Exchange blood transfusion in the management of severe pertussis in young infants

Use and Waste of Reconstituted Whole Blood Exchange Transfusions: An 11-year National Observational Study

OBJECTIVES

To identify indications for exchange transfusions, assess the use and waste of exchange transfusion products (ie, reconstituted whole blood exchange transfusions), and determine nationwide distribution and prevalence of these transfusions in the Netherlands.

STUDY DESIGN

All 9 neonatal intensive care units and 15 non-neonatal intensive care unit hospitals participated in this retrospective, observational, cohort study. We retrieved data on the indications for and use of all exchange transfusion products ordered by participating centers over an 11-year period.

RESULTS

A total of 574 patients for whom 1265 products were ordered were included for analyses. Severe ABO (32.6%) and non-ABO (25.2%) immune hemolysis and subsequent hyperbilirubinemia were the most frequent indications. Rare indications were severe leukocytosis in Bordetella pertussis (2.1%) and severe anemia (1.5%). Approximately one-half of all ordered products remained unused. In 278 of 574 neonates (48.4%), ≥1 products were not used, of which 229 (82.7%) were due to the resolving of severe hyperbilirubinemia with further intensification of phototherapy. The overall prevalence of neonates who received an exchange transfusion was 14.6:100 000 liveborn neonates.

CONCLUSIONS

A considerable proportion of products remained unused, and annually a limited number of patients are treated with an exchange transfusion in the Netherlands, highlighting the rarity of the procedure in the Netherlands.

Malignant pertussis in infants: factors associated with mortality in a multicenter cohort study

BACKGROUND

Malignant pertussis (MP) affects young infants and is characterized by respiratory distress, perpetual tachycardia and hyperleukocytosis up to 50 G/l, leading to multiple organ failure and death in 75% of cases. Leukodepletion may improve prognosis. A therapeutic strategy based on leukodepletion and extracorporeal life support (ECLS) according to different thresholds of leucocytes has been proposed by Rowlands and colleagues. We aimed at identifying factors associated with death and assess whether the respect of the Rowlands' strategy is associated with survival.

METHODS

We reviewed all MP infants hospitalized in eight French pediatric intensive care units from January 2008 to November 2013. All infants younger than 3 months of age, admitted for respiratory distress with a diagnosis of pertussis and WBC count ≥ 50 G/l were recorded. Evolution of WBC was analyzed and an optimal threshold for WBC growth was obtained using the ROC-curve method. Clinical and biological characteristics of survivors and non-survivors were compared. Therapeutic management (leukodepletion and/or ECLS) was retrospectively assessed for compliance with Rowlands' algorithm (indication and timing of specific treatments).

RESULTS

Twenty-three infants were included. Nine of 23 (40%) died: they presented more frequently cardiovascular failure (100% vs 36%, p = 0.003) and pulmonary hypertension (PHT; 100% vs 29%, p = 0.002) than survivors and the median [IQR] WBC growth was significantly faster among them (21.3 [9.7-28] G/l/day vs 5.9 [3.0-6.8] G/l/day, p = 0.007). WBC growth rate > 12 G/l/day and lymphocyte/neutrophil ratio < 1 were significantly associated with death (p = 0.001 and p = 0.003, respectively). Ten infants (43%) underwent leukodepletion, and seven (30%) underwent ECLS. Management following Rowlands' strategy was associated with survival (100% vs 0%; p < 0.001, relative risk of death = 0.18, 95%-CI [0.05-0.64]).

CONCLUSIONS

A fast leukocyte growth and leukocytosis with neutrophil predominance during acute pertussis infection were associated with death. These findings should prompt clinicians to closely monitor white blood cells in order to early identify infants at risk of fatal outcome during the course of malignant pertussis. Such an early signal in infants at high risk of death would increase feasibility of compliant care to Rowlands' strategy, with the expectation of a better survival.

[Research advances in the treatment strategies for severe pertussis in children]

At present, effective antibiotics and comprehensive symptomatic/supportive treatment as early as possible are mainly used for the treatment of severe pertussis in clinical practice. However, some children with severe pertussis have unsatisfactory response to commonly used drugs and treatment measures in the intensive care unit and thus have a high risk of death. Studies have shown that certain treatment measures given in the early stage, such as exchange transfusion, may help reduce deaths, but there is still a lack of uniform implementation norms. How to determine the treatment regimen for severe pertussis and improve treatment ability remains a difficult issue in clinical practice. This article reviews the advances in the treatment of severe pertussis, in order to provide a reference for clinical treatment and research.

