Insights into the role of the respiratory tract microbiome in defense against bacterial pneumonia

The respiratory tract microbiome (RTM) is a microbial ecosystem inhabiting different niches throughout the airway. A critical role for the RTM in dictating lung infection outcomes is underlined by recent efforts to identify community members benefiting respiratory tract health. Obligate anaerobes common in the oropharynx and lung such as Prevotella and Veillonella are associated with improved pneumonia outcomes and activate several immune defense pathways in the lower airway. Colonizers of the nasal cavity, including Corynebacterium and Dolosigranulum, directly impact the growth and virulence of lung pathogens, aligning with robust clinical correlations between their upper airway abundance and reduced respiratory tract infection risk. Here, we highlight recent work identifying respiratory tract bacteria that promote airway health and resilience against disease, with a focus on lung infections and the underlying mechanisms driving RTM-protective benefits.

Haemophilus influenzae Bacteremia and Pneumonia: A Case Report

This study reports a case of respiratory failure and pneumonia attributed to infection from a confirmed case of Haemophilus influenzae in a patient with past medical history of interstitial lung disease following a COVID-19 infection. An 88-year-old man with significant past medical history of interstitial lung disease (ILD) and self-catheterization due to benign prostatic hyperplasia (BPH) presented to the ED with shortness of breath and cough. Examination revealed reduced respiratory effort and scattered rhonchi throughout the lung fields. Urine cultures were positive for extended spectrum beta-lactamase (ESBL) Escherichia coli. In addition, blood cultures and chest X-ray findings confirmed a case of H. influenzae bacteremia and pneumonia. The following case highlights the unusual finding of invasive H. influenzae disease and corresponds with the data provided by the Active Bacterial Core surveillance supported by the Centers for Disease Control and Prevention (CDC).

Haemophilus influenzae Urethritis: A Localization to Consider

Urethritis may be acute or subacute and can be classified as gonococcal or nongonococcal. Nongonococcal urethritis is mainly dominated by Chlamydia trachomatis. Other bacteria such as Haemophilus influenzae have been implicated in some cases. We report the case of a 56-year-old diabetic man with H. influenzae urethritis following unprotected oral sex. The patient initially received treatment with ciprofloxacin, but this proved to be ineffective. Once our diagnosis was made, we switched the patient to cefixime for a period of seven days, which resulted in a successful clinical outcome.

Non-typeable Haemophilus influenzae Osteomyelitis and Discitis of the Cervical Vertebrae in an Elderly Adult: A Case Report and Literature Review

While Haemophilus influenzae type B (Hib) is well described in the literature to cause osteomyelitis, non-typeable H. influenzae has not. In areas where vaccination is routine, the prevalence of Hib has declined, whereas, in contrast, the prevalence of non-typeable H. influenza has increased. Generally, the non-typeable strains are less invasive but can access the vascular system by transmural migration through epithelial tight junctions or by an independent intercellular mechanism. Herein, we described a case of a 79-year-old man with the first case of non-typeable H. influenzae causing cervical osteomyelitis with associated bacteremia in an elderly adult.

Hemophilus Septicemia Meningitis in an 11-Month-Old Vaccinated Infant

Haemophilus influenzae is a gram-negative pleomorphic coccobacillus associated with many diseases, such as meningitis, pneumonia, septicemia, cellulitis, and otitis media. The most virulent and most common serotype is H. influenzae type b (Hib), which was responsible for the majority of meningitis cases until the development of vaccines that led to a decrease in its incidence worldwide. Here, we report the case of an 11-month-old female infant who was previously healthy and fully vaccinated against Hib and developed sepsis and meningitis. The patient was managed as a case of partially treated bacterial meningitis but failed to respond to a short-duration course of antibiotics and had focal seizures of the left hand. Non-contrast brain MRI revealed multiple and bilateral brain abscesses more evident on the left side. The patient was then followed up with imaging every 10-14 days to monitor the response and resolution of the brain abscesses. She was successfully treated with a full course of intravenous ceftriaxone for six weeks until imaging was clear and the brain abscesses were nearly undetected. Invasive H. influenzae infections are considered emerging cases, and there is a need to consider and suspect the disease even in fully vaccinated patients.

