Epidemiology of nasopharyngeal colonization with nontypeable Haemophilus influenzae in the first two years of life.

A total of 200 children were followed from birth through 2 years of age with nasopharyngeal (NP) cultures to determine the normal colonization pattern of nontypeable H. influenzae (NTHI) in young children. NP cultures were obtained routinely at 13 scheduled visits. 44% of children became colonized by 2 years; acquisition was greatest in the first year. Colonization with the initial strain, as determined by outer membrane proteins, persisted from 1-5 months, median 2 months. Children carried one predominant strain at a time but became colonized with up to 7 different strains, mean 2.2, over 2 years. Three patterns of colonization were observed: i) rapid elimination of the initial strain, ii) prolonged colonization with the initial strain, and iii) colonization with different strains. Reacquisition of a previously carried strain was rare. Changes in outer membrane protein patterns reflected acquisition of new strains rather than phenotypic changes of old strains. Children colonized with 1 strain for < or = 2 months generated a greater mucosal antibody response, log 2.35, U/ng/ml SIgA, than children colonized with different strains, log 1.89, U/ng/ml SIgA, p <0.01. These data suggest that duration of colonization with one strain and the acquisition of a new strain is regulated by the local specific SIgA.

Epidemiology of nasopharyngeal colonization with nontypeable Haemophilus influenzae in the first 2 years of life.

Two hundred children were followed from birth through 2 years of age with nasopharyngeal cultures to determine the normal colonization pattern of nontypeable Haemophilus influenzae. Forty-four percent of the children were colonized on one or more occasions; the acquisition rate was greatest in the first year. Monthly prevalence rates were 11%. Colonization with the initial strain persisted 1-5 months (median, 2). Children carried 1 predominant strain at a time but became colonized with up to 7 different strains (mean, 2.2). Children colonized with a single strain for < or = 2 months produced a greater nasopharyngeal secretory IgA to nontypeable H. influenzae response than did children colonized with different strains (log 2.35 +/- 0.68 vs. 1.89 +/- 0.25 U of P6 secretory IgA/ng/mL of total secretory IgA, P < .01). The duration of colonization with a strain and acquisition of a new strain may be affected in part by the local production of specific secretory IgA.

The release of leukotrienes in the respiratory tract during infection with respiratory syncytial virus: role in obstructive airway disease.

Samples of nasopharyngeal secretions from a group of 73 infants with bronchiolitis or upper respiratory illness alone during infection with respiratory syncytial virus were analyzed for leukotriene C4 (LTC4) content using a reverse-phase high-pressure liquid chromatography assay with confirmation by radioimmunoassay. Titers of respiratory syncytial virus (RSV)-specific IgE in nasopharyngeal secretion (NPS) specimens were determined using an enzyme-linked immunosorbent assay. The highest concentrations of LTC4 were found in the first 3 to 8 days after the onset of illness, and LTC4 was detectable in progressively lower concentrations in samples obtained up to 28 days after the onset of illness. LTC4 was detected in samples of NPS obtained in the acute phase of illness from 67% of infants with bronchiolitis due to RSV and in 33% of samples of NPS obtained during the same interval from infants with upper respiratory illness alone (p less than 0.025). Concentrations of LTC4 in children with bronchiolitis were 5-fold higher (1271 pg/ml) than the mean concentration of LTC4 in children with upper respiratory illness (224 pg/ml, p less than 0.02). LTC4 was detected in 83% of the children developing an RSV-IgE response and in 24% of subjects not developing an RSV-IgE response (p less than 0.001). Quantities of LTC4 measured in NPS were directly correlated with the magnitude of the RSV-IgE response in secretions (r = 0.33, p less than 0.02). These studies lend support to previous investigations suggesting that severe bronchiolitis due to RSV results from IgE-mediated hypersensitivity reactions to viral antigens, with release of chemical mediators of airway obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)