Current Epidemiology and Trends in Invasive Haemophilus influenzae Disease-United States, 2009-2015

The emergence of transposon-driven multidrug resistance in invasive nontypeable Haemophilus influenzae over the last decade

Nontypeable Haemophilus influenzae (NTHi), once considered a harmless commensal, has emerged as a significant concern due to the increased prevalence of multidrug-resistant (MDR) strains and their association with invasive infections. This study aimed to explore the epidemiology and molecular resistance mechanisms of 51 NTHi isolates collected from patients with invasive infections in northern Taiwan between 2011 and 2020. This investigation revealed substantial genetic diversity, encompassing 29 distinct sequence types and 18 clonal complexes. Notably, 68.6% of the isolates exhibited ampicillin resistance, with 28 categorised as MDR and four isolates were even resistant to up to six antibiotic classes. Among the MDR isolates, 18 pulsotypes were identified, indicating diverse genetic lineages. Elucidation of their resistance mechanisms revealed 18 β-lactamase-producing amoxicillin-clavulanate-resistant (BLPACR) isolates, 12 β-lactamase-producing ampicillin-resistant (BLPAR) isolates, and 5 β-lactamase-nonproducing ampicillin-resistant (BLNAR) isolates. PBP3 analysis revealed 22 unique substitutions in BLPACR and BLNAR, potentially contributing to cephem resistance. Notably, novel transposons, Tn7736-Tn7739, which contain critical resistance genes, were discovered. Three strains harboured Tn7739, containing seven resistance genes [aph(3')-Ia, blaTEM-1, catA, sul2, strA, strB, and tet(B)], while four other strains carried Tn7736, Tn7737, and Tn7738, each containing three resistance genes [blaTEM-1, catA, and tet(B)]. The emergence of these novel transposons underscores the alarming threat posed by highly resistant NTHi strains. Our findings indicated that robust surveillance and comprehensive genomic studies are needed to address this growing public health challenge.

Invasive Nontypeable Haemophilus influenzae Disease Outbreak at an Elementary School - Michigan, May 2023

In May 2023, the Detroit Health Department was notified of four cases of invasive nontypeable Haemophilus influenzae (Hi) disease among students attending the same elementary school and grade, all with illness onsets within 7 days. Three patients were hospitalized, and one died. Most U.S. cases of invasive Hi disease are caused by nontypeable strains. No vaccines against nontypeable or non-type b Hi strains are currently available. Chemoprophylaxis is not typically recommended in response to nontypeable Hi cases; however, because of the high attack rate (four cases among 46 students; 8.7%), rifampin prophylaxis was recommended for household contacts of patients with confirmed cases and for all students and staff members in the school wing where confirmed cases occurred. Only 10.8% of students for whom chemoprophylaxis was recommended took it, highlighting gaps in understanding among caregivers and health care providers about persons for whom chemoprophylaxis was recommended. Public health authorities subsequently enhanced communication and education to the school community, improved coordination with health care partners, and established mass prophylaxis clinics at the school. This outbreak highlights the potential for nontypeable Hi to cause serious illness and outbreaks and the need for chemoprophylaxis guidance for nontypeable Hi disease. Achieving high chemoprophylaxis coverage requires education, communication, and coordination with community and health care partners.

Development and implementation of a core genome multilocus sequence typing scheme for Haemophilus influenzae

Haemophilus influenzae is part of the human nasopharyngeal microbiota and a pathogen causing invasive disease. The extensive genetic diversity observed in H. influenzae necessitates discriminatory analytical approaches to evaluate its population structure. This study developed a core genome multilocus sequence typing (cgMLST) scheme for H. influenzae using pangenome analysis tools and validated the cgMLST scheme using datasets consisting of complete reference genomes (N = 14) and high-quality draft H. influenzae genomes (N = 2297). The draft genome dataset was divided into a development dataset (N = 921) and a validation dataset (N = 1376). The development dataset was used to identify potential core genes, and the validation dataset was used to refine the final core gene list to ensure the reliability of the proposed cgMLST scheme. Functional classifications were made for all the resulting core genes. Phylogenetic analyses were performed using both allelic profiles and nucleotide sequence alignments of the core genome to test congruence, as assessed by Spearman's correlation and ordinary least square linear regression tests. Preliminary analyses using the development dataset identified 1067 core genes, which were refined to 1037 with the validation dataset. More than 70% of core genes were predicted to encode proteins essential for metabolism or genetic information processing. Phylogenetic and statistical analyses indicated that the core genome allelic profile accurately represented phylogenetic relatedness among the isolates (R 2 = 0.945). We used this cgMLST scheme to define a high-resolution population structure for H. influenzae, which enhances the genomic analysis of this clinically relevant human pathogen.

An Investigation of Pediatric Case-patients With Invasive Haemophilus influenzae in Alaska, 2005-2011

BACKGROUND

Haemophilus influenzae (Hi) can cause severe disease in children. This study aimed to identify risk factors related to invasive Hi disease in Alaska children and evaluate carriage in people around them.

METHODS

From 2005 to 2011, we investigated episodes of invasive, typeable Hi disease in Alaska children <10 years old. Three age-matched control children were enrolled for each case-patient. We evaluated oropharyngeal Hi carriage in people in close contact with Hi case-patients (contacts) as well as control children and their household members. Individual and household risk factors for illness and carriage were evaluated using questionnaires and chart reviews.

RESULTS

Thirty-eight of 44 (86%) children with invasive, typeable Hi disease were recruited: 20 Hi serotype a (53%), 13 serotype b (Hib) (34%) and 5 serotype f (13%). Children with the invasive Hi disease were more likely than controls to have underlying health problems (67% vs. 24%, P = 0.001), other carriers of any Hi in their household (61% vs. 15%, P < 0.001), and inadequate Hib vaccination (26% vs. 9%, P = 0.005). People who carried Hi were younger than noncarriers (mean 12.7 vs. 18.0 years, P = 0.008). The carriage was clustered within case-patient households, with carriage in 19% of household contacts, while only 6.3% of nonhousehold contacts and 5.5% of noncontacts carried the Hi serotype of interest ( P < 0.001).

CONCLUSIONS

Factors associated with invasive Hi disease in children included underlying health problems, household carriage and inadequate Hib vaccination. The high level of carriage in case-patient households is important to consider when evaluating treatment and prophylaxis strategies.

Bacitracin agar vs. oleandomycin disk supplemented chocolate agar for the recovery of Haemophilus influenzae in diagnostic samples: A prospective comparison

Haemophilus influenzae is an important pathogen able to cause various forms of respiratory and invasive disease. To provide high sensitivity for detection, culture media must inhibit growth of residential flora from the respiratory tract. This study aimed to identify and compare the diagnostic and economic advantages of using bacitracin containing selective agar (SEL) or oleandomycin disk supplemented chocolate agar (CHOC). Growth and semi-quantitative abundance of H. influenzae and growth suppression of residential flora was prospectively assessed in a 28-week period. H. influenzae was identified in 164 (5 %) of all included samples: CHOC and SEL, CHOC only, and SEL only were positive in 95, 24, and 45 cases. Diagnostic superiority of SEL was primarily attributable to the results of throat swabs. However, on average, € 200 had to be spent for the detection of each additional isolate that was recovered only because of additional incubation on SEL.

