title: Analysis of invasive Haemophilus influenzae infections after extensive vaccination against H. influenzae type b.
abstract: Little clinical and microbiological information is available about invasive Haemophilus influenzae infection after widespread vaccination against H. influenzae type b (Hib). We conducted an active community surveillance study on invasive H. influenzae during a 2-year period in a community of more than 5 million people after vaccination against Hib in children was introduced. The median incidence was 16.3 cases/100000 persons per year in children less than 1-year-old and 4.41 cases/100000 persons in children less than <5 years old. The highest incidence in adults was observed in patients greater than 70 years old. Clinical diagnoses included bacteremia, pneumonia, and meningitis. Of the H. influenzae-infected patients, 74.3% had underlying predisposing conditions, including impaired immunity and respiratory diseases. A total of 73.6% of the isolates were nontypeable and 16.5, 6.6, and 3.3% were types b, f, and e, respectively. Infections due to capsulated strains b, e, and f were evenly distributed between children and adults. Ampicillin and cotrimoxazole resistance occurred at frequencies of 24.2 and 48.4%, respectively. Antibiotic resistance was more prevalent in capsulated than in noncapsulated H. influenzae. Invasive isolates were highly resistant to antibiotics that were used infrequently in the community. Nontypeable H. influenzae were genetically much more heterogeneous than capsulated strains. Capsule-deficient mutants (b(-)) were not detected. Plasmid carriage was linked to antibiotic resistance and capsulated strains. Over the study period, the incidence of invasive H. influenzae infections, either encapsulated or not, did not increase. In the post-Hib vaccination era, most invasive infections were due to noncapsulated strains and occurred in the extreme ages of life in patients with predisposing conditions.
authors.affiliation: Instituto de Salud Carlos III División de Fármaco-Vigilancia, Agencia Española del Medicamento, Ministry of Health, Majadahonda. Instituto de Salud Pública, Consejería de Sanidad, Comunidad de Madrid, Madrid, Spain. jcampos@iscii.es
authors.forename: José
authors.initials: J
authors.lastname: Campos
authors.forename: Margarita
authors.initials: M
authors.lastname: Hernando
authors.forename: Federico
authors.initials: F
authors.lastname: Román
authors.forename: María
authors.initials: M
authors.lastname: Pérez-Vázquez
authors.forename: Belén
authors.initials: B
authors.lastname: Aracil
authors.forename: Jesús
authors.initials: J
authors.lastname: Oteo
authors.forename: Edurne
authors.initials: E
authors.lastname: Lázaro
authors.forename: Francisco
authors.initials: F
authors.lastname: de Abajo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016667:Bacterial Capsules; D002648:Child; D002675:Child, Preschool; D006192:Haemophilus Infections / Q000145:classification / Q000276:immunology*; D018073:Haemophilus Vaccines / Q000627:therapeutic use*; D019741:Haemophilus influenzae type b / Q000187:drug effects / Q000276:immunology* / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D011135:Polysaccharides, Bacterial / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D011135:Polysaccharides, Bacterial