Mutant prevention concentration of levofloxacin alone and in combination with ceftazidime against levofloxacin and ceftazidime sensitive and resistant isolates of Pseudomonas aeruginosa

Abstract EN

The study includes 23 isolates of Pseudomonas aeruginosa isolated from wound infections .The Minimum Inhibitory Concentration (MIC) to each of Levofloxacin and Ceftazidime for these isolates were determined.

The results showed 11(47.8 %) isolates sensitive to antibiotics, 5 (21.7 %) isolates resistant to each one of the antibiotics and 7 (30.5 %) isolates appeared resistance to one of them and sensitive to the other.

Mutant Prevention Concentration (MPC) to both Levofloxacin and Ceftazidime alone and in combination were determined to the 5 sensitive and 5 resistant isolates to both antibiotics.

Mutant Selection Window (MSW) was calculated according to the data of MPC and MIC to both levofloxacin and Ceftazidime alone and in combination to the same isolates which their MPC were determined (10 isolates).

The decrease in the value of MSW by 1-2 times were noted when both antibiotics together (in combination) were used in comparison with its value when Levofloxacin was used alone (before combination) to the sensitive isolates (5 isolates), and this indicates a synergistic action whereas, no synergistic action appeared in the resistant isolates (5 isolates) according to the MSW values, this emphasizes that the combination between levofloxacin and ceftazidime against resistant isolates is useless.