Changing Landscape of Haemophilus influenzae Meningitis and Implication on Public Health

Haemophilus influenzae (H. influenzae) has evolved as a prominent pathogen, with nontypeable strains (NTHi) emerging as a leading cause of invasive disease, particularly among the elderly. Since the introduction of Haemophilus influenzae B (Hib) vaccine, invasive infection has shifted from children with Hib to the elderly with NTHi. NTHi affects those primarily with predisposing factors such as an immunocompromised state, CSF leakage, or ENT infections. We present two cases that emphasize the shift of invasive infection, risk factors, and elevated intracranial pressure (ICP) as a complication. Case 1. A 75-year-old female with a sudden onset of weakness and respiratory symptoms deteriorated rapidly. Imaging revealed mastoid effusion and ventriculitis, likely originating from otomastoiditis. Lumber puncture confirmed NTHi. ICU course complicated by elevated ICP prompted repeat lumbar puncture. The patient recovered after 8 days but not near baseline. Case 2. A 50-year-old female with altered mental status, headache, and ear pain exhibited signs of pansinusitis and pseudotumor cerebri. Elevated ICP was evident upon lumbar puncture, and NTHi was isolated in CSF and blood cultures. MRI of the brain showed prominent optic nerve sheaths and transverse sinus arachnoid granulations' concern for underlying pseudotumor cerebri. Repeat lumbar puncture or ventricular drainage was deferred after discussion with neurosurgery. Diabetes was identified as a comorbidity. The patient's condition improved after 14 days of antibiotics and dexamethasone. These cases emphasize the shifting landscape of H. influenzae meningitis, primarily driven by NTHi, especially among the elderly. Although NTHi infections were considered less invasive, recent epidemiology review indicated it as the leading cause of H. influenzae meningitis. With the increasing prevalence of NTHi and its increase in invasive patterns, it is crucial to implement vaccination strategies and develop new vaccines targeting NTHi.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Postmeningitic pediatric hearing loss from non-type b Haemophilus influenzae

BACKGROUND

Postmeningitic hearing loss from Haemophilus influenzae (H. influenzae) is increasingly due to encapsulated serotypes other than type b (Hib) and nontypeable strains (collectively, nHiB H. influenzae). Pediatric hearing loss after nHib H. influenzae meningitis remains poorly described.

METHODS

Retrospecive case series of nHiB H. influenzae meningitis cases identified from a microbiologic database at Children's Hospital Colorado from 2000 to 2020. Literature regarding nHiB H. influenzae and H. influenzae postmeningitic hearing loss was also reviewed.

RESULTS

Eleven cases of nHib H. influenzae meningitis (median age 15.9 months) were identified due to serotype f (36 %), serotype a (27 %), and nontypable strains (36 %). Seven (64 %) patients were male, 55 % were white and 18 % were Hispanic or Latino. Hearing loss was initially identified in 4 children (40 %), with two patients with moderate conductive hearing loss (CHL) and one child with unilateral moderate sensorineural (SNHL) hearing loss patients recovering normal hearing. One patient with bilateral profound sensorineural hearing loss and associated labyrinthitis ossificans required cochlear implantation. All children (4) with identified hearing loss were noted to have additional intracranial sequelae, which included empyema (2), sinus thrombosis (2), and seizures (2). Of patients receiving steroids, 25 % had hearing loss on initial testing, compared to 66 % of those who did not receive steroids.

CONCLUSIONS

nHib H. influenzae can cause both transient and permanent postmeningitic hearing loss. Steroids may offer otoprotection in nHib H. influenzae meningitis similar to Hib meningitis. Given the limited literature, further study is needed to better characterize hearing outcomes after nHib H. influenzae meningitis.

Vaccination to Reduce Antimicrobial Resistance Burden-Data Gaps and Future Research

Antimicrobial resistance (AMR) poses an immediate danger to global health. If unaddressed, the current upsurge in AMR threatens to reverse the achievements in reducing the infectious disease-associated mortality and morbidity associated with antimicrobial treatment. Consequently, there is an urgent need for strategies to prevent or slow the progress of AMR. Vaccines potentially contribute both directly and indirectly to combating AMR. Modeling studies have indicated significant gains from vaccination in reducing AMR burdens for specific pathogens, reducing mortality/morbidity, and economic loss. However, quantifying the real impact of vaccines in these reductions is challenging because many of the study designs used to evaluate the contribution of vaccination programs are affected by significant background confounding, and potential selection and information bias. Here, we discuss challenges in assessing vaccine impact to reduce AMR burdens and suggest potential approaches for vaccine impact evaluation nested in vaccine trials.

Genome Characterisation of Invasive Haemophilus influenzae in Pregnancy: The Noticeable Placental Tissue Tropism Is Distributed across the Species Rather Than Linked with Capsulation or Particular Clones

Pregnancy is associated with a 5-26 times increased risk of invasive Haemophilus influenzae infection and subsequent adverse pregnancy outcomes. Incidence rate and outcome are published in some regions, but the characterisation of bacterial isolates is limited. We performed comparative genomic analyses of isolates from 12 pregnancy-associated cases, cultured from maternal bacteraemia in pregnancy (nine), postpartum bacteraemia (one), neonatal bacteraemia (one), and placental tissue (one). In two bacteraemia cases, identical isolates were also cultured from cervical swabs. Eight cases occurred early in pregnancy (gestational week 7-26), and seven of them resulted in miscarriage or neonatal death. All bacterial genomes were devoid of capsule loci, and they were evenly distributed in the major phylogenetic group I of the species. The conspicuous tropism of H. influenzae for pregnancy and placental tissue is associated with the species rather than specific clonal subtypes.

Characteristics of Haemophilus influenzae carriage among healthy children in China: A meta-analysis

BACKGROUND

Haemophilus influenzae (Hi) commonly causes invasive and noninvasive bacterial infections. Nationwide investigation on the carriage characteristics of H influenzae in healthy children in China is lacking. We reviewed the prevalence of H influenzae infections in this population.

METHODS

PubMed, CNKI, Wanfang, VIP, and CBM databases were electronically searched to collect cross-sectional studies on the prevalence of Hi among healthy children in China from inception to November 2021. Two reviewers independently screened the literature, extracted the data, and assessed the risk of bias in the included studies. Meta-analysis was performed using Stata 14.0.

RESULTS

A total of 28 studies involving 14,301 children were included, among whom there were 2878 children with Hi. The pooled carriage rate of Hi was 0.21 (95% CI: 0.17-0.25). Subgroup analysis indicated no significant sex- or age-related differences. The proportion of Hi in winter (29%) was higher than that in other seasons. Results indicated significant differences among the provinces, with carriage proportions ranging from 0.11 to 0.60. The proportion of nontypeable H influenzae (NTHi) was higher than that of the capsular type. The proportion of Hib in the capsular type (2%) was higher than that in other serotypes.

CONCLUSIONS

The carriage rate of Hi in healthy children in China was 21% with no sex-related age differences. The proportion of Hi in winter was high, and the proportions of Hi in different regions were significantly different. NTHi was the predominant serotype detected in children.

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).

In Vivo Validation of Novel Synthetic tbp1 Peptide-Based Vaccine Candidates against Haemophilus influenzae Strains in BALB/c Mice

Haemophilus influenzae is a Gram-negative bacterium characterized as a small, nonmotile, facultative anaerobic coccobacillus. It is a common cause of a variety of invasive and non-invasive infections. Among six serotypes (a-f), H. influenzae type b (Hib) is the most familiar and predominant mostly in children and immunocompromised individuals. Following Hib vaccination, infections due to other serotypes have increased in number, and currently, there is no suitable effective vaccine to induce cross-strain protective antibody responses. The current study was aimed to validate the capability of two 20-mer highly conserved synthetic tbp1 (transferrin-binding protein 1) peptide-based vaccine candidates (tbp1-E1 and tbp1-E2) predicted using in silico approaches to induce immune responses against H. influenzae strains. Cytokine induction ability, immune simulations, and molecular dynamics (MD) simulations were performed to confirm the candidacy of epitopic docked complexes. Synthetic peptide vaccine formulations in combination with two different adjuvants, BGs (Bacterial Ghosts) and CFA/IFA (complete/incomplete Freund's adjuvant), were used in BALB/c mouse groups in three booster shots at two-week intervals. An indirect ELISA was performed to determine endpoint antibody titers using the Student's t-distribution method. The results revealed that the synergistic use of both peptides in combination with BG adjuvants produced better results. Significant differences in absorbance values were observed in comparison to the rest of the peptide-adjuvant combinations. The findings of this study indicate that these tbp1 peptide-based vaccine candidates may present a preliminary set of peptides for the development of an effective cross-strain vaccine against H. influenzae in the future due to their highly conserved nature.

A Pediatric Investigators Collaborative Network on Infections in Children (PICNIC) multi-centre Canadian descriptive analysis of Haemophilus influenzae bacteremia in children: Emerging serotypes

Background

There has been dramatic reduction in Haemophilus influenzae serotype b (Hib) since introduction of Hib vaccines, but children still experience serious invasive Haemophilus influenzae (Hi) disease caused by various serotype and non-typeable bacteria. The object of this study was to describe the serotype distribution and clinical spectrum of Hi bacteremia in children admitted to Canadian hospitals.