Leukoreduction and hydroxyurea in malignant pertussis: A case series

We report five cases of malignant pertussis, a rare but life-threatening illness. Current therapies include supportive care and leukoreduction. Notably, leukoreduction might be more effective when initiated prior to the development of organ failure and pulmonary hypertension.

Risk factors associated with death in infants <120 days old with severe pertussis: a case-control study

Background and purpose

Pertussis is a serious infectious disease in young infants, and severe cases frequently cause death. Our study explored risk factors for death from severe pertussis.

Method

A case-control study of infants with severe pertussis admitted to the paediatric intensive care unit (PICU) in the Children’s Hospital of Chongqing Medical University, China, from January 1, 2013, to June 30, 2019, was conducted. Pertussis was confirmed by clinical features and laboratory examinations. Severe pertussis was defined as patients with pertussis resulting in PICU admission or death. To understand the risk factors for death, we compared fatal and nonfatal cases of severe pertussis in infants aged < 120 days by collecting clinical and laboratory data.

Results

The participants included 63 infants < 120 days of age with severe pertussis. Fifteen fatal cases were confirmed and compared with 44 nonfatal severe pertussis cases, Four patients with termination of treatment were excluded. In the univariate analysis, the risk factors associated with death included apnoea (P = 0.001), leukocytosis (white blood cell (WBC) count≥30 × 10⁹/L (P = 0.001) or ≥ 50 × 10⁹/L (P = 0)), highest lymphocyte count (P = 0), pulmonary hypertension (P = 0.001), and length of PICU stay (P = 0.003). The multivariate analysis revealed that apnoea (OR 23.722, 95%CI 2.796–201.26, P = 0.004), leukocytosis (OR 63.708, 95%CI 3.574–1135.674, P = 0.005) and pulmonary hypertension (OR 26.109, 95%CI 1.800–378.809, P = 0.017) were significantly associated with death.

Conclusion

Leukocytosis and pulmonary hypertension exhibited the greatest associations with death in infants with severe pertussis admitted to the PICU. Vaccination is still the most effective protection method against pertussis.

Pertussis (Keuchhusten)

Pertussis wird durch das gramnegative Bakterium Bordetella pertussis verursacht. Die Krankheitsmanifestationen reichen von unspezifischem Husten bis zu lebensbedrohlichen Verläufen mit Hyperleukozytose und respiratorischer Insuffizienz, v.a. bei jungen Säuglingen. Die Diagnose basiert auf klinischer Symptomatik und mikrobiologischen Nachweisverfahren. Die Therapie besteht aus Makrolidantibiotika; bei Apnoen kann Koffein versucht werden. Die Inzidenz beträgt 10–40 Fälle/100.000 Bevölkerung und Jahr, bei Säuglingen ist sie am höchsten (ca. 50), gefolgt von Jugendlichen (30–35). Mehr als 50 % der in den ersten 5 Lebensmonaten an Pertussis erkrankten Kinder werden hospitalisiert. Die Impfprävention umfasst Grundimmunisierung und regelmäßige Auffrischimpfungen mit azellulären Impfstoffen. Um schwere Verläufe bei jungen Säuglingen zu verhindern, ist die Impfung schwangerer Frauen am erfolgversprechendsten. Säuglinge geimpfter Mütter sollen zeitgerecht ab dem Alter von 2 Monaten für den Eigenschutz immunisiert werden.

[Pertussis (whooping cough)]

Pertussis wird durch das gramnegative Bakterium Bordetella pertussis verursacht. Die Krankheitsmanifestationen reichen von unspezifischem Husten bis zu lebensbedrohlichen Verläufen mit Hyperleukozytose und respiratorischer Insuffizienz, v.a. bei jungen Säuglingen. Die Diagnose basiert auf klinischer Symptomatik und mikrobiologischen Nachweisverfahren. Die Therapie besteht aus Makrolidantibiotika; bei Apnoen kann Koffein versucht werden. Die Inzidenz beträgt 10–40 Fälle/100.000 Bevölkerung und Jahr, bei Säuglingen ist sie am höchsten (ca. 50), gefolgt von Jugendlichen (30–35). Mehr als 50 % der in den ersten 5 Lebensmonaten an Pertussis erkrankten Kinder werden hospitalisiert. Die Impfprävention umfasst Grundimmunisierung und regelmäßige Auffrischimpfungen mit azellulären Impfstoffen. Um schwere Verläufe bei jungen Säuglingen zu verhindern, ist die Impfung schwangerer Frauen am erfolgversprechendsten. Säuglinge geimpfter Mütter sollen zeitgerecht ab dem Alter von 2 Monaten für den Eigenschutz immunisiert werden.

