动物模型,中耳炎 z-bo 2020-08-12 509

　　Otitis media (Otitis media) is a clinically common disease in children, and 19% to 62% of infants have the disease at least once within one year of age. Streptococcus pneumoniae is the main pathogen of otitis media. About half of otitis media are caused by pneumococcus. The bacteria can enter the middle ear through the eustachian tube, tympanic membrane perforation or blood, causing otitis media. At present, guinea pigs, gerbils, rats, etc. have been used to establish pneumococcal otitis media models. Since the anatomical structure of the middle ear of rats is most similar to humans, rats are used to establish pneumococcal otitis media models at home and abroad.

　　(1) Replication method Type 3 pneumococcus was successively passaged through the abdominal cavity of mice 3 times to enhance the virulence. The bacteria were grown on the blood plate for 18 hours, and a bacterial suspension of 6×10000000 CFU/ml was made with sterile saline. Take a male rat with normal ears and inject ketamine-xylazine mixture intramuscularly at a dose of 0.25～3ml/100g body weight for anesthesia. The animal shall be placed in a supine position. Aseptic surgery is performed at a position about 0.5cm below the level of the hyoid bone. Make an incision to separate and expose the anterior cervical muscles. Separate the hyoid scapularis and hyoid sternum at the hyoid bone to see the bottom wall of the ear blister. Sterile saline was injected into the left ear of the rat as a control, 50μl of bacterial suspension (containing 3×1000000 CFU bacteria) was injected into the right ear of the rat, the injection hole of the ear vesicle wall was closed with bone wax, and the incision was sutured layer by layer. 4 to 7 days after the right ear was injected with pneumococcus, all model rats developed otitis media, with extensive congestion and swelling of the tympanic membrane, and yellow effusion in the tympanic cavity was visible through the tympanic membrane. At 2 weeks, about half of the rats’ ear tympanic membrane had reduced or normal color; after 1 month, most ear tympanic membranes appeared normal; after 3 months, about 1/3 of the animals had chronic otitis media with mild ear tympanic membrane congestion, 6 months later The ear tympanic membrane of model rats is still moderately congested.

　　(2) Model characteristics The model was made with a large amount of inoculated bacteria. Although most of the experimental mouse otitis media manifested as self-limiting disease, the disease course was prolonged, some turned to chronic otitis media, and the pathological changes were obvious or serious. Absorption destruction, labyrinthitis and new bone formation, fibrogranulation tissue hyperplasia and glandular metaplasia are similar to the pathological changes of human otitis media. The experimental ear with the appearance of the tympanic membrane returned to normal still had inflammatory changes at 6 months, indicating that pneumococcal otitis media in rats is not completely a self-limiting disease. The pathological development and severity of inflammation are related to the amount of bacteria injected into the middle ear. Individual differences in mouse immune mechanisms may also be related.

　　(3) Comparing medicine. Different bacterial species or different bacterial strains of the same bacterial species require different bacterial counts to cause otitis media; the severity and duration of the caused otitis media are also different; the severity of otitis media caused by different doses of pneumococcus is also different , Small doses only cause serous otitis media, while large doses can induce suppurative otitis media. The results of comparative anatomy studies show that among experimental animals, the anatomical structure of the middle ear of rats is most similar to that of humans. The performance of the middle ear after infection with Streptococcus pneumoniae is also similar to that of humans. Therefore, rats are often used to establish pneumococcal otitis media models. . Otitis media can appear in this model animal infected with Streptococcus for 4 to 7 days, and the inflammation is reduced from the second week, but about 1/3 of the animals become chronic otitis media, and the ear tympanic membrane can still show moderate hyperemia and inflammation until 6 months which performed. Acute and chronic otitis media caused by streptococcus can be successfully replicated in rats. This model provides a good foundation for studying its pathogenic mechanism, pathological manifestations and drug treatment.