Carriage of Haemophilus influenzae in the oropharynx of young children and molecular epidemiology of the isolates after fifteen years of H. influenzae type b vaccination in Italy

An infant mouse model of influenza-driven nontypeable Haemophilus influenzae colonization and acute otitis media suitable for preclinical testing of novel therapies

Nontypeable Haemophilus influenzae (NTHi) is a major otitis media (OM) pathogen, with colonization a prerequisite for disease development. Most acute OM is in children <5 years old, with recurrent and chronic OM impacting hearing and learning. Therapies to prevent NTHi colonization and/or disease are needed, especially for young children. Respiratory viruses are implicated in driving the development of bacterial OM in children. We have developed an infant mouse model of influenza-driven NTHi OM, as a preclinical tool for the evaluation of safety and efficacy of clinical therapies to prevent NTHi colonization and the development of OM. In this model, 100% of infant BALB/cARC mice were colonized with NTHi, and all developed NTHi OM. Influenza A virus (IAV) facilitated the establishment of dense (1 × 105 CFU/mL) and long-lasting (6 days) NTHi colonization. IAV was essential for the development of NTHi OM, with 100% of mice in the IAV/NTHi group developing NTHi OM compared with 8% of mice in the NTHi only group. Histological analysis and cytokine measurements revealed that the inflammation observed in the middle ear of the infant mice with OM reflected inflammation observed in children with OM. We have developed the first infant mouse model of NTHi colonization and OM. This ascension model uses influenza-driven establishment of OM and reflects the clinical pathology of bacterial OM developing after a respiratory virus infection. This model provides a valuable tool for testing therapies to prevent or treat NTHi colonization and disease in young children.

Multiple interspecies recombination events documented by whole-genome sequencing in multidrug-resistant Haemophilus influenzae clinical isolates

Introduction

Haemophilus influenzae (Hi) was long known as an easy-to-treat bacterium, but increasing resistance against beta-lactams and other critically important antibiotics is now a growing concern. We describe here the whole-genome sequencing (WGS) analysis of three non-typeable Hi isolates received in 2018-2019 by the Belgian National Reference Centre (NRC) for Haemophilus influenzae, as they presented an unusual multi-resistant profile.

Methods

All three isolates were sequenced by WGS and mapped to the reference isolate Hi Rd KW20. Shorten uptake signal sequences (USSs) known to be associated with homologous recombination were sought in ftsI, murE and murF genes, and inner partial sequences were compared against the blast nucleotide database to look for similarity with other Haemophilus species. Their antimicrobial resistance (AMR) genotype was studied. Core-genome multilocus sequence typing (MLST) was performed on the NTHi database pubMLST to place our isolates in the actual worldwide epidemiology.

Results

The isolates also harboured interspecies recombination patterns in the murF-murE-ftsI region involved in cell wall synthesis. The three isolates were multidrug resistant and two of them were also resistant to amoxicillin-clavulanic acid and showed a reduced susceptibility to meropenem. All three isolates belonged to the MLST clonal complex (CC) 422, and WGS revealed that the three were very similar. They harboured mobile genetic elements (carrying blaTEM-1B, mefA and msrD genes associated with resistance), mutations in gyrA and parC linked to fluoroquinolone resistance as well as remodelling events in ompP2 that might be related to lower carbapenem susceptibility.

Conclusion

The Hi evolution towards antimicrobial multiresistance (AMR) is a complex and poorly understood phenomenon, although probably linked to a large degree to the presence of USSs and exchange within the family Pasteurellaceae. To better understand the respective roles of clonal expansion, horizontal gene transfers, spontaneous mutations and interspecies genetic rearrangements in shaping Hi AMR, both analysis of Hi communities over time within individuals and worldwide monitoring of non-typeable Hi causing infections should be conducted.

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.

Trends in invasive Haemophilus influenzae serotype a disease in England from 2008-09 to 2021-22: a prospective national surveillance study

BACKGROUND

Invasive Haemophilus influenzae serotype a (Hia) disease is rare, with most cases reported among Indigenous populations in North America. In England, national surveillance was enhanced following an increase in laboratory-confirmed invasive Hia disease since the 2016-17 epidemiological year. This study aimed to describe the epidemiological trends, clinical characteristics of cases, and assess potential genomic drivers.

METHODS

Hospital laboratories in England routinely submit invasive H influenzae isolates to the UK Health Security Agency for confirmation and serotyping. In this prospective national surveillance study we contacted the general practitioners and clinicians of all patients with laboratory-confirmed invasive Hia from the 2008-09 to the 2021-22 epidemiological year to complete a clinical questionnaire on demographics, underlying conditions, clinical presentation, complications, outcomes, and travel history of the patient. All Hia invasive isolates from residents in England were included in the study; non-invasive isolates were excluded. Multilocus sequence typing (MLST), whole genome single-nucleotide polymorphism, and k-mer-based analysis of bacterial isolates were performed following Illumina whole-genome sequencing (WGS). Outcomes included epidemiological trends, clinical characteristics of confirmed Hia cases, and genomic analyses.

FINDINGS

From the 2008-09 to the 2021-22 epidemiological years, there were 52 cases of invasive infection with H influenzae serotype a in England (25 [48%] in female patients and 27 [52%] in male patients). There were zero to two annual Hia cases (accounting for <0·5% of serotyped H influenzae isolates) until 2015-16, after which cases increased across England to 19 cases in 2021-22 (incidence 0·03 cases per 100 000), when Hia accounted for 19 (4%) of 484 serotyped H influenzae isolates, 19 (19%) of 100 capsulated cases, and 37% (19 of 52) of all H influenzae cases between 2008-09 and 2021-22. Most of the recent increase in cases occurred among individuals aged 65 years and older (17 [33%] of 52), who typically presented with bacteraemic pneumonia (13 [76%] of 17), and infants younger than 1 year, who had the highest incidence and were more likely to present with meningitis (five [50%] of ten). Overall case fatality rate was 7·7% (95% CI 2·1-19·7; four of 52 patients). WGS found that closely related MLST sequence types ST1511 (20 [39%] of 51), ST23 (13 [25%] of 51), and ST56 (seven [14%] of 51) accounted for most cases, with no evidence of serotype b strains switching capsule to Hia. Duplication of the capsule operon, associated with more severe disease, was present in 32 (80%) of 40 of these sequence types. Analysis of the core and accessory genome content grouped most isolates into a single strain.