Risk Factors of Pneumonia in Primary Antibody Deficiency Patients Receiving Immunoglobulin Therapy: Data from the US Immunodeficiency Network (USIDNET)

BACKGROUND

Despite immunoglobulin replacement (IgRT) therapy, some patients with primary antibody deficiency (PAD) continue to develop respiratory infections. Recurrent and severe respiratory infections, particularly pneumonia, can lead to significant morbidity and mortality. Therefore, we sought to determine the risk factors of developing pneumonia in PAD patients, already receiving IgRT.

METHODS

We evaluated clinical and laboratory features of PAD patients enrolled in the US Immune Deficiency Network (USIDNET) registry by April 2017. Patients were included if they met the following criteria: (1) PAD diagnosis (common variable immunodeficiency (CVID), agammaglobulinemia, hypogammaglobinemia, and specific antibody deficiency (SAD) and (2) available data on infections before and after IgRT. Patients were excluded if they were not receiving IgRT, or if no pre/post infections data were available. Descriptive and multivariable logistic regression analyses were used to identify factors associated with pneumonia post-IgRT.

RESULTS

A total of 1232 patients met the inclusion criteria. Following IgRT, 218 patients (17.7%) were reported to have at least one pneumonia episode. Using multivariate logistic regression analysis, we found a statistically significant increased risk of pneumonia in patients with asthma (OR: 2.55, 95% CI (1.69-3.85), p < 0.001) bronchiectasis (OR: 3.94, 95% CI (2.29-6.80), p < 0.001), interstitial lung disease (ILD) (OR: 3.28, 95%CI (1.43-7.56), p < 0.005), splenomegaly (OR: 2.02, 95%CI (1.08-3.76), p < 0.027), allergies (OR: 2.44, 95% CI [1.44-4.13], p = 0.001), and patients who were not on immunosuppressives (OR: 1.61; 95%CI [1.06-2.46]; p = 0.027). For every 50 unit increase in IgA, the odds of reporting pneumonia post IgRT decreased (OR: 0.86, 95% CI [0.73-1.02], p = 0.062). Infectious organisms were reported in 35 of 218 patients who reported pneumonia after IgRT. Haemophilus influenzae was the most frequently reported (n = 11, 31.43%), followed by Streptococcus pneumoniae (n = 7, 20.00%).

CONCLUSION

Our findings suggest PAD patients with chronic and structural lung disease, splenomegaly, and allergies were associated with persistent pneumonia. However, our study is limited by the cross-sectional nature of the USIDNET database and limited longitudinal data. Further studies are warranted to identify susceptible causes and explore targeted solutions for prevention and associated morbidity and mortality.

CLINICAL IMPLICATIONS

Patients with primary antibody deficiency with structural lung disease, allergies, and splenomegaly are associated with persistent pneumonia post-IgRT.

Use of Inhaled Corticosteroids and Risk of Acquiring Haemophilus influenzae in Patients with Chronic Obstructive Pulmonary Disease

Background: Inhaled corticosteroids (ICS) are widely used in chronic obstructive pulmonary disease (COPD), despite the known risk of severe adverse effects including pulmonary infections. Research Question: Our study investigates the risk of acquiring a positive Haemophilus influenzae airway culture with use of ICS in outpatients with COPD. Study Design and Methods: We conducted an epidemiological cohort study using data from 1 January 2010 to 19 February 2018, including 21,218 outpatients with COPD in Denmark. ICS use 365 days prior to cohort entry was categorised into low, moderate, and high, based on cumulated ICS dose extracted from a national registry on reimbursed prescriptions. A Cox proportional hazards regression model was used to assess the future risk of acquiring H. Influenzae within 365 days from cohort entry, and sensitivity analyses were performed using propensity score matched models. Results: In total, 801 (3.8%) patients acquired H. Influenzae during follow-up. Use of ICS was associated with a dose-dependent increased risk of acquiring H. Influenzae with hazard ratio (HR) 1.2 (95% confidence interval (CI) 0.9−1.5, p value = 0.1) for low-dose ICS; HR 1.7 (95% CI 1.3−2.1, p value < 0.0001) for moderate dose; and HR 1.9 (95% CI 1.5−2.4, p value < 0.0001) for high-dose ICS compared to no ICS use. Results were confirmed in the propensity-matched model using the same categories. Conclusions: ICS use in outpatients with COPD was associated with a dose-dependent increase in risk of isolating H. Influenzae. This observation supports that high dose ICS should be used with caution.

