[The establishment of a rat model of chronic pulmonary infection due to Pseudomonas aeruginosa].

OBJECTIVE

To establish a rat model of chronic pulmonary infection by inoculating two different Pseudomonas aeruginosa embedded in minute seaweed alginate beads made by an ejection set with an acuminata hole to Sprague-Dawley rats. To evaluate the animal model with bacteriology and pathology values.

METHODS

(1) 300 healthy, clean Sprague-Dawley rats were divided into 3 groups randomly: the wide-type Pseudomonas aeruginosa group (PAO(1) group), the mutant type Pseudomonas aeruginosa group (PAO-JP2 group) and the control group. (2) Two different Pseudomonas aeruginosa were embedded in minute seaweed alginate beads by an ejection set with an acuminata hole. Then the beads were inoculated into the rats' lung through tracheal intubation. The bacteria numbers in lung and pathology scores were measured 3, 7, 14, 28 days after infection.

RESULTS

(1) The bacteriology values: No bacterium were detected in the control group. PAO(1) and PAO-JP2 were detected from rats of PAO1 and PAO-JP2 infected groups respectively. Bacterial number was higher than 10(5) CFU/g 3, 7 days after infection (LgCFU/g): 3 d: PAO1 group: 19 +/- 6, PAO-JP2 group: 17 +/- 7; 7 d: PAO1 group: 13 +/- 4, PAO-JP2 group: 12 +/- 4) and higher than 10(3) CFU/g 14, 28 days after infection (LgCFU/g: 14 d: PAO1 group: 11.3 +/- 2.8, PAO-JP2 group: 9.6 +/- 3.3; 28 d: PAO1 group: 9.1 +/- 1.5, PAO-JP2 group: 4.2 +/- 3.0). (2) The pathological changes showed: 3, 7 days after infection, lung abscess, edema, consolidation, haemorrhage can be seen from lungs of both groups. And at optical microscopic, alginate-Pseudomonas aeruginosa caused a pronounced inflammatory reaction with polymorphonuclear cells surrounding a bead. Small microcolonies formed at the periphery of the bead were also seen. 14, 28 days after infection, the consolidation reduced gradually and lung atelectasis, fibrinous adhesions and granulomas became the major pathological changes, which is more significant in the PAO(1) group.

CONCLUSIONS

The animal model of chronic pulmonary infection can be established by inoculating Pseudomonas aeruginosa embedded in minute seaweed alginate beads made by an ejection set with an acuminata hole to Sprague-Dawley rats.