Clinical Profile of Critical Pertussis in Children at a Pediatric Intensive Care Unit in Northern India

Objective

To delineate the clinical profile, complications, intensive care needs, and predictors of mortality in children with critical pertussis.

Methods

Retrospective analysis of case records of children in the pediatric intensive care unit of a tertiary-care hospital, with a diagnosis of critical pertussis over 3 years. Diagnostic criteria included CDC case definition and confirmation by polymerase chain reaction (PCR), when available. Survivors and nonsurvivors were compared to identify predictors of mortality.

Results

36 records were analysed, most cases were infants (31, 86.1%). 10 (27.7%) were (below 6 weeks of age). In the rest, 16 (61.5%) were partially immunized or unimmunized against pertussis. Rapid breathing (88.9%), paroxysmal cough (86.1%) and apnea (41.7%) were common presenting complaints. Hypoxemia (97.2%), hyperleukocytosis (61.1%) and encephalopathy (52.8%) were common complications. Intensive care needs were mechanical ventilation in 11 (30.6%), vasoactive support in 7 (19.4%) and exchange transfusion in 3 (8.3%). Female gender, apnea, hyperleukocytosis, encephalopathy, need for vasoactive support, and mechanical ventilation predicted mortality.

Conclusion

Pertussis demands attention due to its varied presentation, increased complications and higher mortality.

Neutralization of pertussis toxin by a single antibody prevents clinical pertussis in neonatal baboons

Pertussis continues to cause considerable infant mortality world-wide, which could be addressed in part by passive immunization strategies. Antibody hu1B7 is a candidate therapeutic that potently neutralizes pertussis toxin in vitro, prevents leukocytosis in mice and treats established disease in weanling baboons as part of an antibody cocktail. Here, we evaluated the potential for hu1B7 and an extended half-life hu1B7 variant to prevent death, leukocytosis and other clinical symptoms in a newborn baboon model that mimics many aspects of human disease. We administered a single antibody dose to newborn baboons five weeks prior to experimental infection. While all animals were heavily colonized with Bordetella pertussis, prophylaxed animals showed significantly greater survival (P < 0.005), delayed and suppressed leukocytosis (P < 0.01) and enhanced clinical outcomes, including coughing (P < 0.01), as compared to controls. Together, this work demonstrates that a single neutralizing anti-PTx antibody is sufficient to prevent clinical pertussis symptoms.

The 112-Year Odyssey of Pertussis and Pertussis Vaccines-Mistakes Made and Implications for the Future

Effective diphtheria, tetanus toxoids, whole-cell pertussis (DTwP) vaccines became available in the 1930s, and they were put into routine use in the United States in the 1940s. Their use reduced the average rate of reported pertussis cases from 157 in 100 000 in the prevaccine era to <1 in 100 000 in the 1970s. Because of alleged reactions (encephalopathy and death), several countries discontinued (Sweden) or markedly decreased (United Kingdom, Germany, Japan) use of the vaccine. During the 20th century, Bordetella pertussis was studied extensively in animal model systems, and many "toxins" and protective antigens were described. A leader in B pertussis research was Margaret Pittman of the National Institutes of Health/US Food and Drug Administration. She published 2 articles suggesting that pertussis was a pertussis toxin (PT)-mediated disease. Dr Pittman's views led to the idea that less-reactogenic acellular vaccines could be produced. The first diphtheria, tetanus, pertussis (DTaP) vaccines were developed in Japan and put into routine use there. Afterward, DTaP vaccines were developed in the Western world, and definitive efficacy trials were carried out in the 1990s. These vaccines were all less reactogenic than DTwP vaccines, and despite the fact that their efficacy was less than that of DTwP vaccines, they were approved in the United States and many other countries. DTaP vaccines replaced DTwP vaccines in the United States in 1997. In the last 13 years, major pertussis epidemics have occurred in the United States, and numerous studies have shown the deficiencies of DTaP vaccines, including the small number of antigens that the vaccines contain and the type of cellular immune response that they elicit. The type of cellular response a predominantly, T2 response results in less efficacy and shorter duration of protection. Because of the small number of antigens (3-5 in DTaP vaccines vs >3000 in DTwP vaccines), linked-epitope suppression occurs. Because of linked-epitope suppression, all children who were primed by DTaP vaccines will be more susceptible to pertussis throughout their lifetimes, and there is no easy way to decrease this increased lifetime susceptibility.

