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

Molecular characteristics and biofilm formation capacity of nontypeable Haemophilus influenza strains isolated from lower respiratory tract in children

With the widespread introduction of the Hib conjugate vaccine, Nontypeable Haemophilus influenzae (NTHi) has emerged as the predominant strain globally. NTHi presents a significant challenge as a causative agent of chronic clinical infections due to its high rates of drug resistance and biofilm formation. While current research on NTHi biofilms in children has primarily focused on upper respiratory diseases, investigations into lower respiratory sources remain limited. In this study, we collected 54 clinical strains of lower respiratory tract origin from children. Molecular information and drug resistance features were obtained through whole gene sequencing and the disk diffusion method, respectively. Additionally, an in vitro biofilm model was established. All clinical strains were identified as NTHi and demonstrated the ability to form biofilms in vitro. Based on scanning electron microscopy and crystal violet staining, the strains were categorized into weak and strong biofilm-forming groups. We explored the correlation between biofilm formation ability and drug resistance patterns, as well as clinical characteristics. Stronger biofilm formation was associated with a longer cough duration and a higher proportion of abnormal lung imaging findings. Frequent intake of β-lactam antibiotics might be associated with strong biofilm formation. While a complementary relationship between biofilm-forming capacity and drug resistance may exist, further comprehensive studies are warranted. This study confirms the in vitro biofilm formation of clinical NTHi strains and establishes correlations with clinical characteristics, offering valuable insights for combating NTHi infections.

Comparison of the adherence of nontypeable haemophilus influenzae to lung epithelial cells

OBJECTIVE

Nontypeable Haemophilus influenzae (NTHi) plays an important role in respiratory tract infections, and adherence to lung epithelial cells is the first step in lung infections. To explore the role of NTHi in childhood lung infections, a comparative study was conducted on the adherence of strains isolated from sputum culture and bronchoalveolar lavage fluid to A549 lung epithelial cells.

METHODS

Haemophilus influenzae strains were obtained from the sample bank of Shenzhen Children's Hospital, and identified as NTHi via PCR detection of the capsule gene bexA. NTHi obtained from healthy children's nasopharyngeal swabs culture were selected as the control group, and a comparative study was conducted on the adherence of strains isolated from sputum culture or bronchoalveolar lavage fluid of patients to A549 cells.

RESULTS

The adherence bacterial counts of NTHi isolated from the nasopharyngeal cultures of healthy children to A549 cells was 58.2 CFU. In patients with lung diseases, NTHi isolated from bronchoalveolar lavage fluid was 104.3 CFU, and from sputum cultures was 115.1 CFU, both of which were significantly higher in their adherence to A549 cells compared to the strains isolated from the healthy control group. There was no significant difference in adherence between the strains isolated from sputum cultures and bronchoalveolar lavage fluid (t = 0.5217, p = 0.6033).

CONCLUSION

NTHi played an important role in childhood pulmonary infections by enhancing its adherence to lung epithelial cells.

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.

Characterization of Serotypes and Molecular Drug Resistance Patterns of Haemophilus influenzae in Kunming Children

The present study aimed to determine the capsular serotype distribution and antimicrobial drug resistance patterns of Haemophilus influenzae from children in the Kunming region of China. This information could guide policymakers in clinical treatment. In the present study, H. influenzae isolates were tested for their serotypes, antimicrobial susceptibility pattern, and presence of β-lactamases. One-hundred forty-eight H. influenzae strains isolated from children 0-2 years old were investigated for capsular types by glass slide agglutination and molecular methods, and biotyped by the biochemical reactions. The drug resistance-encoding genes TEM-1, ROB-1, and the ftsI gene mutations PBP3-3, and PBP3-BLN were detected with real-time quantitative polymerase chain reaction (qPCR). The prevalence of β-lactamase-producing strains (60.3%) was significantly higher (p < 0.05) than non-enzyme-producing strains. β-Lactamase-producing strains were multidrug resistant to various antibiotics such as ampicillin, tetracycline, sulfamethoxazole/trimethoprim, chloramphenicol, cefuroxime, and cefaclor. Among β-lactamase-producing strains, the detection rates of the TEM-1, PBP3-BLN, PBP3-s, and ROB-1 were 54.1%, 18.9%, 11.8%, and 6.9%, respectively. The biotyping results show that most H. influenzae strains were of type II and III. Non-typeable H. influenzae (NTHi) accounted for 89.3% of the strains. NTHi strains were the most prevalent in this region; most belonged to biological types II and III. β-Lactamase-positive ampi-cillin-resistant (BLPAR) strains were prevalent among H. influenzae isolates in this region.

Can non-typeable Haemophilus influenzae carriage surveillance data infer antimicrobial resistance associated with otitis media?

Importance

In remote communities of the Northern Territory, Australia, children experience high rates of otitis media (OM), commonly caused by non-typeable Haemophilus influenzae (NTHi). Few data exist on antibiotic susceptibility of NTHi from OM.

Objective

To determine whether population-level nasopharyngeal NTHi antibiotic susceptibility data could inform antibiotic treatment for OM.