Viral Encephalitis in Adults: A Narrative Review

Viral infections of the central nervous system cause frequent hospitalization. The pathogenesis of viral encephalitis involves both the direct action of invading pathogens and the damage generated by the inflammatory reaction they trigger. The type of signs and symptoms presented by the patient depends on the severity and location of the ongoing inflammatory process. Most of the viral encephalitides are characterized by an acute development, fever, variable alterations in consciousness (confusion, lethargy, even coma), seizures (focal and generalized) and focal neurologic signs. The specific diagnosis of encephalitis is usually based on lumbar puncture. Cerebrospinal fluid examination should be performed in all patients unless absolutely contraindicated. Also, electroencephalogram and neuroimaging play a prominent role in diagnosis. Airway protection, ventilatory support, the management of raised intracranial pressure and correction of electrolyte disorders must be immediately considered in a patient with altered mental status. The only therapy strictly recommended is acyclovir in HSV encephalitis. The use of adjunctive glucocorticoids has poor-quality evidence in HSV, EBV, or VZV encephalitis. The role of antiviral therapy in other types of viral encephalitis is not well defined.

Paraplegia From a Spinal Epidural Abscess Caused by Pasteurella multocida

Pasteurella multocida is a common cause of infection following bites or scratches caused by cats and dogs. It is a rarely reported and often overlooked pathogen. Typical presentation is a rapidly developing cellulitis at the infection site. Here we present a rare case of worsening lower extremity paraplegia due to a spinal epidural abscess caused by P. multocida. The patient was a 56-year-old female who had been experiencing several days of back pain, became septic and went on to develop paraplegia. Failure to improve prompted re-evaluation of the diagnosis with subsequent imaging notable for a spinal epidural abscess. Blood cultures grew P. multocida but were initially misidentified as Haemophilus influenzae and only with targeted antibiotic therapy and neurosurgical intervention did she begin to improve. Obtaining an animal history and knowing when to re-evaluate a diagnosis are essential skills for any clinician.

Haemophilus influenzae type b disease in the era of conjugate vaccines: critical factors for successful eradication

INTRODUCTION

Prior to implementation of Haemophilus influenzae type b (Hib)-conjugate vaccination programs in the 1990s, Hib was the commonest cause of bacterial meningitis in children aged <5 years. While the burden of all Hib disease has significantly decreased in the post-vaccination era, Hib still accounted for >29,000 deaths worldwide in children aged <5 years in 2015.

AREAS COVERED

We reviewed literature data on the most widely used Hib vaccines and vaccination strategies which led to the global prevention and control of Hib disease and aim to highlight important factors for continued disease control and elimination in the future.

EXPERT COMMENTARY

More than 90% of countries worldwide have implemented Hib-conjugate vaccination in their national immunization programs. Vaccines containing Hib polyribosylribitol phosphate (PRP) conjugated with tetanus toxoid (Hib-TT) are the most commonly used. Neisseria meningitidis outer membrane protein complex of PRP (Hib-OMP) is also used. Although the kinetics of the immune response varies with Hib vaccine and schedule used, high control of Hib disease was observed in all settings/scenarios. Further improving global Hib vaccination coverage may result in disease elimination. Plain language summary What is the context? Haemophilus influenzae is causing a variety of diseases, from otitis media and sinusitis to invasive disease (e.g. meningitis and pneumonia). H. influenzae type b (Hib) was the most common cause of bacterial meningitis in children <5 years of age, and especially among <2-year-olds. Even with appropriate treatment, up to 40% of children with bacterial meningitis can suffer permanent disabilities and up to 5% will die. The development of vaccines to protect against Hib disease has started in the late 1970s and has culminated with the licensure of 4 Hib conjugate vaccines, of which 2 are currently widely used. What is new? In this review, we gathered evidence on the different Hib vaccines and vaccination strategies that have contributed to the global prevention and control of Hib disease. The review indicates: the incidence of Hib disease has decreased considerably due to the introduction of Hib vaccines in national immunization programs worldwide. However, Hib disease is not yet completely eradicated. the vaccines currently used offer protection against Hib over long periods of time. carriage of the pathogen by healthy individuals seem to be less frequent, but data are still needed to fully evaluate the impact of vaccination. other H. influenzae types are now more frequent. Why is this important? Despite the huge success of Hib vaccination, continuous surveillance is needed to anticipate potential re-emergences and devise the best strategies for prevention and control of disease. Hib vaccination should be considered in the few countries who have not yet implemented it, to decrease associated morbidity and mortality.

