title: Haemophilus influenzae infections in adults: characterization of strains by serotypes, biotypes, and beta-lactamase production.
abstract: One hundred three cases of bacteremia or meningitis due to Haemophilus influenzae in adults were evaluated. Among 96 episodes of bacteremia, 60% were due to pneumonia and 15% to genital-related infections; 10% had no apparent source of infection. Of 42 isolates serotyped in routine fashion by slide agglutination, 79% were reported as type b. In contrast, of 45 isolates from the same interval with confirmed serotyping (usually by counterimmunoelectrophoresis), only 29% were type b and 64% were nontypable; 26% had been misidentified by routine slide agglutination. The majority (85%) of confirmed typable strains were biotype I. Four (40%) of 10 nontypable obstetrical isolates belonged to the relatively rare biotype IV. Only 2% of isolates were ampicillin-resistant, despite a high resistance rate among pediatric isolates in the same communities. When serotyping is carefully performed, nontypable organisms appear to be the major cause of invasive H. influenzae disease in adults.
mesh_terms: D000328:Adult; D000372:Agglutination Tests; D003378:Counterimmunoelectrophoresis; D006192:Haemophilus Infections / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000145:classification* / Q000201:enzymology / Q000302:isolation & purification; D006801:Humans; D012703:Serotyping; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D001618:beta-Lactamases