INTERPRETATION

The persistent increase in invasive Hia cases across England and across all age groups suggests widespread transmission, consistent with reports from other European countries, and will require close monitoring.

FUNDING

UK Health Security Agency.

Diagnostic utility of oropharyngeal swabs as an alternative to lower respiratory tract samples for PCR-based syndromic testing in patients with community-acquired pneumonia

Syndromic PCR-based analysis of lower respiratory tract (LRT) samples in patients with community-acquired pneumonia (CAP) improves the bacterial yield and time-to-results compared to culture-based methods. However, obtaining adequate sputum samples can be challenging and is frequently not prioritized in the emergency department (ED). In this study, we assess the concordance of microbiological detections between oropharyngeal- (OP) and LRT samples from patients presenting to the ED with CAP using a syndromic PCR-based respiratory panel [Biofire FilmArray Pneumonia plus (FAP plus)]. Paired OP- and high-quality LRT samples were collected from 103 patients with confirmed CAP, who had been included in a randomized controlled trial (NCT04660084) or a subsequent observational study at Haukeland University Hospital, and analyzed using the FAP plus. The LRT samples were obtained mainly by sputum induction (88%). Using the LRT samples as a reference standard, the positive percent agreement (PPA), negative percent agreement (NPA), and overall percent agreement for the most common bacterial pathogens in CAP, Streptococcus pneumoniae and Haemophilus influenzae, were 85%, 99% and 95%, and 86%, 98% and 93%, respectively. For Moraxella catarrhalis, the PPA was lower (74%), while the NPA was 100%. For bacteria that are less likely causes of uncomplicated CAP (e.g., Staphylococcus aureus and Enterobacterales) the results were more divergent. In conclusion, the FAP plus detects the most common CAP pathogens S. pneumoniae and H. influenzae from OP samples with high PPAs and excellent NPAs when compared with LRT samples. For these pathogens, the PPAs for OP samples were higher than previous reports for nasopharyngeal samples. This suggests that analysis of OP samples with syndromic PCR panels could represent an alternative approach for rapid microbiological testing in the ED, especially in patients where LRT samples are difficult to obtain. Divergent results for bacteria that are less likely to cause uncomplicated CAP do, however, emphasize the need for clinical evaluation of positive test results.

MALDI-TOF MS Indirect Beta-Lactamase Detection in Ampicillin-Resistant Haemophilus influenzae

Rapid identification of beta-lactamase-producing strains of Haemophilus influenzae plays key role in diagnostics in clinical microbiology. Therefore, the aim of this study was the rapid determination of beta-lactamase's presence in H. influenzae isolates via indirect detection of degradation ampicillin products using MALDI-TOF MS. H. influenzae isolates were subjected to antibiotic resistance testing using disk diffusion and MIC methodologies. Beta-lactamase activity was tested using MALDI-TOF MS, and results were compared to spectral analysis of alkaline hydrolysis. Resistant and susceptible strains of H. influenzae were distinguished, and strains with a high MIC level were identified as beta-lactamase-producing. Results indicate that MALDI-TOF mass spectrometry is also suitable for the rapid identification of beta-lactamase-producing H. influenzae. This observation and confirmation can accelerate identification of beta-lactamase strains of H. influenzae in clinical microbiology, which can have an impact on health in general.

Molecular epidemiology and antimicrobial resistance of Haemophilus influenzae in Guiyang, Guizhou, China

Background

The widespread use of antimicrobials and Haemophilus influenzae type b (Hib) vaccine worldwide has altered the epidemiological patterns of invasive H. influenzae. Nonetheless, little is currently known on the epidemiological characteristics of H. influenzae in Guiyang, Guizhou, China.

Objective

To determine the serotype distribution, antimicrobial resistance and Multilocus Sequence Typing (MLST) of H. influenzae in hospitalized patients in Guiyang City.

Methods

A total of 196 clinical isolates from hospitalized patients were collected. Serotypes were determined according to the specific capsule gene, bexA, amplified by PCR. According to the guidelines of Clinical and Laboratory Standards Institute (CLSI) 2020 drug susceptibility tested, and the results determined. The chromogenic cephalosporin nitrocefin method was used to detect β-lactamase production, β-lactamase negative, ampicillin-resistant (BLNAR) strains were detected by PCR amplification and sequencing of the penicillin-binding protein 3 (PBP3) locus of ftsI. Multilocus Sequence Typing was performed for molecular typing.

Results

All isolates studied were non-typeable H. influenzae (NTHi). Most patients originated from the pediatrics department (78.6%, 154/196), and suffered from lung with respiratory tract infection (pneumonia and bronchitis, 68.4%, 134/196). The resistance rates of ampicillin, cefaclor and azithromycin were 71.4% (140/196), 36.7% (72/196) and 34.2% (67/196), respectively. 40.3% (79/196) of strains were β-lactamase positive ampicillin-resistant (BLPAR). All BLPAR carried the TEM-1 gene. 9.2% (18/196) were β-lactamase negative ampicillin-resistant strains (BLNAR). The PBP3 mutation was detected in the ampicillin-resistant strains (n = 113), of which 18 belonged to group IIa. A total of 49 sequence types (ST) and 23 clonal complexes (CC) were detected, among which CC107 (ST107, n = 27; ST1002, n = 5; ST1218, n = 5) was the most frequent clonal complexes. BLPAR isolates mostly belonged to ST107 (20/79), while BLNAR was predominantly distributed in ST12 (5/18).

Conclusion

H. influenzae infections are predominately caused by genetically diverse NTHi among hospitalized patients in Guiyang. The prevalence of β-lactamase production and PBP3 mutation may contribute to the high local ampicillin resistance rate.

Bacterial colonization of the upper airways of children positive and negative for SARS-CoV-2 during the COVID-19 pandemic

Background

Our understanding of the influence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on bacterial colonization in the children’s upper nasopharyngeal tract during the coronavirus infectious disease (COVID-19) pandemic is limited. This study aimed to determine whether there were any differences in bacterial colonization between asymptomatic children with or without a positive SARS-CoV-2 quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) results in the community setting.

