[The effect of biofilms on the production of beta-lactamases in Pseudomonas aeruginosa].

OBJECTIVE

To investigate the effect of formation of biofilms on the expression of beta-lactamases in Pseudomonas aeruginosa.

METHOD

Four strains of Pseudomonas aeruginosa producing TEM and CARB extended spectrum beta-lactamases were induced by 3 antimicrobials (Ciprofloxacin, Ceftazidime and Imipenem) to generate beta-lactamases before and after the formation of biofilms. Different expression of beta-lactamases-mRNA was determined by relatively quantitative polymerase chain reaction.

RESULTS

Before biofilm formation, the relative level of mRNA expression of TEM beta-lactamase was 1.000 +/- 0.495 before and 2.038 +/- 0.036, 3.308 +/- 0.010, and 8.654 +/- 0.026 after induction with the 3 antimicrobials. After biofilm formation, the relative level of mRNA expression of TEM beta-lactamase was 1.766 +/- 0.026 before and 13.849 +/- 0.004, 16.372 +/- 0.044 and 34.581 +/- 0.143 respectively after antimicrobial induction with the above 3 antimicrobials (t = 6.94 - 582.14, P = 0.000). Before biofilm formation, the relative level of mRNA expression of CARB beta-lactamase was 1.000 +/- 0.069 before and 3.506 +/- 0.036, 5.878 +/- 0.190, and 8.771 +/- 0.066 after induction with the 3 antimicrobials; while for biofilm strains, the relative level of mRNA expression of CARB beta-lactamase was 2.937 +/- 0.164 before and 9.528 +/- 0.050, 10.844 +/- 0.062, and 21.900 +/- 0.087 respectively after induction with the 3 antimicrobials (t = 5.77 - 20.03, P = 0.000). Before biofilm formation, the increase of relative level of TEM mRNA expression after induction by antimicrobials was lower than that of CARB mRNA (5.49 +/- 4.32 vs 6.15 +/- 2.26; t = 3.31, P = 0.05), while after biofilm formation, the increase of the relative level of TEM mRNA after antimicrobial induction was higher than that of CARB mRNA (12.40 +/- 6.95 vs 4.92 +/- 2.33; t = 5.94, P = 0.01).

CONCLUSIONS

The formation of biofilms could influence the ability of Pseudomonas aeruginosa in expressing different beta-lactamases; and the amplitude of TEM beta-lactamase was higher than that of CARB beta-lactamase after biofilm formation, suggesting that the formation of biofilms may have different effects on Pseudomonas aeruginosa strains with different genotypes.