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[Study investigating the activity of several fluoroquinolones against Pseudomonas aeruginosa using the mutant
Elia Sirvent1, Montserrat Ruiz, Juan C Rodríguez
1Servicio de Microbiología, Hospital General Universitario de Elche, Universidad Miguel Hernández, Alicante, España.
Introduction:
The objective of this study was to compare the activity of ciprofloxacin, levofloxacin, moxifloxacin, gatifloxacin and ofloxacin against Pseudomonas aeruginosa by determining the mutant prevention concentration (MPC).
Methods:
Thirty-four clinical isolates of Pseudomonas aeruginosa causing nosocomial infection were studied. MPC values were determined using an inoculum of 10(10) cfu/mL on Mueller-Hinton plates with serial dilutions of the antibiotics. The microorganisms were classified according to whether the patients had been previously treated with fluoroquinolones or not.
Results:
The fluoroquinolone with the lowest MPC values was ciprofloxacin, followed by levofloxacin. Analysis of strains from patients previously treated with fluoroquinolones showed persistent susceptibility according to the CLSI criteria, but with lower activity of all the drugs.
Conclusions:
Although the microorganism remained susceptible to fluoroquinolones according to classical methods, the suitability of using these drugs in patients with severe infection and a history of fluoroquinolone use should be evaluated.
Insights
Ciprofloxacin and levofloxacin showed the lowest mutant prevention concentration (MPC) against Pseudomonas aeruginosa. Even with persistent susceptibility, reduced activity was noted in patients with prior fluoroquinolone exposure, warranting careful drug selection.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Pseudomonas aeruginosa is a common cause of nosocomial infections.
- Fluoroquinolones are widely used antibiotics, but resistance is a growing concern.
Purpose of the Study:
- To compare the mutant prevention concentration (MPC) of five fluoroquinolones against Pseudomonas aeruginosa.
- To evaluate the impact of prior fluoroquinolone treatment on drug activity.
Main Methods:
- Determined MPC values for ciprofloxacin, levofloxacin, moxifloxacin, gatifloxacin, and ofloxacin.
- Utilized a high inoculum (10(10) cfu/mL) on Mueller-Hinton agar.
- Classified isolates based on previous fluoroquinolone exposure.
Main Results:
- Ciprofloxacin exhibited the lowest MPC, followed by levofloxacin.
- All tested fluoroquinolones showed reduced activity against strains from previously treated patients, despite maintaining susceptibility by CLSI criteria.
Conclusions:
- While Pseudomonas aeruginosa may remain susceptible by standard criteria, reduced fluoroquinolone activity is observed in patients with prior exposure.
- Clinical suitability of fluoroquinolones in severe infections with a history of fluoroquinolone use requires careful consideration.
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