) for the isolation of Bordetella pertussis from clinical specimens was evaluated with 3,632 nasal swabs from children and adults with suspected whooping cough or from their family contacts. The liquid enrichment medium was subcultured on charcoal agar with 10% defibrinated horse blood. Charcoal agar and soft charcoal agar served as the standard procedure to detect B. pertussis. We isolated 772 strains of B. pertussis (21%). Charcoal agar alone detected 87% of all strains (n = 668), soft charcoal agar grew 78% (n = 602), and 637 strains (83%) were isolated when Stainer-Scholte broth with heptakis was used. We detected 590 isolates with all three media. Whereas 65 strains grew only on charcoal agar, 27 strains were detected by soft charcoal agar. Supplemented Stainer-Scholte broth allowed the isolation of an additional 77 strains which did not primarily grow on charcoal media (P less than 0.05). Our data indicate that Stainer-Scholte medium supplemented with heptakis can be effectively used as an enrichment medium for detection of B. pertussis in clinical specimens.     

Marked difference between adults and children in Bordetella pertussis DNA load in nasopharyngeal swabs

Bordetella pertussis is the aetiologic agent of whooping cough, a common cause of severe respiratory illness in children and prolonged mild cough in adults. To understand some of the reasons for differences in clinical symptoms between adults and children, we measured B. pertussis DNA loads in nasopharyngeal swabs (NPS) from 19 adults and 40 children (including 14 infants) by quantitative IS481 real-time PCR. All cases had been pre-diagnosed with the B. pertussis-specific loop-mediated isothermal amplification method. The mean PCR threshold cycles for adult and child NPS were 34.9 and 27.1, respectively, indicating a significantly lower B. pertussis DNA load in adults than in children (p <0.001). Moreover, adults had very low DNA loads during both early and later stages of the disease. When corresponding bacterial loads in NPS were calculated for B. pertussis Tohama cells using a standard curve, the mean number of bacterial cells taken with a rayon-tipped swab from an adult, older child and infant was estimated to be 320 (95% CI 120–910), 2.1 × 10⁴ (95% CI 5.3 × 10³ to 8.3 × 10⁴) and 1.1 × 10⁶ cells (95% CI 1.2 × 10⁵ to 8.9 × 10⁶), respectively. This indicates that the B. pertussis load in NPS is closely correlated with patient age. Our observations suggest that adult pertussis is characterized by a lower bacterial load in the nasopharynx, resulting in milder symptoms and negative cultures.     

Contact tracing for vancomycin-resistant Enterococcus faecium (VRE): evaluation of the Dutch policy of quintuple screening cultures

Detection of vancomycin-resistant Enterococcus faecium (VRE) is hampered by low sensitivity of rectal swab cultures. This study aimed to define the number of screening cultures needed to increase sensitivity to detect VRE transmission, and to determine time from presumed exposure to detectable colonization. In a tertiary care setting, we retrospectively analyzed data from 9 VRE outbreaks. As a proxy or estimation for time to detectable colonization, the time between first positive culture of the presumed index patient and that of their contacts was determined. Only 64% of secondary cases were positive in the first out of five cultures. By using the first three out of five rectal swabs, 89% (95%CI: 78–95%) of all secondary cases would have been identified. The median number of days between the positive culture of the index patient and the first positive culture of secondary cases was 9 days. Eleven percent of secondary cases would have been missed if only three rectal samples would have been obtained. Furthermore, our results show that one or more rectal swabs taken around day 9 after presumed exposure should at least be included in the screening approach. In our setting, obtaining a fourth and a fifth rectal swab showed a relevant additional value compared to only one to three swabs. Our findings are useful for determining the most effective VRE contact tracing approach to prevent transmission.