Methods

A cross-sectional community-based exploratory study was conducted from March to May 2021 in Semarang, Central Java Province, Indonesia. Using stored nasopharyngeal swabs collected from children under 18 years as a contact tracing program, we performed a real-time quantitative (qPCR) for the most important bacterial colonizing pathogens: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and Klebsiella pneumoniae.

Results

Swabs from a total of 440 children were included in this study, of which 228 (51.8%) were RT-qPCR-confirmed SARS-CoV-2 positive. In the 440 children, colonization rates were highest for H. influenzae (61.4%), followed by S. pneumoniae (17.5%), S. aureus (12.0%), and K. pneumoniae (1.8%). The co-occurrence of both S. pneumoniae and H. influenzae in the upper respiratory tract was significantly associated with a SARS-CoV-2 negative RT-qPCR. In contrast, colonization with only S. aureus was more common in SARS-CoV-2-positive children.

Conclusion

Overall, this exploratory study concludes that there is a significant difference in the bacterial nasopharyngeal colonization pattern between SARS-CoV-2 positive and negative in asymptomatic children in the community in Indonesia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07851-z.

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.

The prevalence and influencing factors of the oropharyngeal carriage of Haemophilus influenzae in healthy children in a high-altitude area of China: A cross-sectional study

Haemophilus influenzae is a common commensal organism of the human upper respiratory tract and an important cause of human disease. No data on H influenzae carriage rate has been carried out on the Qinghai-Tibet Plateau of China. This study aims to present the H influenzae carriage rate and influencing factors of H influenzae in healthy children <15 years of age in Qinghai Province, an area located on the Qinghai-Tibet Plateau in China. Oropharyngeal swabs for the detection of H influenzae DNA were collected between September and October 2019. Taqman real-time polymerase chain reaction was used to detect the nucleic acids from the oropharyngeal swabs. Self-designed questionnaires were used to investigate the related information among this group of children. A number of 284 children were enrolled in this study. The carriage rate of H influenzae was 44.7%. The carriage rate in cities was 47.5%, in rural areas was 21.9%, and in pastoral areas was 52.8%. The carriage rate was found to be higher among children of minority ethnic groups than those of Han ethnicity (55.6% vs 38.1%). H influenzae carriage rate was influenced by tobacco smoke exposure (adjusted odds ratio [aOR] = 2.31, 95% CI [confidence interval]: 1.14-4.70), having siblings <5 years of age (aOR = 2.36, 95% CI: 1.21-4.59), respiratory infections during the last 30 days (aOR = 2.37, 95% CI: 1.11-5.06), and parent/guardian education level (aOR = 0.08, 95% CI: 0.02-0.27). H influenzae was highly prevalent in healthy children in Qinghai Province, especially among children of minority ethnicities and those living in pastoral areas. Tobacco smoke exposure, having siblings <5 years of age, and respiratory infections during the last 30 days were risk factors for H influenzae carriage. Parents or guardians having education levels of college or higher was a protective factor for H influenzae carriage. It is of critical importance that the government take effective measures to reduce the carriage rate and the occurrence of H influenzae related diseases in susceptible populations.

Antimicrobial resistance among Haemophilus influenzae isolates responsible for lower respiratory tract infections in Poland, 2005-2019

Haemophilus influenzae is a human-specific pathogen responsible for respiratory tract infections, meningitis, and sepsis. The study aimed to characterize antibiotic resistance in H. influenzae strains isolated from patients with lower respiratory tract infections over 15 years in Poland. The minimum inhibitory concentrations (MICs) of clinically relevant antibiotics were determined by broth microdilution method. Screening for beta-lactam resistance was performed in all isolates following EUCAST recommendation. Finally, relevant changes in penicillin-binding protein 3 (PBP3) were detected by PCR screening. Of the 1481 isolates collected between 2005 and 2019, 12.6%, 0.2%, 17.1%, and 0.2% were resistant to ampicillin, amoxicillin/clavulanate, cefuroxime, and ceftriaxone, respectively. Among them, 74.4% (1102/1481) of isolates were categorized as BLNAS (β-lactamase negative, ampicillin-susceptible), 13.0% (192/1481) as BLNAS with modified PBP3 (mutations in ftsI gene), 2.6% (39/1481) as BLNAR (β-lactamase negative, ampicillin-resistant), and 0.2% had PBP3 modifications typical for high-BLNAR. Production of β-lactamase characterized 9.7% of isolates (8.6% BLPAR-β-lactamase-positive, ampicillin-resistant, and 1.1% BLPACR-β-lactamase-positive, amoxicillin-clavulanate resistant). Three isolates with PBP3 modifications typical for high-BLNAR proved resistant to ceftriaxone (MIC > 0.125 mg/L). Resistance to ciprofloxacin, chloramphenicol, tetracycline, and trimethoprim-sulfamethoxazole was observed in 0.1%, 0.5%, 1.6%, and 24.7% of isolates, respectively. This is the first report of Polish H. influenzae isolates resistant to third-generation cephalosporins. Polish H. influenzae isolates demonstrate similar susceptibility trends as in many other countries. The substantial proportion of β-lactam-resistant isolates and the emergence of those resistant to third-generation cephalosporins are of great concern and should be under surveillance.

Increase in invasive disease caused by Haemophilus influenzae b, the Netherlands, 2020 to 2021

The incidence of most respiratory-transmitted diseases decreased during the COVID-19 pandemic as a result of containment measures. In contrast, in the Netherlands we noted an increase in invasive disease caused by Haemophilus influenzae b (Hib) (from < 0.3/100,000 before 2019 to 0.39 and 0.33/100,000 in 2020 and 2021) in vaccinated and unvaccinated age groups. We did not find a change in vaccine effectiveness against Hib invasive disease (effectiveness > 90%). We discuss factors that may have contributed to this rise.

