Relationship between biofilm formation of Pseudomonas aeruginosa and susceptibility to rifaximin and ofloxacin.

Pseudomonas aeruginosa is responsible for many infectious diseases related to antibiotic resistance. Biofilm formation may help bacteria to pass the treatment with antibiotics and overcome the immune system. Here, the relationship between antibiotics (rifaximin and ofloxacin) susceptibility and biofilm formation was evaluated. Ten isolates of P. aeruginosa were isolated from 110 urine specimens obtained from urinary tract infections (UTIs) patients. The spectrophotometric method was used to measure biofilm formation on polystyrene microtiter plates. Inhibitory zone onto agar plates was used to measure the antibiotic susceptibility of rifaximin and ofloxacin against the ten P. aeruginosa (Pa1, Pa2, Pa3, Pa15, Pa18, Pa22, Pa23, Pa25, Pa26 and Pa27) isolates. The highest inhibition zones were seen against Pa 25 and Pa 3 respectively, while the lowest inhibition zones of rifaximin were seen against Pa3, Pa23 and Pa25. Moreover, the lowest inhibition zones of both antibiotics were seen in the cases of Pa1 and Pa27 respectively. The maximum biofilm formation was seen in the case of Pa3, while Pa27 produced the lowest biofilm. The study showed no relationship between biofilm formation and susceptibility to rifaximin and ofloxacin (P>0.05).