     

Effectiveness of rapid multiplex polymerase chain reaction for early diagnosis and treatment of pertussis

BackgroundPertussis, is an infectious respiratory disease caused by Bordetella pertussis. The incidence of pertussis has been increasing in South Korea to due to waning vaccine-induced immunity. Culture has a low sensitivity and a long turnaround time (TAT). Recently, a rapid multi-polymerase chain reaction (mPCR) test with a TAT of about 1 h was developed for the detection of respiratory pathogens (17 viruses and three bacteria), including B. pertussis. This study aimed to investigate the effectiveness of mPCR for early diagnosis and treatment of pertussis.MethodsWe performed a retrospective study of patients with pertussis diagnosed from May 2017 to June 2019 at a university hospital in South Korea. Nasopharyngeal swab specimens were tested using mPCR. Data were extracted from medical records.ResultsA total of 27 patients with a median age of 48.9 years (range: 3.3–82.2 years) were diagnosed with pertussis, of whom 9 (33.3%) were male. Eleven (40.7%) had fever, 12 (44.4%) had dyspnea, three (11.1%) had paroxysmal cough, and nine (33.3%) had inspiratory whooping. The median interval from symptom onset to diagnosis was 9.0 days (range: 1–31 days). Twenty-four patients (81.5%) were diagnosed within 2 weeks from symptom onset. All but one patient was prescribed macrolide antibiotics. Twenty-two patients (81.5%) required hospitalization, including three (11.1%) who required intensive care unit care for ventilation.ConclusionTesting patients with respiratory symptoms using mPCR can improve early diagnosis of pertussis, ensure proper treatment, and may help with outbreak control.     

Mixed outbreak ofBordetella pertussis andBordetella parapertussis infection in Finland

The epidemiology of whooping cough in a vaccinated population was studied during an outbreak of paroxysmal cough in an elementary school with 258 pupils in Turku, Finland. Nasopharyngeal specimens for isolation ofBordetella pertussis and/or sera for ELISA detection of antipertussis immunoglobulin M, A and G antibodies were taken from 94 % of children who were prospectively followed for two months.Bordetella pertussis was isolated in six patients, and 17 culture-positive cases withBordetella parapertussis were identified. Patients withBordetella pertussis orBordetella parapertussis were found simultaneously in the same classrooms. Comparison of immunoglobulin M responses toBordetella pertussis andBordetella parapertussis was used for differential diagnosis of these two infections. Twenty-six cases with pertussis and 27 cases with parapertussis were diagnosed. The results of this prospective study suggest thatBordetella parapertussis is a more common etiologic agent of mild respiratory tract infection among vaccinated school-aged children than is generally recognised. The possibility thatBordetella pertussis was converted toBordetella parapertussis during this outbreak is discussed.     

Failure of charcoal-horse-blood broth with cephalexin to significantly increase rate of Bordetella isolation from clinical specimens.

In a field trial conducted in cooperation with pediatricians in private practice, 198 nasopharyngeal swabs from children with suspected whooping cough were placed into charcoal-horse-blood transport medium with cephalexin (40 mg/liter). After preincubation at 36 degrees C for 1 to 2 days, the transport systems were mailed to the laboratory. There, the swabs were plated onto charcoal-horse-blood agar with cephalexin and were subsequently incubated for 48 h in cephalexin-containing charcoal-horse-blood broth which was then subcultured onto the agar. Forty-six Bordetella pertussis strains and seven Bordetella parapertussis strains were isolated (Bordetella isolation rate, 26.8%). Only three (5.7%) of the 53 Bordetella strains were detected exclusively by use of the broth. This low rate of additional isolates is probably explained by the fact that the swabs had been submitted in charcoal-horse-blood transport medium which itself acts as an enrichment medium.     

Serodiagnosis as Adjunct Assay for Pertussis Infection in S?o 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.     