Methods

All children with Hi bacteremia admitted 2013 through 2017 to 10 centres across Canada were included. Demographic, clinical, treatment and outcome data were collected.

Results

Haemophilus influenzae bacteremia occurred in 118 children of median age 12 months (inter-quartile range: 7-48 months). Forty-three (36%) isolates were non-typeable (NTHi) and 8 were not typed. Of the 67 typeable (THi), Hia (H. influenzae serotype a) (n=36, 54%), Hif (serotype f) (n=19, 26%) and Hib (serotype b) (n=9, 13%) dominated. The THi was more likely than NTHi bacteremia to present as meningitis (p<0.001), particularly serotype a (p=0.04) and less likely to present as pneumonia (p<0.001). Complicated disease (defined as intensive care unit admission, need for surgery, long-term sequelae or death) occurred in 31 (26%) cases and were more likely to have meningitis (p<0.001) than were those with uncomplicated disease.

Conclusion

In the era of efficacious conjugate Hib vaccines, NTHi, Hia and Hif have emerged as the leading causes of invasive Hi in Canadian children, with Hia being most likely to result in meningitis and complicated disease. A vaccine for all NTHi and THi would be ideal, but knowledge of the current disease burden from circulating strains will inform prioritization of vaccine targets.

Epidemic Trends and Biofilm Formation Mechanisms of Haemophilus influenzae: Insights into Clinical Implications and Prevention Strategies

Haemophilus influenzae (H. influenzae) is a significant pathogen responsible for causing respiratory tract infections and invasive diseases, leading to a considerable disease burden. The Haemophilus influenzae type b (Hib) conjugate vaccine has notably decreased the incidence of severe infections caused by Hib strains, and other non-typable H. influenzae (NTHi) serotypes have emerged as epidemic strains worldwide. As a result, the global epidemic trends and antibiotic resistance characteristics of H. influenzae have been altered. Researches on the virulence factors of H. influenzae, particularly the mechanisms underlying biofilm formation, and the development of anti-biofilm strategies hold significant clinical value. This article provides a summary of the epidemic trends, typing methods, virulence factors, biofilm formation mechanisms, and prevention strategies of H. influenzae. The increasing prevalence of NTHi strains and antibiotic resistance among H. influenzae, especially the high β-lactamase positivity and the emergence of BLNAR strains have increased clinical difficulties. Understanding its virulence factors, especially the formation mechanism of biofilm, and formulating effective anti-biofilm strategies may help to reduce the clinical impact. Therefore, future research efforts should focus on developing new approaches to prevent and control H. influenzae infections.

Molecular characterization of multidrug-resistant non-typeable Haemophilus influenzae with high-level resistance to cefuroxime, levofloxacin, and trimethoprim-sulfamethoxazole

BACKGROUND

Non-typeable Haemophilus influenzae (NTHi) has become the major cause of invasive H. influenzae diseases in the post-H. influenzae type b vaccine era. The emergence of multidrug-resistant (MDR) NTHi is a growing public health problem. Herein, we investigated the molecular basis of MDR in NTHi. The isolated NTHi were subjected to antimicrobial susceptibility testing for 12 agents. Whole genome and plasmid sequencing were conducted and analyzed to identify significant genetic variations and plasmid-encoded genes conferred antibiotic resistance.

RESULTS

Thirteen (50%) MDR NTHi isolates were obtained; of these, 92.3% were non-susceptible to ampicillin, 30.8% to amoxicillin-clavulanate, 61.5% to cefuroxime, 61.5% to ciprofloxacin/levofloxacin, 92.3% to trimethoprim-sulfamethoxazole, 30.8% to tetracycline, and 7.7% to azithromycin. Eight ampicillin-resistant isolates were β-lactamase positive; of these, 6 carried bla_TEM-1 and 2 carried bla_ROB-1, whereas 4 were β-lactamase negative. Genetic variations in mrdA, mepA, and pbpG were correlated with amoxicillin-clavulanate non-susceptibility, whereas variations in ftsI and lpoA conferred cefuroxime resistance. Five variations in gyrA, 2 in gyrB, 3 in parC, 1 in parE, and 1 in the parC-parE intergenic region were associated with levofloxacin/ciprofloxacin non-susceptibility. Among these genes, 8 variations were linked to high-level levofloxacin resistance. Six variations in folA were associated with trimethoprim-sulfamethoxazole resistance. Plasmid-bearing tet(B) and mef(A) genes were responsible for tetracycline and azithromycin resistance in 4 and 1 MDR isolates, respectively.

CONCLUSIONS

This study clarified the molecular epidemiology of MDR in NTHi. This can benefit the monitoring of drug resistance trends in NTHi and the adequate medical management of patients with NTHi infection.

Epidemiology of Invasive Nontypeable Haemophilus influenzae Disease-United States, 2008-2019

BACKGROUND

Nontypeable Haemophilus influenzae (NTHi) is the most common cause of invasive H. influenzae disease in the United States (US). We evaluated the epidemiology of invasive NTHi disease in the US, including among pregnant women, infants, and people with human immunodeficiency virus (PWH).

METHODS

We used data from population- and laboratory-based surveillance for invasive H. influenzae disease conducted in 10 sites to estimate national incidence of NTHi, and to describe epidemiology in women of childbearing age, infants aged ≤30 days (neonates), and PWH living in the surveillance catchment areas. H. influenzae isolates were sent to the Centers for Disease Control and Prevention for species confirmation, serotyping, and whole genome sequencing of select isolates.

RESULTS

During 2008-⁠2019, average annual NTHi incidence in the US was 1.3/100 000 population overall, 5.8/100 000 among children aged <1 year, and 10.2/100 000 among adults aged ≥80 years. Among 225 reported neonates with NTHi, 92% had a positive culture within the first week of life and 72% were preterm. NTHi risk was 23 times higher among preterm compared to term neonates, and 5.6 times higher in pregnant/postpartum compared to nonpregnant women. More than half of pregnant women with invasive NTHi had loss of pregnancy postinfection. Incidence among PWH aged ≥13 years was 9.5 cases per 100 000, compared to 1.1 cases per 100 000 for non-PWH (rate ratio, 8.3 [95% confidence interval, 7.1-9.7]; P < .0001).

CONCLUSIONS

NTHi causes substantial invasive disease, especially among older adults, pregnant/postpartum women, and neonates. Enhanced surveillance and evaluation of targeted interventions to prevent perinatal NTHi infections may be warranted.

Report of Haemophilus Influenzae serotype a intracranial infections in older children

Introduction

Haemophilus influenzae (Hi) is subdivided into typeable (a-f) and non-typeable groups. Hi serotype b (Hib) has historically been one of the important pathogens responsible for invasive infection. However, after widespread Hib vaccination, the emergence of other Hi serotypes, specifically Hi serotype a (Hia), was noted during the last few decades, mostly in children younger than 5 years of age.

Case presentation

We present two cases of severe intracranial infections with detected Hia in patients > 5 years of age within a short time frame and within the same geographic area.

Conclusion

Epidemiological studies and surveillance on Hia-related illnesses in all age groups worldwide are needed to better understand the clinical and epidemiological characteristics of Hia. This can establish a platform to develop a candidate vaccine against Hia that might protect children of all ages.

Vaginal carriage of Haemophilus influenzae in a non-pregnant reproductive-age population

BACKGROUND

Haemophilus influenzae (Hi) is an emerging cause of early onset neonatal sepsis, but mechanisms of transmission are not well understood. We aimed to determine the prevalence of vaginal carriage of Hi in reproductive age women and to examine behavioral and demographic characteristics associated with its carriage.

METHODS

We performed a secondary analysis of stored vaginal lavage specimens from a prospective cohort study of nonpregnant reproductive-age women. After extraction of bacterial genomic DNA, samples were tested for the presence of the gene encoding Haemophilus protein d (hpd) by quantitative real-time polymerase chain reaction (PCR) using validated primers and probe. PCR for the V3-V4 region of the 16 S rRNA gene (positive control) assessed sample quality. Samples with cycle threshold (CT) value < 35 were defined as positive. Sanger sequencing confirmed the presence of hpd. Behavioral and demographic characteristics associated with vaginal carriage of Hi were examined.

