Haemophilus influenzae Carriage among Healthy Children in Portugal, 2015–2019

Abstract

Haemophilus influenzae is an important cause of mucosal and invasive infections and a common colonizer of the upper respiratory tract. As there are no recent data on H. influenzae carriage in Portugal, we aimed to characterize carriage samples and investigate possible parallelisms with disease isolates. Between 2016–2019, 1524 nasopharyngeal samples were obtained from children (0–6 years) attending day-care. H. influenzae were serotyped and screened for β-lactamase production. Strains producing β-lactamase and/or those that were encapsulated were further characterized by antibiotype; encapsulated strains were also investigated for MLST and the presence of antimicrobial resistance and virulence genes (extracted from whole genome sequencing). The overall carriage rate was 84.1%. Most isolates (96.7%) were nonencapsulated. Encapsulated strains were of serotypes f (1.8%), e (1.1%), a (0.3%), and b (0.1%). MLST showed clonality within serotypes. Although the lineages were the same as those that were described among disease isolates, colonization isolates had fewer virulence determinants. Overall, 7.5% of the isolates were β-lactamase positive; one isolate had blaTEM-82, which has not been previously described in H. influenzae. A single isolate, which was identified as H. parainfluenzae, had an incomplete f-like cap locus. In conclusion, circulation of serotype b is residual. The few encapsulated strains are genetically related to disease-causing isolates. Thus, surveillance of H. influenzae carriage should be maintained.

Haemophilus influenzae Type b Vaccine Failure in Portugal: A Nationwide Multicenter Pediatric Survey

“…A longitudinal study performed between 2015 and 2019 in Portuguese children up to 6 years old living in Lisbon showed an expected high rate of Hi nasopharyngeal colonization (84.3%), but Hib was detected only in 1 of 1524 samples (0.06%). 27 In the pre-vaccine period, serotype b carriage among Portuguese day-care center attendees was 3.8% suggesting that Hib vaccination nearly eliminated carriage of this serotype. 28 The serologic inquiry performed in Portugal in 2015-2016 showed a prevalence of protective antibodies titers (IgG > 1.0 μg/ mL) in 88.5% of the 2-4 years old, 86% of the 5-9 years old, 75.9% of the 10-14 years old and 79.4% of the 15 19 years old.…”

“…A longitudinal study performed between 2015 and 2019 in Portuguese children up to 6 years old living in Lisbon showed an expected high rate of Hi nasopharyngeal colonization (84.3%), but Hib was detected only in 1 of 1524 samples (0.06%). 27 In the pre-vaccine period, serotype b carriage among Portuguese day-care center attendees was 3.8% suggesting that Hib vaccination nearly eliminated carriage of this serotype. 28…”

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

“…However, in their study, ampicillin was tested in the concentration range of 8 to 0.25 mg/L. For example, the authors Bajanca-Lavdo et al [36] tested 96 isolates of β-lactamase-producing strains of H. influenzae resistant to ampicillin and reported a lower MIC (4 mg/L) for tested strains. On the contrary, the authors Thiên-Trí Lâm et al [37] recorded a much higher MIC for tested isolates of H. influenzae.…”

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

“… 120 In Portugal, the β-lactamase positivity rate was 7.5% (96/1282). 12 In contrast, in France, the rate of β-lactamase positivity was as high as 27.1% (157/580) and 35.0% (208/595) for the BLNAR strains. 121 In Belgium, β-lactamase positivity was 23.8% (132/554) and 16.0% (15/94) in the carrier and invasive groups, respectively.…”

“… 11 The total carrying rate of H. influenzae among children aged 0–6 in daycare was 84.1% (1282/1524), of which 96.7% (1240/1282) were NTHi. 12 A study in Shanghai, China found that all 51 isolates collected were NTHi, of which 5.9% (3/51) caused invasive infections, with ST103 (7.84%, 4/51) being the most common. 13 A multicenter study in Zhejiang, China, found that H. influenzae infections accounted for 18.5% (280/1514) and NTHi accounted for 93.6% (262/280).…”