Cloning and Characterization of Immunological Properties of Haemophilus influenzae Enolase

Haemophilus influenzae is a common organism of the human upper respiratory tract; this bacterium is responsible of a wide spectrum for respiratory infections and can generate invasive diseases such as meningitis and septicemia. These infections are associated with H. influenzae encapsulated serotype b. However, the incidence of invasive disease caused by nontypeable H. influenzae (NTHi) has increased in the post-H. influenzae serotype b (Hib) vaccine era. Currently, an effective vaccine against NTHi is not available; due to this, it is important to find an antigen capable to confer protection against NTHi infection. In this study, 10 linear B cell epitopes and 13 CTL epitopes and a putative plasminogen-binding motif (₂₅₂FYNKENGMY₂₆₀) and the presence of enolase on the surface of different strains of H. influenzae were identified in the enolase sequence of H. influenzae. Both in silico and experimental results showed that recombinant enolase from H. influenzae is immunogenic that could induce a humoral immune response; this was observed mediating the generation of specific polyclonal antibodies anti-rNTHiENO that recognize typeable and nontypeable H. influenzae strains. The immunogenic properties and the superficial localization of enolase in H. influenzae, important characteristics to be considered as a new candidate for the development of a vaccine, were demonstrated.

Characteristics and Antibiotic Resistance of Haemophilus influenzae in Children with Lower Respiratory Tract Infection in Chengdu, China

Background: Haemophilus influenzae is an opportunistic pathogen of the human respiratory tract. Haemophilus influenzae can cause not only respiratory tract infection in children but also otitis media, epiglottitis and sinusitis. With the widespread use of antibiotics, the positive rate of β-lactamase in H. influenzae is increasing, and the rate of antimicrobial resistance is also increasing, which increases the difficulty of clinical treatment. Objectives: To study the infection characteristics of patients and the antibiotic resistance of H. influenzae in lower respiratory tract samples of children in Chengdu, so as to provide a reference for its clinical diagnosis and the rational use of antibiotics. Methods: Sputum samples of 15891 children aged 0-14 years with lower respiratory tract infection were collected. Haemophilus influenzae was cultured and identified, its drug susceptibility tested, and the results determined according to the guidelines of CLSI 2020. Results: A total of 15891 clinical isolate strains in sputum were detected for drug sensitivity from December 2018 to January 2020, of which 5488 were H. influenzae, accounting for 34.54% (5488/15891). The sex of children infected with H. influenzae was not skewed (P > 0.05). The detection rate of H. influenzae was the highest in children aged 7 - 11 months, and the lowest was in the age group ≤ 28 d. The detection rate was the highest in spring and the lowest in autumn. The positive rate of β-lactamase was 92.0%, the resistance rate to ampicillin was 92.0%, the sensitivity to amoxicillin/clavulanate was 70.2%, and the sensitivity to cefotaxime, ofloxacin, tetracycline, chloramphenicol, and rifampicin was more than 90.0%. Conclusions: Children aged 7 months to 14 years were generally susceptible to H. influenzae in spring, and the positive rate of β-lactamase was high. Doctors should refer to the infection characteristics and drug resistance of H. influenzae and choose antibiotics correctly to better control the infection.

Effect of Haemophilus influenzae Type b Vaccination on Nasopharyngeal Carriage Rate in Children, Tehran, 2019

Background

Haemophilus influenzae (H. influenzae) strains, which commonly reside as commensals within the human pharynx and can remain as an asymptomatic carrier, but become invasive leading to pneumonia, septic arthritis, or meningitis. The Pentavac (pentavalent vaccine, manufactured by India, SII (DTwP-HepB-Hib)) was introduced to the Iranian National Immunization Plan in November 2014. The aim of this study is to investigate H. influenzae type b (Hib) carrier rate among children under 6 years old in Tehran.

Methods

This cross-sectional study was performed on 902 children including vaccinated/unvaccinated in the age of 6 months to 6 years, in Tehran. Sampling was performed from July 2019 to September 2019. Nasopharyngeal samples were taken from children by sterile swab. The PCR method was used to extract DNA. Then, all H. influenzae isolates were initially confirmed by molecular tests. BexA was used to distinguish typeable H. influenzae strains from nontypeable Haemophilus influenzae (NTHi).

Results

A total of 902 children were enrolled in the study: 452 were female (51%). H. influenzae carriage rate was 267 (29%), of that 150 samples (16.6%) were typeable. The nasopharyngeal Hib carrier rate in the children was 2.6% (24/902). 262 cases did not receive Hib vaccine. Analysis in nonnursery's children aged 4 to 6 (unvaccinated) years showed that the lower educational level of father, mother, and family number correlated with increased odds of colonization of children with Hib.

Conclusion

Our findings showed a significant decrease (60%) in the overall Hib nasopharyngeal carriage in healthy children under six years after 5 years after the start of Hib vaccination.

Carriage of Haemophilus influenzae among children attending childcare centres in Kuala Lumpur, Malaysia in the post vaccination era: A cross-sectional study

BACKGROUND

Haemophilus influenzae (H. influenzae) is a human upper respiratory tract colonizer which causes wide range of disease especially in children<5 years old and in the elderly. Although worldwide incidence in industrialised countries where Hib vaccination is commonly used has dropped sharply since implementation of H. influenzae type b (Hib) vaccination, there is limited data on the disease burden caused by H. influenzae in Malaysia post vaccination era. A change in predominant serotype from type b to non-b serotypes of H. influenzae in invasive diseases was reported worldwide. We investigated the carriage of H. influenzae post vaccination era among 2-4 years old.

METHODOLOGY

Randomly, we collected 436 oropharyngeal swabs from healthy children aged 2-4 years in 30 registered childcare centres in Kuala Lumpur (August 2018-May 2019). Informed consent and written questionnaires were obtained from parents. H. influenzae was identified by standard microbiological methods. Univariable analysis was carried out to describe variables associated with colonization. All variables with p < 0.25 were included in multivariable logistic regression model. A p value < 0.05 was considered significant.

RESULTS

A higher carriage rate was noted among the unvaccinated children (4/28; 14.3%) compared to vaccinated children (16/326; 4.9%) but were not statistically significant. The serotypes were type a (9; 37.5%), type b (5; 20.8%), type c (3; 12.5%), type d (2; 8%), type e (1; 4.2%) and type f (4; 16.7%). Variables like age, basic sanitation, immunization status, body mass index were included in multivariable logistic regression test since p values in univariate analysis were<0.25. Planned sewage system was found to be significant (Adjusted OR, 0.06; 95% CI, 0.01-0.46; p = 0.006).