Use of the polymerase chain reaction to detectBordetella pertussis in patients with mild or atypical symptoms of infection

Nasopharyngeal aspirates and nasopharyngeal swabs from 177 children exhibiting mild to severe clinical symptoms of whooping cough were tested by the polymerase chain reaction (PCR) and culture for the presence ofBordetella pertussis. In the PCR analysis amplifications of samples prepared with and without DNA extraction were compared. In 26 % of samples prepared without DNA extraction, the PCR was found to be inhibited, whereas no inhibition was detected after DNA extraction. Twelve percent (21/177) of the samples were positive in both culture and the PCR, and an additional 49 % (87/177) of the samples were positive exclusively in the PCR. Thirty-eight percent (8/21) of culture-positive patients and 63 % (55/87) of the patients in whom infection was detected only by PCR had mild or atypical clinical symptoms. Of these groups 26% (5/19) and 50 % (39/78), respectively, had been fully vaccinated with three or more doses of diphtheria, tetanus and pertussis vaccine.     

Pertussis IgE and atopic disease

Background Pertussis toxin (PT) stimulates IgE production in animals, and pertussis vaccination and whooping cough may have similar effects in man. Methods We analyzed IgE responses to PT (FT-IgE) in sera from children primarily immunized with three doses of either an acellular 2- or 5-component vaccine, or a whole-cell (We) pertussis vaccine, and in children after whooping cough. The study comprised 50 children with both atopic disease and positive skin prick test, 99 nonatopic controls, and 40 children with verified pertussis.
Results Immunoglobulin E antibodies against PT were demonstrated in 19% and 24% of sera from vaccinated children at 7 and 12 months, respectively, and in 9% at 2.5 years. At 7 months, PT-IgE was more common after vaccination with acellular (24%) than with the We vaccine (3%, P = 0,02), PT-IgE was also more common (P = 0.00l) after vaccination in children classified as atopic (36%) than in the control group (10%). Thirty percent of the children with pertussis had PT-IgE, more often so in atopic than nonatopic children (P = 0.02), Conciusions Transient production of PT-lgE seems to be common after primary pertussis immunization with acellular vaccines, and after whooping cough, particularly in atopic subjects.     

Current evidence for human yersiniosis in Ireland

Yersiniosis associated with abdominal pain was commonly reported in Ireland in the 1980s. However, the Health Protection Surveillance Centre (HPSC) currently records only three to seven notified cases of yersiniosis per year. The most common cause of yersiniosis worldwide is Yersinia enterocolitica, and the leading source for this organism is consumption of pork-based food products. In contrast to the apparent current scarcity of yersiniosis cases in humans in Ireland, pathogenic Y. enterocolitica are detectable in a high percentages of pigs. To establish whether the small number of notifications of human disease was an underestimate due to lack of specific selective culture for Yersinia, we carried out a prospective culture study of faecal samples from outpatients with diarrhoea, with additional culture of throat swabs, appendix swabs and screening of human sewage. Pathogenic Yersinia strains were not isolated from 1,189 faeces samples, nor from 297 throat swabs, or 23 appendix swabs. This suggested that current low notification rates in Ireland are not due to the lack of specific Yersinia culture procedures. Molecular screening detected a wider variety of Y. enterocolitica-specific targets in pig slurry than in human sewage. A serological survey for antibodies against Yersinia YOP (Yersinia Outer Proteins) proteins in Irish blood donors found antibodies in 25?%, with an age-related trend to increased seropositivity, compatible with the hypothesis that yersiniosis may have been more prevalent in Ireland in the recent past.     

Prevalence,diagnosis, and disease course of pertussis in adults with acute cough: a prospective,observational study in primary care

Background

Most cases of adult pertussis probably remain undiagnosed.

Aim

To explore the prevalence, diagnosis, and disease course of acute pertussis infection in adult patients presenting with acute cough.

Design and setting

Prospective observational study between 2007 and 2010 in primary care in 12 European countries.

Method

Adults presenting with acute cough (duration of ≤28 days) were included. Bordetella pertussis infection was determined by polymerase chain reaction (from nasopharyngeal flocked swabs and sputa) and by measurement of immunoglobulin G antibodies to pertussis toxin (PT) in venous blood at day 28. An antibody titre to PT of ≥125 IU/ml or PCR positive result in a respiratory sample defined recent infection. Patients completed a symptom diary for 28 days.