RESULTS

415 samples were available. 315 (75.9%) had sufficient bacterial DNA and were included. 14 (4.4%) were positive for hpd. There were no demographic or behavioral differences between the women with Hi vaginal carriage and those without. There was no difference in history of bacterial vaginosis, vaginal microbiome community state type, or presence of Group B Streptococcus in women with and without vaginal carriage of Hi.

CONCLUSION

Hi was present in vaginal lavage specimens of 4.4% of this cohort. Hi presence was unrelated to clinical or demographic characteristics, though the relatively small number of positive samples may have limited power to detect such differences.

Nontypeable Hemophilus Influenza Meningitis in a Primary Sjögren's Syndrome Patient on Hydroxychloroquine

Primary Sjögren's syndrome is a multisystem autoimmune disease that less commonly requires immunosuppression compared to other systemic connective tissue diseases and classically has a poorer correlation with increased incidence of infections. Herein, we describe a 61-year-old female without predisposing factors diagnosed with the uncommon nontypeable Hemophilus influenza meningitis complicated by sepsis.

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.

Secondary Cases of Invasive Disease Caused by Encapsulated and Nontypeable Haemophilus influenzae - 10 U.S. Jurisdictions, 2011-2018

Haemophilus influenzae (Hi) can cause meningitis and other serious invasive disease. Encapsulated Hi is classified into six serotypes (a-f) based on chemical composition of the polysaccharide capsule; unencapsulated strains are termed nontypeable Hi (NTHi). Hi serotype b (Hib) was the most common cause of bacterial meningitis in children in the pre-Hib vaccine era, and secondary transmission of Hi among children (e.g., to household contacts and in child care facilities) (1,2) led to the Advisory Committee on Immunization Practices (ACIP) recommendation for antibiotic chemoprophylaxis to prevent Hib disease in certain circumstances.* High Hib vaccination coverage since the 1990s has substantially reduced Hib disease, and other serotypes now account for most Hi-associated invasive disease in the United States (3). Nevertheless, CDC does not currently recommend chemoprophylaxis for contacts of persons with invasive disease caused by serotypes other than Hib and by NTHi (non-b Hi). Given this changing epidemiology, U.S. surveillance data were reviewed to investigate secondary cases of invasive disease caused by Hi. The estimated prevalence of secondary transmission was 0.32% among persons with encapsulated Hi disease (≤60 days of one another) and 0.12% among persons with NTHi disease (≤14 days of one another). Isolates from all Hi case pairs were genetically closely related, and all patients with potential secondary infection had underlying medical conditions. These results strongly suggest that secondary transmission of non-b Hi occurs. Expansion of Hi chemoprophylaxis recommendations might be warranted to control invasive Hi disease in certain populations in the United States, but further analysis is needed to evaluate the potential benefits against the risks, such as increased antibiotic use.

A Case of Acute Non-typeable Hemophilus influenza Infective Endocarditis in a Patient with Hypocomplementemia

Hemophilus influenzae is a gram-negative bacteria responsible for significant cases of invasive infections, especially in the pediatric population and in immunosuppressed adult patients. Before vaccination, most cases were frequently caused by capsulated or typeable variants. Due to the absence of effective vaccination against the nontypeable variant, it is now responsible for most invasive infections. Predisposing risk factors in adults include asplenia, hypocomplementemia, cancer, human immunodeficiency virus infection, and chronic cardiopulmonary disease. Immunity to the nontypeable variants causing disease is perplexing and not yet wholly described as they are genetically diverse. Infective endocarditis (IE) is a cardiac infection with devastating consequences if not detected earlier and treated appropriately. Gram-positive bacteria are the primary cause of IE overall, followed by gram-negative bacteria. Hemophilus species belong to the HACEK group of gram-negative bacteria responsible for causing IE in the pediatric population more than in adults. Hemophilus species, especially the nontypeable variant, is a rare cause of IE in adults. Here we present a case of IE due to Nontypeable Hemophilus influenzae in a 49-year-old caucasian male with hypocomplementemia.

Evaluation of the World Health Organization Global Invasive Bacterial Vaccine-Preventable Disease (IB-VPD) Surveillance Network's Laboratory External Quality Assessment Programme, 2014-2019

Introduction. In 2009, the World Health Organization (WHO) established the Global Invasive Bacterial Vaccine Preventable Disease (IB-VPD) Surveillance Network (GISN) to monitor the global burden and aetiology of bacterial meningitis, pneumonia and sepsis caused by Haemophilus influenzae (Hi), Neisseria meningitidis (Nm) and Streptococcus pneumoniae (Sp).Hypothesis/Gap Statement. The GISN established an external quality assessment (EQA) programme for the characterization of Hi, Nm and Sp by culture and diagnostic PCR.Aim. To assess the performance of sentinel site laboratories (SSLs), national laboratories (NLs) and regional reference laboratories (RRLs) between 2014 and 2019 in the EQA programme.Methodology. Test samples consisted of bacterial smears for Gram-staining, viable isolates for identification and serotyping or serogrouping (ST/SG), plus simulated cerebrospinal fluid (CSF) samples for species detection and ST/SG by PCR. SSLs and NLs were only required to analyse the slides for Gram staining and identify the species of the live isolates. RRLs, and any SLs and NLs that had the additional laboratory capacity, were also required to ST/SG the viable isolates and analyse the simulated CSF samples.Results. Across the period, 69-112 SS/NL labs and eight or nine RRLs participated in the EQA exercise. Most participants correctly identified Nm and Sp in Gram-stained smears but were less successful with Hi and other species. SSLs/NLs identified the Hi, Nm and Sp cultures well and also submitted up to 56 % of Hi, 62 % of Nm and 33 % of Sp optional ST/SG results each year. There was an increasing trend in the proportion of correct results submitted over the 6 years for Nm and Sp. Some SSLs/NLs also performed the optional detection and ST/SG of the three organisms by PCR in simulated CSF from 2015 onwards; 89-100 % of the CSF samples were correctly identified and 76-93 % of Hi-, 90-100 % of Nm- and 75-100 % of Sp-positive samples were also correctly ST/SG across the distributions. The RRLs performed all parts of the EQA to a very high standard, with very few errors across all aspects of the EQA.Conclusion. The EQA has been an important tool in maintaining high standards of laboratory testing and building of laboratory capacity in the GISN.

Epidemiology of invasive Haemophilus influenzae serotype a disease in the North American Arctic, 2006-2017

Invasive Haemophilus influenzae type a (iHia) disease was detected in Alaska and Northern Canada in 2002 and 2000, respectively. From 2006 to 2017, 164 iHia cases (Alaska=53, Northern Canada=111) were reported. Rates of iHia disease per 100,000 persons were higher in Northern Canada compared to Alaska and were significantly higher in Indigenous (Alaska 2.8, Northern Canada 9.5) compared to non-Indigenous populations (Alaska 0.1, Northern Canada=0.4). Disease rates were highest in Indigenous children <2 years of age (Alaska 56.2, Northern Canada=144.1) and significantly higher than in non-Indigenous children <2 (Alaska 0.1, Northern Canada 0.4). The most common clinical presentation in children <5 years was meningitis of age and pneumonia in persons ≥5 years old. Most patients were hospitalised (Alaska=87%, Northern Canada=89%) and fatality was similar (Alaska=11%, Northern Canada=10%). MLST testing showed sequence types ST23 and ST576 in Northern Canada and ST576, ST23 and ST56 in Alaska. Alaska and Northern Canada have high rates of iHia disease. A vaccine is needed in these regions to protect young children.

Immunoinformatics design of multi-epitope peptide-based vaccine against Haemophilus influenzae strain using cell division protein

Haemophilus influenzae is a pathogen that causes invasive bacterial infections in humans. The highest prevalence lies in both young children and adults. Generally, there are no vaccines available that target all the strains of Haemophilus influenzae. Hence, the purpose of this research is to employ bioinformatics and immunoinformatics approaches to design a Multi-Epitope Vaccine candidate employing the pathogenic cell division protein FtsN that specifically combat all the Haemophilus influenzae strains. The current research focuses on developing subunit vaccine in contrast to vaccines generated from the entire pathogen. This will be accomplished by combining multiple bioinformatics and immunoinformatics approaches. As a result, prospective T cells (helper T lymphocyte and cytotoxic T lymphocytes) and B cells epitopes were investigated. The human leukocyte antigen allele having strong associations with the antigenic and overlapping epitopes were chosen, with 70% of the total coverage of the world population. To construct a linked vaccine design, multiple linkers were used. To increase the immunogenic profile, an adjuvant was linked using EAAAK linker. The final vaccine construct with 149 amino acids was obtained after adjuvants and linkers were added. The developed Multi-Epitope Vaccine has a high antigenicity as well as viable physiochemical features. The 3D conformation was modeled and undergoes refinement and validation using bioinformatics methods. Furthermore, protein-protein molecular docking analysis was performed to predict the effective binding poses of Multi-Epitope Vaccine with the Toll-like receptor 4 protein. Besides, vaccine underwent the codon translational optimization and computational cloning to verify the reliability and proper Multi-Epitope Vaccine expression. In addition, it is necessary to conduct experiments and research in the laboratory to demonstrate that the vaccine that has been developed is immunogenic and protective.