CONCLUSION

Fewer carriage rates were observed among children post Hib vaccination era. Hib carriage is still possible after vaccination. The presence non-b serotypes may imply emerging replacement serotypes.

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.

Evaluation of the adequacy of the antimicrobial therapy of invasive Haemophilus influenzae infections: A pharmacokinetic/pharmacodynamic perspective

INTRODUCTION

In Europe, non-typeable H. influenzae (NTHi) is the leading cause of invasive H. influenzae disease in adults and is associated with high mortality. The goal of this study was to determine whether current antimicrobial treatments for H. influenzae infection in Spain are suitable based on their probability of achieving pharmacokinetic/pharmacodynamic (PK/PD) targets.

METHODS

Pharmacokinetic parameters for the antibiotics studied (amoxicillin, amoxicillin/clavulanic acid, ampicillin, cefotaxime, ceftriaxone, imipenem and ciprofloxacin) and susceptibility data for H. influenzae were obtained from literature. A Monte Carlo simulation was used to estimate the probability of target attainment (PTA), defined as the probability that at least a specific value of a PK/PD index is achieved at a certain MIC, and the cumulative fraction of response (CFR), defined as the expected population PTA for a specific drug dose and a specific microorganism population.

RESULTS

Regardless of dosing regimen, all antibiotics yielded CFR values of 100% or nearly 100% for all strains, including BL+, BL- and BLNAR, except amoxicillin and ampicillin for BL+. Thus, if an infection is caused by BL+ strains, treatment with amoxicillin and ampicillin has a high probability of failure (CFR≤8%). For standard doses of amoxicillin, amoxicillin/clavulanic acid and imipenem, PK/PD breakpoints were consistent with EUCAST clinical breakpoints. For the other antimicrobials, PK/PD breakpoints were higher than EUCAST clinical breakpoints.

CONCLUSIONS

Our study confirms by PK/PD analysis that, with the antimicrobials used as empirical treatment of invasive H. influenzae disease, a high probability of therapeutic success can be expected.

Widespread of non-typeable Haemophilus influenzae with high genetic diversity after two decades use of Hib vaccine in China

BACKGROUND

The aim of this study was to analyze the microbiological characteristics of nasopharyngeal carriage Haemophilus influenzae isolates collected from children with respiratory infections in Beijing hospital and Youyang Hospital of China.

METHODS

The serotypes of all isolates were determined using latex agglutinated antisera (a-f). The minimum inhibitory concentrations (MICs) of 11 antibiotics were determined using E-test strips. For the beta-lactamase-negative ampicillin-resistant (BLNAR) isolates, ftsI gene was sequenced based on fragments amplified by PCR. STs of H influenzae isolates were determined by multi-locus sequence typing.

RESULTS

The overall carriage rate of H influenzae in the study population was 9.1% (362/3984). One hundred and ninety H influenzae isolates which were selected in our study were non-typeable (NTHi) and 44 (23.2%) of them were positive for β-lactamase. All isolates were susceptible to ceftriaxone and levofloxacin. Susceptibility rates to erythromycin and sulfamethoxazole-trimethoprim in Beijing were significantly higher than Youyang (P < .05). Thirty-six BLNAR isolates were identified. The MLST analysis showed 108 STs in 190 isolates, the most common of which were ST408 (11, 5.8%), ST914 (10, 5.3%), ST57 (9, 4.7%), and ST834 (6, 3.2%). Twelve STs were detected in both of the study sites, which covered 63 isolates.

CONCLUSIONS

All isolates in the present study were NTHi, which suggested widespread of this type in China. The BLNAR isolates were detected more frequently than before. Because high genetic diversity of NTHi isolates of H influenzae exists worldwide, it is important to continuously monitor these bacteria in the future.

The Effect of the 10-Valent Pneumococcal Nontypeable Haemophilus influenzae Protein D Conjugate Vaccine on H. influenzae in Healthy Carriers and Middle Ear Infections in Iceland

Vaccinations with the 10-valent pneumococcal conjugated vaccine (PHiD-CV) started in Iceland in 2011. Protein D (PD) from H. influenzae, which is coded for by the hpd gene, is used as a conjugate in the vaccine and may provide protection against PD-positive H. influenzae.

Vaccinations with the 10-valent pneumococcal conjugated vaccine (PHiD-CV) started in Iceland in 2011. Protein D (PD) from H. influenzae, which is coded for by the hpd gene, is used as a conjugate in the vaccine and may provide protection against PD-positive H. influenzae. We aimed to evaluate the effect of PHiD-CV vaccination on H. influenzae in children, both in carriage and in acute otitis media (AOM). H. influenzae was isolated from nasopharyngeal swabs collected from healthy children attending 15 day care centers in 2009 and from 2012 to 2017 and from middle ear (ME) samples from children with AOM collected from 2012 to 2017. All isolates were identified using PCR for the hpd and fucK genes. Of the 3,600 samples collected from healthy children, 2,465 were culture positive for H. influenzae (68.5% carriage rate); of these, 151 (6.1%) contained hpd-negative isolates. Of the 2,847 ME samples collected, 889 (31.2%) were culture positive for H. influenzae; of these, 71 (8.0%) were hpd negative. Despite the same practice throughout the study, the annual number of ME samples reduced from 660 in 2012 to 330 in 2017. The proportions of hpd-negative isolates in unvaccinated versus vaccinated children were 5.6% and 7.0%, respectively, in healthy carriers, and 5.4% and 7.8%, respectively, in ME samples. The proportion of hpd-negative isolates increased with time in ME samples but not in healthy carriers. The number of ME samples from children with AOM decreased. The PHiD-CV had no effect on the proportion of the hpd gene in H. influenzae from carriage, but there was an increase in hpd-negative H. influenzae in otitis media. The proportions of hpd-negative isolates remained similar in vaccinated and unvaccinated children.

