Table 1.

Parameters determining the infection rate after middle ear challenge with histamine and Pn

CharacteristicInfection rate (%)a
Single administrationRepeated administration
Histamine concn (M)
 00.00.0
 10−533.3
 10−416.673.9b, c
 10−350.050.0
 10−250.066.7
Pn 14 concn (log CFU)
 40.0
 566.7
 666.7
 766.7
 873.9c
No. of days after challenge
 673.9
 966.7
 1216.7c
 1533.3
 1816.7d
Pn serotype
 6B41.7e
 1473.9
 19F50.0
 23F33.3
  • a All infection rates represent percentages of animals with Pn-positive middle ear lavages in separate groups with n being 6, unless otherwise indicated. Also, unless indicated otherwise, these results were obtained on day 6 after standard challenge procedure with Pn 14.

  • b A repeated dosage of 10−4 M histamine is significantly more effective than a single dose (P < 0.05) , as calculated by a Fisher's exact test.

  • c For this group, n was 24.

  • d The r2 for linear correlation is 0.72; the value of P is 0.0029; both were calculated over the total measurement range of 6 to 18 days.

  • e For this group, n was 12.