Laboratory surveillance of invasive Haemophilus influenzae disease in Argentina, 2011-2019

The incorporation of Haemophilus influenzae type b (Hib) vaccine into the Argentine National Immunization Program in 1998 resulted in a dramatic decrease in the incidence of invasive disease due to this serotype. We assessed 1405 H. influenzae (Hi) isolates causing invasive infections referred to the National Reference Laboratory between 2011 and 2019. Non-encapsulated Hi were the most common strains (44.5%), followed by types b (41.1%) and a (10.0%). Significant increase in the proportion of type b was observed, from 31.2% in 2011, to 50% in 2015, correlating with the peak incidence rate, later decreasing to 33.6% by 2019. We compared the genetic relationship between clones circulating during the period of increased Hib incidence (2011-2015) and those of the prevaccination-transition period (1997-1998). Four pulsotypes predominated in both periods, G, M, P and K, G being the most common. Multi-locus sequence typing revealed that the 4 pulsotypes belonged to ST6, or one of its simple or double locus variants. Isolates from fully vaccinated individuals did not differ from those of the rest of the population studied. After ruling out aspects associated with emergence of specific clones, we concluded that factors such as low booster coverage rates, delayed vaccination schedules and use of different vaccines may have contributed to the reemergence of Hib infections.

Fetal Loss and Preterm Birth Caused by Intraamniotic Haemophilus influenzae Infection, New Zealand

H. influenzae is as a rare but major cause of pregnancy-associated invasive disease.

Invasive Haemophilus influenzae infection during pregnancy can cause preterm birth and fetal loss, but the mechanism is unclear. We investigated 54 cases of pregnancy-associated invasive H. influenzae disease in 52 unique pregnancies in the Auckland region of New Zealand during October 1, 2008‒September 30, 2018. Intraamniotic infection was identified in 36 (66.7%) of 54 cases. Outcome data were available for 48 pregnancies. Adverse pregnancy outcomes, defined as fetal loss, preterm birth, or the birth of an infant requiring intensive/special care unit admission, occurred in 45 (93.8%) of 48 (pregnancies. Fetal loss occurred in 17 (35.4%) of 48 pregnancies, before 24 weeks’ gestation in 13 cases, and at >24 weeks’ gestation in 4 cases. The overall incidence of pregnancy-associated invasive H. influenzae disease was 19.9 cases/100,000 births, which exceeded the reported incidence of pregnancy-associated listeriosis in New Zealand. We also observed higher rates in younger women and women of Māori ethnicity.

Molecular epidemiology and antibiotic resistance profiles of invasive Haemophilus influenzae from Norway 2017-2021

Invasive Haemophilus influenzae (Hi) disease has decreased in countries that included Hi type b (Hib) vaccination in their childhood immunization programs in the 1990s. Non-typeable (NT) and non-b strains are now the leading causes of invasive Hi disease in Europe, with most cases reported in young children and the elderly. Concerningly, no vaccines toward such strains are available and beta-lactam resistance is increasing. We describe the epidemiology of invasive Hi disease reported to the Norwegian Surveillance System for Communicable Diseases (MSIS) (2017-2021, n = 407). Whole-genome sequencing (WGS) was performed on 245 isolates. We investigated the molecular epidemiology (core genome phylogeny) and the presence of antibiotic resistance markers (including chromosomal mutations associated with beta-lactam or quinolone resistance). For isolates characterized with both WGS and phenotypic antibiotic susceptibility testing (AST) (n = 113) we assessed correlation between resistance markers and susceptibility categorization by calculation of sensitivity, specificity, and predictive values. Incidence rates of invasive Hi disease in Norway ranged from 0.7 to 2.3 per 100,000 inhabitants/year (mean 1.5 per 100,000) and declined during the COVID-19 pandemic. The bacterial population consisted of two major phylogenetic groups with subclustering by serotype and multi-locus sequence type (ST). NTHi accounted for 71.8% (176). The distribution of STs was in line with previous European reports. We identified 13 clusters, including four encapsulated and three previously described international NTHi clones with bla TEM-1 (ST103) or altered PBP3 (rPBP3) (ST14/IIA and ST367/IIA). Resistance markers were detected in 25.3% (62/245) of the isolates, with bla TEM-1 (31, 50.0%) and rPBP3 (28, 45.2%) being the most frequent. All isolates categorized as resistant to aminopenicillins, tetracycline or chloramphenicol possessed relevant resistance markers, and the absence of relevant substitutions in PBP3 and GyrA/ParC predicted susceptibility to cefotaxime, ceftriaxone, meropenem and quinolones. Among the 132 WGS-only isolates, one isolate had PBP3 substitutions associated with resistance to third-generation cephalosporins, and one isolate had GyrA/ParC alterations associated with quinolone resistance. The detection of international virulent and resistant NTHi clones underlines the need for a global molecular surveillance system. WGS is a useful supplement to AST and should be performed on all invasive isolates.

Invasive Haemophilus influenzae disease among adults in Japan during 2014-2018

PURPOSE

We describe the epidemiology of invasive Haemophilus influenzae disease (IHD) among adults in Japan.

METHODS

Data for 200 adult IHD patients in 2014-2018 were analyzed. The capsular type of H. influenzae was determined by bacterial agglutination and polymerase chain reaction (PCR), and non-typeable Haemophilus influenzae (NTHi) was identified by PCR.

RESULTS

The annual incidence of IHD (cases per 100,000 population) was 0.12 for age 15-64 years and 0.88 for age ≥ 65 years in 2018. The median age was 77 years, and 73.5% were aged ≥ 65 years. About one-fourth of patients were associated with immunocompromising condition. The major presentations were pneumonia, followed by bacteremia, meningitis and other than pneumonia or meningitis (other diseases). The case fatality rate (CFR) was 21.2% for all cases, and was significantly higher in the ≥ 65-year group (26.1%) than in the 15-64-year group (7.5%) (p = 0.013). The percentage of cases with pneumonia was significantly higher in the ≥ 65-year group than in the 15-64-year group (p < 0.001). The percentage of cases with bacteremia was significantly higher in the 15-64-year group than in the ≥ 65-year group (p = 0.027). Of 200 isolates, 190 (95.0%) were NTHi strains, and the other strains were encapsulated strains. 71 (35.5%) were resistant to ampicillin, but all were susceptible to ceftriaxone.

CONCLUSION

The clinical presentations of adult IHD patients varied widely; about three-fourths of patients were age ≥ 65 years and their CFR was high. Our findings support preventing strategies for IHD among older adults, including the development of NTHi vaccine.

