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Hematogenous pneumococcal meningitis in the infant rat: description of a model
A F Rodriguez1, S L Kaplan, E P Hawkins
1Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030.
Insights
Streptococcus pneumoniae meningitis can cause sensorineural deafness in children. This study used an infant rat model to investigate how S. pneumoniae invades the inner ear, finding inflammation primarily in the perilymphatic space.
Area of Science:
- Microbiology
- Pathogenesis
- Otolaryngology
Background:
- Sensorineural deafness affects 20%-30% of children post-Streptococcus pneumoniae meningitis.
- Understanding inner ear invasion by S. pneumoniae is crucial for preventing hearing loss.
Purpose of the Study:
- To establish an infant rat model of S. pneumoniae meningitis.
- To investigate the pathogenesis of S. pneumoniae inner ear invasion.
Main Methods:
- Infant rats (5-day-old) received intraperitoneal S. pneumoniae type 6 for 3 days.
- Bacteremia and meningitis were assessed via blood and cerebrospinal fluid (CSF) cultures.
- Histopathological analysis (Hematoxylin-eosin, Gram's stain) examined inner ear and meningeal inflammation.
Main Results:
- Meningitis and bacteremia were most frequent 4 days post-infection.
- Inflammation was observed in the meninges (82%), scala tympani (82%), and scala vestibuli (55%).
- No inflammation was found in the scala media; perilymphatic inflammation significantly exceeded endolymphatic inflammation (P < .001).
Conclusions:
- The infant rat model successfully replicated S. pneumoniae meningitis and inner ear invasion.
- S. pneumoniae preferentially invades the perilymphatic space of the inner ear, leading to inflammation.
- These findings provide insights into the mechanisms of meningitis-associated hearing loss.
Abstract:
Sensorineural deafness occurs in 20%-30% of children after Streptococcus pneumoniae meningitis. An infant rat model of S. pneumoniae meningitis was developed to study the pathogenesis of inner ear invasion by S. pneumoniae. S. pneumoniae type 6 was administered intraperitoneally (inoculum: 1-10 x 10(8) cfu) every 24 h for 3 days to 5-day-old rats. Bacteremia (12 [50%] of 24) and meningitis (11 [46%] of 24) were detected most frequently 4 days after the three doses. The mean cerebrospinal fluid (CSF) white blood count for rats with positive CSF cultures was 7271/mm3 (range, 81-20,475). Hematoxylin-eosin-stained brain tissue from the 11 rats with positive CSF cultures showed inflammation in the meninges and scala tympani in 9 each (82%), and scala vestibuli in 6 (55%), but none in the scala media. Gram's-stained brain and inner ear sections from the same 11 rats showed organisms in the meninges in 5 (45%) and scala tympani or vestibuli in 2 (18%). Perilymphatic inflammation occurred significantly (P less than .001) more than did endolymphatic inflammation.