Results

Serum and/or respiratory samples were obtained in 3074 patients. Three per cent (93/3074) had recent B. pertussis infection. Prior cough duration >2 weeks discriminated to some extent between those with and without pertussis (adjusted odds ratio 1.89, 95% confidence interval = 1.17 to 3.07; P = 0.010). Median cough duration after presentation was 17 and 12 days in patients with and without pertussis, respectively (P = 0.008). Patients with pertussis had longer duration of phlegm production (P = 0.010), shortness of breath (P = 0.037), disturbed sleep (P = 0.013) and interference with normal activities or work (P = 0.033) after presentation.

Conclusion

Pertussis infection plays a limited role among adults presenting with acute cough in primary care, but GPs should acknowledge the possibility of pertussis in uncomplicated lower respiratory tract infection. As in children, pertussis also causes prolonged symptoms in adults. However, pertussis is difficult to discern from other acute cough syndromes in adults at first presentation.     

Interactions between Bordetella pertussis and the complement inhibitor factor H

Bordetella pertussis causes whooping cough in humans, a highly contagious disease of the upper respiratory tract. An increase in cases of whooping cough in adolescents and adults in many countries has been reported, despite high immunization rates in children. To efficiently colonize the host the bacteria have to resist complement, the first defence line of innate immunity. B. pertussis has previously been shown to bind the classical pathway inhibitors C4b-binding protein and C1-inhibitor being thereby able to escape the classical pathway of complement. In this study recent clinical isolates of B. pertussis and B. parapertussis were found to survive alternative pathway attack in fresh non-immune serum better than the reference B. pertussis strain, Tohama I. By using adsorption assays, flow cytometry and a radioligand binding assay we observed that both B. pertussis and B. parapertussis bound the alternative pathway inhibitor factor H (FH) from normal human serum. The surface attached FH maintained its complement regulatory activity and promoted factor I-mediated cleavage of C3b. The main binding region was located to the C-terminal part of FH, into short consensus repeat domains 19-20. In contrast, the avian pathogen B. avium did not bind FH and was sensitive to the alternative pathway of human complement. In conclusion, the human pathogens B. pertussis and B. parapertussis are able to evade the alternative complement pathway by surface acquisition of the host complement regulator FH.     

Proficiency Program for Real-Time PCR Diagnosis of Bordetella pertussis Infections in French Hospital Laboratories and at the French National Reference Center for Whooping Cough and other Bordetelloses

