[The assay of beta-lactamase activity in Pseudomonas aeruginosa biofilm].

OBJECTIVE: To analyze the resistance mechanism of Pseudomonas aeruginosa biofilm bacteria. METHODS: An in vitro model of Pseudomonas aeruginosa bacterial biofilm was established in silicon disk with modified flat-board method and a rapid staining procedure of AgNO3 was used to verify it. Biofilm was observed under scanning electron microscopy. The test was carried out in three groups. Group A was planktonic bacteria of Pseudomonas aeruginosa, group B biofilm bacteria of Pseudomonas aeruginosa and group C biofilm bacteria induced by imipenem. The activity of beta-lactamase was quantitated with a spectrophotometric assay method and beta-lactamase quantitation was determined by using Bio-Rad protein assay. RESULTS: The activity and protein content of beta-lactamase in group B was higher than that in group A by 4.67 and 2.09 times. The activity of group C was 21.86 times as much as that in group A and 4.68 times as much as that in group B. The quantitation in group C was 6.28 times as much as that in group A and 3.00 times as much as that in group B. The activity and quantitation of the three groups were different significantly from each other (P < 0.01). CONCLUSION: The production of beta-lactamase in Pseudomonas aeruginosa biofilm bacteria is one of the main reasons of its resistance.