[Complications of pertussis]

Patients with pertussis can have a variety of complications, including pneumonia and subconjunctival hemorrhage. Severe complications, such as pulmonary hypertension and encephalopathy, can be life-threatening. Younger children with pertussis may lack the characteristic clinical manifestations of pertussis, and therefore, a deeper understanding of the complications of pertussis may help to improve the diagnosis, treatment, and prognosis of pertussis. However, there is still no standard for the diagnosis and treatment of pertussis complications, and there are great differences in diagnostic name, basis, and data used in different reports. This article reviews the complications of pertussis which have been reported so far, such as pulmonary complications (pneumonia, pulmonary hypertension, pneumothorax, and mediastinal or subcutaneous emphysema), fractures, hernias, circulatory system complications, nervous system complications (convulsion, encephalopathy, hemorrhage, and hematoma), urinary system complications, and secondary infections, so as to provide a reference for the clinical diagnosis and treatment of pertussis complications, scientific research on pertussis complications, and the promotion of standardized diagnosis and treatment of pertussis complications.

SEVERE PERTUSSIS IN CHILDHOOD: UPDATE AND CONTROVERSY - SYSTEMATIC REVIEW

Objective:

Through a systematic review, this essay aimed at revising the concepts of severe pertussis, updating the epidemiology, pathophysiology, clinical presentation, antibiotic therapy and auxiliary therapeutic options for symptomatology and complications.

Data sources:

This review considered publications from the last 30years in the databases US National Library of Medicine (PubMed), Scientific Electronic Library Online (SciELO), Literatura Latino-americana e do Caribe em Ciências da Saúde (LILACS), Cochrane, Google Scholar, as well as protocols of the Ministry of Health and recommendations of the Centers for Disease Control and Prevention, related to childhood pertussis (whooping cough), with emphasis on its severe form. This research was based on keywords derived from the terms “pertussis”, “azithromycin”, “antitussives”, “leukocyte reduction” in Portuguese and English. Duplicate studies and those with unavailable full-text were excluded.

Data synthesis:

Among 556 records found, 54 were selected for analysis. Pertussis, as a reemerging disease, has affected all age groups, evidencing the transient immunity conferred by infection and vaccination. Severe cases occur in neonates and infants, with secondary viral and bacterial complications and malignant pertussis, a longside hyperleukocytosis, respiratory failure and shock. Macrolides continue to be the chosen antibiotics, while antitussives for coughing remain without efficacy. The prompt treatment in Intensive Care Units improved the prognostic in severe cases, and transfusion was promising among procedures for leukoreduction.

Conclusions:

Approaching severe pertussis in childhood remains a challenge for diagnostic and therapy, as the available therapeutic options are still unsatisfactory. Strategies of prevention are expected to reduce the occurrence of severe cases, while new studies should confirm the role of auxiliary therapies.

Extracorporeal membrane oxygenation with prone position ventilation successfully rescues infantile pertussis: a case report and literature review

BACKGROUND

Bordetella pertussis can cause fatal illness with severe acute respiratory distress syndrome (ARDS) and pulmonary hypertension (PHT).

CASE PRESENTATION

A 6-month-old non-vaccinated boy with B. pertussis infection who developed ARDS was treated by extracorporeal membrane oxygenation (ECMO). During his ECMO support stage, sudden occurred decreasing of ECMO flow implied increasing intrathoracic pressure. The airway spasm followed caused sudden drop of ventilator tidal volume as well as poor lung compliance. Prone position ventilation and bundle care were conducted as lung protection ventilator strategy. After 297-h of ECMO support, the patient was weaned off ECMO, and extubated one week later.

CONCLUSIONS

In this patient with severe ARDS caused by Bordetella pertussis, ECMO was performed for cardiopulmonary support and rescued the infant with severe pertussis. During ECMO support period, prone position ventilation and care bundle nursing strategy contributed to the relief of continuous airway spasm.

Fatal malignant pertussis with hyperleukocytosis in a Chinese infant: A case report and literature review

RATIONALE

Pertussis has re-emerged on a global scale and is an ongoing public health problem, even in countries with high rates of vaccination. Hyperleukocytosis [white blood cell (WBC) count >100 × 10/L] is a rare complication that strongly predicts mortality in cases of severe pertussis.

