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Updated: May 22, 2026
Assessing Respiratory Immune Responses to Haemophilus Influenzae
Published on: June 29, 2021
Methodology optimization and diversification for the investigation of virulence potential in Haemophilus influenzae
Mihaela Cristina Giucă1, Monica Străuţ, Maria Surdeanu
1"Cantacuzino" National Institute of Research-Development for Microbiology and Immunology, Bucharest. giucamihaela@yahoo.com
Abstract:
Ten Haemophilus influenzae strains were isolated from patients aged between 1.6 - 24 years, with various diagnoses (acute meningitis, acute upper respiratory infection, otitis media and acute sinusitis). Identification was based on phenotypic and molecular characteristics; antibiotic susceptibility testing was performed by diffusion method according to CLSI standards 2011 for seven antibiotics. The results of molecular testing showed that all the studied strains produced an amplicon of 1000 bp with ompP2 primers indicating that all strains were H. influenzae. For six strains, the PCR amplicon obtained with bexA specific primers, proving that the strains were capsulated. The results of phenotypic testing showed that four strains were ampicillin nonsusceptible and (beta-lactamase-positive. The virulence potential of H. influenzae clinical strains was investigated by phenotypic methods, including the assessment of the soluble virulence factors on specific media containing the biochemical substratum for the investigated enzymatic factor, as well as the adherence and invasion capacity to HeLa cells monolayer using Cravioto modified method. The studied strains exhibited mainly a diffuse adherence pattern and different adherence indexes. Interestingly, two strains isolated from the same pacient (blood and CSF) showed a different degree of invasiveness, the strain isolated from blood being 20 times more invasive than the one isolated from CSF.
Insights
This study identified Haemophilus influenzae strains from pediatric patients, finding some resistant to ampicillin. Virulence factors like adherence and invasion varied among strains, with one blood isolate being significantly more invasive.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Biology
Background:
- Haemophilus influenzae is a significant pathogen causing various infections in children.
- Understanding the characteristics of clinical isolates is crucial for effective treatment and control.
- Previous studies have highlighted the emergence of antibiotic resistance and virulence factors.
Purpose of the Study:
- To characterize clinical isolates of Haemophilus influenzae from pediatric patients.
- To determine antibiotic susceptibility, identify capsulated strains, and assess virulence factors.
- To investigate the adherence and invasion capabilities of these clinical isolates.
Main Methods:
- Phenotypic and molecular methods were used for strain identification.
- Antibiotic susceptibility testing was performed using the diffusion method.
- Polymerase Chain Reaction (PCR) was employed to detect specific genes (ompP2, bexA).
- Virulence potential was assessed through soluble factor analysis and adherence/invasion assays in HeLa cells.
Main Results:
- All ten H. influenzae strains were confirmed by ompP2 gene amplification.
- Six strains were identified as capsulated based on bexA gene detection.
- Four strains exhibited ampicillin non-susceptibility and beta-lactamase production.
- Strains showed varying adherence patterns; one isolate from blood was 20 times more invasive than a co-isolated CSF strain.
Conclusions:
- Clinical H. influenzae isolates display diverse characteristics, including antibiotic resistance and variable virulence.
- The presence of capsular genes and beta-lactamase production are notable findings.
- Differences in invasiveness between strains from different body sites warrant further investigation for understanding disease pathogenesis.
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