Antimicrobial Susceptibility Survey of Invasive Haemophilus influenzae in the United States in 2016

Antibiotics are important for the treatment and prevention of invasive Haemophilus influenzae disease. Reduced susceptibility to clinically relevant drugs, except ampicillin, has been uncommon in the United States. Susceptibility of 700 invasive H. influenzae isolates, collected through population-based surveillance during 2016, was assessed for 15 antibiotics using broth microdilution, according to the CLSI guidelines; a subset of 104 isolates were also assessed for rifampin susceptibility using Etest. Genomes were sequenced to identify genes and mutations known to be associated with reduced susceptibility to clinically relevant drugs. A total of 508 (72.6%) had reduced susceptibility to at least one antibiotic and more than half of the isolates exhibited reduced susceptibility to only one (33.6%) or two (21.6%) antibiotic classes. All tested isolates were susceptible to rifampin, a chemoprophylaxis agent, and <1% (n = 3) of isolates had reduced susceptibility to third generation cephalosporins, which are recommended for invasive disease treatment. In contrast, ampicillin resistance was more common (28.1%) and predominantly associated with the detection of a β-lactamase gene; 26.2% of isolates in the collection contained either a TEM-1 or ROB-1 β-lactamase gene, including 88.8% of ampicillin-resistant isolates. β-lactamase negative ampicillin-resistant (BLNAR) isolates were less common and associated with ftsI mutations; resistance to amoxicillin-clavulanate was detected in <2% (n = 13) of isolates. The proportion of reduced susceptibility observed was higher among nontypeable H. influenzae and serotype e than other serotypes. US invasive H. influenzae isolates remain predominantly susceptible to clinically relevant antibiotics except ampicillin, and BLNAR isolates remain uncommon. IMPORTANCE Antibiotics play an important role for the treatment and prevention of invasive Haemophilus influenzae disease. Antimicrobial resistance survey of invasive H. influenzae isolates collected in 2016 showed that the US H. influenzae population remained susceptible to clinically relevant antibiotics, except for ampicillin. Detection of approximately a quarter ampicillin-resistant and β-lactamase containing strains demonstrates that resistance mechanisms can be acquired and sustained within the H. influenzae population, highlighting the continued importance of antimicrobial resistance surveillance for H. influenzae to monitor susceptibility trends and mechanisms of resistance.

Naturally acquired antibody against Haemophilus influenzae type a in pediatric saliva

We developed a salivary assay for the detection of naturally acquired IgA antibody against Haemophilus influenzae type a (Hia) capsular polysaccharide in healthy Indigenous children from Northwestern Ontario, Canada. Hia-specific IgA antibody was detected in the saliva of 93% of Indigenous children aged 2-7 years.

Epidemiology and burden of Haemophilus influenzae disease in Thai children before implementation of the routine immunisation programme: A National Health Data Analysis

OBJECTIVES

To conduct the first pre-Haemophilus influenzae (Hi) type b (Hib) immunisation programme-based epidemiological study using national health data.

METHODS

We analysed National Health Security Office data, which cover 72% of the Thai population. The study population included children aged <18 years admitted for Hi disease from 2015 to 2019. Hi disease diagnosis and death were based on the International Statistical Classification of Diseases and Related Health Problems (10th revision) hospital discharge summary codes. We estimated the hospital cost per admission using diagnosis-related grouping with a global budget.

RESULTS

A total of 1125 children aged <18 years were admitted for Hi disease. During the 5-year-study, the annual incidence of Hi disease varied from 1.5 to 1.9 per 100,000 children, with an overall case fatality rate (CFR) of 2%. Pneumonia was the most common clinical form, followed by meningitis and sepsis. The incidence, clinical forms and severity of Hi disease were age specific. Infant CFR was higher than that of other age groups. The incidence of Hi disease in children aged <5 years was 4.9 per 100,000 (CFR = 2.0%). Sepsis was the primary cause of infant death, whereas pneumonia was the cause of death in children aged >5 years. The hospital cost ranged from 25,000 to 30,000 THB per admission.

CONCLUSIONS

This analysis provided epidemiological data of Hi in Thai children before the Hib routine immunisation programme. The incidence of Hi disease was lower than that previously speculated. Our results could facilitate an assessment of the impact of Hib immunisation programme in Thailand.

Phylogenetic Structure and Comparative Genomics of Multi-National Invasive Haemophilus influenzae Serotype a Isolates

Recent reports have indicated a rise of invasive disease caused by Haemophilus influenzae serotype a (Hia) in North America and some European countries. The whole-genome sequences for a total of 410 invasive Hia isolates were obtained from 12 countries spanning the years of 1998 to 2019 and underwent phylogenetic and comparative genomic analysis in order to characterize the major strains causing disease and the genetic variation present among factors contributing to virulence and antimicrobial resistance. Among 410 isolate sequences received, 408 passed our quality control and underwent genomic analysis. Phylogenetic analysis revealed that the Hia isolates formed four genetically distinct clades: clade 1 (n = 336), clade 2 (n = 13), clade 3 (n = 3) and clade 4 (n = 56). A low diversity subclade 1.1 was found in clade 1 and contained almost exclusively North American isolates. The predominant sequence types in the Hia collection were ST-56 (n = 125), ST-23 (n = 98) and ST-576 (n = 51), which belonged to clade 1, and ST-62 (n = 54), which belonged to clade 4. Clades 1 and 4 contained predominantly North American isolates, and clades 2 and 3 predominantly contained European isolates. Evidence of the presence of capsule duplication was detected in clade 1 and 2 isolates. Seven of the virulence genes involved in endotoxin biosynthesis were absent from all Hia isolates. In general, the presence of known factors contributing to β-lactam antibiotic resistance was low among Hia isolates. Further tests for virulence and antibiotic susceptibility would be required to determine the impact of these variations among the isolates.

Direct Real-Time PCR for the Detection and Serotyping of Haemophilus influenzae without DNA Extraction

To monitor the burden and changes in Haemophilus influenzae (Hi) disease, direct real-time PCR (drt-PCR) assays have been developed for Hi detection in monoplex form and its six serotypes in triplex form, directly from cerebrospinal fluid (CSF) specimens. These assays target the phoB gene for the species detection (Hi-phoB) and serotype-specific genes in region II of the capsule biosynthesis locus (Hi-abf and Hi-cde), identified through comparative analysis of Hi and non-Hi whole-genome sequences. The lower limit of detection (LLD) is 293 CFU/mL for the Hi-phoB assay and ranged from 11 to 130 CFU/mL for the triplex serotyping assays. Using culture as a reference method, the sensitivity and specificity of Hi-phoB, Hi-abf, and Hi-cde were 100%. Triplex serotyping assays also showed 100% agreement for each serotype compared to their corresponding monoplex serotyping assay. These highly sensitive and specific drt-PCR assays do not require DNA extraction and thereby reduce the time, cost, and handling required to process CSF specimens. Furthermore, triplex drt-PCR assays combine the detection of three serotypes in a single reaction, further improving testing efficiency, which is critical for laboratories that process high volumes of Hi specimens for surveillance and diagnostic purposes.

Comparative pangenome analysis of capsulated Haemophilus influenzae serotype f highlights their high genomic stability

Haemophilus influenzae is an opportunistic pathogen adapted to the human respiratory tract. Non-typeable H. influenzae are highly heterogeneous, but few studies have analysed the genomic variability of capsulated strains. This study aims to examine the genetic diversity of 37 serotype f isolates from the Netherlands, Portugal, and Spain, and to compare all capsulated genomes available on public databases. Serotype f isolates belonged to CC124 and shared few single nucleotide polymorphisms (SNPs) (n = 10,999), but a high core genome (> 80%). Three main clades were identified by the presence of 75, 60 and 41 exclusive genes for each clade, respectively. Multi-locus sequence type analysis of all capsulated genomes revealed a reduced number of clonal complexes associated with each serotype. Pangenome analysis showed a large pool of genes (n = 6360), many of which were accessory genome (n = 5323). Phylogenetic analysis revealed that serotypes a, b, and f had greater diversity. The total number of SNPs in serotype f was significantly lower than in serotypes a, b, and e (p < 0.0001), indicating low variability within the serotype f clonal complexes. Capsulated H. influenzae are genetically homogeneous, with few lineages in each serotype. Serotype f has high genetic stability regardless of time and country of isolation.

Nasopharyngeal carriage of Haemophilus influenzae among adults with co-morbidities

After the widespread use of Haemophilus influenzae type b (Hib) vaccine, H. influenzae invasive disease is now commonly due to non-encapsulated (NTHi), affecting mostly the youngest and the elderly. The objective of this study was to investigate H. influenzae nasopharyngeal carriage rate in adults with co-morbidities and possible associated risk factors.

METHODS

Patients aged >50 years with co-morbidities attending medical centres were examined. A nasopharyngeal swab was analysed for H. influenzae presence by cultural and molecular methods (RT-PCR). Univariable and multivariable analysis of risk factors for H. influenzae carriage were performed. Serotype of isolates was determined by PCR capsular genotyping. Minimum inhibitory concentration (MIC) was determined by MIC gradient test and β-lactamase production was detected by the nitrocephin test. Genotyping was performed by Multilocus sequence typing (MLST). Phylogenetic relationships among carriage and invasive NTHi strains were assessed.

