FIG. 3.

Increased clearance of MGAS5005, but not MGAS5005 Δsrv, was observed over the course of experimental chinchilla otitis media within effusion samples. (A) Higher concentrations (CFU per milliliter) of MGAS5005 Δsrv were recovered from middle ear effusions and washes. Conversely, more middle ear effusion samples were cleared of MGAS5005 infection over time. Statistics were determined by using an unpaired Student t test. (B) Bacterial concentrations (CFU per gram) recovered from middle ear macroscopic structures. Higher concentrations of MGAS5005 Δsrv were recovered from homogenized macroscopic structures at 2 and 4 dpi. At 7 dpi, macroscopic structures recovered from all 8 MGAS5005-infected ears were positive for GAS. Only 2 structures recovered from MGAS5005 Δsrv-infected ears were positive for GAS at 7 dpi. Of note, 2 MGAS5005 Δsrv-infected animals had to be euthanized before the day 7 time point was reached. *, P ≤ 0.05 at 4 dpi. (C) Kaplan-Meier survival curves showing the relative rates of chinchilla mortality caused by MGAS5005 and MGAS5005 Δsrv. Two groups of 21 (MGAS5005) and 21 (MGAS5005 Δsrv) animals received ∼2 × 10⁵ CFU/ml by transbullar inoculation. While the results were not statistically significant (Wilcoxon test; P value ≤ 0.0755), more animals succumbed to MGAS5005 Δsrv infection. All remaining animals were euthanized at day 7.