A Rare Case of Waterhouse-Friderichsen Syndrome Without Purpura Secondary to Haemophilus Influenzae

The Waterhouse-Friderichsen syndrome is an entity consisting of shock, petechial rash and haemorrhages in both adrenal glands leading to adrenal failure. This syndrome is usually secondary to meningococcal septicaemia, but there are many documented cases caused by other bacteria. Purpura is an essential part of the syndrome, but it is not always there. In the current study, a case of Waterhouse-Friderichsen syndrome without purpura in an elderly patient with Haemophilus influenzae bacteraemia has been described. This patient was being managed for sepsis due to pneumonia and an incidental finding of bilateral adrenal haemorrhage was made on a CT of the thorax which was meant to evaluate empyema. This case shows the need to suspect bilateral adrenal haemorrhage in every patient with septic shock.

Contemporary management of bronchiectasis in children

Introduction: Bronchiectasis is increasingly recognized as a major cause of morbidity and mortality worldwide. It affects children of all ethnicities and socioeconomic backgrounds and represents a far greater burden than cystic fibrosis (CF). Bronchiectasis often begins in childhood and the radiological changes can be reversed, when mild, with optimal management. As there are limited pediatric studies in this field, current treatment approaches in children are based largely upon adult and/or CF studies. The recent establishment of bronchiectasis registries will improve understanding of pediatric bronchiectasis and increase capacity for large-scale research studies in the future. Areas covered: This review summarizes the current management of bronchiectasis in children and highlights important knowledge gaps and areas for future research. Current treatment approaches are based largely on consensus guidelines from international experts in the field. Studies were identified through searching Medline via the Ovid interface and Pubmed using the search terms 'bronchiectasis' and 'children' or 'pediatric' and 'management' or 'treatments'. Expert opinion: Bronchiectasis is heterogeneous in nature and a one-size-fits-all approach has limitations. Future research should focus on advancing our understanding of the aetiopathogenesis of bronchiectasis. This approach will facilitate development of targetted therapeutic interventions to slow, halt or even reverse bronchiectasis in childhood.

Haemophilus influenzae Type f Meningitis Complicated by Bilateral Subdural Empyema, Central Venous Thrombosis, and Bilateral Sensorineural Hearing Loss in an Immunocompetent 12-month-old

Haemophilus influenzae is a gram-negative coccobacillus that colonizes the nasopharyngeal surface and upper respiratory tract of healthy individuals and includes six encapsulated serotypes as well as non-encapsulated, non-typeable strains. Since the widespread use of the Haemophilus influenzae type b (Hib) conjugate vaccine implemented in 1990, the majority of invasive illness now seen in the United States is secondary to capsular serotypes other than type b and non-typeable strains with the largest burden of disease affecting the extremes of age-infants and the elderly. We report a case of acute Haemophilus influenzae type f meningitis in a 12-month-old female who was previously healthy and had been fully immunized. She demonstrated clinical improvement on ceftriaxone, but persistent fever and ear-tugging resulted in obtaining an MRI that displayed bilateral subdural empyemas requiring burr-hole craniotomy, central venous thrombosis requiring anticoagulation, and bilateral sensorineural hearing loss requiring cochlear implants. Immunological studies confirmed immunocompetency and appropriate response to her previous Hib vaccination, suggesting a significant impact of bacterial virulence. These complications, with the exception of sensorineural hearing loss, have not been reported in the literature for Haemophilus influenzae type f and should be considered in the care of these patients despite clinical appearance given the severity of complications and potential for acute decompensation. Despite the success of vaccination in reducing invasive disease, cases of H. influenzae meningitis continue to occur via less common encapsulated serotypes with unknown complications, making the management and treatment of these infections more difficult for practitioners.

[Postoperative pulmonary disease associated with haemophilus influenzae and neisseria meningitidis in a diabetic child]

Haemophilus influenzae is a saprophyte that colonizes the nasopharynx in nearly two thirds of children and adults. Neisseria meningitidis is a strict human bacterium which lives in the nasopharynx. It can cause benign nasopharyngitis or asymptomatic colonization. We report the case of a diabetic child with postoperative pneumonia associated with Haemophilus influenzae and Neisseria meningitidis. A 3-year old diabetic patient admitted to the Department of Cardiac Surgery due to delayed surgical treatment. The postoperative course was marked by a worsening of respiratory status caused by abundant secretions requiring patient admission to the intensive care unit. An assessment for the detection of infections was performed, including protected distal sampling which revealed the association of Neisseria meningitidis with Haemophilus influenzae. This case study allowed us to highlight bacterial associations in certain high-risk situations. Each of these two species is responsible for various infections. However their presence in the same infected site is rare.