PATIENT CONCERNS

We report a case of severe pertussis in an infant who initially presented with persistent cyanotic cough, tachypnea, and grunting. The infant's condition deteriorated rapidly, and she was transferred to the pediatric intensive care unit (PICU) during her third hour of hospitalization. On the third hospital day, her WBC count had increased to 101.85 × 10/L with a lymphocyte count of 36.76 × 10/L, and her hemoglobin level had fallen to 6.9 g/dL. Bone marrow examination found no evidence of tumor cells. Her initial echocardiogram showed no abnormal findings; however, a subsequent echocardiogram 10 days later revealed pulmonary hypertension.

DIAGNOSES

The patient was diagnosed with severe pneumonia, which was confirmed to be pertussis based on a persistent cough in the infant's mother and the polymerase chain reaction and culture of the infant's nasopharyngeal secretions being positive for Bordetella pertussis.

INTERVENTIONS

The infant was treated with supportive care, early macrolide antibiotics, and broad-spectrum antibiotics before being transferred to the PICU for further management, including continuous venovenous hemodiafiltration.

OUTCOMES

Unfortunately, the infant died as a result of pulmonary hypertension and multiorgan failure.

LESSONS

Exchange transfusion should be considered in all infants who present with severe pertussis with hyperleukocytosis. This guideline is supported by the findings of a comprehensive literature review, which is included in this article, as well as newly published criteria for exchange transfusion therapy. Finally, we hope that adults in China will be vaccinated against B. pertussis in order to prevent the infection of infants within their households.

An Observational Study of Severe Pertussis in 100 Infants ≤120 Days of Age

BACKGROUND

Pertussis in young infants is a unique, severe, afebrile, cough illness that is frequently fatal.

METHODS

All pertussis cases ≤120 days of age admitted to a pediatric intensive care unit in California between October 1, 2013, and April 25, 2015, were evaluated.

RESULTS

Of 100 pertussis patients ≤120 days of age admitted to pediatric intensive care unit, there were 5 deaths. The white blood cell counts in the fatal cases were significantly higher than in the nonfatal cases. Thirty-four percent of patients were intubated, 18% received inotropic and/or vasoactive support, 22% received steroid, 4% received extracorporal membrane oxygenation, and 3% underwent exchange blood transfusion. The median age at the time of illness onset in the patients who died was 23 days.

CONCLUSIONS

These data, as well as data from previous California studies, suggest updated strategies for the management of severe pertussis. These include perform serial white blood cell counts, treat all presumptive cases with azithromycin, evaluate for pulmonary hypertension, intubate and administer oxygen for apneic episodes and administer inotropic/vasoactive agents for cardiogenic shock. Do not administer steroids or nitric oxide. Criteria for exchange blood transfusion therapy for leukocytosis with lymphocytosis are suggested.

Extracorporeal Membrane Oxygenation for Pertussis: Predictors of Outcome Including Pulmonary Hypertension and Leukodepletion

OBJECTIVE

The recent increase of pertussis cases worldwide has generated questions regarding the utility of extracorporeal membrane oxygenation for children with pertussis. We aimed to evaluate factors associated with extracorporeal membrane oxygenation outcome.

DESIGN

The study was designed in two parts: a retrospective analysis of the Extracorporeal Life Support Organization Registry to identify factors independently linked to outcome, and an expanded dataset from individual institutions to examine the association of WBC count, pulmonary hypertension, and leukodepletion with survival.

SETTING

Extracorporeal Life Support Organization Registry database from 2002 though 2015, and contributions from 19 international centers.

PATIENTS

Two hundred infants from the Extracorporeal Life Support Organization Registry and expanded data on 73 children.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 200 infants who received extracorporeal membrane oxygenation for pertussis, only 56 survived (28%). In a multivariable logistic regression analysis, the following variables were independently associated with increased chance of survival: older age (odds ratio, 1.43 [1.03-1.98]; p = 0.034), higher PaO2/FIO2 ratio (odds ratio, 1.10 [1.03-1.17]; p = 0.003), and longer intubation time prior to the initiation of extracorporeal membrane oxygenation (odds ratio, 2.10 [1.37-3.22]; p = 0.001). The use of vasoactive medications (odds ratio, 0.33 [0.11-0.99]; p = 0.047), and renal neurologic or infectious complications (odds ratio, 0.21 [0.08-0.56]; p = 0.002) were associated with increased mortality. In the expanded dataset (n =73), leukodepletion was independently associated with increased chance of survival (odds ratio, 3.36 [1.13-11.68]; p = 0.03) while the presence of pulmonary hypertension was adverse (odds ratio, 0.06 [0.01-0.55]; p = 0.01).