RESULTS

Among 248 enrolled patients (median age: 73 years), the carriage rate was 5.6% and 10.5% by cultural method or RT-PCR, respectively. Colonization with H. influenzae was significantly associated with the presence of acute respiratory symptoms (adjusted OR = 12.16, 95% CI: 3.05-48.58, p < 0.001). All colonizing isolates were NTHi. Three isolates (3/14, 21.4%) were resistant to ampicillin and beta-lactamase positive. MLST revealed a high degree of genetic diversity, with 11 different STs from 14 isolates. Eight out of the 11 (72.7%) STs were shared among carriage and invasive isolates.

CONCLUSIONS

Adults ≥50 years old with co-morbidities are occasionally colonized by H. influenzae, even if the presence of co-morbidities is not a risk factor for colonization. The presence of acute respiratory symptoms is the only factor associated with H. influenzae colonization. Colonizing H. influenzae are all NTHi. Colonizing H. influenzae often belong to the same STs of invasive disease isolates.

Epidemiology and population structure of Haemophilus influenzae causing invasive disease

This study provides an update on invasive Haemophilus influenzae disease in Bellvitge University Hospital (2014–2019), reporting its evolution from a previous period (2008–2013) and analysing the non-typeable H. influenzae (NTHi) population structure using a clade-related classification. Clinical data, antimicrobial susceptibility and serotyping were studied and compared with those of the previous period. Population structure was assessed by multilocus sequence typing (MLST), SNP-based phylogenetic analysis and clade-related classification. The incidence of invasive H. influenzae disease remained constant between the two periods (average 2.07 cases per 100 000 population), while the 30 day mortality rate decreased (20.7–14.7 %, respectively). Immunosuppressive therapy (40 %) and malignancy (36 %) were the most frequent comorbidities. Ampicillin and fluoroquinolone resistance rates had increased between the two periods (10–17.6 % and 0–4.4 %, respectively). NTHi was the main cause of invasive disease in both periods (84.3 and 85.3 %), followed by serotype f (12.9 and 8.8 %). NTHi displayed high genetic diversity. However, two clusters of 13 (n=20) and 5 sequence types (STs) (n=10) associated with clade V included NTHi strains of the most prevalent STs (ST3 and ST103), many of which showed increased frequency over time. Moreover, ST103 and ST160 from clade V were associated with β-lactam resistance. Invasive H. influenzae disease is uncommon, but can be severe, especially in the elderly with comorbidities. NTHi remains the main cause of invasive disease, with ST103 and ST160 (clade V) responsible for increasing β-lactam resistance over time.

Laboratory diagnosis of bacterial meningitis by direct detection, serotyping and Next Generation Sequencing: How 10 years of testing in New York State has evolved to improve laboratory diagnosis and public health

Since 2005, the Wadsworth Center (WC) has provided molecular testing on cerebrospinal fluid (CSF) and whole blood specimens in close collaboration with epidemiologists in New York State and New York City. In this study, we analyzed 10 years of data to demonstrate the significant value of utilizing molecular methods to assess patient specimens for etiologic agents of bacterial meningitis. A comprehensive molecular testing algorithm to detect and serotype/serogroup bacterial agents known to cause bacterial meningitis (Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae and Streptococcus agalactiae) has evolved, and retrospective specimen testing has been essential for each improvement. Over a ten-year span from 2010 to 2019 the WC received 831 specimens from 634 patients with suspected bacterial meningitis. Real-time PCR was positive for at least one of the agents in 223 (27%) specimens from 183 patients (29%). Of the 223 positives, 146 (66%) were further characterized by real-time PCR into serogroup/serotype. Additionally, examination of 131 paired specimens of CSF and whole blood from the same patients found better detection in CSF, but whole blood is a useful alternative for diagnosis when CSF is not available. For specimens initially PCR-negative, 16S rDNA Sanger sequencing was requested by the submitter for 146 cases resulting in the identification of bacterial agents in an additional 24 (16%) specimens. In a retrospective study, Next Generation Sequencing (NGS) was evaluated for the detection of pathogens in 53 previously tested PCR-negative CSF specimens and identified bacteria in 14 (26%) specimens. This molecular testing algorithm has provided clinicians a diagnosis when culture is negative with the potential to guide therapy. It has also aided public health in determining when antibiotic prophylaxis was needed, augmented surveillance data to yield a fuller picture of community prevalence, and highlighted gaps in the spectrum of agents that cause bacterial meningitis.

Atypical Presentation of Haemophilus influenzae Septic Arthritis: A Case Report

INTRODUCTION

Septic arthritis is a destructive form of acute arthritis that requires expeditious recognition. as delayed treatment yields significant morbidity and mortality.

CASE REPORT

A 40-year-old male presented to the emergency department with right elbow pain. Examination revealed tachycardia, swelling, redness, tenderness, and decreased range of motion of the right humeroulnar joint. Synovial fluid analysis was consistent with an inflammatory etiology, but blood and joint cultures ultimately revealed Haemophilus influenzae.

DISCUSSION

This case highlights the importance of trusting clinical findings over laboratory evidence in patients with suspected septic arthritis.

Invasive bacterial diseases in northern Canada, 1999 to 2018

Background

The International Circumpolar Surveillance (ICS) program conducts surveillance on five invasive bacterial diseases: pneumococcal disease (IPD), group A streptococcus (iGAS), Haemophilus influenzae (Hi), meningococcal disease (IMD) and group B streptococcus (GBS). Invasive bacterial diseases have a higher burden of disease in northern populations than the rest of Canada.

Methods

To describe the epidemiology of invasive bacterial diseases in northern Canada from 1999 to 2018, data for IPD, iGAS, Hi, IMD and GBS were extracted from the ICS program and the Canadian Notifiable Diseases Surveillance System (CNDSS) and analyzed.

Results

The annualized incidence rates for IPD, iGAS, Hi, GBS and IMD were 23.3, 10.5, 8.9, 1.9 and 1.1 per 100,000 population, respectively. The incidence of IPD, iGAS and Hi serotype b were 2.8, 3.2 and 8.8 times higher, respectively, in northern Canada than in the rest of Canada. Rates of disease decreased statistically significantly for IPD (β=-0.02) and increased statistically for iGAS (β=0.08) and Hi serotype a (β=0.04) during the study period. In Northern Canada, the annualized incidence rates for IPD, iGAS and Hi were statistically higher for Indigenous residents than for non-Indigenous residents. The highest incidence rates were among the very young and older age groups.

Conclusion

Invasive bacterial diseases represent a high burden of disease in Canada's northern populations. Indigenous peoples, children and seniors are particularly at risk.

Racial Disparities in Invasive Haemophilus influenzae Disease-United States, 2008-2017

BACKGROUND

Since the introduction of Haemophilus influenzae serotype b (Hib) conjugate vaccines in the United States, invasive H. influenzae disease epidemiology has changed, and racial disparities have not been recently described.

METHODS

Active population- and laboratory-based surveillance for H. influenzae was conducted through Active Bacterial Core surveillance at 10 US sites. Data from 2008-2017 were used to estimate projected nationwide annual incidence, as cases per 100 000.

RESULTS

During 2008-2017, Active Bacterial Core surveillance identified 7379 H. influenzae cases. Of 6705 patients (90.9%) with reported race, 76.2% were White, 18.6% were Black, 2.8% were Asian/Pacific Islander, and 2.4% were American Indian or Alaska Native (AI/AN). The nationwide annual incidence was 1.8 cases/100 000. By race, incidence was highest among AI/AN populations (3.1) and lowest among Asian/Pacific Islander populations (0.8). Nontypeable H. influenzae caused the largest incidence within all races (1.3), with no striking disparities identified. Among AI/AN children aged <5 years, incidence of H. influenzae serotype a (Hia) was 16.7 times higher and Hib incidence was 22.4 times higher than among White children. Although Hia incidence was lower among White and Black populations than among AI/AN populations, Hia incidence increased 13.6% annually among White children and 40.4% annually among Black children aged <5 years.

CONCLUSIONS

While nontypeable H. influenzae causes the largest H. influenzae burden overall, AI/AN populations experience disproportionately high rates of Hia and Hib, with the greatest disparity among AI/AN children aged <5 years. Prevention tools are needed to reduce disparities affecting AI/AN children and address increasing Hia incidence in other communities.

