Lack of the hyaluronan receptor CD44 affects the course of bacterial otitis media and reduces leukocyte recruitment to the middle ear

Table 1 Impaired bacterial clearance of middle ears in mice with CD44 deficiency

Time after NTHi inoculation	C57BL/6 WT culture positive plates	C57BL/6 WT mean NTHi DS	C57BL/6 WT CFU/mL	CD44 ^−/− culture positive plates	CD44 ^−/− mean NTHi DS	CD44 ^−/− CFU/mL
Day 1	6/6 (100%)	3.20	6 × 10⁴	4/6 (67%)	1.70	6 × 10⁴
Day 2	3/6 (50%)	1.30	1 × 10⁴	4/6 (67%)	1.80	2 × 10⁵
Day 3	1/6 (17%)	0.50	1 × 10³	2/6 (33%)	1.30	2 × 10⁵
Day 7	0/8 (0%)	0.00	0	1/8 (13%)	0.50	1 × 10⁵
Day 10	0/6 (0%)	0.00	0	1/6 (17%)	0.70	8 × 10⁴

Bacterial colonization of chocolate-agar plates was evaluated using quantitatively and semi-quantitative methods to generate an NTHi detection score (DS): 0 indicated no colony-forming unit (CFU) on the plate; 1 indicated CFUs in one quadrant; 2 indicated CFUs in two quadrants; 3 indicated CFUs in three quadrants; and 4 indicated CFUs in all four quadrants on the plate. The colonies on the 4 quadrants were also counted and multiplied by 10³ to provide a CFU count per mL. At least 6 ears (n ≥ 3 mice) were cultured for each time points of WT and CD44^−/− mice. NTHi clearance by CD44 KO animals was significantly worse than for C57/BL6 controls by ANOVA (p = 0.0114)

ISSN: 1471-2172