CONCLUSIONS

The survival rate for infants with pertussis who received extracorporeal membrane oxygenation support remains poor. Younger age, lower PaO2/FIO2 ratio, vasoactive use, pulmonary hypertension, and a rapidly progressive course were associated with increased mortality. Our results suggest that pre-extracorporeal membrane oxygenation leukodepletion may provide a survival advantage.

The use of cytapheresis in the treatment of infectious diseases

Cytapheresis (removal of cellular blood components) has been employed for treatment of infectious diseases since the 1960s. Techniques have included thrombocytapheresis (buffy coat apheresis) for loiasis, erythrocytapheresis for malaria and babesiosis, and leukocytapheresis for pertussis-associated lymphocytosis. Published data on these applications is largely limited to case level data and small observational studies; as such, recommendations for or against the use of cytapheresis in the treatment of infections have been extrapolated from these limited (and at times flawed) data sets. Consequently, utilization of cytapheresis in many instances is not uniform between institutions, and typically occurs at the discretion of treating medical teams. This review revisits the existing literature on the use of cytapheresis in the treatment of four infections (loasis, malaria, babesiosis, and pertussis) and examines the rationale underlying current treatment recommendations concerning its use.

Pertussis in Young Infants Throughout the World

In typical pertussis in young infants, the child will appear deceptively well; he or she will have coryza, sneezing, and a mild cough. There is no fever. This progresses to gagging, gasping, eye bulging, bradycardia, cyanosis, and vomiting. There is leukocytosis with lymphocytosis and apneic episodes. Deaths relate to leukocytosis, pulmonary hypertension, and pneumonia. The source of pertussis in young infants is most often a family member with cough illness that is not recognized as pertussis. Diagnosis is based on culture/polymerase chain reaction and leukocytosis with lymphocytosis. Treatment depends on macrolide antibiotic therapy and intubation, with assisted ventilation and oxygen. Prevention is based on prophylactic macrolide treatment, immunization starting at 6 weeks of age, and immunization of all pregnant women in the second or third trimester.

Bordetella pertussis

Pertussis is a highly infectious vaccine-preventable cough illness that continues to be a significant source of morbidity and mortality around the world. The majority of human illness is caused by Bordetella pertussis, and some is caused by Bordetella parapertussis. Bordetella is a Gram-negative, pleomorphic, aerobic coccobacillus. In the past several years, even countries with high immunization rates in early childhood have experienced rises in pertussis cases. Reasons for the resurgence of reported pertussis may include molecular changes in the organism and increased awareness and diagnostic capabilities, as well as lessened vaccine efficacy and waning immunity. The most morbidity and mortality with pertussis infection is seen in infants too young to benefit from immunization. Severe infection requiring hospitalization, including in an intensive care setting, is mostly seen in those under 3 months of age. As a result, research and public health actions have been aimed at better understanding and reducing the spread of Bordetella pertussis. Studies comparing the cost benefit of cocooning strategies versus immunization of pregnant women have been favorable towards immunizing pregnant women. This strategy is expected to prevent a larger number of pertussis cases, hospitalizations, and deaths in infants <1 year old while also being cost-effective. Studies have demonstrated that the source of infection in infants usually is a family member. Efforts to immunize children and adults, in particular pregnant women, need to remain strong.

Pertussis leukocytosis: mechanisms, clinical relevance and treatment

The significant and sometimes dramatic rise in the number of circulating white blood cells (leukocytosis) in infants suffering from pertussis (whooping cough) has been recognized for over a century. Although pertussis is a disease that afflicts people of all ages, it can be particularly severe in young infants, and these are the individuals in whom leukocytosis is most pronounced. Very high levels of leukocytosis are associated with poor outcome in infants hospitalized with pertussis and modern treatments are often aimed at reducing the number of leukocytes. Pertussis leukocytosis is caused by pertussis toxin, a soluble protein toxin released by Bordetella pertussis during infection, but the exact mechanisms by which this occurs are still unclear. In this minireview, I discuss the history of clinical and experimental findings on pertussis leukocytosis, possible contributing mechanisms causing this condition and treatments aimed at reducing leukocytosis in hospitalized infants. Since recent studies have detailed significant associations between specific levels of pertussis leukocytosis and fatal outcome, this is a timely review that may stimulate new thinking on how to understand and combat this problem.