The pharyngeal carriage of Haemophilus influenzae among healthy population in China: a systematic review and meta-analysis

BACKGROUND

A nationwide investigation on the carriage proportion of H. influenzae among healthy populations is lacking in China. The purpose of the study was to review the prevalence of pharyngeal carriage of H. influenzae among healthy populations in China, and explore its influencing factors. The serotypes distribution of H. influenzae was also analyzed.

METHODS

A systematic search was conducted with key words "Haemophilus influenzae", "Carriage", and "China" or "Chinese" from inception to March 2018. After careful screening, the data of included articles were extracted with a pre-designed excel form. Then, the pooled carriage proportion of H. influenzae was calculated using the random effect model.

RESULTS

A total of 42 studies with 17,388 participants were included. The overall pooled carriage proportion of H. influenzae was 0.17 (95% CI: 0.13-0.21), and the carriage proportion largely varied by province. Subgroup analysis indicated that the pooled carriage proportion was 0.17 (0.13-0.21) for children, and 0.14 (0.7-0.23) for adults. There were no statistically significant heterogeneity between subgroups by age (p = 0.65), sex (p = 0.88), and season (p = 0.10). The pooled carriage proportion of Hib was 0.01 (0-0.02), while the carriage proportion of NTHi was 0.22 (0.13-0.31).

CONCLUSION

In China, the carriage proportion of H. influenzae among healthy population was low, but it largely varied by provinces.

Bacterial Meningitis Caused by β-lactamase Non-producing Ampicillin-resistant Haemophilus influenzae Type f in an Immunocompetent Woman

We report the case of a 36-year-old previously healthy woman who presented with fever and headache. Blood and cerebrospinal cultures and a bacterial analysis revealed the presence of β-lactamase non-producing ampicillin-resistant Haemophilus influenzae type f (Hif) with sequence type 124. Accordingly, the patient was diagnosed with bacterial meningitis with bacteremia caused by Hif. She had normal humoral immunity, and antibiotic therapy rapidly improved her condition. Our case indicates that serotype replacement can occur in Japan and suggests that a certain sequence type causes invasive Haemophilus influenzae disease, regardless of host immunity.

Increasing Prevalence of Group III Penicillin-Binding Protein 3 Mutations Conferring High-Level Resistance to Beta-Lactams Among Nontypeable Haemophilus influenzae Isolates from Children in Korea

This study investigated the roles of β-lactamase and penicillin-binding protein 3 (PBP3) alterations in the development of recent antimicrobial resistance in nontypeable Haemophilus influenzae (NTHi) isolated from Korean children. Nasopharyngeal NTHi isolates from children at a tertiary children's hospital were tested for antimicrobial susceptibility using E-test. β-lactamase production was screened by the paper disc test, and polymerase chain reaction amplification of bla_TEM and bla_ROB-1 was performed. The ftsI gene was amplified to identify PBP3 alteration. Of the 53 NTHi isolates, 69.8% were ampicillin nonsusceptible. The nonsusceptibility rates for cefaclor were 81.1%, cefpodoxime 69.8%, and amoxicillin/clavulanate 32.1%. About 60.3% and 32.1% of the isolates were genetically β-lactamase-nonproducing ampicillin-resistant (gBLNAR) and genetically β-lactamase-producing amoxicillin/clavulanate-resistant (gBLPACR) strains, respectively. Group III amino acid substitutions comprised 65.6% of the gBLNAR strains and 70.6% of the gBLPACR strains. MIC₅₀ for amoxicillin/clavulanate, cefaclor, cefuroxime, cefpodoxime, and cefixime were more than 2-80 times higher in the gBLNAR and gBLPACR strains compared with gBLPAR strains. Group III gBLNAR strains had significantly higher ampicillin, amoxicillin/clavulanate, cefpodoxime, and cefixime minimum inhibitory concentrations than group II strains. Group III gBLNAR and gBLPACR NTHi strains are highly prevalent in Korea, raising the alarm about increasing β-lactam resistance in NTHi.

Increasing trend in invasive non-typeable Haemophilus influenzae disease and molecular characterization of the isolates, Italy, 2012-2016

Routine immunization of infants with conjugate vaccines against Haemophilus influenzae type b (Hib) has greatly reduced the incidence of invasive Hib disease; however changes in the epidemiology of H. influenzae disease have occurred. We describe the epidemiology of invasive H. influenzae disease and the characterization of isolates collected in Italy between 2012 and 2016. Trends in the overall incidence of invasive H. influenzae disease were calculated. Isolates were characterized by PCR capsular genotyping, antimicrobial susceptibility testing, ampicillin resistance-associated gene sequencing and MLST. Trends in incidence by serotype and serotype-specific distribution were estimated using multiple imputation of missing data. The overall incidence of invasive H. influenzae disease increased 22.5% yearly (from 0.11/100,000 in 2012 to 0.24/100,000 in 2016). Most cases (82.0%) were due to non-typeable H. influenzae (NTHi). An increasing trend in NTHi disease burden was estimated; the highest rise was among infants <12 months (40.8% annual increase). Invasive Hib disease showed a fluctuating trend with a clear increase in 2016, while we found an increasing trend for disease due to non-Hib capsulated serotypes in the elderly (32.9% annual increase). Ampicillin resistance mediated by either β-lactamase or altered penicillin-binding proteins 3 (PBP3) increased. In spite of genetic diversity of NTHi, sequence types (STs) associated with ampicillin resistance status were identified (ST103/ST106 linked to β-lactamase production and ST14 linked to a specific PBP3 substitution pattern). The increasing trend in invasive NTHi disease in infants is of concern underlying the need for the development of a future vaccine against NTHi.

The return of Pfeiffer's bacillus: Rising incidence of ampicillin resistance in Haemophilus influenzae

Haemophilus influenzae, originally named Pfeiffer's bacillus after its discoverer Richard Pfeiffer in 1892, was a major risk for global health at the beginning of the 20th century, causing childhood pneumonia and invasive disease as well as otitis media and other upper respiratory tract infections. The implementation of the Hib vaccine, targeting the major capsule type of H. influenzae, almost eradicated the disease in countries that adapted the vaccination scheme. However, a rising number of infections are caused by non-typeable H. influenzae (NTHi), which has no capsule and against which the vaccine therefore provides no protection, as well as other serotypes equally not recognised by the vaccine. The first line of treatment is ampicillin, but there is a steady rise in ampicillin resistance. This is both through acquired as well as intrinsic mechanisms, and is cause for serious concern and the need for more surveillance. There are also increasing reports of new modifications of the intrinsic ampicillin-resistance mechanism leading to resistance against cephalosporins and carbapenems, the last line of well-tolerated drugs, and ampicillin-resistant H. influenzae was included in the recently released priority list of antibiotic-resistant bacteria by the WHO. This review provides an overview of ampicillin resistance prevalence and mechanisms in the context of our current knowledge about population dynamics of H. influenzae.

