Pertussis: what the pediatric infectious disease specialist should know

Pertussis detection in children with cough of any duration

Background

The diagnosis of pertussis in clinical practice continues to be a challenge worldwide as the symptoms are variable. We aimed to determine the prevalence of pertussis in Chinese children irrespective of cough duration and explore the clinical characteristics of children with pertussis with different cough durations.

Methods

This was a prospective study of children 1 month to 11 years of age with different cough durations in one large Chinese hospital. Bilateral deep posterior nasopharyngeal swabs and venepuncture for full blood count, CRP and serology and sputum were obtained when possible for investigation. E-test strips were used for testing the susceptibility of the B.pertussis isolates against erythromycin, azithromycin, sulphamethoxazole/trimethoprim, levofloxacin, amoxicillin and doxycycline. Demographic, clinical and laboratory information on culture and antimicrobial susceptibility testing was collected from children, and analyzed using SAS v.10 (SAS Institute Inc., USA).

Results

After exclusions we analyzed 312 children. Ninety-seven (31.1%) children had laboratory evidence of pertussis. When grouped by cough duration, few characteristics were significant between children with and without pertussis. Of the 36 isolates, 72.2% (26/36)could not be inhibited by erythromycin and azithromycin at all. The MIC50 and MIC90 to amoxicillin were 0.75 mg/L and 1 mg/L respectively, sensitive to amoxicillin by the EUCAST points.

Conclusions

The “one-size-fits-all” clinical pertussis case definition is no longer optimal to recognize this disease. A large comprehensive study of children with all types of cough is required to make substantial inroads into increasing both the sensitivity and specificity in pertussis diagnosis, which will have a beneficial impact on public health. Amoxicillin maybe an alternative for children with marolide-resistant B.pertussis infection; however, local sensitivities are required to inform clinical practice.

Development of a thermostable spray dried outer membrane vesicle pertussis vaccine for pulmonary immunization

Worldwide resurgence of whooping cough calls for improved, next-generation pertussis vaccines that induce broad and long-lasting immunity. A mucosal pertussis vaccine based on outer membrane vesicles (omvPV) is a promising candidate. Further, a vaccine that is stable outside the cold chain would be of substantial advantage for worldwide distribution and application. A vaccine formulated as a powder could both stabilize the vaccine as well as make it suitable for pulmonary vaccination. To that end, we developed a spray dried omvPV with improved stability compared to the liquid omvPV formulation. Spray drying did not affect the structural integrity of the omvPV. The antigenicity of Vag8, a major antigen in omvPV was diminished slightly and an altered tryptophan fluorescence indicated some changes in protein structure. However, when administered via the pulmonary route in mice after reconstitution, spray dried omvPV showed comparable immune responses and protection against challenge with live B. pertussis as liquid omvPV. Mucosal IgA and Th17 responses were established in addition to broad systemic IgG and Th1/Th17 responses, indicating the induction of an effective immunity profile. Overall, a spray dried omvPV was developed that maintained effective immunogenic properties and has an improved storage stability.

[Recent progress in clinical research on pertussis]

Pertussis is a highly contagious respiratory disease. Despite the high vaccination coverage, re-emergence of pertussis has been reported in many countries over the past two decades. With the increase in the incidence of pertussis, there has been a shift in the epidemiological features: an increased incidence of pertussis has been noted in older children and adults, who normally lack typical clinical manifestations, and who may be easily missed according to current diagnostic references for pertussis. In order to achieve better prevention and treatment of pertussis, this review article summarized the recent research progress in the epidemiology, clinical features, etiology, diagnosis, treatment, and prevention of pertussis, particularly focusing on the diagnosis of pertussis in older children and adults.

Rediscovering Pertussis

Pertussis, caused by Bordetella (B.) pertussis, a Gram-negative bacterium, is a highly contagious airway infection. Especially in infants, pertussis remains a major health concern. Acute infection with B. pertussis can cause severe illness characterized by severe respiratory failure, pulmonary hypertension, leucocytosis, and death. Over the past years, rising incidence rates of intensive care treatment in young infants were described. Due to several virulence factors (pertussis toxin, tracheal cytotoxin, adenylate cyclase toxin, filamentous hemagglutinin, and lipooligosaccharide) that promote bacterial adhesion and invasion, B. pertussis creates a unique niche for colonization within the human respiratory tract. The resulting long-term infection is mainly caused by the ability of B. pertussis to interfere with the host's innate and adaptive immune system. Although pertussis is a vaccine-preventable disease, it has persisted in vaccinated populations. Epidemiological data reported a worldwide increase in pertussis incidence among children during the past years. Either acellular pertussis (aP) vaccines or whole-cell vaccines are worldwide used. Recent studies did not detect any differences according to pertussis incidence when comparing the different vaccines used. Most of the currently used aP vaccines protect against acute infections for a period of 6-8 years. The resurgence of pertussis may be due to the lack of herd immunity caused by missing booster immunizations among adolescents and adults, low vaccine coverages in some geographic areas, and genetic changes of different B. pertussis strains. Due to the rising incidence of pertussis, probable solution strategies are discussed. Cocooning strategies (vaccination of close contact persons) and immunizations during pregnancy appear to be an approach to reduce neonatal contagiousness. During the past years, studies focused on the pathway of the immune modulation done by B. pertussis to provide a basis for the identification of new therapeutic targets to enhance the host's immune response and to probably modulate certain virulence factors.