Pertussis: Microbiology, Disease, Treatment, and Prevention

Pertussis is a severe respiratory infection caused by Bordetella pertussis, and in 2008, pertussis was associated with an estimated 16 million cases and 195,000 deaths globally. Sizeable outbreaks of pertussis have been reported over the past 5 years, and disease reemergence has been the focus of international attention to develop a deeper understanding of pathogen virulence and genetic evolution of B. pertussis strains. During the past 20 years, the scientific community has recognized pertussis among adults as well as infants and children. Increased recognition that older children and adolescents are at risk for disease and may transmit B. pertussis to younger siblings has underscored the need to better understand the role of innate, humoral, and cell-mediated immunity, including the role of waning immunity. Although recognition of adult pertussis has increased in tandem with a better understanding of B. pertussis pathogenesis, pertussis in neonates and adults can manifest with atypical clinical presentations. Such disease patterns make pertussis recognition difficult and lead to delays in treatment. Ongoing research using newer tools for molecular analysis holds promise for improved understanding of pertussis epidemiology, bacterial pathogenesis, bioinformatics, and immunology. Together, these advances provide a foundation for the development of new-generation diagnostics, therapeutics, and vaccines.

A cocktail of humanized anti-pertussis toxin antibodies limits disease in murine and baboon models of whooping cough

Despite widespread vaccination, pertussis rates are rising in industrialized countries and remain high worldwide. With no specific therapeutics to treat disease, pertussis continues to cause considerable infant morbidity and mortality. The pertussis toxin is a major contributor to disease, responsible for local and systemic effects including leukocytosis and immunosuppression. We humanized two murine monoclonal antibodies that neutralize pertussis toxin and expressed them as human immunoglobulin G1 molecules with no loss of affinity or in vitro neutralization activity. When administered prophylactically to mice as a binary cocktail, antibody treatment completely mitigated the Bordetella pertussis-induced rise in white blood cell counts and decreased bacterial colonization. When administered therapeutically to baboons, antibody-treated, but not untreated control animals, experienced a blunted rise in white blood cell counts and accelerated bacterial clearance rates. These preliminary findings support further investigation into the use of these antibodies to treat human neonatal pertussis in conjunction with antibiotics and supportive care.

Protecting Newborns Against Pertussis: Treatment and Prevention Strategies

Pertussis is a potentially severe respiratory disease, which affects all age groups from young infants to older adults and is responsible for an estimated 195,000 deaths occurred globally in 2008. Active research is ongoing to better understand the pathogenesis, immunology, and diagnosis of pertussis. For diagnosis, molecular assays (e.g., polymerase chain reaction) for detection of Bordetella pertussis have become more widely available and support improved outbreak detection. In children, pertussis vaccines have been incorporated into routine immunization schedules and deployed for pertussis outbreak control. Lower levels of vaccine coverage are now being observed in communities where vaccine hesitancy is rising. Additionally, recognition that newborn babies are at risk of pertussis in the USA and UK has led to recommendations to immunize pregnant women. Among adolescents and older adults in the USA, Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular pertussis (Tdap) Vaccines are recommended, but substantial individual- and system-level barriers exist that will make achieving national Healthy People 2020 targets for immunization challenging. Current antimicrobial regimens for pertussis are focused on reducing the severity of disease, reducing rates of sequelae, and minimizing transmission of infection to susceptible individuals. Continued surveillance for pertussis will be important to identify opportunities for reducing young infants' exposure and reducing the impact of outbreaks among school-aged children. Laboratory-based surveillance for newly emerging strains of B. pertussis will be important to identify strains that may evade protection elicited by currently available vaccines. Efforts to develop new-generation pertussis vaccines should be considered now in anticipation of vaccine development programs, which may require ten or more years to deliver a licensed vaccine.

[Malignant pertussis and exchange transfusion]

CASE REPORT

Malignant pertussis is a critical clinical state associated with fatal outcome in 70% of cases. The severity criteria are a lung infection with pulmonary hypertension and hyperleukocytosis usually above 50 G/L. We report the case of a 2.5-month-old girl hospitalized with critical pertussis in a pediatric intensive care unit. She had acute respiratory distress syndrome with pulmonary hypertension complicated by a bacterial secondary infection with Enterobacter cloacae managed by high-frequency oscillatory ventilation associated with pulmonary vasodilatation therapy. In the absence of clinical improvement and before considering extracorporeal life support, exchange transfusion was performed at day 9 to reduce hyperleukocytosis at 70 G/L. Exchange transfusion was successfully performed with a reduction of leukocytes to under 40 G/L followed by steady improvement of pulmonary function. Weaning from mechanical ventilation and discharge took place at day 23 and 38, respectively.

