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Penicillin treatment accelerates middle ear inflammation in experimental pneumococcal otitis media
M Kawana1, C Kawana, G S Giebink
1Otitis Media Research Center, University of Minnesota School of Medicine, Minneapolis 55455.
Abstract:
Most Streptococcus pneumoniae strains are killed by very low concentrations of penicillin and other beta-lactam antibiotics, yet middle ear inflammation and effusion persist for days to weeks after treatment in most cases of pneumococcal otitis media. To study the effect of beta-lactam antibiotic treatment on pneumococci and the middle ear inflammatory response during pneumococcal otitis media, we measured concentrations of pneumococci, inflammatory cells, and lysozyme in middle ear fluid (MEF) by using the chinchilla model. Procaine penicillin G given intramuscularly 12 and 36 h after inoculation of pneumococci into the middle ear caused a significant acceleration in the MEF inflammatory cell concentration compared with that in untreated controls, with a significant peak in the inflammatory cell concentration 24 h after pneumococcal inoculation. The lysozyme concentration in MEF also increased more rapidly in treated than in control animals. Viable pneumococci were not detected in MEF after the second dose of penicillin, but the total pneumococcal cell concentration remained unchanged for at least 45 days. Therefore, penicillin treatment accelerated middle ear inflammation while killing pneumococci, but treatment did not accelerate clearance of the nonviable pneumococcal cells from MEF. Further studies will need to define the contribution of these responses to acute and chronic tissue injury.
Insights
Penicillin treatment for pneumococcal otitis media kills bacteria but accelerates middle ear inflammation. Nonviable bacteria persist, potentially impacting tissue injury.
Area of Science:
- Otolaryngology
- Infectious Diseases
- Pharmacology
Background:
- Otitis media caused by Streptococcus pneumoniae often persists despite beta-lactam antibiotic treatment.
- The inflammatory response in the middle ear during pneumococcal otitis media requires further investigation.
Purpose of the Study:
- To investigate the impact of beta-lactam antibiotic treatment on Streptococcus pneumoniae and the middle ear inflammatory response.
- To analyze the concentrations of bacteria, inflammatory cells, and lysozyme in middle ear fluid (MEF).
Main Methods:
- Utilized the chinchilla model of pneumococcal otitis media.
- Administered procaine penicillin G intramuscularly at 12 and 36 hours post-inoculation.
- Measured pneumococcal, inflammatory cell, and lysozyme concentrations in MEF.
Main Results:
- Penicillin treatment significantly accelerated inflammatory cell concentration in MEF compared to controls.
- Lysozyme concentration in MEF increased more rapidly in treated animals.
- Viable pneumococci were eradicated, but nonviable bacterial cell concentration remained unchanged for at least 45 days.
Conclusions:
- Penicillin therapy accelerates middle ear inflammation and eliminates viable Streptococcus pneumoniae.
- Treatment does not expedite the clearance of nonviable pneumococcal cells from MEF.
- Further research is needed to understand the role of these responses in acute and chronic tissue injury.