Genotypic characterization of Haemophilus influenzae isolates from paediatric patients in Japan

Purpose. β-lactamase-negative ampicillin-resistant (BLNAR) Haemophilus influenzae is frequently isolated from respiratory samples and is particularly problematic in Japan. The aim of this study was to characterize circulating isolates of H. influenzae genotypically by BLNAR-PCR and multilocus sequence typing (MLST), and to determine any associations between them.Methods. H. influenzae isolates (n=191) were collected from paediatric patients (1 month to 12 years old) between 2000 and 2011 for three types of infections: pneumonia (n=61), acute otitis media (AOM) (n=68) and meningitis (n=62). All were characterized for capsular type by agglutination tests, and for β-lactam resistance by real-time PCR. The sequence types (STs) determined by MLST were analysed using eburst v3.Results. Eighty-eight out of 191 (46.1 %) H. influenzae isolates were BLNAR by PCR; 37 of 61 (60.7 %) from pneumonia; 33 of 68 (48.5 %) from AOM and 18 of 62 (29.0 %) from meningitis cases. MLST identified 40 and 44 STs among isolates from pneumonia and AOM, respectively. BLNAR were found in singletons such as ST156 in pneumonia, and ST161 and ST396 in AOM. In contrast, eight STs were identified in meningitis, of which seven were genotypically closely related, while ST54 was the most frequent (62.9 %), unlike in the MLST database registrations, where ST6 predominated.Conclusion. Non-typeable H. influenzae (NTHi), mostly derived from pneumonia and AOM, were genetically diverse, in contrast to the predominance of H. influenzae type b (Hib) among meningitis cases. The associations between certain STs and β-lactam resistance among NTHi were confirmed.

Epidemiology of Invasive Haemophilus influenzae Disease, Europe, 2007-2014

We describe the epidemiology of invasive Haemophilus influenzae disease during 2007-2014 in 12 European countries and assess overall H. influenzae disease trends by serotype and patient age. Mean annual notification rate was 0.6 cases/100,000 population, with an increasing annual trend of 3.3% (95% CI 2.3% to 4.3%). The notification rate was highest for patients <1 month of age (23.4 cases/100,000 population). Nontypeable H. influenzae (NTHi) caused 78% of all cases and showed increasing trends among persons <1 month and >20 years of age. Serotype f cases showed an increasing trend among persons >60 years of age. Serotype b cases showed decreasing trends among persons 1-5 months, 1-4 years, and >40 years of age. Sustained success of routine H. influenzae serotype b vaccination is evident. Surveillance systems must adopt a broad focus for invasive H. influenzae disease. Increasing reports of NTHi, particularly among neonates, highlight the potential benefit of a vaccine against NTHi.

Phenotypic diversity of Haemophilus influenzae and Haemophilus parainfluenzae isolates depending on origin and health condition

Background. Haemophili are common human microbiota representatives. The aim of our study was to investigate a diversity of Haemophilus spp. isolates selected from clinical specimens on the basis of biochemical characteristics, biotypes distribution, protein profiles and antimicrobial resistance. Results. A total of 893/1025 (87%) of haemophili isolates were identified: 260/1025 (25%) as H. influenzae and 633/1025 (62%) as H. parainfluenzae. Moreover, a group of 107/1025 (10%) isolates without species identification (with e.g. abnormal numerical profile) was described as Haemophilus spp. Within the H. influenzae isolates, biotypes II and III were in a great majority (92/893; 10%, each), whereas among H. parainfluenzae, the most commonly occurring was biotype I and II (301/893, 34% and 178/893, 20%, respectively). A similar prevalence of biotypes was obtained regardless of the patient’s age or health condition or the type of specimen. A production of beta-lactamases was shown in 46/893 (5%) haemophili, both H. influenzae (13/46, 28%) and H. parainfluenzae (33/46, 72%) isolates. On the basis of haemophili biochemical characteristics, the cluster analysis using the UPGMA method demonstrated a high degree of phenotypic similarity due to a small distances between isolates taken from both unhealthy children and adults. Conclusion. Based on biochemical characteristics, about 90% of haemophili clinical isolates representing human-specific respiratory microbiota were positively identified as H. influenzae and H. parainfluenzae. The same differences in biotypes and antimicrobial resistance among isolates selected from healthy people or from patients with chronic and recurrent diseases were detected.

Epidemiology of Nasopharyngeal Carriage by Haemophilus influenzae in Healthy Children: A Study in the Mediterranean Coast Region

BACKGROUND

Haemophilus influenzae, a colonizer of the nasopharynx, in children causes mainly otitis and sinusitis. The primary objective of this study was to determine the prevalence of pharyngeal colonization by H. influenzae, and the secondary objectives were to identify risk factors associated with H. influenzae colonization and its antibiotic susceptibility.

METHODS

A prospective, multicenter study of nasopharyngeal carriers of H. influenzae was conducted in the pediatric consulting rooms of 10 primary healthcare centers in Murcia (Spain). The study consisted of 404 healthy children less than 5 years of age and was carried out during winter (January-March) and summer (July-September) of 2015. A nasopharyngeal sample was collected from each child, and an epidemiologic survey was completed by a pediatrician.

RESULTS

In total, 112 (27.7%) children had colonization by H. influenzae, with 73.2% of cases in winter and 26.8% of cases in summer (P < 0.001). The median (interquartile range) age in months of the colonized children (13 months, 12-47.5) was lower than that of the noncolonized children (46 months, 12-49) (P < 0.001). All H. influenzae found were nontypeable H. influenzae (NTHi). Among 112 isolates, 20% were ampicillin resistant, of which 10% produced β-lactamase, and 9% were ampicillin resistant and did not produce β-lactamase. A logistic regression analysis showed that young age (odds ratio: 0.98) and the winter period (odds ratio: 3.41; P < 0.001) were risk factors for colonization by NTHi.