COMMENTS

Exchange transfusion should be considered in infants suffering from malignant pertussis with extreme leukocytosis before hemodynamic failure to improve the survival prognosis.

Whooping cough in 2014 and beyond: an update and review

Pertussis, or whooping cough, has had a dramatic resurgence in the past several years and is the most common vaccine-preventable disease in the world. The year 2012 marked the most cases in the United States in &gt; 50 years. Large outbreaks have occurred in multiple states, and infant deaths have drawn the attention of not only health-care providers but also the media. Although the disease is theoretically preventable by vaccination, it remains a challenge to control. New vaccination strategies have been implemented across different age groups and populations of patients, but vaccine coverage remains dismally low. Acellular vaccines, although safe, do not afford the same long-lasting immunity as the previously used whole-cell vaccine. Ultimately, improvements in the development of vaccines and in vaccination coverage will be essential to decrease the burden of pertussis on society. This article provides a review of pertussis infection and discusses advances related to the epidemiology, diagnosis, treatment, and prevention of infection, as well as continued areas of uncertainty.

Pathogenesis and histopathology of pertussis: implications for immunization

Pertussis is a unique infectious disease in that it can be severe and fatal but occurs without fever and other evidence of an inflammatory illness. The authors with others have studied the histopathology of fatal pertussis and also the unique characteristics of severe pertussis in young infants. Histopathologic observations from approximately 100 years ago, and from recent evaluation, indicate that the histopathologic changes of the upper respiratory tract of patients with fatal pertussis are often relatively normal unless there is a secondary bacterial infection. Bordetella pertussis contains many protein antigens and perhaps a polysaccharide capsule which contribute to the infectious process. However, only two of these antigens contribute to clinical illness. These antigens are pertussis toxin and the yet to be identified 'cough toxin'. The authors speculate as to the nature of the 'cough toxin' and discuss the implications of their observations and concepts for the future control of pertussis.

Severe Pertussis Pneumonia managed with Exchange Transfusion

We describe in this case report one month old baby admitted to our Pediatric Intensive Care Unit (PICU) with severe pertussis pneumonia. The baby was deteriorating despite being on supportive management including High Frequency Oscillator ventilation (HFOV). However, she showed dramatic improvement after exchange blood transfusion (ET) and was discharged home. We hope that this report will add to the previously published experiences in management of severe pertussis. It will also alert general physicians about pertussis pneumonia and the importance of early referral and abrupt management for a better prognosis.

Severe pertussis and hyperleukocytosis: is it time to change for exchange?

BACKGROUND

Pertussis is an important cause of infant death worldwide and continues to be a public health concern even in countries with high vaccination coverage. Severe (critical) pertussis with hyperleukocytosis is a severe form of the disease with up to 80% mortality rate. Attempts have been reported to reduce the white blood cell burden by exchange transfusion (ET) with conflicting conclusions.

CASE REPORT

We report a case of critical pertussis in a neonate who was treated with ET, in view of a comprehensive literature review.

RESULTS

The patient was discharged without any sequelae.

CONCLUSION

ET should be considered in all infants suffering from critical pertussis and hyperleukocytosis, even in secondary care community hospitals.

Bronchoscopy with N-acetylcysteine lavage in severe respiratory failure from pertussis infection

Pertussis is an illness that causes significant morbidity and mortality, especially in infants younger than 3 months old. In the most severe cases, it can cause pneumonia, respiratory failure, acute respiratory distress syndrome, pulmonary hypertension, and death. There are reports of using rescue extracorporeal membrane oxygenation (ECMO) as a rescue therapy. However, the mortality of ECMO with pertussis is higher than with other causes of pediatric respiratory failure. We report here the case of a 2-month-old boy with severe respiratory failure and pulmonary hypertension who satisfied ECMO criteria but was successfully treated with repeated bronchoscopy with instillation of N-acetylcysteine. Our patient's respiratory failure was refractory to multiple therapies that have shown benefit in pediatric hypoxemic respiratory failure, including open lung strategies, prone positioning, intratracheal surfactant, and inhaled nitric oxide. Although pulmonary hypertension is a key factor in most cases of fatal pertussis, the adverse effects of hyperinflation and air leaks were more important in this patient's clinical course. Because bronchiolar obstruction from inflammatory, mucous, and airway epithelial debris can be seen in severe pertussis, a regimen of repeated therapeutic bronchoscopy was initiated, and thick, inspissated secretions were retrieved. The patient's airway obstruction gradually resolved, and he eventually recovered with minimal sequelae.