Increased Incidence of Invasive Haemophilus influenzae Disease Driven by Non-Type B Isolates in Ontario, Canada, 2014 to 2018

Haemophilus influenzae can cause serious invasive disease. We report the epidemiology and antimicrobial susceptibility of invasive H. influenzae in Ontario, Canada, from 2014 to 2018 from laboratory-based data. Blood was the most common specimen source (89.5%). Consistent with widespread vaccination against serotype b (Hib), the incidence of Hib in Ontario remained low (0.04 cases per 100,000 population). H. influenzae disease primarily afflicted those <1 and ≥65 years of age. From 2014 to 2018, cases of invasive H. influenzae increased 5.6%, from 1.67 to 2.06 cases per 100,000 population, the majority of which were attributed to a 7.6% increase in the incidence of H. influenzae in those ≥65 years old. H. influenzae disease was primarily caused by nontypeable H. influenzae (NTHi) (74.2%) and, to a much lesser extent, serotype a (Hia) (8.9%) and serotype f (Hif) (10.2%). Serotype-dependent trends in antimicrobial susceptibility were observed. Hia and Hif isolates were predominantly susceptible to all antibiotics tested, while 27.2% of NTHi isolates were nonsusceptible to ampicillin. Resistance to ceftriaxone and meropenem, first-line antibiotics for invasive disease treatment, was nonexistent. The incidence of invasive H. influenzae in Ontario is increasing. The incidence and antimicrobial susceptibility of all serotypes and nontypeable H. influenzae should be monitored. IMPORTANCE H. influenzae can cause serious invasive, life-threatening disease and is considered 1 of 12 priority pathogens by the World Health Organization. Widespread vaccination against H. influenzae serotype b (Hib) has resulted in very low incidence of Hib in Ontario and other regions that have vaccination programs. However, the epidemiology of non-Hib serotypes and nontypeable H. influenzae (NTHi) remains poorly understood. Here, we describe the epidemiology of all invasive H. influenzae isolates (N = 1,338) received by our laboratory over the 5-year period and report on the antimicrobial susceptibility patterns by serotype. Overall, we observed an increase in the incidence of invasive disease over the study period, primarily driven by NTHi. Serotype-dependent trends in antimicrobial susceptibility were also observed. This work contributes to the global understanding of H. influenzae epidemiology and antimicrobial resistance and is additionally important for further vaccine planning initiatives.

Hib Vaccines: Their Impact on Haemophilus influenzae Type b Disease

Haemophilus influenzae serotype b (Hib) is an important cause of serious, invasive infections, particularly in young children. Since 1985, a series of vaccines composed of the type b capsular polysaccharide polyribosylribitol phosphate (PRP), followed by PRP conjugated to various proteins, have been licensed for use in the United States and worldwide. The conjugated vaccines offer increased immunogenicity and prolonged durability of immune protection compared to the plain PRP vaccine and increasingly are combined with other childhood vaccines for decreased cost and increased ease of vaccination. Hib vaccines have a very favorable safety profile, have been found to be either cost-saving or cost-effective by many public health agencies, and, in most countries, are initiated during early infancy as part of routine childhood immunization programs. As a result of widespread use of the vaccines, the incidence of Hib infections, and their associated morbidity and mortality, has fallen dramatically across the globe. Yet, many children remain unimmunized or underimmunized against Hib, particularly in limited-resource countries. Future efforts to further reduce the disease burden of Hib infections remain a high priority.

Cross-reactivity of Haemophilus influenzae type a and b polysaccharides: molecular modeling and conjugate immunogenicity studies

Haemophilus influenzae is a leading cause of meningitis disease and mortality, particularly in young children. Since the introduction of a licensed conjugate vaccine (targeting the outer capsular polysaccharide) against the most prevalent serotype, Haemophilus influenzae serotype b, the epidemiology of the disease has changed and Haemophilus influenzae serotype a is on the rise, especially in Indigenous North American populations. Here we apply molecular modeling to explore the preferred conformations of the serotype a and b capsular polysaccharides as well as a modified hydrolysis resistant serotype b polysaccharide. Although both serotype b and the modified serotype b have similar random coil behavior, our simulations reveal some differences in the polysaccharide conformations and surfaces which may impact antibody cross-reactivity between these two antigens. Importantly, we find significant conformational differences between the serotype a and b polysaccharides, indicating a potential lack of cross-reactivity that is corroborated by immunological data showing little recognition or killing between heterologous serotypes. These findings support the current development of a serotype a conjugate vaccine.

Impact of Vaccination on Haemophilus influenzae Type b Carriage in Healthy Children Less Than 5 Years of Age in an Urban Population in Nepal

Background

Reduction in detection of asymptomatic carriage of Haemophilus influenzae type b (Hib) can be used to assess vaccine impact. In Nepal, routine vaccination against Hib in children at 6, 10, and 14 weeks of age was introduced in 2009. Before vaccine introduction, Hib carriage was estimated at 5.0% among children aged <13 years in Nepal, with higher rates among children under 5. Large-scale evaluation of Hib carriage in children has not been investigated since the introduction of the pentavalent diphtheria-tetanus-pertussis/Hib/hepatitis B (DTP-Hib-HepB) vaccine in Nepal.

Methods

A total of 666 oropharyngeal swabs were collected between August and December 2018 from healthy children between 6 months and 5 years of age attending the vaccination clinic at Patan Hospital, Kathmandu, Nepal. Of these 666 swabs, 528 (79.3%) were tested for Hib by culture. Demographic and vaccination data were collected.

Results

Among 528 swabs tested for Hib, 100% came from fully vaccinated children. No swabs were positive for Hib (95% confidence interval, .0–.7). The absence of Hib in 2018 suggests vaccine-induced protection against Hib carriage 9 years after vaccine introduction.

Conclusions

Following 3 doses of pentavalent DTP-Hib-HepB vaccine, Hib carriage in children under the age of 5 years in Nepal is no longer common. Ongoing high coverage with Hib vaccine in early childhood is expected to maintain protection against Hib disease in Nepal.

Haemophilus influenzae Prevalence, Proportion of Capsulated Strains and Antibiotic Susceptibility During Colonization and Acute Otitis Media in Children, 2019-2020

BACKGROUND

The objective of this study was to determine the prevalence, proportion of encapsulated strains and antibiotic susceptibility of Haemophilus influenzae isolated from young children.

METHODS

Children, 6 months to 30 months old, were prospectively enrolled from September 2019 to September 2020 at Rochester, NY, pediatric clinics. H. influenzae isolates from nasopharynx (NP) at healthy visits and disease isolates from NP and middle ear fluid (MEF) at onset of acute otitis media (AOM) were characterized by capsular typing, β-lactamase production and antibiotic susceptibility.

RESULTS

Samples from 565 healthy visits and 130 AOM visits were collected. H. influenzae was detected 5.9% and 27% in the NP from healthy and AOM visits, respectively. In the MEF, H. influenzae was isolated in 43% of samples. Eight percent of H. influenzae isolates were encapsulated, 88% type f. Overall 39.7% of isolates were β-lactamase producing; 43% for MEF isolates. Ampicillin, trimethoprim/sulfamethoxazole, erythromycin and clarithromycin nonsusceptibility were found in more than 25% of isolates. None of the encapsulated H. influenzae isolates were positive for β-lactamase production or ampicillin nonsusceptibility. 9.2% of isolates were β-lactamase negative, ampicillin resistant (β-lactamase negative, ampicillin resistant + β-lactamase negative, ampicillin intermediate).

CONCLUSIONS

The prevalence of H. influenzae in the NP of young children is very low at times of health, but H. influenzae is highly prevalent in MEF at onset of AOM. Nontypeable H. influenzae accounts for >90% of all H. influenzae isolates. Type f predominated among encapsulated strains. β-lactamase production and antibiotic nonsusceptibility among H. influenzae strains isolated from the NP and MEF are common.

Molecular Epidemiology of Contemporary Invasive Haemophilus influenzae Isolates in Texas Children

Although vaccination has reduced the incidence of Haemophilus influenzae type b, nontypeable H. influenzae and other encapsulated types remain a health threat. Little is known regarding the contemporary molecular epidemiology of these organisms. We conducted multilocus sequence typing on invasive H. influenzae during a period of increasing incidence.