Susceptibility to antimicrobial agents of Pseudomonas aeruginosa attached to siliconized latex urinary catheters.

The effect of siliconized latex urinary catheters on the in vitro activity of amikacin, ceftazidime, ciprofloxacin, norfloxacin and meropenem against Pseudomonas aeruginosa was determined by a microdilution assay. MICs of amikacin and meropenem increased at least 4-fold and 16-fold respectively in the presence of catheter material. The effect of catheter material on meropenem activity was not strain dependent and was similar for different brands of catheters. The susceptibility to antimicrobial agents of Pseudomonas aeruginosa attached to catheters for 6 and 24 hours was also evaluated. When bacteria attached for 6 hours were used as inoculum, MBCs increased at least 8-fold for amikacin, 64-fold for ceftazidime, 64-fold for ciprofloxacin, 32-fold for norfloxacin and 2048-fold for meropenem. Similar results were observed when bacteria attached to catheters for 24 hours were used as inoculum. It is concluded that catheter material itself affected the in vitro activity of meropenem, and that the bactericidal activity of all antimicrobial agents against Pseudomonas aeruginosa present in biofilms on the surface of siliconized latex urinary catheters decreased dramatically, this effect being more pronounced with meropenem.