With the support of a ministerial program for innovative and expensive technologies, dedicated to the economic evaluation of laboratory diagnosis of pertussis by real-time PCR, external quality assessment for real-time IS481 PCR was carried out. Coordinated by the National Centre of Reference of Pertussis and other Bordetelloses (NCR), this study aimed to harmonize and to assess the performances of eight participating microbiology hospital laboratories throughout the French territory. Between January 2006 and February 2007, 10 proficiency panels were sent by the NCR (ascending proficiency program), representing a total of 49 samples and including eight panels to analyze and evaluate the global sensitivity and specificity of real-time PCR, one to assess the limit of detection, and one to evaluate nucleic acid extraction methods. As part of the descending proficiency program, extracted DNA from clinical samples was sent by the eight participating laboratories in different panels and analyzed by the NCR. In the ascending proficiency analysis, the sensitivity and specificity of the real-time PCR methods were 92.2% and 94.3%, respectively. The limit of detection of the different methods ranged between 0.1 and 1 fg/μl (0.2 to 2 CFU/μl). The nucleic acid extraction methods showed similar performances. During the descending proficiency analysis, performed with 126 samples, the result of the NCR for 15 samples (11.9%) was discordant with the result obtained by the source laboratory. Despite several initial differences, harmonization was easy and performances were homogeneous. However, the risk of false-positive results remains quite high, and we strongly recommend establishment of uniform quality control procedures performed regularly.Bordetella pertussis is the etiological agent of whooping cough, a highly contagious respiratory disease with a long course occurring exclusively in humans (9, 24). Despite the widespread vaccination of children in France since 1966, whooping cough remains a major public health problem, with adults and adolescents now transmitting the infection to vulnerable infants. Whooping cough is the leading cause of death from community-acquired bacterial infections in infants between the ages of 10 days and 2 months in developed countries and is the third most frequent cause of death from bacterial infection in children of all ages (8). In addition, nosocomial infections with the bacterium, leading to outbreaks of whooping cough in hospitals, are now also being reported (4, 6, 10, 23).Unvaccinated children present the typical clinical symptoms of whooping cough, whereas the clinical symptoms are much more variable and milder in neonates and previously vaccinated adults. Clinical diagnosis must therefore be confirmed by biological tests. Rapid and sensitive diagnostic methods are required to guide treatment and to prevent transmission. The specific tests available are culture, real-time PCR, and the detection of anti-pertussis toxin (PT) antibodies. All these techniques have limitations in terms of sensitivity, specificity, and practicability. B. pertussis culture remains the gold standard method for diagnosis but has low sensitivity, takes a long time, and may be difficult in practical terms. The detection of anti-PT antibodies by reference enzyme-linked immunosorbent assay is highly specific (1), but there is a lack of validated commercial tests (22). Furthermore, the increasing use of adult vaccination renders this approach to diagnosis much less useful (2).Real-time PCR assays were developed to overcome these limitations and have been shown to be sensitive and rapid but technically difficult to perform. The insertion sequence element IS481, found in several hundred copies in the B. pertussis genome, is frequently used as a target for B. pertussis detection and has a much greater analytical sensitivity than assays with single-copy target sequences, such as that of the pertussis toxin promoter (1). The European consensus group EUPertStrain has issued several recommendations for the standardization of real-time PCR diagnosis to increase the quality of the results (20). However, many laboratories using nucleic acid amplification tests (NAATs) do not follow these recommendations, and a multitude of in-house NAATs are currently used. Several kits with CE approval are now available, but they are expensive, making the continued use of in-house PCR likely. Real-time PCR technology is very flexible, and many alternative machines and fluorescent probe systems are currently available. Consequently, NAATs are highly variable in terms of nucleic acid extraction methods, equipment, probes, extraction, and amplification controls.Under a French Ministry of Health program providing support for innovative and expensive technologies (STIC no. IC050870, “Diamocoq”), a collaboration was established between eight hospital microbiology laboratories located throughout France and the French National Reference Center for Whooping Cough and other Bordetelloses (NRC) for a medical and economic evaluation of the use of real-time PCR for whooping cough diagnosis. The objectives of this project were to assess the economic impact of laboratory diagnosis of whooping cough by real-time PCR, which takes less than 24 h, by comparison with standard practices yielding results within 3 to 5 days. As a first step toward achieving this objective, we needed to make uniform the in-house real-time PCR techniques used. This process included the establishment of quality control for all the laboratories involved in the study.We report here the results of the first proficiency program for the diagnosis of whooping cough by real-time PCR for eight French hospital laboratories and the NRC. This program included the design and analysis of results obtained with 10 independent proficiency panels.     

Epidemiological Aspects of Pertussis among Adults and Adolescents in a Korean Outpatient Setting: A Multicenter,PCR-Based Study

Epidemiological data of Bordetella pertussis infection among adolescents and adults are limited in Korea. Patients (≥ 11 yr of age) with a bothersome cough for less than 30 days were enrolled during a 1-yr period at 22 hospitals in Korea. Nasopharyngeal swabs were collected for polymerase chain reaction (PCR) and for bacteriologic culture. In total, 490 patients were finally enrolled, and 34 (6.9%) patients tested positive for B. pertussis; cough duration (14.0 days [7.0-21.0 days]) and age distribution were diverse. The incidence was the highest in secondary referral hospitals, compared to primary care clinics or tertiary referral hospitals (24/226 [10.6%] vs. 3/88 [3.4%] vs. 7/176 [4.0%], P = 0.012), and the peak incidence was observed in February and August (15.8% and 15.9%), with no confirmed cases between March and June. In the multivariate analysis, post-tussive vomiting was significantly associated with pertussis (odds ratio, 2.508; 95% confidence interval, 1.146-5.486) and secondary referral hospital showed a borderline significance. In conclusion, using a PCR-based method, 6.9% of adolescent and adult patients with an acute cough illness had pertussis infection in an outpatient setting. However, hospital levels and seasonal trends must be taken into account to develop a better strategy for controlling pertussis.