Tendencia de la mortalidad y morbilidad por tos ferina en Colombia 2002-2012

<p class="Default"><strong>Introducción.</strong> La tos ferina es un problema de salud pública que afecta principalmente a niños menores de un año en quienes los desenlaces son altamente letales; es una enfermedad reemergente, prevenible con inmunización.</p><p><strong>Objetivo.</strong> Analizar la tendencia de la mortalidad y morbilidad por tos ferina en Colombia entre los años 2002-2012.</p><p><strong>Materiales y métodos.</strong> Estudio descriptivo cuantitativo de las muertes por tos ferina entre 2002-2012 con fuente de información secundaria según certificados de defunción del Departamento Administrativo Nacional de Estadística, y casos reportados al Sistema Nacional de Vigilancia en Salud Pública 2005-2012. Se calcularon medidas de frecuencia, tasas de morbilidad y mortalidad y sobremortalidad femenina.</p><p><strong>Resultados.</strong> El 51,2% de las muertes ocurrieron en mujeres; el año con más defunciones fue 2012; el 67,3% pertenecían al área urbana y el 43,5% estaban afiliados al régimen subsidiado de salud. El riesgo de enfermar fue de 1,88 por mil nacidos vivos con mayor riesgo en Vaupés y Vichada. El riesgo de morir fue de 0,02 por mil nacidos vivos; la tendencia de la letalidad mostró disminución.</p><p><strong>Conclusión.</strong> La mortalidad y morbilidad por tos ferina ha mostrado reemergencia; al ser esta una enfermedad prevenible por medio de la vacunación se recomienda mayor control y mejora en las coberturas de vacunación tanto en niños como en adultos que son un importante reservorio de la enfermedad; para un efectivo control de la tos ferina se recomienda un trabajo continuo orientado a su identificación oportuna; también es preciso adelantar acciones para mejorar la calidad del dato con el fin de facilitar análisis y generación de información cada vez más válida.</p>

[Pertussis vaccine. Reemergence of the disease and new vaccination strategies]

Pertussis continues to be a public health problem despite the significant decrease in its incidence due to routine vaccination. Resurgence of the disease in countries that have maintained high vaccination coverage has been observed in recent years. Although vaccination is the most effective preventive control measure, both natural and artificial immunity wane over time, and thus the protection offered by current vaccines is not long-lasting. Furthermore, acellular vaccines are less effective. The implementation of new vaccine strategies is required. Vaccination of pregnant women is the most effective strategy for preventing pertussis in young infants, who are the most vulnerable, and should be recommended together with cocooning, ie vaccination of future household and extra-domiciliary contacts who are the main transmitters of the disease.

Epidemiology of Bordetella pertussis in San Luis Potosí, Mexico

We analyzed data from 147 patients with suspected pertussis in San Luis Potosí, Mexico. Bordetella pertussis was detected by real-time polymerase chain reaction in 59 (40.1%) cases. The incidence of B. pertussis infection was 2.3 per 100,000 population. There were 6 deaths among the study patients. We conclude that the impact of pertussis in our state is significantly higher than previously estimated.

Pertussis: a review of disease epidemiology worldwide and in Italy

Pertussis continues to be a relevant public-health issue. The high coverage rates achieved have decreased the spread of the pathogen, but the waning of immunity implies a relevant role of adolescents and adults in the infective dynamics as they may represent a significant source of infection for unvaccinated or incompletely immunized newborns. The passive surveillance system is affected by many limitations. The underestimation of pertussis in adolescents, young adults and adults is mainly related to the atypical clinical characteristics of cases and the lack of lab confirmation. The real epidemiological impact of pertussis is not always perceived, anyway, the unavailability of comprehensive data should not hamper the adoption of active prophylactic interventions aimed at preventing the impact of waning immunity on pertussis. To avoid an increase of the mean age of acquisition of the infection, a booster dose of low-antigen content combined vaccine should be adopted in adolescents and adults. A decreased risk of infection in newborns can be achieved with the cocoon strategy, although the debate on this aspect is still open and enhanced surveillance and further studies are needed to fine-tune the pertussis prevention strategy.