CONCLUSIONS

Colonization by NTHi is high in this Mediterranean coast region with remarkable ampicillin resistant. Younger age and the winter period were facilitating factors.

The most appropriate therapeutic strategy for acute lower respiratory tract infections: a Delphi-based approach

Lower respiratory tract infections (LRTIs) cause high morbidity and mortality worldwide. Empiric therapy often base the choice of antibiotic treatment on antibacterial spectrum of the agent rather than on its pharmacological properties or the pathogen resistance profile. Inappropriate prescribing leads to therapeutic failure and antibiotic resistance, with increasing direct and indirect health costs. A consensus on appropriate prescribing in LRTI therapy was appraised by this Delphi exercise, based on a panel of 70 pulmonologists, coordinated by a Scientific Committee of nine experts in respiratory medical care. Full or very high consensus was reached on several issues, including the role of oral cephalosporins in first-line treatments of LRTIs and the appropriateness of cefditoren, with balanced spectrum and high intrinsic activity, in LRTI treatment. Evidence-based medicine approach and a comprehensive process of disease management, from diagnosis to therapy and follow-up, should guide antibiotic prescribing.

Vaccine Candidates against Nontypeable Haemophilus influenzae: a Review

Nonencapsulated, nontypeable Hemophilus influenzae (NTHi) remains an important cause of acute otitis and respiratory diseases in children and adults. NTHi bacteria are one of the major causes of respiratory tract infections, including acute otitis media, cystic fibrosis, and community-acquired pneumonia among children, especially in developing countries. The bacteria can also cause chronic diseases such as chronic bronchitis and chronic obstructive pulmonary disease in the lower respiratory tract of adults. Such bacteria express several outer membrane proteins, some of which have been studied as candidates for vaccine development. Due to the lack of effective vaccines as well as the spread and prevalence of NTHi worldwide, there is an urgent need to design and develop effective vaccine candidates against these strains.

The spread and clinical impact of ST14CC-PBP3 type IIb/A, a clonal group of non-typeable Haemophilus influenzae with chromosomally mediated β-lactam resistance-a prospective observational study

OBJECTIVES

Increasing incidences of non-typeable Haemophilus influenzae (NTHi) with β-lactam resistance mediated through mutations in penicillin-binding protein 3 (BLNAR or rPBP3) have been observed in the past decades. Recently, an rPBP3 NTHi sequence type (ST) 14 with PBP3 type IIb/A caused a disease outbreak in a nursing home in Sweden with severe outcomes, indicating increased bacterial virulence. In this prospective observational study, the epidemiology and clinical significance of the corresponding clonal group (ST14CC-PBP3IIb/A) in Skåne, Sweden was investigated.

METHODS

ST14CC-PBP3IIb/A isolates were identified through partial multilocus sequence typing and ftsI(PBP3 gene)-sequencing of prospectively collected H. influenzae from patients with respiratory tract or invasive infections (n=3262) in 2010-2012. Data on type of infection, hospitalization and outcomes were analysed, and the geographical distribution of isolates from different groups was investigated.

RESULTS

Isolates belonging to ST14CC-PBP3IIb/A constituted 26% (n=94/360) of respiratory tract rPBP3 NTHi. From mapping of patient addresses, a dynamic geographical spread was apparent during the study period. Furthermore, patients with infections by ST14CC-PBP3IIb/A isolates had higher hospitalization rates compared with patients infected with other rPBP3 NTHi (14/83 versus 21/255, p 0.025) and to a group of patients infected with susceptible NTHi (14/83 versus 13/191, p 0.010). ST14CC-PBP3IIb/A isolates constituted 25% (n=2/8) of invasive rPBP3 NTHi during the study period.

CONCLUSIONS

Our investigation suggests that the ST14CC-PBP3IIb/A clonal group is associated with increased clinical virulence, resistance to several antimicrobial agents, and is persistent over time. We conclude that virulence varies between different NTHi, and that NTHi disease may be more dependent on bacterial factors than previously recognized.

Why we need a vaccine for non-typeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is increasingly recognized as emerging pathogen. The routine immunization of infants with conjugated vaccines against H. influenzae type b (Hib) has greatly reduced the incidence of invasive Hib disease; however a marked change in the predominant invasive serotype from Hib to NTHi has occurred. Localized infections where the role of H. influenzae is important, such as otitis media in children and acute exacerbations in chronic obstructive pulmonary disease (COPD) in adults, are almost exclusively associated with NTHi isolates. The implementation of pneumococcal conjugate vaccines has resulted in changes in frequency of nasopharynx colonizing pathogens with an increase of NTHi, although this data is yet under debate. An effective vaccine against NTHi is not currently available. The major challenge in developing a successful vaccine is the intrinsic heterogeneity of NTHi. H. influenzae protein D is used as carrier protein in the licensed 10-valent pneumococcal conjugate vaccine (Synflorix, GlaxoSmithKline), but no robust evidences for protective efficacy against NTHi otitis have been until now obtained. Several other vaccine candidates are under investigations and we hope that significant advancements in vaccine development will be achieved in the next future. Genome-based vaccine strategy might provide an additional useful tool for discovering further vaccine antigens.

Developing a vaccine to prevent otitis media caused by nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is a predominant organism of the upper respiratory nasopharyngeal microbiota. Its disease spectrum includes otitis media, sinusitis, non-bacteremic pneumonia and invasive infections. Protein-based vaccines to prevent NTHi infections are needed to alleviate these infections in children and vulnerable populations such as the elderly and those with chronic obstructive pulmonary disease (COPD). One NTHi protein is included in a pneumococcal conjugate vaccine and has been shown to provide efficacy. Our lab has been interested in understanding the immunogenicity of NTHi vaccine candidates P6, protein D and OMP26 for preventing acute otitis media in young children. We expect that continued investigation and progress in the development of an efficacious protein based vaccine against NTHi infections is achievable in the near future.