Graphical Abstract

相似文献   

Comparison of posterior pharyngeal wall and nasopharyngeal swabbing as a means of detecting the carriage of Neisseria meningitidis in adolescents

The purpose of this investigation was to evaluate the effectiveness of posterior pharyngeal and nasopharyngeal swabs in identifying and quantifying meningococcal carriage. Two swab samples were obtained from 564 healthy adolescents aged 15–19 years, the first taken from the posterior pharyngeal wall through the mouth and the second through the nose. Bacterial genomic DNA was extracted and screened for Neisseria meningitidis by means of two separate singleplex real-time polymerase chain reactions (real-time PCRs) in order to identify the CtrA and sodC genes. Subsequently, N. meningitidis-positive samples underwent a further singleplex real-time PCR in order to determine the N. meningitidis serogroup, and the DNA was quantified by means of standard curves. Thirty-seven subjects (6.6 %) were found to be carriers of N. meningitidis. The most frequently carried serogroup was serogroup B (15 cases, 40.5 %); serogroups A, Y, X, W135 and Z were found in, respectively, two (5.4 %), five (13.5 %), four (10.8 %), three (8.1 %) and one subject (2.7 %); the serogroup was not identified in seven cases. The detection of carrier status was significantly more frequent using posterior pharyngeal swabs (5.3 % vs. 2.1 %; p?=?0.004), which also contained a significantly larger number of N. meningitidis genomic copies (4.91?±?1.39 vs. 2.50?±?0.8 log₁₀ genomic copies/mL; p?<?0.001). Posterior pharyngeal swabs seem to be better than nasopharyngeal swabs for detecting N. meningitidis carriage in large-scale epidemiological studies because they identify a significantly larger number of pathogen carriers and recover a significantly larger amount of bacterial DNA.     

Paroxysmal cough injury, vascular rupture and 'shaken baby syndrome'

It is widely assumed that subdural and retinal haemorrhage in infants can only result from traumatic rupture of vulnerable blood vessels. An alternative aetiology, that of vascular rupture resulting from excessive intraluminal pressure, is presented in three disease conditions. (1) Perlman et al., studying premature neonates requiring mechanical ventilation for respiratory distress syndrome, observed "cough-like" fluctuations in oesophageal pressure greater than 18 cms H2O, whose timing matched fluctuations in anterior cerebral artery flow. When 14 out of 24 neonates were paralysed (to prevent abdominal muscle activity) intraventricular haemorrhage developed in all 10 controls but in only one of the paralysed group during paralysis. (2) New analysis of pressure data extracted from a previous study of prolonged expiratory apnoea showed alveolar collapse induced 100 mmHg intrathoracic cough pressure surges. Superior vena cava pressures up to 50 mmHg were implied, and radial artery systolic pressures over 180 mmHg recorded. (3) Bordetella pertussis bacteria attach to cilia in the airways, but do not invade the underlying tissue. The irritation causes the powerful coughing paroxysms of whooping cough. Brain haemorrhages and retinal detachment have been observed to result from the high intravascular pressures produced. The data suggest that any source of intense airway irritation not easily removed (laryngeal infection, inhalation of regurgitated feed, fluff, smoke etc.) could induce similar bleeding, a paroxysmal cough injury (PCI). Additional objective evidence of inflicted trauma is necessary to distinguish between 'shaken baby syndrome' and PCI.