Methods

NTHi isolates (n = 92) collected from ear discharge between 2003 and 2013 were selected to time- and age-match NTHi isolates from the nasopharyngeal carriage (n = 95). Antimicrobial susceptibility were tested. Phylogenomic trees and a genome-wide association study (GWAS) were performed to determine the similarity of nasopharyngeal and ear isolates at a population level.

Results

Among 174 NTHi isolates available for antimicrobial susceptibility testing, 10.3% (18/174) were resistant to ampicillin and 9.2% (16/174) were resistant to trimethoprim-sulfamethoxazole. Small numbers of isolates (≤3) were resistant to tetracycline, chloramphenicol, or amoxicillin-clavulanic acid. There was no statistical difference in the proportion of ampicillin-resistant (P = 0.11) or trimethoprim-sulfamethoxazole-resistant isolates (P = 0.70) between ear discharge and nasopharynx-derived NTHi isolates. Three multi-drug resistant NTHi isolates were identified. Phylogenomic trees showed no clustering of 187 Haemophilus influenzae isolates based on anatomical niche (nasopharynx or ear discharge), and no genetic variations that distinguished NTHi derived from ear discharge and nasopharyngeal carriage were evident in the GWAS.

Interpretation

In this population-level study, nasopharyngeal and ear discharge isolates did not represent distinct microbial populations. These results support tracking of population-level nasopharyngeal NTHi antibiotic resistance patterns to inform clinical management of OM in this population.

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.

Real-time multiple cross displacement amplification assay for rapid and sensitive detection of Haemophilus influenzae

Haemophilus influenzae is an opportunistic pathogen usually causing bacteremia, meningitis, and pneumonia in children. Here, we developed a method based on multiple cross displacement amplification (MCDA) method and real-tme fluorescence technique for rapid detection of H. influenzae. A set of 10 primers was designed for the H. influenzae real-time MCDA reaction, and a core primer was modified with a restriction endonuclease recognition sequence, a fluorescent, and a quencher according to the principle of the real-time MCDA assay. The H. influenzae real-time MCDA reactions were performed using a fluorescence instrument at 63°C for 40 min. The H. influenzae real-time MCDA assay can specifically detect H. influenzae without any cross-reaction with other bacteria as our results confirmed. The sensitivity of our assay is as low as 10 CFU per reaction. To validate its feasibility, our assay was applied to 40 DNA extracted from sputum samples. The results obtained from H. influenzae real-time MCDA were compared with that of H. influenzae–loop-mediated isothermal amplification (H. influenzae-LAMP) and MCDA-based lateral flow biosensor (MCDA-LFB). The positive rate of the real-time MCDA assay was 62.5%, which was consistent with the H. influenzae-MCDA-LFB assay, but was more sensitive than H. influenzae-LAMP (57.5%). Furthermore, the H. influenzae real-time MCDA assay takes only 40 min, which was less than that of a traditional PCR test. Taken together, the H. influenzae real-time MCDA assay reported here offers a new and valuable diagnostic tool for the reliable and rapid detection of H. influenzae.

Nontypeable Haemophilus influenzae P5 Binds Human C4b-Binding Protein, Promoting Serum Resistance

Exposure of P5 at the surface of NTHi positively correlates with C4BP binding.

C4BP bound to the bacterial surface retains its complement inhibitory capacity.

C4BP binding to P5 is important for NTHi serum resistance.

Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative human pathogen that causes infections mainly in the upper and lower respiratory tract. The bacterium is associated with bronchitis and exacerbations in patients suffering from chronic obstructive pulmonary disease and frequently causes acute otitis media in preschool children. We have previously demonstrated that the binding of C4b binding protein (C4BP) is important for NTHi complement evasion. In this study, we identified outer membrane protein 5 (P5) of NTHi as a novel ligand of C4BP. Importantly, we observed significantly lower C4BP binding and decreased serum resistance in P5-deficient NTHi mutants. Surface expression of recombinant P5 on Escherichia coli conferred C4BP binding and consequently increased serum resistance. Moreover, P5 expression was positively correlated with C4BP binding in a series of clinical isolates. We revealed higher levels of P5 surface expression and consequently more C4BP binding in isolates from the lower respiratory tract of chronic obstructive pulmonary disease patients and tonsil specimens compared with isolates from the upper respiratory tract and the bloodstream (invasive strains). Our results highlight P5 as an important protein for protecting NTHi against complement-mediated killing.

Invasive non-typeable Haemophilus influenzae infection due to endometritis associated with adenomyosis

Background

The widespread administration of the Haemophilus influenzae type b vaccine has led to the predominance of non-typable H. influenzae (NTHi). However, the occurrence of invasive NTHi infection based on gynecologic diseases is still rare.

Case presentation

A 51-year-old Japanese woman with a history of adenomyoma presented with fever. Blood cultures and a vaginal discharge culture were positive with NTHi. With the high uptake in the uterus with ⁶⁷Ga scintigraphy, she was diagnosed with invasive NTHi infection. In addition to antibiotic administrations, a total hysterectomy was performed. The pathological analysis found microabscess formations in adenomyosis.

Conclusions

Although NTHi bacteremia consequent to a microabscess in adenomyosis is rare, this case emphasizes the need to consider the uterus as a potential source of infection in patients with underlying gynecological diseases, including an invasive NTHi infection with no known primary focus.

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.