Clinical Characterization of Invasive Disease Caused by Haemophilus influenzae Serotype b in a High Vaccination Coverage Setting

Impact of a Single-Tube PCR Assay for the Detection of Haemophilus influenzae Serotypes a, c, d, e and f on the Epidemiological Surveillance in Greece

Background: The decrease in the rate of meningitis due to Haemophilus influenzae type b after vaccine introduction and a possible change in epidemiology of H. influenzae disease highlights the need for continuous serotype surveillance. Methods: A single-tube multiplex PCR assay for serotyping of H. influenzae was developed and deployed. Results: During 2003−2020, 108 meningitis cases due to H. influenzae were notified; 86 (80%) were confirmed and serotyped by molecular methods. The overall specificity and sensitivity of the assay were estimated (100% PPV and NPV respectively). The overall mean annual reported incidence for H. influenzae was 0.02, while for Hib and non-b meningitis equaled 0.02 and 0.03 per 100 000, respectively. Analysis by age group revealed that H. influenzae peaks in toddlers and children 0−4 years and in adults >45 years old. Among the serotyped cases, 39.8% were identified as Hib, 46.3% as NTHi, and 0.9% and 2.8% as serotypes a (Hia) and f (Hif)) respectively. Conclusions: Low incidence due to Hib was observed while non-typeable H. influenzae (NTHi) and serotypes Hia and Hif seem to emerge. The application of the current assay discloses the ongoing change of invasive H. influenzae disease trends during the Hib post-vaccine era.

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.

Polymorphism of ftsI gene in Haemophilus influenzae and emergence of cefotaxime resistance in two Tunisian hospitals

The decreased affinity to β-lactams in Haemophilus influenzae is usually caused by specific alterations in penicillin-binding protein 3 due to varieties of substitutions in ftsI gene. This study aimed to characterize the polymorphism of ftsI gene in 19 H. influenzae strains, isolated between 2014 and 2016 (different resistance phenotypes to β-lactams (n = 9) and susceptible strains (n = 10) used for comparative purposes).

All strains were characterized for capsular type by PCR and agglutination tests and for β-lactam resistance by amplification and sequencing of ftsI. Biotyping and clonality were performed by API-NH and pulsed-field gel electrophoresis, respectively.

Four strains were β-lactamase-negative ampicillin-resistant and five were β-lactamase-positive clavulanic-acid-resistant. One strain from each group was resistant to cefotaxime. Our isolates belonged mainly to biotype IV and I and were non-typeable and genetically unrelated. According to mutation profiles of their ftsI, strains were classified as group I (n = 3), group II (n = 4), group–III–like (n = 1) and group III (n = 1). All group II strains were further classified as subgroup IIb, except for one strain, which harboured a new mutation (N422I). Ampicillin MICs of β-lactamase-negative ampicillin-resistant strains were 6 to 12 times the MICs of susceptible strains. Only bla_TEM-1 was detected in β-lactamase-positive clavulanic-acid-resistant strains, and was responsible for high MICs for ampicillin (>256 mg/L), whatever the ftsI mutational resistance group.

The emergence of cefotaxime-resistant isolates in our country is a matter of concern and requires strict surveillance and rationalization of antibiotic use to preserve these molecules.