A population-based study of hospital admission incidence rate and bacterial aetiology of acute lower respiratory infections in children aged less than five years in Bangladesh

The research was carried out to study the rate of population-based hospital admissions due to acute lower respiratory infections (ALRIs) and bacterial aetiology of ALRIs in children aged less than five years in Bangladesh. A cohort of children aged less than five years in a rural surveillance population in Matlab, Bangladesh, was studied for two years. Cases were children admitted to the Matlab Hospital of ICDDR,B with a diagnosis of severe ALRIs. Bacterial aetiology was determined by blood culture. Antimicrobial resistance patterns of Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae (Spn) isolates were determined using the disc-diffusion method. In total, 18,983 children aged less than five years contributed to 24,902 child-years of observation (CYO). The incidence of ALRI-related hospital admissions was 50.2 per 1,000 CYO. The incidences of ALRI were 67% higher in males than in females and were higher in children aged less than two years than in older children. About 34% of the cases received antibiotics prior to hospitalization. Of 840 blood samples cultured, 39.4% grew a bacterial isolate; 11.3% were potential respiratory pathogens, and the rest were considered contaminants. The predominant isolates were Staphylococcus aureus (4.5%). Hib (0.4%) and Spn (0.8%) were rarely isolated; however, resistance of both these pathogens to trimethoprim-sulphamethoxazole was common. The rate of ALRI-related hospitalizations was high. The high rate of contamination, coupled with high background antibiotic use, might have contributed to an underestimation of the burden of Hib and Spn. Future studies should use more sensitive methods and more systematically look for resistance patterns of other pathogens in addition to Hib and Spn.

Haemophilus influenzae and Streptococcus pneumoniae induce different intracerebral mRNA cytokine patterns during the course of experimental bacterial meningitis

Using in situ hybridization with radiolabelled oligonucleotide probes, we studied the mRNA expression of IL-1beta, IL-4, IL-6, IL-10, IL-12, tumour necrosis factor-alpha (TNF-alpha), TNF-beta, interferon-gamma (IFN-gamma), and transforming growth factor-beta (TGF-beta) in the brain during the lethal course of experimental meningitis in a rat model inoculated intracisternally with Haemophilus influenzae type b (Hib) or Streptococcus pneumoniae and in uninfected control rats inoculated with the same volume of PBS. The production of IL-1beta, IL-4, IL-6 and IFN-gamma was also evaluated by immunohistochemistry. In the brain of Hib-inoculated rats, there was marked mRNA expression of IL-1beta, IL-6, TNF-alpha, IL-12 and IFN-gamma. IL-1beta, IL-6 and TNF-alpha were up-regulated throughout the observation period at 2, 8 and 18 h post-inoculation (p.i.), with similar patterns of induction. The Th1 cytokines IFN-gamma and TNF-beta were up-regulated within 8 h p.i. IL-10 and TGF-beta were down-regulated at 18 h p.i., while IL-4 was not detected. In contrast, the brain of S. pneumoniae-inoculated rats showed lower levels of IL-1beta, IL-6 and TNF-alpha, but higher levels of TNF-beta and detectable mRNA expression of IL-4 when compared with Hib-inoculated rats. IL-12, IFN-gamma, IL-10 and TGF-beta exhibited similar patterns of induction in the brains of Hib- and S. pneumoniae-inoculated rats. At 18 h p.i., immunohistochemistry showed similar patterns of IL-1beta, IL-4, IL-6 and IFN-gamma as mRNA expression in the brains of Hib- and S. pneumoniae-inoculated rats. The differences of cytokine profiles induced by the two bacterial strains may imply that different immunomodulating approaches should be considered, depending on etiology.

Pericarditis caused by beta-lactamase-producing Haemophilus influenzae: report of two cases in adults and review of the literature

Two adult patients with pericarditis caused by beta-lactamase producing Haemophilus influenzae are reported and their management reviewed. Both had pharyngitis, epiglottitis, pneumonia, empyema, or septicemia and were cured with antimicrobics and pericardial drainage (one by catheter and one by surgery). Eleven previously reported cases of pericarditis caused by Haemophilus influenzae are also reviewed. In reviewing this rare cause of bacteria pericarditis, it is important to recognize the antibiotic resistance profile, the incidence of pericardial tamponade, and the use of surgical drainage. Antibiotic selection for this organism is also discussed, as well as the importance of biotyping.